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Issue n°16 - December 2010

Issue n°16 - December 2010
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Editorial - IMBIZO II - Integrating biogeochemistry and ecosystems in a changing ocean: regional comparisons

Sophie Beauvais, IMBER IPO, France

IMBER held its second IMBIZO (Zulu word meaning ‘a gathering’) at the Hellenic Centre for Marine Research (HCMR) in Crete, Greece from the 10-14 October 2010. This symposium led by Julie Hall (NIWA, New Zealand), brought together the food web and biogeochemistry communities to consider the integration of biogeochemistry and ecosystems in a changing ocean.

More than 120 scientists from all over the world attended this meeting. They divided into three concurrent workshops, each structured to provide a synthesis of current knowledge and key questions for future research within IMBER. The workshops had common plenary, poster and report back sessions. Workshop 1 considered the effects of varying element ratios (C, N, P, Si and trace metals) on community structure at low trophic levels and food quality at mid and high trophic levels under present oceanic conditions and possible future climate changes. Workshop 2 reviewed regional comparisons of marine biogeochemistry and ecosystem processes over a range of space and time scales. Workshop 3 investigated potential effects of enhanced stratification on food webs and biogeochemical cycles. Reports by the Chairs of the workshops, as well as some science highlights by participants are presented below.

You will also find several articles written by the winners of the best young scientists awards.

Participants also had the opportunity to attend an interactive Data Management workshop, the day before the official start of IMBIZO II. The presenters illustrated the benefits of good data management practices for scientists. They also provided the IMBER community with useful resources and tools to facilitate data sharing. Cyndy Chandler and Alberto Piola, the co-Chairs of this workshop, give us their feedback about this “Dry cruise, but not dry topic” workshop!

The local organisers (Alexandra Gogou and Evangelos Papathanassiou) provide us with their perspective about hosting such an event. We take this opportunity to thank them, and the rest of the local organizing committee, for their dedication, generosity and enthusiasm. Without them IMBIZO II would not have been so successful!

IMBIZO II would not have happened at all without the support of other several partner organizations. We thank SCOR, who provided support for five scientists from developing countries, the EUR-OCEANS Consortium, HCMR, the Cretaquarium, PICES, KORDI, NSF, CNRS and UBO for their generous contributions.

We hope that you will enjoy reading of this special IMBIZO II report. It will remind the participants about the scientific discussions and interactions that occurred during IMBIZO II. And for those who were not lucky enough to attend, it will provide an idea of the level of scientific excellence that we hope will encourage you to attend IMBIZO III in 2012!

More info...

IMBIZO II
IMBIZO II participants

IMBIZO II participants

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Reports from the workshops

The effect of varying element ratios on community structure at low trophic levels and food quality at mid and high trophic levels

Dan Repeta, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

Rory Wilson, Swansea University, Swansea, UK

REPETA Dan
WILSON Rory

Seventy-five years have passed since Alfred Redfiel published his classic paper on elemental ratios and the composition of phytoplankton in the ocean. Although the ratios of macro- (C, N, P, S, Si) and perhaps micro (iron, vitamins and other trace metals) nutrients in seawater are considered to be an emergent property of the contemporary marine system, the metabolic requirements and flexibility in the range of elemental stoichiometry manifest at the cellular and organismal level is now known to be quite large. How do we reconcile the flexibility of elemental composition at the level of a microbial cell with the relatively fixed ratios of nutrients in the deep ocean, and how might a changing climate impact the ratio of essential nutrients in the sea?

The concept of ecological stoichiometry and bioessential elements has stimulated research into the nutrient requirements of marine producers and consumers at all levels in marine food webs, the chemical speciation of macro- and micro-nutrients, and the function and coupling of many biogeochemical cycles. Beyond this, the incorporation of elements into body tissue takes many forms, with different emphasis on integration into material used for structural stability, somatic tissue, that used as an energy source and that invested in reproduction, according to position in the food web. The workshop discussions focused on the role of elemental stoichiometry in structuring marine ecosystems at low trophic levels, and in determining food quality at mid and high trophic levels. Presentations highlighted the range of elemental ratios in the environment and in laboratory cultures, the concept of elemental stoichometry for essential trace elements (an “extended RKR ratio” for Fe, Co, Ni…), and the cellular processes that impact these ratios (substitution of S for P, Zn for Co), the role of grazing in maintaining elemental stoichiometry. Biogeochemical cycling at station ALHOA where N:P is 1:16 was compared to the Mediterranean Sea where N:P is 16:1. At higher trophic levels discussions and presentations focused on the shift in emphasis from nutrient limitation to energy limitation, on the distribution of heterotrophs in relation to their food sources, and on the impact of top predators in shaping microbial communities. These topics led to additional discussions on the role of organic matter cycling and related biogeochemical processes on maintaining and buffering elemental ratios in seawater, and on our knowledge of elemental ratios at higher trophic levels. A summary and perspectives paper, describing the current state of our knowledge on elemental ratios in seawater and across all trophic levels, is currently in preparation.

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Large-scale regional comparisons of marine biogeochemistry and ecosystem processes - research approaches and results

Raleigh Hood, University of Maryland Center for Environmental Science, Cambridge, Maryland, USA

Ken Drinkwater, Institute of Marine Research and Bjerknes Centre for Climate Research, Bergen, Norway

HOOD Raleigh
DRINKWATER Ken

As experimental controls cannot be imposed in studies of large marine systems, an alternative method of investigation is the comparative approach. Within such an approach, insights into biogeochemical, physical and ecological processes, as well as the overall structure and functioning of systems were sought during the workshop by comparing different geographical regions. Regional comparative methods and studies in widely diverse systems of the world’s oceans were reviewed and discussed. These included studies conducted in marine systems that span a wide range of time and space scales using idealized models as well as more realistic models, in situ, satellite and historical data, and as part of large multidisciplinary programs. Well-studied regions in the Arctic and Antarctic were noted as particularly good targets for comparative studies where large programs have been conducted and diverse databases can be combined. Studies of time-series stations (HOTS, BATS, ESTOC) and modeling studies resulted in intra- and inter-basin comparisons of physical forcing and biogeochemical response. Global comparative studies were presented on fisheries, ecosystems, and biogeochemical fluxes. Although diverse, these studies can be partitioned according to degree of use of data and models versus ecosystem structure, function, services and effects on biogeochemistry, which provides a means of organizing them in a sensible and tractable way.

These studies demonstrated that such comparisons can be particularly useful for identifying knowledge gaps and revealing how ecosystems might respond differently to perturbations and change. Comparative studies can also reveal where potential “tipping points” might be and they can be used to generate hypotheses for guiding research. However, there are still social, institutional and scientific barriers that can make it difficult to carry out comparative studies in marine systems. Moreover, combined biogeochemical and food web studies (especially for higher trophic levels) are usually not carried out at the same time and/or place in marine systems. The workshop participants concluded that the time is right: both data and models are now available to facilitate greater use of comparative studies in more marine systems and IMBER should promote them. The IMBER regional programs need to define specific, testable scientific questions/hypotheses that demand integration of biogeochemistry and food web research. Motivation of a workshop or working group focused on developing ideas and target regions for comparative studies is recommended.

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Sensitivity of marine food webs and biogeochemical cycles to enhanced stratification

Michael Landry, Scripps Institution of Oceanography/UCSD, San Diego, USA

Michio Kishi, Hokkaido University, Sapporo, Hokkaido, Japan

LANDRY Michael
KISHI Michio

Increased stratification of the upper oceans is a predicted general consequence of global climate warming that could impact nutrient fluxes, metabolic rates and balances in the euphotic zone, and the timing of seasonal production cycles. Projected ecological and biogeochemical sensitivities include: altered biomass, size structure, composition and diversity of the plankton community; timing effects on the coupling of production and grazing processes, trophic controls and reproductive cycles of key species; timing and route of fish migration; alterations in the ratios of nutrient availability, utilization and remineralization within the euphotic zone; and modified rates and pathways (particle flux, DOC, active migrations) of carbon and nutrient export out of the euphotic zone. How these potential effects may play out in specific regions of the oceans is poorly understood due to climate-related impacts on the timing and magnitude of physical drivers and the complexities and adaptations of biological systems.

The workshop brought together observational, modeling and experimental perspectives to consider the organizing principles and major unknowns for assessing food web and biogeochemical responses to stratification, including regional variability and strategies for further study. Insights were drawn from regional and temporal variations in the contemporary ocean, from paleo-reconstructions of past ocean conditions, and from models extending to future scenarios. Participants emphasized the ongoing need for long-term observations, process studies and experimental manipulations that improve understanding of basic ocean physics, ecology and biogeochemistry and their interactions on regional scales. Within such studies, however, there is a need for additional focus on the potential “difference makers”, organisms with unconventional energetic or life-history strategies - such as N2 fixers, mixotrophs, specialized large diatoms, large gelatinous suspension feeders and predators - that may be selected for by enhanced stratification and significantly impact trophic and biogeochemical pathways. Relevant knowledge about such organisms must not only be tested and demonstrated but also incorporated into models that can evaluate their potential impacts in future ocean scenarios. Moreover, because regional responses to stratification can be nonlinear and impact one another through downstream flows, we cannot expect to understand future changes from past behaviours or by assuming a constancy of historical boundary conditions between systems. Models that explore ocean responses to changes in heating and physical forcing thus need to be global, incorporating land-air-ocean interactions, to the best of our knowledge, and feedbacks and connections among systems

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Presentation by Farooq Azam

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Posters

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Workshop 2 participants at work

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Bonus IMBIZO II workshop! Dry Cruise workshop

Alberto Piola, Servicio de Hidrografia Naval, Buenos Aires, Argentina

Cyndy Chandler, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

The Dry Cruise workshop was convened prior to the IMBER IMBIZO II at the Hellenic Centre for Marine Research (HCMR), Crete, Greece on 10 October 2010. The workshop was co-chaired by Alberto Piola (IMBER SSC, Argentina) and Cyndy Chandler (BCO-DMO, USA). Its goal was to enhance awareness of the need to establish data management procedures, the advantages arising from following these procedures, and to provide hands-on training on data management and data preservation. The Dry Cruise was attended by more than 30 IMBIZO II participants and local students.

The workshop was opened by Eileen Hofmann, Chair of the IMBER SSC. After a brief introduction by Alberto Piola, Cyndy Chandler presented an overview of Data Management for IMBER researchers. This addressed the changes in data management needs, funding agency requirements, data policies and how IMBER data management is implemented and the challenges that lie ahead. She also provided a set of recommendations or ‘recipes’ for Better Practices for Shipboard Data Management. Gwen Moncoiffé (BODC, UK) addressed Better Practices for Data Reporting. Todd O’Brien (NOAA, USA) described the lessons learned from the Coastal & Oceanic Plankton Ecology, Production, & Observation Database project (COPEPOD). The Dry Cruise presentations provided the IMBER community with useful tips on how their science will benefit from improved data management practices and how the latter will facilitate data sharing.

Many of the issues discussed during the Dry Cruise are described in more detail in the IMBER Data Management Cookbook, which contains simple ‘recipes’ to guide researchers through data collection and documentation.

Because of the success of the Dry Cruise workshop, and because we recognize that YOU, the IMBER scientists, are interested in integrating better data management practices into your research programmes, we have decided to organize similar data management training events on a regular basis. We welcome your ideas for future short training subjects.

More info...

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The Dry cruise workshop presenters. From left to right: Alberto Piola, Gwen Moncoiffé, Todd O’Brien and Cyndy Chandler.

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Science highlights from IMBIZO II

Linking diatoms to nutrient availability and regional hydrological changes in fjords of Northern Patagonia, Chile

Jose Luis Iriarte, Universidad Austral de Chile, Puerto Montt, Chile; Universidad de Concepción, COPAS-Sur Austral, Chile and.(CIEP), Coyhaique, Chile

L Rebolledo, Instituto de Biología Marina, Universidad Austral de Chile, Valdivia, Chile

S Pantoja, Universidad de Concepción, COPAS-Sur Austral, Chile

HE González, Universidad Austral de Chile, Valdivia, Chile; Universidad de Concepción, COPAS-Sur Austral, Chile and (CIEP) Coyhaique, Chile

M Van Ardelan, Norwegian University of Science and Technology, Trondheim, Norway

 

It has been estimated that about half of the export flux of carbon to the deep ocean is synthesized by diatoms, thus it is important to consider the factors influencing the relative contribution of diatoms to total primary production and its response to climate change. Furthermore, carbon fixed in surface waters is recycled to the atmosphere, back into seawater, or buried in sediments. Since Patagonian fjords have been suggested as “CO2 sink” areas during the productive season (Torres & Ampuero 2009), it will be relevant to understand the processes/factors that modulate the efficiency of the biological pump in these systems.

Patagonian fjords ecosystems have experienced new scenarios mainly due to climatic variability (decreasing annual precipitation and glaciers melting) as well as anthropogenic effects (intensive fish-farm aquaculture, dam construction) along its shoreline. Additionally, large scales phenomena (i.e. El Niño, Global Change) may decrease freshwater stream flow, with actual lower river discharges, as suggested for larger northern Patagonian rivers (Lara et al. 2008). In this scenario, we hypothesise that a decrease in freshwater input (and hence, decrease in silicic acid inputs) and nutrient loading from anthropogenic activities (mainly nitrate and ammonia) may directly influence phytoplankton populations and community properties, such as shift in species composition (from diatoms to flagellates), and decrease in autotrophic biomass and primary productivity of coastal waters of Patagonian fjords (Figure 1). Here we hypothesise the following possible scenarios:

  1. A potential shift in dominance from diatoms to flagellates/bacteria (Si:N ratio departed of 1);
  2. A potential decrease in average primary productivity (due to reduction in diatom growth);
  3. A potential reduction in the diatom flux through a diminished “biological pump” and a reduction in the fjord capacity to act as a “sink” for CO2.
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Figure 1: Conceptual model of the Comau Fjord showing higher freshwater inflows loaded with silicate, that might result in a dominance of diatom and an enhanced diatom flux towards the sediment, in Spring than Summer.

Primary productivity, composition of the dominant species and their relationships with environmental factors have been studied in the Patagonian fjords system during the 2005-2009 period. The region is characterized by horizontal buoyancy input of freshwater from river run-off with important ecological-oceanographic implications. Primary productivity in fjord areas varies greatly in magnitude (0.1 and 4.0g C m-2 d-1; González et al 2010). In general, the vertical flux of POC out of the photic zone (5 – 30%) is largely size-dependent and highly variable on a seasonal scale. Micro-phytoplankton (>20µm), mainly chain-forming (Chaetoceros, Thalassiosira) and large single-cell (Rhizosolenia pungens) diatoms, contribute more (50 – 70%) to primary production and biomass in the fjords region during spring-summer seasons. The high autotrophic biomass and primary productivity estimates at the studied fjords are associated with higher stability of the water column, being favourable to growth of cold waters phytoplankton.

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Figure 2: Geochemical characteristics of the cores 6B recovered in the Relocavi fjord. The y axis represents the ages of the respective cores. The shaded area represents the sand layer. The green circles (Fig. 2c) show the total diatom abundances (valves g-1) for the core 6B. The black bars (Fig. 2f) represent the percentage of autochthonous material (marine) and the grey bars the percentage of allochthonous material (terrigenous).

Sediment analysis:

Sediment cores as dated by 14C and 210Pb, showed an increase in SiOPAL and diatom valves stratigraphy in concomitance with a decreased in C/N ratio and d13Corg from 1750 AD to the present. The mixing model of both cores showed a clear decrease of allochthonous material (Fig. 2f), possibly related to the decrease in rainfall and Puelo River streamflow (Lara et al., 2008). In addition, in both cores an increase in SiOPAL from ~ 1600 AD, associated with a higher abundance of marine diatoms. The relative high contribution of marine diatom species in present time sediments, compared to freshwater diatoms, suggests relatively high rates of production under conditions of moderate to high nutrient availability. Shift in diatom groups (marine versus freshwater diatom assemblages) or phytoplankton groups (diatoms versus flagellates) may be used to infer changes in oceanographic conditions in Patagonian fjord systems.

Water column experiments:

Phytoplankton chlorophyll a, cell abundance and taxonomic composition responded positively to nitrate and ammonia addition. In experimental approaches, the microphytoplankton assemblages of fjords showed that after a 5-day lag-time (slow phytoplankton growth), a relatively rapid chlorophyll a biomass, cell abundances and taxa/assemblage changes in response to enhanced nitrogen (nitrate, ammonia) concentrations in spring and summer. In these stratified marine systems, diatoms appeared to be nitrogen-limited. We argue that changes in nutrient loading (nitrate, ammonia or silicic acid) would have an impact on phytoplankton composition (diatoms to flagellates/ciliates), carbon biomass (low to high) and primary production (high to low).

The results obtained in four Patagonian fjords during the last five years represent an unique opportunity to carry out the next observational/experimental studies of future scenarii of low/high availability of nutrients for diatoms where the primary production and nutrient flues are important. In the pelagic habitat, diatoms have short generation times and are sensitive to their environments, and they may be excellent indicators of water masses and freshwater-seawater fronts (horizontal/vertical) observed in fjords. Results may provide information on the response of marine phytoplankton to nutrients change. Such information will be critical to understand the past, and maybe the future changes in the marine carbon cycle and changes induced by the input of nutrient compounds into the fjords from anthropogenic activities/climate changes.

References

González, H.G., Calderón, M.J., Castro, L., Clement, A., Cuevas, L.A., Daneri, G., Iriarte, J.L., Lizárraga, L., Martínez, R., Menschel, E., Silva, N., Carrasco, C., Valenzuela, C., Vargas, C.A. and Molinet, C. (2010) Primary production and its fate in the pelagic food web of the Reloncaví Fjord and plankton dynamics of the Interior Sea of Chiloé, Northern Patagonia, Chile. Marine Ecology Progress Series, 402, 13– 30.

Lara, A., Villalba, R. and Urrutia, R. (2008) A 400-year tree-ring record of the Puelo River summer-fall streamflow in the Valdivian Rainforest eco-region, Chile. Climate Change, 86, 331–356.

Torres R & P Ampuero. 2009. Strong CO2 outgassing from high nutrient low chlorophyll coastal waters off central Chile (30S): the role of dissolved iron. Estuarine, Coastal and Shelf Science, 83, 129-132.

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Rich biodiversity of copepods in the Bay of Bengal: a multi-decadal study

Rosamma Stephen, Scientist (retired), National Institute of Oceanography, Kochi, Kerala, India.

Rashiba A.P., Department of Zoology, Farook College, Kozhikode, Kerala, India

Rosamma Stephen was sponsored by SCOR.

STEPHEN Rosamma

Peninsular India divides the northern Indian Ocean into two basins – the Arabian Sea (AS) and the Bay of Bengal (BoB). The AS is characterized by intense upwelling and is biologically one of the richest environments of the world’s oceans. The BoB is traditionally known as less productive. A special feature of the BoB is extreme variability of the physical properties especially episodic cyclones with torrential rains mostly during the summer (April - May) and winter (October - November) monsoons. Our knowledge of the general distribution of copepods of the AS and BoB emanated from the studies of the zooplankton samples of the International Indian Ocean Expedition (IIOE, 1962-1965). This major oceanographic venture covered the northern Indian Ocean in a uniform and systematic method. Prior to this expedition, the taxonomy and general distribution of copepods were dealt with by Sewell (1929, 1947 and 1949). From 1973-1990 copepods of the coastal waters were studied in various programs under the investigations of National Institute of Oceanography (Stephen, 1984, 1992, Stephen and Kunjamma, 1987 and Stephen et al, 1992). Data on copepods of the BoB are limited compared to the AS. In the last decade studies from BoB were confined to BoB Process Studies. However, intensive observations were carried out in AS during JGOFS and are listed by Smith and Madhupraptap (2005). This paper deals with the copepods collected from BoB during different cruises of FORV Sagar Sampada under the multi disciplinary program “Marine Research on Living Resources (MR-LR) (Figure 1) during 1998 – 2005 (NIO, 2007) and is compared with the reports available from AS.

Samples were collected with the MPN net from five different strata from 0 – 1000m, namely Mixed layer, top of thermocline to bottom of thermocline, bottom of thermocline to 300m, 300 to 500m and 500 to 1000m. Collections were taken from fixed stations covering all the seasons along pre-set transects. Figure 2 shows the hydro-biological stations in BoB.

Copepod species composition:

A total of 318 species were identified during the period of study. In addition to the common species cited in the previous studies many Indo- Pacific bathypelagic species were encounterd in the 1000-0m. From IIOE onwards the earlier studies indicate high diversity in the BoB, although density is low compared to the AS. Stephen (1984) observed 54 species from BoB against 32 from AS. From 100-0m, Haridas and Madhupratap (1983) recorded only 72 species. In BoB, Veronica and Ramaiah (2009) reported132 calanoid species.

While reviewing the earlier studies the significant difference noticed is the increase in cyclopoids namely Oithona spp. in the upper strata. In the mixed layer, Paracalanus indicus and Acrocalanus longicornis, the small-sized herbivores were very abundant compared to large size species such as Eucalanus and Calanids. The density of carnivores, both large and small size forms, have increased. Lucicutia grandis, an indicator of lower OMZ were rare, whereas other species of the family occurred frequently.

The physical oceanography of BoB is different from that of the AS. The sea surface temperature varied between 26.3°C in winter to 29.5°C in summer. Although there is no large scale upwelling, signatures of cold-core eddies were discernable from the upheaval of isotherms below the surface (Prasannakumar et al, 2004). Sea surface salinity ranged from 28.0 to 35.5psu in different seasons, resulting in a strongly stratified top layer. Dissolved oxygen varied between140 - 180µM. Nutrient concentrations were low with nitrate concentration less than 2µM.

The biogeochemistry of the region plays akey role in the distribution and diversity of pelagic copepods. Although the surface layers are highly stratified, a very rich copepod fauna exists below the MLD. Prasannakumar et al (2004) proposed eddy pumping as a possible mechanism to transfer nutrient-rich deep water across the halocline to the oligotrophic euphotic zone during the summer monsoon. The recurring cyclones and the eddies are instrumental in bringing the deep population to the mixed layer. Further Prasannakumar et al (2010) attributed reduction in sunlight penetration, due to varied reasons, responsible for less biological production but suggests possible shifting of deep waters to the MLD. The study of copepods after the super-cylone in 1999 showed many of the bathypelagic species being shifted to the MLD (Stephen et al, 2005). The BoB is subjected to several episodic events compared to AS and transport of water from deeper layers during these dynamic physical processes helps to maintain high species diversity. The intrusion of Indo-Pacific species into the BoB may also be contributing to the higher diversity in the 1000-0m strata studied.

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Figure 1: Stations covered during Marine Research on Living Resources (MR-LR) (1998-2005)

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Figure 2: Hydro-biological stations in Bay of Bengal (BoB)

Participation at the IMBIZO ll was made possible by the financial help from SCOR through the IMBIZO II organizers. The author is grateful to both scientific bodies.

References:

Stephen, R., K. Saraladevi, P.P. Meenakshikunjamma, T.C. Gopalakrishnan and M. Saraswathy, 1992. Calanoid copepods of the Indian Ocean Expedition collections. B.N. Desai (Ed.) Oceanography of the Indian Ocean, Oxford/IBH New Delhi, 143-156.

Stephen, R. 1984. Distribution of Calanoid copepods in the Arabian Sea andBay of Bengal. Mahasagar Bull. Natn. Inst. Oceanogr. 17(3), 161-171.

Stephen, R. and P.P. Meenakshikunjamma, 1987. Vertical distribution of calanoid copepods in the equatorial Indian Ocean. Third International Conference on Copepoda, London, P. 63.

Stephen, R. 1992. Copepod composition along southwest coast and southeast coasts of India. B.N. Desai (Ed.) Oceanography of the Indian Ocean, Oxford/IBH New Delhi, 121-127.

Stephen, R., K. Saraladevi, P.P. Meenakshikunjamma, T.C. Gopalakrishnan and M. Saraswathy, 1992. Calanoid copepods of the Indian Ocean Expedition collections. B.N. Desai (Ed.) Oceanography of the Indian Ocean, Oxford/IBH New Delhi, 143-156.

Stephen, R., A.P. Rashiba, N.V.Madhu and K.K.C.Nair, 2005. Cyclone in the Bay of Bengal and induction of mesopelagic calanoid copepod species into the mixed layer. Dynamic Planet 2005, 22-26 August, 2005, Cairns, Australia (Proceedings under publication).

NIO, 2007. Environment and productivity patterns in the Indian EEZ. CMLRE Report. RC of NIO, Kochi

Prasanna Kumar, S., Nuncio, M., Narvekar, J., Kumar A, Sardesai, S.,. de Souza S. N., Gauns, M., Ramaiah,N., Madhupratap, M., 2004. Geophysical Research Letters, VOL. 31, L07309, 5 PP 2004

Prasanna Kumar, S.; Narvekar, J.; Nuncio, M.; Kumar, A.; Ramaiah, N.; Sardessai, S.; Gauns, M.; Fernandes, V.; Paul, J 2010. Current Science, vol. 98(10) 1331-1339

Sewell,1947

Smith, S.L. and Madhupratap, M. 2005. Progress in oceanography, Vol.65; 214-239

Fernandes, V. and N. Ramaiah, 2009. Aquat. Ecol., Vol.43(4) 951-963

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Implications of intensified stratification in the Black Sea for nutrient cycling and primary production between 1971 and 2001

Heather Cannaby, Akif Korkmaz, Bettina A. Fach, Baris Salihoglu and Temel Oguz, Institute of Marine Sciences, Middle East Technical University, Turkey

Viktor Dorofeev and Alexander Kubriyakov, Marine Hydrophysical Institute, Sevastopol, Ukraine

Heather Cannaby was sponsored by SCOR.

CANNABY Heather

The state of the environment of the Black Sea has declined dramatically since the late 1960s. Eutrophication, overfishing and a population explosion of the invasive ctenophore Mnemiopsis leidyi contributed to a decline in the health of the pelagic ecosystem and a crash in fish stocks between 1988 and 1991. Since 1982, outbreaks of Mnemiopsis and others gelatinous species have become increasingly important in defining the ecosystem structure of the Black Sea, with interannual variations in the bloom dynamics of these species shaping the pelagic food web. Since 1992, riverine nutrient loadings to the Black Sea have decreased, favouring an improvement in environmental conditions. Despite reports of a decrease in algal biomass and an increase in phytoplankton diversity during the past decade, however, there are no signs of recovery in piscivorous species (Oguz and Velicova, 2010). The current ecosystem structure continues to support a high biomass of (mainly non-native) gelatinous species as well as the non-native dinoflagellate Noctulica scintillans and remains unstable and highly vulnerable to environmental pressures.

The Black Sea is characterized by shallow mixed-layer depths ranging from ~5m in summer to ~70m in winter. A permanent halocline at 100 to 150m depth prevents deep winter convection and ventilation of the anoxic sub-pycnocline waters. Interannual variability in super-pycnocline water temperatures tends to mirror interannual variability in regional air temperatures, making the habitable regions of the Black Sea particularly susceptible to changes in climatic forcing (Oguz et al., 2006). We report changes in the physical characteristics of the Black Sea over the 30 year period from 1971-2001 and discuss the implications for ecosystem functioning. This study is part of the EU 7th Framework Project MEECE (Marine Ecosystem Evolution in a Changing Environment).

As there are few long-term time series available during the study period, we rely on model simulations to assess multidecadal scale trends over this period. The physical model applied in this study is the Princeton Ocean Model forced by ERA40 surface fluxes and monthly mean climatological river input. The model assimilates gridded CTD data during the period 1971-1993 and satellite altimetry data during the period 1992-2001. The physical model is coupled to the pelagic ecosystem model Bims-Eco, a nitrogen based model describing interactions between small and large phytoplankton groups, small and large zooplankton groups, Noctiluca scintillans and two gelatinous groups (Mnemiopsis leidyi and Aurelia aurita) (Oguz et al., 2001). The physical model has been validated by comparing modelled mixed-layer depths and mixed-layer temperature and salinities to those derived from 918 discrete CTD casts overlapping the simulation period. Model results compare well with the observations, with mean errors much smaller than observed trends.

The Black Sea exhibits a warming and freshening trend over the study period. Basin-averaged annual mean sea surface temperature (SST) anomalies show an increasing trend of 0.7ºC between 1971 and 2001 (Figure 1a) and a decreasing trend in salinity of 0.4 over the same period. Comparison of the simulated SST data to the gridded HadSST2 data set (Rayner et al., 2006) and to AVHRR data (PO-DAAC) demonstrates that the trends and variability in the simulated data reflect observations. Routine measurements from the Turkish national Black Sea monitoring programme suggest that the trends observed during the study period have continued until the present time, with the first 10 months of 2010 being the warmest and freshest on record. The warming and freshening trend during the study period coincided with an increase in the intensity of seasonal stratification and a shallowing of the surface mixed-layer. Basin averaged annual mean mixed-layer depths exhibit a statistically significant shallowing trend of 6.3m over the 30 year study period (Figure 1(b)). The shallowing of the mixed-layer in the model simulations results from a net heat gain over the study period (there is no concurrent trend in wind stress magnitude). It is interesting to note that whilst the Black Sea accumulated heat on an almost annual basis during the study period, the most rapid heat gain occurred over a six year period from 1986 to 1991 (Figure 2).

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Figure 1: Basin-averaged annual mean (a) SST and (b) mixed-layer depth anomalies. Model data including CTD assimilation (1971-1991) are shown as blue bars, model data with altimetry assimilation (1993-2001) are shown as red bars. Figure (a) is overlain by AVHRR data (1986-2001; green bars), and HADSST2 data (1971-2001; cyan bars).

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Figure 3: Annual mean surface concentrations of chlorophyll a from SeaWiFS (left) and modelled sea surface temperatures (right) for the years (a) 1998 (b) 1999 (c) 2000 (d) 2001.  The warmest year, 2001, is associated with particularly high production.

As expected, model simulations revealed a reduction in nitrate availability at the base of the euphotic zone, associated with increased water column stability. The period over which nitrate is seasonally depleted from the mixed layer, approximately from May to September, is lengthened by several weeks over the study period. As nitrate is a limiting nutrient for phytoplankton growth, primary production is expected to mirror nitrate availability and this is the case in the model simulations. Away from the direct influence of river plumes, however, warmer years are associated with higher resident phytoplankton concentrations, despite reduced nitrate availability. Hence, chlorophyll concentrations do not exhibit a simple relationship with stratification or nutrient availability. A comparison of satellite SST data from AVHRR (PO-DAAC) and chlorophyll-a data from SeaWiFS suggests that, in agreement with the model, higher chlorophyll concentrations exist during warmer years. Figure 3 provides, as an example, annual mean SST and chlorophyll-a maps for the years 1998-2001. The warmest year in the study, 2001, is associated with particularly high phytoplankton concentrations.

Top down control of ecosystem dynamics is typically associated with unresilient ecosystems, particularly where overfishing has resulted in the depletion of top predators as in the Black Sea case. Whilst simulated primary production rates are related to nutrient availability, resident phytoplankton concentrations are controlled primarily by grazing pressure and are thus a direct function of zooplankton abundance. Likewise, simulated zooplankton concentrations are dominated by the grazing pressure imposed by gelatinous species. As the growth rates and bloom timing of the gelatinous species are linked to water temperature (Oguz and Gilbert, 2007) our results support the idea that temperature indirectly influences the grazing pressure exerted on phytoplankton. In summary, model results suggest a positive feedback of reduced grazing pressure on phytoplankton during warm years due to increased grazing control on zooplankton by gelatinous species (i.e. Mnemiopsis leidyi). This result highlights the probable significance of top down control in the determining Black Sea ecosystem dynamics and provides a possible explanation for the increased phytoplankton concentrations observed during warm years. It is not possible, however, to draw concrete conclusions on ecosystem functioning from such a modelling study as many factors relating to production efficiency, e.g. photoacclimation, remain unresolved in the model simulations. Further refinement of the model requires an improvement in our understanding of the system and should follow focused observational studies.

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Figure 2: Basin averaged annual heat accumulation estimated from ERA40 data.

References:

Oguz, T. and V. Velicova, 2010. Abrupt transition of the northwestern Black Sea shelf ecosystem from a eutrophic to an alternative pristine state, Marine Ecology Progress Series, 405: 231–242.

Oguz, T., J. W. Dippner and Z. Kaymaz 2006. Climatic regulation of the Black Sea hydro-meteorological and ecologica properties at interannual-to-decadal timescales, Journal of Marine Systems, 60: 235-254.

Oguz, T., P. Malanotte-Rizzoli, H.W. Ducklow 2001. Simulations of phytoplankton seasonal cycle with multi-level and multi-layer physical-ecosystem models: The Black Sea example. Ecological Modelling, 144, 295-314. 

Rayner, N. A., P. Brohan, D. E. Parker, C. K. Folland, J. K. Kennedy, M. Vanicek, T. J. Ansell, et al. 2006. Improved analysis of changes and uncertainties in sea surface temperature measured in situ since the mid-nineteenth century: the HadSST2 dataset. Journal of Climate, 19: 446–469.

The AVHRR Oceans Pathfinder SST data were obtained through the online PO.DAAC Ocean ESIP Tool (POET) at the Physical Oceanography Distributed Active Archive Centre (PO.DAAC), NASA Jet Propulsion Laboratory, Pasadena, CA, USA.

Oguz, T. and Gilbert, D. (2007) Abrupt transitions of the top-down controlled Black Sea pelagic ecosystem during 1960-2000: Evidence for regime-shifts under strong fishery exploitation and nutrient enrichment modulated by climate induced variables.  Deep Sea Research, 220-242.

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Influence of stratification on DOM dynamics in the Mediterranean Sea

Chiara Santinelli, CNR-IBF, Pisa, Italy
SANTINELLI Chiara

Dissolved Organic Matter (DOM) is a complex mixture of molecules, most of them yet unknown. It plays a key role in the global carbon cycle as it represents the largest reservoir of reactive carbon (700x1015gC) on the Earth. DOM also plays a key role in the marine ecosystem (Figure 1). In fact, it is released at all the levels of the food web, through different processes, and it represents the main source of food for heterotrophic prokaryotes (Carlson, 2002). The consumption of DOM by prokaryotes starts the microbial loop; through the microbial loop, DOM can be:

  1. transformed into prokaryote biomass and channeled again in the food web;
  2. mineralized to CO2 and inorganic nutrients;
  3. transformed and newly released as DOM (Figure 1).
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Figure 1: Schematization of marine carbon cycle; the central role of DOM highlighted.

The fraction of DOM capable of absorbing light (PAR, UV-A and UV-B) is defined chromophoric DOM (CDOM). CDOM determines the underwater light availability in the open ocean and coastal waters. It can undergo photochemical reactions with a consequent reduction of its absorbing light capacity. This process represents an important source of CO, CO2 and oxygen radicals.

A seasonal study on DOC distribution in the Southern Adriatic Sea (Figure 2) evidences that stratification affects the DOC accumulation in the surface waters and its export below the mixed layer in the winter (Santinelli et al., 2010a). In the surface layer (0-50 m) DOC shows a clear seasonal pattern. In late summer, when a marked thermocline occurs DOC values in the mixed layer are at their maximum (60-80 µM). In winter, when the water column is completely mixed, DOC drops to values of 50-54µM. This finding can be explained by DOC accumulation in the mixed layer, probably due to nutrient limitation of bacterial consumption, when the water column is well stratified. When the thermocline breaks, the accumulated DOC is exported below the mixed layer. The integrated values of DOC in the upper 50m indicate a DOC accumulation from February 2007 to September 2007 of 0.47mol m-2, and a DOC export due to winter mixing of 0.64mol m-2. This amount is significantly higher than the particulate organic carbon (POC) export (0.3mol m-2 y-1) reported in the same area (Boldrin et al., 2002).

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Figure 2: Seasonal distribution of DOC in the Southern Adriatic Sea, data were collected in the framework of the Italian project VECTOR (Figure adapted from Santinelli et al., 2010a).

Stratification can also affect the amount of DOC exported at depth during deep water (DW) formation. Mediterranean DW are characterized by highly variable DOC concentrations (35-70µM), with very high values in recently ventilated DW (Figure 3) (Santinelli et al., 2010b). These values are significantly higher than those reported for the ocean. In addition, in the DW of the Southern Adriatic Sea, very high rate of microbial utilization of DOC (1.2 µM C month-1) were estimated, with 92% of oxygen consumption due to DOC mineralization (Santinelli et al., 2010b). This finding indicates that a high fraction of the exported DOC is labile. The DOC exported at depth during DW formation in the Western Mediterranean Sea can be of 0.76-3.02 Tg C month-1, if a DW formation rate of 2.4Sv is considered. This amount will be significantly reduced (0.045-1.52 Tg C month-1) if DW forms with a rate of 0.14-1.2Sv (Santinelli et al., 2010b). These observations suggest that stratification could influence the export of DOM at depth in two ways:

  1. affecting DW formation rates, in fact an increase in stratification will probably results in a decrease of the DW formation rates;
  2. affecting the quality of DOM in the surface layer; if DOM remains in the surface layer for a long period, it will undergoe biological and photochemical reactions that will probably change its properties.
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Figure 3: Horizontal distributions of DOC and AOU in the bottom waters (2001-2008). This work was supported by the SESAME Project, EC Contract No GOCE-036949 (Figure from Santinelli et al., 2010b).

The influence of stratification in coastal areas was observed by studying the DOC data collected in the Gulf of Naples (Marechiara station) bi-monthly in 2007-2008. Very high DOC concentrations (>100µM) were observed during high stratification period. When the water column is stratified, the input of fresher water, rich in DOC and nutrients, increases the stability of the water column and the terrestrial inputs remains visible.

Finally, in the Southern Tyrrhenian Sea in August 2009 and 2010, the absorption of CDOM at 355nm showed a minimum (<0.1m-1) in the mixed layer, in correspondence with the highest DOC values (> 68µM). This finding clearly indicates the occurrence of CDOM photobleaching.

From these data we can infer that enhanced stratification could determine:

  • An increase in DOM concentration in the mixed layer, because the bacteria consumption is limited by nutrients;
  • A change in the amount and quality of DOM exported below the mixed layer each winter;
  • A decrease in the C export due to the reduced DW formation rates;
  • An increase in DOM concentration in coastal waters directly and/or indirectly linked to terrestrial inputs
  • A higher flux of CO, CO2 and volatile organic carbon compounds in the atmosphere, due to the increase in CDOM photobleaching

References:

Boldrin A., Miserocchi S., Rabitti S., Turchetto M.M., Balboni V. & Socal G. Particulate matter in the Southern Adriatic and Ionian Sea: characterisation and downward fluxes. Journal of Marine Systems 33–34, 389–410 (2002).

Carlson C.A. Production and removal Processes. In: Biogeochemistry of Marine Dissolved Organic Matter. Hansell D.A. &, Carlson C.A. (eds.), Elsevier, San Diego, 91-151 (2002).

Santinelli C., Ribera D'Alcalà M., Civitarese G., Lavezza R. & Seritti A. DOC export below the mixed layer in the southern Adriatic Sea. 39th CIESM Congress proceedings, in press (2010a).

Santinelli C., Nannicini L. & Seritti A.. DOC dynamics in the meso and bathypelagic layers of the Mediterranean Sea. Deep Sea research II, 57, 1446-1459 (2010b).

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Vertical distribution of zooplankton in the Oxygen Minimum Zone of the Mexican tropical Pacific during autumn and the Habitat Compression Hypothesis

Jaime Färber Lorda, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Mexico

Emilio Beier, Unidad La Paz, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), La Paz, Mexico

Victor M. Godínez, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Mexico

Jaime Farber Lorda was sponsored by SCOR.

FÄRBER-LORDA Jaime

The IMBER IMBIZO II provided us with the opportunity to present our results from the low oxygen area of the Mexican Tropical Pacific. This was a very important forum to present our ideas and results to a broad audience of specialists. The workshops at this meeting were a useful and efficient way to communicate our ideas and for perspectives to direct our future research.

We presented the results of the PROCOMEX XI, an oceanographic cruise that sailed from 17-29 November 2009, with the purpose of studying the zooplankton’s vertical distribution in relation to trophic conditions, oxygen concentration and hydrography. Former work in the area showed no day-night differences in zooplankton biomasses (Färber Lorda et al.; 2004b, 2004c). With historical data, Férnandez-Álamos and Färber Lorda (2006) showed that in certain areas with shallow low oxygen the night:day ratio of zooplankton bio-volumes was 1. Thus, it is supposed that vertical migration is blocked by a shallow Oxygen Minimum (OM) (Färber Lorda, Summer ASLO 2006, Victoria, Canada). These observations gave rise to the Habitat Compression Hypothesis, where zooplankton habitat will be reduced to the oxygenated layer with a thickness of ~ 40-150m, and trophic interactions will be facilitated, or altered, possibly producing a shallow higher productivity layer. The implications of these findings are important, since the trophic relationship and carbon fluxes will be different from those areas that do not present these characteristics.

To test the hypothesis, sampling with MOCNESS tows took place along two transects as described in Figure 1. Water samples were filtered to study the biochemical composition of Particulate Organic Matter (POM) as an indicator of food supply for zooplankton. A multidisciplinary study was undertaken, with nutrient determinations for the area, pCO2, water pH, total alkalinity, aragonite and Dissolved Inorganic Carbon (DIC). We present partial results on vertical distribution in relation to hydrography and oxygen (Figure 2).

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Figure 1. Stations sampled during the PROCOMEX cruise in November 2009. Zooplankton data at the station D3 are shown in Figure 3.

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Figure 2: Hydrography of the B (a and c) and D transects (b and d). Solid black lines in (a) and (b) correspond to temperature and colours to salinity. Solid white lines in (c) and (d) correspond to dissolved oxygen and colours to chlorophyll fluorescence. A more stratified profile is present in the southern D transect, which is evident also in the more clearly defined two pigment maxima, and a shallower oxycline (~4 µmoles kg-1). The dotted line shows the station in which the zooplankton data shown in Figure 3, were obtained.

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Figure 3: A vertical CTD profile at the 48-hours station D03, plotted with zooplankton volume data. The relationship between low oxygen and low zooplankton abundance and bio-volumes are clear. The solid blue line is the day tow, and the dotted blue line the night tow. Note the two peaks in fluorescence, as described by Cepeda et al., (2009).

MOCNESS tows were performed at given stations. It is evident from our results (Figure 3) that the OMZ is most likely conditioning the vertical distribution of zooplankton, with a drastic reduction of zooplankton bio-volumes under 100m depth, which roughly corresponds to the depth at which the OMZ starts. The vertical distribution of zooplankton does not vary from day to night, with the possible exception of euphausiids. The presence of different taxonomical groups gradually reduced with depth, with a striking reduction of abundance. At a fixed point at a 48-hours station, the vertical distribution did not change between day and night, with great copepod abundances during broad daylight, an uncommon feature. Only euphausiids showed low abundances down to 150m during the day, and restricted to the first 100m at night, apparently showing incursions within the OMZ. However, at the deeper (300-400 and 400-500m) layers we see a small rise in the abundance of groups like copepods, foraminifera, and radiolaria. The question that rises is: how did these animals get there? At some near-shelf stations, at the 0-50m or 0-100m layers or both, great abundances of ostracodes were found, a frequent feature for the area (Färber Lorda unpublished data) found during other cruises. There is a striking coincidence of low oxygen with low abundances, this is quite evident and supports our Habitat Compression Hypothesis. Other data obtained are under evaluation and will be published soon.

References:

Cepeda-Morales J., E. Beier, G. Gaxiola-Castro, M. Lavín, VM Godínez, (2009) Effect of the Oxygen minimum zone on the second chlorophyll maximum in the Eastern Tropical Pacific off México. Ciencias Marinas (2009), 35(4): 389–403

Färber-Lorda J., Lavin M. A., Guerrero M. A. (2004b) Effect of the wind forcing on the trophic conditions, zooplankton biomass and krill biochemical composition in the Gulf of Tehuantepec. Deep-Sea Research II. 51, 6-9, 601-614.

Färber-Lorda J., A. Trasviña, P. Cortes. (2004c) Trophic conditions and zooplankton distribution in the entrance of the Sea of Cortes during summer. Deep-Sea Research II. 51, 6-9, 615-627.

Fernandez, M. A., J. Färber-Lorda (2006) Zooplankton and the Oceanography of the Eastern Tropical Pacific: A review. Progress in Oceanography, 69, 318-359.

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The nitrogen cycle of the eastern Mediterranean Sea from a stable isotope perspective

Paraskevi Mara, University of Crete, Greece & IfBM University of Hamburg, Germany

Paraskevi Mara won the prize for the best oral presentation by a young scientist in Workshop1 at the recent IMBER IMBIZO II. The prize was the book "Marine Ecosystems and Global Change" edited by M. Barange et al., Oxford Univ. Press.

 

For more than a century scientists around the world have carried out intensive research in order to reveal, and therefore to understand, the global significance of the biogeochemical cycles of important elements. One element whose biogeochemical cycling is important for the sustainability of life, is nitrogen (N), which comprises a large fraction of Earth’s atmosphere. The transformations and the processes occurring in the biogeochemical cycling of nitrogen, generate a variety of chemical nitrogen-compounds that play a key role in the maintenance and the productivity of the ecosystems.

Nitrates are usually considered as the limiting factor of primary production in most of the world’s oceans. However, there are certain environments where the major chemical variable that limits primary production is different. Such a case is the Eastern Mediterranean Sea (EMS), which, compared to other oceanic environments, is phosphorus-limited with impoverished phytoplankton biomass and productivity levels (Figure 1). The EMS is also unique because the ratio of dissolved nitrate to phosphate (DIN:DIP) in all the sub-thermocline water masses is higher than Redfield’s ratio, ranging from 20 to 28 (Krom et al., 1991). Interestingly, the nitrogen isotopic ratio (15N/14N; expressed as δ15N) of nitrates, suspended matter and surface sediments is significantly lower in the EMS than those of other oligotrophic oceans (Pantoja et al., 2002; Çoban-Yidiz et al., 2006; Emeis et al., 2010).

In order to explain both the excess reactive nitrogen concentrations and the unusually depleted N-isotope ratios of nitrates in the EMS’s intermediate and deep waters, the relative contribution of the different nitrogen sources was examined, by analysing their isotopic fingerprints. The study focused mainly on the determination of the δ15N of nitrates (δ15N-NO3) deriving from atmospheric bulk (wet+dry) deposition, wet deposition (single rainwater events) and aerosol samples which had been collected in Crete from April 2006 to September 2007, and from marine samples collected from several depths during the M71-3 METEOR cruise (EMS, January-February/2007). In this way it was considered possible:

  • to establish the atmospheric isotopic fingerprint and probably identify important nitrogen sources in this boundary region, between the anthropogenically affected air masses from Europe and the relatively unpolluted air masses from N. Africa;
  • to examine whether the depleted δ15Ν-NO3 in deep waters might be explained by atmospheric deposition and/or by other processes occurring in the marine environment of the EMS.

The analysis of the samples was performed with the ‘‘denitrifier method’’, as described extensively by Sigman et al. (2001). The results of the atmospheric samples (Figure 2) showed that both bulk deposition and rainwater had consistently negative δ15N values, implying nitrogen-depleted atmospheric sources (Mara et al., 2009). The δ15N values of the rainwater were in agreement with the δ15N values reported from other environments. The bulk deposition presented two well-distinguished periods: the dry period, from May to September and the wet period, from October to April. Their depleted values were attributed to low δ15N deriving from depleted sea-salt (NaNO3) and lithogenic (Ca(NO3)2) sources. Furthermore the analysis of the aerosol samples presented an additional δ15N-depleted source, the nitric acid (HNO3), that appeared as the dominant nitrogen species during the dry period. Finally, the flux-weighted annual average of the measured δ15Ν in the atmospheric nitrates was estimated to be -3.1‰ (Mara et al., 2009). Based on the results obtained, it was clear that the input of atmospheric NO3 could not be left out when investigating the present-day nitrogen-cycle in the oligotrophic EMS.

During the M71-3 cruise, samples of different N-reactive pools were collected and also analysed for their isotopic signature. On the same cruise the stable oxygen isotopic values of nitrates (δ18O-NO3) were also estimated, in order to bring additional information to the N-cycling of the EMS. The obtained δ15N results were shown to be different among the stations and among the different depths (Emeis et al., 2010). The average δ15N of the different N pools and especially the δ15N of nitrates in the deep water (δ15N-NO3: 2.15±0.21‰), were shown to be lower compared to those of the global ocean. This was not the case for the δ18O-NO3, where the obtained values (3.7±0.9‰) were higher compared to the values referred in the literature (Sigman et al., 2009). Based on the results obtained Emeis et al. (2010) calculated the Δ(15,18) ratio, a parameter that combines both δ15N-NO3 and δ18O-NO3 and can be an indicator for the isotopic nitrate sources. The Δ(15,18) value in the mixed layer was found around -3‰ with a decrease towards the sea surface (Figure 3). By applying a model calculation of Δ(15,18) for some possible processes occurring in the marine environment of the EMS, Emeis et al. (2010), suggested a number of possible combinations of external and internal sources that can theoretically result in the nitrate isotope anomaly observed in the EMS. However, the preferred interpretation of the data was that they represent a mixture of regenerated nitrate and atmospheric NOx deposition, because both are known to be inputs to the mixed layer in the necessary magnitudes and isotopic ranges to fully describe the changes observed.

The data on the nitrogen stable isotopes presented at the IMBER IMBIZO II in Crete, underlined the significance of the atmospheric NOx inputs to the basin, and stressed the importance for their incorporation into mass-based and isotope-based budgets of the N-cycle in the Eastern Mediterranean Sea.

References:

Çoban-Yildiz, Y. et al., 2006. Deep Sea Research II, 53: 1875-1892.

Krom, M. D. et al., 1991. Limnology & Oceanography, 363: 424-432.

Mara, P. et al., 2009. Global Biogeochemical Cycles, 23 (GB4002): 1-11.

Pantoja, S. et al., 2002. Deep-Sea Research Part I, 49: 1609-1621.

Sigman, D. M. et al., 2001. Analytical Chemistry, 73 (17): 4145-4153.

Sigman, D. M. et al., 2009.Deep-Sea Research Part I, 56 (9): 1419-1439.

Emeis, K-C. et al., (in press). Journal of Geophysical Research-Biogeoscience doi:10.1029/2009JG001214

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A role for prey type in structuring planktonic food webs

Joel K. Llopiz, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

Currently at Woods Hole Oceanographic Institution, Woods Hole, Massachusetts.

Joel Llopiz won the prize for the best poster presentation by a young scientist in Workshop 2 at the recent IMBER IMBIZO II. The prize was the "Atlas of the Patagonian Sea: Species and Spaces" edited by Falabella et al., 2009.

LLOPIZ Joel

Larval fishes represent an important link between planktonic food webs and higher trophic levels in the ocean. However, the specific trophic roles of larval fishes in the oceanic plankton are not well understood and have been largely ignored as components of planktonic food webs-especially in lower latitudes. This may be due, in part, to the impression that all fish larvae can be grouped as a single link in the food web, and that they have a rather insignificant influence on the overall structure of planktonic food webs. In low-latitude oceanic waters, an added obstacle to understanding the larval fish component of food webs is the high diversity of both fish larvae and their zooplankton prey-time and resource constraints have thus far precluded detailed, taxon-specific analyses of the feeding of many taxa of larval fishes. Additionally, low levels of primary and secondary productivity in tropical, oceanic waters may allow fish larvae in these regions to exert a much greater predatory impact upon zooplankton than their counterparts in more productive waters.

As part of a large-scale study on the plankton and planktonic environment of the Straits of Florida (led by Robert Cowen at RSMAS), we have been able to address many of the aforementioned gaps in our knowledge. We focused on the following objectives:

  1. documenting the feeding ecologies of the larval fish families that compose nearly the entire larval fish community in the oceanic plankton of the Straits of Florida;
  2. constructing a quantitative food web illustrating the major trophic pathways to larval fish;
  3. examining the degree to which the taxon-specific variability in larval fish abundance and diet composition (i.e. via prey selectivity differences) influences the variability in the larval fish food web.

To accomplish this, a transect of 17 stations in the Straits of Florida was sampled monthly over two years. In total, 223,000 fish larvae were sorted and identified, with zooplankton community analyses performed on a subset of samples. Subsamples of the 33 fish families that together represented 90% of all larvae collected were inspected for gut contents. A total of 4704 larvae were inspected, from which 33,814 prey were excised.

Despite high degrees of spatial and temporal co-occurrence of larval fish families, diets varied greatly by family (Figure 1), with most families exhibiting some level of feeding selectivity that resulted in either very narrow diets or the complete exclusion of prey types commonly fed upon by other families. For example, cusk-eel and cardinalfish larvae consumed calanoid copepods almost exclusively, while wrasses and dragonets fed upon cyclopoids and harpacticoids but almost no calanoids. Some taxa (tunas and flounders) consumed nearly no crustaceans and fed only on appendicularians.

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Figure 1: Numerical proportions of zooplankton prey types in the diets of several families of fish larvae collected across the Straits of Florida.

In combination with diet data, we utilized results on family-specific larval abundances and consumption levels to construct a quantitative food subweb of larval fishes and their prey (Figure 2). In addition to the overall complexity of the web, several conclusions and patterns can be drawn from it. The upper black bars represent the predatory impact of each fish family, taking into account each family’s abundance in the plankton and the number of prey in the gut of each larva. Jacks had the greatest impact despite the dominant lanternfishes being over four times more abundant. The most important prey (represented by the lower bars) to the entire larval fish community were calanoid copepods, with consumption by jacks contributing the most to this importance (represented by the base of the triangles).

Not shown here is how this food web changes in space and time. Such changes are related to the family-specific diets of the larvae and the variability in their presence and abundance, which itself is influenced by the location and times of spawning by the adults. Another conclusion of this research is that, although fish larvae are gape-limited, feeding by most taxa is clearly influenced by prey type as well as prey size, since many of the prey types are of similar sizes yet not consumed equally across families. Thus, this component of the planktonic food web is not solely size-structured. The selective feeding of each family, in conjunction with their total consumption as a population, will influence the overall pathways of energy transfer from zooplankton through the larval fish community and on to higher trophic levels.

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Figure 2: Quantitative food web of larval fish families and their zooplankton prey. Upper black bars represent the relative consumption of the total population of each fish family (taking into account both larval abundance and the number of prey per larva). Lower black bars represent the relative importance of each prey type to the entire larval fish community, with the contribution by each family to a prey type’s importance represented by the width of the connecting triangle.

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Biological production response to coastal upwelling intensification: insights from a comparative modeling study

Zouhair Lachkar and Niki Gruber, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland

Zouhair Lachkar won the prize for the best oral presentation by a young scientist in Workshop 2 at the recent IMBER IMBIZO II. The prize was the book "Marine Ecosystems and Global Change" edited by M. Barange et al., Oxford Univ. Press.

LACHKAR Zouhair

Equatorward winds along the eastern boundaries of the Atlantic and Pacific induce the upwelling of nutrient-rich water into the euphotic zone, thereby stimulating phytoplankton growth and leading to highly productive marine ecosystems (Pauly and Christensen, 1995). While supporting very rich ecosystems, the Eastern Boundary Upwelling Systems (EBUS) are also vulnerable to various anthropogenic perturbations. Directly driven by the atmospheric circulation, these ecosystems are particularly sensitive to global climate change and its potential impact on alongshore winds. Atmospheric and sedimentary observations point toward a recent strengthening of the coastal upwelling favorable winds (Shannon et al., 1992; Schwing and Mendelssohn, 1997; Mendelssohn, 2002; McGregor et al., 2007). This upwelling intensification has been related to a global warming-induced increase in the land-sea thermal gradient (Bakun, 1990), and is therefore projected to further increase in the future (Snyder et al., 2003, Diffenbaugh et al., 2004). Yet, the effects of enhanced upwelling on marine ecosystems are still largely uncertain. In particular, the question of how biological productivity in these systems might respond to such wind perturbation is still unresolved. While recent observations generally show the expected positive trends in primary production in most EBUS (Kahru et al., 2009, Demarq, 2009), individual ecosystems exhibit very contrasting sensitivities to comparable upwelling-favorable changes. Why do these sensitivities differ?

To answer this question, we undertook a comparative modeling study contrasting two of the four major EBUS, namely the California Current System (California CS) and the Canary Current System (Canary CS). Our goal is to explore the dominant mechanisms controlling the response of these ecosystems to changes in upwelling-favorable winds. The comparison of these two systems provides an adequate framework for generalizing individual observations and for developing a better understanding of the underlying dynamics of EBUS ecosystems in general. We made a series of eddy-resolving simulations of the California CS and the Canary CS using the Regional Oceanic Modeling System – ROMS – coupled to a nitrogen-based Nutrient-Phytoplankton-Detritus-Zooplankton (NPDZ) biogeochemical model (Figure 1). In order to explore the effects of upwelling-favorable wind intensification on coastal productivity, we compare our standard simulations for both EBUS with those forced with increased wind stress.

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Figure 1: Snapshots of simulated surface chlorophyll-a in the Canary CS (left panel) and the California CS (right panel) in early April.

The increased wind simulations show contrasting productivity responses between the California CS and Canary CS (Figure 2). Despite a substantial increase in the nutrient supply associated with the upwelling intensification, the productivity shows only a limited enhancement in the California CS relative to the Canary CS. The reason for these differences are, in part, related to the faster phytoplankton growth in the Canary CS due to warmer temperatures, which results in a more efficient use of nutrients in this system. An additional factor is the rate of water renewal, i.e. the inverse of the residence time, in the nearshore area. Using a Lagrangian diagnostic tool (Blanke and Raynaud, 1997) to evaluate water mass residence times, generally we indeed found that the newly upwelled water masses stay substantially longer in the nearshore area in the case of the Canary CS, before getting subducted farther offshore (Figure 3). This enhances the buildup of biomass in the coastal zone of the Canary CS and leads to a more efficient recycling of nutrients compared to the California CS. Conversely, the substantially shorter residence times in the nearshore region of California CS is associated with a much stronger offshore export of organic matter, resulting in a less efficient buildup of biomass and a weaker recycling of nutrients in the upwelling zone.

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Figure 2: (a) 0-100km nearshore averaged Net Primary Production (NPP) as simulated with different wind forcings in the California CS (orange) and the Canary CS (purple). (b) 0-100km nearshore inventory of nitrate in the euphotic zone as simulated under different wind forcings in the California CS (orange) and the Canary CS (purple).

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Figure 3: Water mass residence times (in days) in the 0-100km nearshore region in the Canary CS (left) and California CS (right).

Longer water residence time in the Canary CS relative to the California CS has no single explanation. The shelf topography and the level of eddy activity probably both contribute. The wider continental shelf in the Canary CS results in an offshore displacement of the upwelling cell, producing an area over the innershelf where the circulation has almost no cross-shore transport (Marchesiello and Estrade, 2009). This prevents coastal water from being advected offshore, increasing the water residence time in the innershelf region. The higher level of eddy activity in the California CS may also play an important role in reducing the water residence times in the coastal region of this system because of a higher eddy-induced subduction and offshore transport (Gruber et al., submitted).

Overall, our results show that factors affecting characteristic timescales of biological growth such as temperature and those related to the dynamics of the lateral circulation in coastal upwelling systems such as the topography of the continental shelf and the level of eddy activity will likely exert a strong control on the magnitude of the biological response to upwelling intensification. This study also shows that the biological response to global warming induced upwelling intensification might substantially vary from one EBUS to another, with major implications for the biogeochemical cycles and fisheries in these rich marine ecosystems.

References:

Bakun, A.: Global Climate Change and Intensification of Coastal Ocean Upwelling, Science, 247, 198– 201, doi:10.1126/science.247.4939.198, 1990.

Blanke, B. and Raynaud, S.: Kinematics of the Pacific Equatorial Undercurrent: an Eulerian and Lagrangian approach from GCM results, J. Phys. Oceanogr., 27, 1038–1053, 1997

Demarcq, H.: Trends in primary production, sea surface temperature and wind in upwelling systems (1998-2007), Progress In Oceanography, Volume 83, Issues 1-4, 2009, Pages 376-385, ISSN 0079-6611, DOI: 10.1016/j.pocean.2009.07.022.

Diffenbaugh NS, Snyder MA, Sloan LC (2004) Could CO2-induced land- cover feedbacks alter near-shore upwelling regimes? Proceedings of the National Academy of Sciences US, 101, 27–32.

N. Gruber, Lachkar Z., Frenzel H., Marchesiello P., Munnich M., McWilliams J. C., Nagai T., Plattner G-K., Mesoscale eddy-induced reduction of biological production in coastal upwelling systems, submitted to Nature.

Kahru, M., Kudela, R., Manzano-Sarabia, M., and Mitchell, B. G.: Trends in primary production in the California Current detected with satellite data,, 2009.

Marchesiello, P. and Estrade, P.: Eddy activity and mixing in upwelling systems: a comparative study of Northwest Africa and California regions, International Journal of Earth Sciences, 98, 299–308, doi:10.1007/s00531-007-0235-6, 2009.

McGregor, H. V., Dima, M., Fischer, H. W., and Mulitza, S.: Rapid 20th-Century Increase in Coastal Upwelling off Northwest Africa, Science, 315, 637–639, doi:10.1126/science.1134839, 2007.

Mendelssohn, R.: common and uncommon trends in SST and wind stress in the California and Peru-Chile current systems, Progress In Oceanography, 53, 141–162, doi:10.1016/S0079-6611(02)00028-9, 2002.

Pauly, D. and Christensen, V.: Primary production required to sustain global fisheries, Nature, 374, 255–257, doi:10.1038/374255a0, 1995.

Shannon, L., Crawford, R., Pollock, D., Hutchings, L., Boyd, A., Taunton-Clark, J., Badenhorst, A., Melville-Smith, R., Augustyn, C., Cochrane, K., Hampton, I., Nelson, G., Japp, D., and Tarr, R.: The 1980s a decade of change in the Benguela ecosystem, South African Journal of Marine Science, 12, 271–296, 1992.

Schwing FB, Mendelssohn R (1997) Increased coastal upwelling in the California current system. Journal of Geophysical Research, 102, 3421–3438.

Snyder MA, Sloan LC, Diffenbaugh NS, Bell JL (2003) Future climate change and upwelling in the California current. Geophysical Research Letters, 30, 1823, doi: 10.1029/2003GL017647.

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Decoupling of the temperature-nutrient relationship in the California current ecosystem with global climate change

Ryan R. Rykaczewski, University Corporation for Atmospheric Research, USA John P. Dunne, NOAA Geophysical Fluid Dynamics Laboratory, USA

Ryan Rykaczewski won the prize for the best oral presentation by a young scientist in Workshop 3 at the recent IMBER IMBIZO II. The prize was the book "Marine Ecosystems and Global Change" edited by M. Barange et al., Oxford Univ. Press.

RYKACZEWSKI Ryan

Increased thermal stratification of the water column in much of the global ocean is a critical aspect of modeled ecosystem responses to continued emissions of greenhouse gases. Climate models included in the fifth assessment report of the IPCC project a global increase in sea surface temperature of 2 to 3°C when forced by the A2 emissions scenario (Meehl et al., 2007). Projected changes in temperature at depth are more muted and uncertain, as they evolve over longer time scales. The resulting increased thermal stratification has the potential to influence a wide array of ecological processes and biogeochemical fluxes, including reduced supply of nutrient-rich deep waters across the pycnocline and enhanced stability of the euphotic zone.

In nutrient-limited subtropical ecosystems, increased stratification on seasonal to interannual time scales is associated with reduced surface nutrient concentrations and decreased productivity. An inverse relationship between temperature and zooplankton biovolume is evident over interannual to decadal time scales in the California Current Ecosystem (CCE; Roemmich and McGowan, 1995), and many have hypothesized that continued warming of the surface ocean associated with global climate change will further decrease productivity in well-stratified marine ecosystems (e.g., Behrenfeld et al., 2006). Changes in wind forcing of the surface ocean also influence surface mixing and upwelling of nutrients from depth (Bakun, 1990).

To further investigate the response of the northeast Pacific ecosystem to future climate conditions, we examined projected changes in nutrient concentrations using a prototype earth system model (ESM2.1) developed at the Geophysical Fluid Dynamics Laboratory. This model includes a representation of major nutrients (N, P, Si, and Fe) and three phytoplankton functional groups with variable stoichiometry. Under the A2 emissions scenario in ESM 2.1, temperature increases by about 2°C in the upper 200 m of the North Pacific between the pre-industrial period and 2100. Across most of the basin, nutrient concentration in this upper portion of the water column decreases, consistent with the conventional hypothesis relating water-column stratification and nutrient supply. However, the projected nitrate concentration of the upper layer of the northeastern Pacific increases by about 80% between the pre-industrial period and year 2100 despite increases in stratification (Figure 1a and b).

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Figure 1: Modeled temperature (a) and nitrate concentration (b) in a control volume representing the CCE from the pre-industrial period (prior to 1860) through 2300 as projected by ESM 2.1 when forced with the A2 emissions scenario. Note the positive trends in nitrate and temperature during the 21st century. Colored, bold lines display the seven-year mean for each season; January through March average in black, April through June in green, July through September in red, and October through December in blue.

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Figure 2: Modeled trajectories of water parcels prior to arrival in the CCE under pre-industrial (1860) and future (2100) conditions. A poleward shift and weakening of westerly winds and a corresponding decrease in the level of negative wind-stress curl over the eastern subtropical North Pacific is projected. This decreases downward pumping of nutrient-depleted surface waters to depths which are subsequently advected to the CCE upwelling system.

Closer examination of the modeled nutrient fluxes and volume transport of waters in the region revealed that this increase in nitrate and productivity is attributed to changes in the nitrate concentration of deep waters supplied to the region rather than an increase in the upwelling rate or surface transport of nitrate. The increased nitrate concentration in these deep source waters was traced to changes in the large-scale wind forcing and resulting decreases in downwelling (Ekman pumping) in the subtropical gyre. Under pre-industrial conditions, Ekman pumping forces nutrient-depleted surface waters to the depths that supply the CCE upwelling system. As the westerlies shift poleward with future increases in greenhouse gas concentrations, this rate of Ekman pumping is expected to weaken. Hence, source waters supplied to the CCE in the future are projected to be older in age and originate from more western locations in the Pacific basin (Figure 2). A longer period of source-water transport and continued remineralization of organic matter results in increased accumulation of nitrate and greater utilization of dissolved oxygen, and so the deep waters supplied to the CCE are enriched in nitrate and deplete in dissolved oxygen in the future period relative to the pre-industrial period.

The projected increase in nitrate with increased stratification is counterintuitive and contrary to the relationship identified by most studies of climate and ecosystems in the region. Often, these studies have been limited in duration by the relatively short period over which chemical and biological measurements have been available. One unique study, however, overcame this limitation by examining estimates of nutricline depth by Secchi disk (Aksnes & Ohman, 2009; also presented during the IMBIZO II workshop by Mark Ohman). These authors documented a multi-decadal shoaling of the euphotic zone despite a secular increase in stratification, a trend consistent with the projected relationship which we have examined using ESM 2.1 and highlighting the value of long-term ecological surveys.

This proposed mechanism relating future nutrient supply to global change in the northeast Pacific deserves continued investigation. Perhaps more important to the general study of ecosystem response to global change is our demonstration that empirical relationships between ecosystem processes and physical forcing at scales associated with global warming may be different (and even opposite in sign) from those observed at interannual to decadal scales. Furthermore, our results demonstrate the importance of considering large-scale, remote influences on local ecosystems; while assumptions of constant boundary conditions may be acceptable for short-term projections, considering changes at the boundaries can be essential when examining ecosystem responses over long periods of time. The slow and persistent changes associated with anthropogenic forcing may influence future ecosystems more so than the shorter-term responses on which conventional hypothesis have been developed. This work demonstrates that past statistical relationships should not be applied to project future changes without careful consideration of potential shifts in the influential mechanisms.

References:

Aksnes, D.L. & Ohman M.D. Multi-decadal shoaling of the euphotic zone in the southern sector of the California Current System. Limnol. Oceanogr. 54, 1272–1281 (2009).

Bakun, A. Global climate change and intensification of coastal ocean upwelling. Science 247, 198–201 (1990).

Behrenfeld, M.J. et al. Climate-driven trends in contemporary ocean productivity. Nature 444, 752–755 (2006).

Meehl G.A. et al. Global climate projections. In: Climate Change 2007: The Physical Science Basis. Solomon, S. et al. (eds), Cambridge University Press, Cambridge, (2007).

Roemmich D. & McGowan J. Climatic warming and the decline of zooplankton in the California Current . Science 267, 1324–1326 (1995).

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Future changes in seasonality of marine ecosystems projected by an eddy-permitting 3-D ecosystem model

Taketo Hashioka1

Takashi T. Sakamoto1

Akio Ishida1,2

and Yasuhiro Yamanaka1, 2, 3

  1. Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan
  2. Core Research for Evolutional Science and Technology (CREST) / Japan Science and Technology Agency (JST), Kawaguchi-shi, Japan
  3. Hokkaido University, Graduate School of Environmental Earth Science, Sapporo, Japan

Taketo Hashioka won the prize for the best poster presentation by a young scientist in Workshop 2 at the recent IMBER IMBIZO II. The prize was the "Atlas of the Patagonian Sea: Species and Spaces" edited by Falabella et al., 2009.

HASHIOKA Taketo

Global warming causes various changes in the physical environment. For production of lower trophic level ecosystems, changes in temperature, strength of stratification, velocity field and light intensity have important roles. For example, rising temperatures cause increases in rates of both photosynthesis and decomposition of organic matter, which might be expected to have a positive effect on production. On the other hand, rising temperature can also increase rates of loss processes for phytoplankton (e.g., increases in phytoplankton respiration rate and grazing rate by zooplankton). Strengthened stratification also tends to enhance the favorable temperature and light conditions for photosynthesis in the surface ocean, while it also decreases nutrient supply to the surface ocean. In this manner, responses of marine ecosystems to global warming are determined as a result of many interactions. Therefore, it is important to identify which processes dominate ecosystem changes within the possible range of future change in physical environment projected by climate models (e.g. IPCC AR4). We also need to understand the spatio-temporal heterogeneity of ecosystem responses.

In this decade, future responses of marine ecosystem to global warming have been discussed using simulated physical fields from climate models. Global warming has been suggested to decrease the annually averaged phytoplankton biomass in the sub-arctic region in the North Pacific (e.g., Boyd et al., 2002; Schmittner et al., 2008). As an impact on the seasonal cycle, Hashioka and Yamanaka (2007) also suggested earlier onset of the spring bloom associated with strengthened stratification. Using an eddy-permitting ecosystem model with a projected physical environment from a high-resolution climate model (i.e., horizontal grid-spacing of 0.28° × 0.19°, Hashioka et al., 2009) found that, under 2×CO2 conditions, in regions where photosynthesis is not strongly limited by nutrients in spring in the western North Pacific, the maximum biomass increases by 20 to 40% associated with rising temperatures, even though the annually averaged biomass decreases slightly. These results reveal that even if global warming weakly affects annually averaged quantities, it could strongly affect certain species and biogeochemical processes which depend on seasonal events such as blooms.

In this study, for better understanding of the effect of changes in each physical component, we conducted sensitivity experiments (Table 1) using the same model of Hashioka et al. (2009). In experiment 1 with rising temperature, the spring bloom tends to occur earlier due to increase in photosynthesis rate of phytoplankton under more favorable temperature conditions (Figure 1). On the other hand, an associated increase in grazing rate by zooplankton leads to the earlier termination of the spring bloom. In experiment 2 with changes in stratification, it is interesting that although the weakened mixing decreases in the nutrient supply to the surface ocean, the magnitude of the spring bloom increases with no change in the timing of the maximum concentration due to favorable light and temperature conditions. In experiment 3 with changes in the velocity field, the increases in chlorophyll a concentration along the southern coast of Japan are mainly caused by enhanced upwelling, which is related the strengthened the Kuroshio current by 30% under global warming (Sakamoto et al., 2005). In experiment 4 with changes in light intensity, earlier and more intense spring blooms are projected in the northern part of the Sea of Okhotsk, a seasonally ice-covered region. This is mainly caused by more favorable light conditions associated with the earlier ice-melting under global warming.

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Table 1: Off-line ecosystem model is driven by several physical forcings including temperature, vertical diffusivity as strength of stratification, vertical and horizontal velocity fields, light intensity. This table shows the experimental setting, i.e., conventions of physical forcing, for control (CTL) and sensitivity experiments (Exp. 0 to 4). “CTL” and “2×CO2” represent the result of the pre-industrial and global warming simulations, respectively.

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Figure 1: The upper figures of CTL show annually and monthly averaged surface Chl-a concentrations in the pre-industrial simulation. The figures of Exp. 0 to 4 show annually averaged and monthly averaged changes in Chl-a concentration from pre-industrial simulations associated with global warming.

Through the sensitivity experiments, we captured the significant tendencies of ecosystem response to each change in physical environment. However, because the overall ecosystem response is non-linear, it is interesting that the integrated result (Exp.0) differs significantly from the simply summed response of all sensitivity experiments (Exp.1-4). The impact of this nonlinearity is greatest for trends in seasonal variations. Therefore, in addition to understanding each physiological and biogeochemical response, a comprehensive approach is essential for understanding the response of ecosystems to climate change.

References:

Boyd, P. W. & Doney, S. C. Modelling regional responses by marine pelagic ecosystems to global climate change, Geophys. Res. Lett., 29(16), 1806 (2001)

Hashioka, T. & Yamanaka, Y. Ecosystem change in the western North Pacific associated with global warming obtained by 3-D NEMURO, Ecol. Modeling., 202(1-2) (2007)

Hashioka, T., Sakamoto, T. T. & Yamanaka, Y. Potential impact of global warming on North Pacific spring blooms projected by an eddy-permitting 3-D ocean ecosystem model, Geophys. Res. Lett., 36, L20604 (2009)

IPCC, Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon et al., 996 pp., Cambridge Univ. Press, New York. (2007)

Sakamoto, T. T., Hasumi, H., Ishii, M., Emori, S., Suzuki, T., Nishimura, T. & Sumi, A., Responses of the Kuroshio and the Kuroshio Extension to global warming in a high-resolution climate model, Geophys. Res. Lett., 32, L14617 (2005)

Schmittner, A., Oschlies, A., Matthews, H. D. & Galbraith, E. D. Future changes in climate, ocean circulation, ecosystems, and biogeochemical cycling simulated for a business-as-usual CO2 emission scenario until year 4000 AD, Global Biogechem. Cycles, 22, GB1013 (2008)

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What they said about IMBIZO II...Perspective from the local organizers

Alexandra Gogou and Evangelos Papathanassiou, Hellenic Centre for Marine Research, Anavyssos, Greece
PAPATHANASSIOU Evangelos
GOGOU Alexandra

The Hellenic Centre for Marine Research (Crete) was the venue for the IMBER IMBIZO II in October 2010. Crete, situated at the crossroads of the Mediterranean Sea, was an ideal choice for this meeting, the main objective of which was the integration of biogeochemistry and ecosystems in a changing ocean, an approach that includes significant regional comparisons. IMBIZO ll played a valuable role as an international platform for interaction between marine scientists from many different fields. The plenary sessions had thought-provoking presentations from outstanding international scientists. The joint discussions between the scientists participating in the three separate workshops had an important outcome: the improvement of our knowledge of the interactions between marine biogeochemistry and ecosystems and the assessment of how these interactions may respond to complex natural and anthropogenic forcing. The IMBIZO II proved to be a genuine communication forum for all the participants, but perhaps more so for the local scientists, to whom it gave an invaluable opportunity to expose their own work to a broader scientific community and thus to develop and/or strengthen collaborations with international delegates.

Another important aspect of IMBIZO II was the educational opportunity that the ‘Dry Cruise’ workshop offered to local students. IMBER sent invitations and announcements to the relevant departments of the University of Crete and other Greek universities, specifically requesting the participation of local students. The presence of scientists from different aquatic disciplines world-wide gave them a great opportunity to meet, discuss and even to raise issues concerning possible future collaborations either as Master or PhD students.

The local young scientists who attended the IMBIZO also benefited from the opportunities that it provided. Preparation and acceptance of their abstracts proved to be highly motivating, as did the awards for the best oral and poster presentations in of each of the workshops. They appreciated the opportunity to meet scientists from all over the world and discuss possible future contributions to marine science, either as post-docs or as collaborators in many different fields. Their feedback indicated that the experience gained from attending and contributing in the oral and poster presentations was highly appreciated.

In addition to the scientific and the educational aspects, IMBIZO II hosted the presentation of Professor Tasso Eleftheriou, the former Director of the Institute of Marine Biology in Crete. The presentation focused mainly on the archaeological history of Knossos, the largest Minoan site on Crete and included interesting references to marine science in the wall-paintings of the Knossos Palace.

As the local organizers, we are very grateful for the sustained effort made by many people: the Scientific Organizing Committee produced an interesting and appealing scientific programme; the IMBER IPO had the hard task of making sure that the meeting organization and logistics went smoothly; the Local Organizing Committee members, staff at HCMR Crete, the Cretaquarium and the University of Crete, were responsible for coordinating local activities, social events and site visits. Generous contributions from all the above-mentioned groups provided a harmonious setting for the meeting, making mutually beneficial scientific exchanges across all disciplines possible. Participants also enjoyed the unique culture of the historic island of Crete, with its traditional hospitality and great natural beauty.

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Science Highlights from ClimECO2 - Articles from the young scientist award winners from ClimECO2

In August 2010, IMBER, in collaboration with IUEM and GIS Europôle Mer, organized the ClimECO2 Summer School in Brest, France.

Entitled: ‘Oceans, Marine Ecosystems, and Society facing Climate Change’, ClimECO2 was by all accounts a great success and enjoyed by more than 70 participants from 26 countries.

Prizes were awarded for the best poster or oral presentations of the Summer School. We are happy to present articles by three of the winners of these awards.

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Estimating dispersal in marine fish to improve resilience to climate change

Malin L. Pinsky, Stanford University, Pacific Grove, CA, USA

Humberto R. Montes, Jr., Visayas State University, Leyte, Philippines

PINSKY Malin

Maintaining the movement of organisms between populations (connectivity) is one of the most commonly advocated conservation strategies in response to climate change (Opdam and Wascher, 2004). However, robust estimates of dispersal are required to design effective connectivity conservation, and there is substantial uncertainty about whether marine species have short or long-distance dispersal. In the ocean, marine currents and long pelagic larval stages for most organisms create a high potential for long-distance dispersal (Roberts, 1997). However, recent studies have found populations that are largely replenished by local offspring, suggesting local dispersal (Swearer et al., 1999; Almany et al., 2007). To address this problem and improve our ability to plan for the impacts of climate change, we developed an approach using population genetics to measure the distances traveled by marine larvae (Pinsky et al., 2010).

Calculating dispersal distances in marine organisms

Population genetics provides a useful tool for studying dispersal because it uses the natural tags present in every organism’s DNA. In particular, when the genetic distance between populations increases with the geographic distance between them (Figure 1), the slope of the relationship can be used to calculate the typical distance traveled by an organism (Rousset, 1997). This pattern is called “isolation-by-distance”.

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Figure 1: Isolation-by-distance genetic patterns for A. clarkii along two islands (Cebu and Leyte) in the central Philippines. The y-axis is a measure of genetic distance.

We demonstrated how to use this method with Amphiprion clarkii, a common clownfish on tropical coral reefs. As a fish with a short larval duration (7 to 11 days) and therefore a species likely to have lower dispersal abilities, adaptation strategies sufficient to maintain connectivity for this species will likely maintain connectivity for a wide range of fishes.

To apply isolation-by-distance methods, we sampled 17-34 fish at 18 sites across 450km of coastline on two islands in the central Philippines. Samples were collected from both adults and juveniles to allow us to estimate density from the strength of genetic drift (see Pinsky et al., 2010 for explanation of these methods). We also estimated adult density from visual transects. This sampling strategy is simple to apply, and therefore should be applicable to a wide range of species.

We then measured genetic distance between each sampled population with 13 microsatellite loci, and we regressed this against geographic distance (Figure 1). Finally, we used the slope of the regression and our estimate of density to estimate that typical dispersal distances in A. clarkii are 11 km (4-27 km) (see Pinsky et al., 2010 for details). Interestingly, this distance is two orders of magnitude larger than has recently been suggested (Shanks, 2009), likely because some previous methods have difficulty detecting long-distance dispersers. The dispersal distance we calculated can then be used to design conservation measures and climate adaptation strategies for clownfish and other marine fish.

Using dispersal knowledge to improve resilience to climate change

When attempting to improve climate change resilience in marine fish, there are two primary considerations: improving the resilience of populations in situ, and allowing populations to move in search of more favorable conditions. Reducing exposure to non-climate-related stressors can strengthen population resilience, and marine protected areas (MPAs) have been one especially effective approach (Lester et al., 2009). MPAs are areas of the ocean where fishing, habitat destruction, and other extractive activities are limited. To sustain a viable population, however, a substantial fraction of the dispersing offspring must stay within the MPA. An isolated MPA for A. clarkii would have to be about 20km wide, or twice the typical dispersal distance (Lockwood et al., 2002).

An alternative is to design networks of much smaller MPAs, each connected to the other by dispersing larvae (Figure 2). MPA networks also have a number of benefits for climate adaptation. In many species, some populations are already adapted to high temperatures and other conditions predicted under climate change (Balanyá et al., 2006). When designed in networks, MPAs create stepping-stones that allow beneficial genes to flow to those populations experiencing climatic extremes for the first time. This process would aid local adaptation to climate change. Without a network of MPAs, habitat destruction and overfishing could create large gaps that would impede beneficial gene flow. MPA networks can also allow populations to move to more favorable conditions by providing the necessary stepping-stones. If local conditions become too extreme, this may be the only survival strategy. Because clownfish, and most coastal marine species, are site-attached as adults, migration will take place primarily during the larval stage. Given what we now know about dispersal in A. clarkii, spacing between MPAs would need to be about 10-20 km to facilitate this movement (Figure 2).

In conclusion, estimates of dispersal are important for designing effective conservation strategies that improve the climate resilience of marine populations. While dispersal distances in marine organisms have been highly uncertain, we have shown how dispersal can be estimated with a genetic method that will be applicable to a wide range of species.

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Figure 2: Map of a marine protected area (MPA) network on the island of Cebu, Philippines. The red rectangles are MPAs. The arrow indicates a gap in the network that may impede connectivity. Map courtesy of the Coastal Conservation and Education Foundation (CCEF, Cebu, Philippines).

References:

Almany G.R., Berumen M.L., Thorrold S.R., Planes S. & Jones G.P. (2007). Local replenishment of coral reef fish populations in a marine reserve. Science, 316, 742-744.

Balanyá J., Oller J.M., Huey R.B., Gilchrist G.W. & Serra L. (2006). Global genetic change tracks global climate warming in Drosophila subobscura. Science, 313, 1773-5.

Lester S.E., Halpern B.S., Grorud-Colvert K., Lubchenco J., Ruttenberg B.I., Gaines S.D., Airamé S. & Warner R.R. (2009). Biological effects within no-take marine reserves: a global synthesis. Mar. Ecol. Prog. Ser., 384, 33-46.

Lockwood D.R., Hastings A. & Botsford L.W. (2002). The effects of dispersal patterns on marine reserves: does the tail wag the dog? Theor. Popul. Biol., 61, 297-309.

Opdam P. & Wascher D. (2004). Climate change meets habitat fragmentation: linking landscape and biogeographical scale levels in research and conservation. Biol. Conserv., 117, 285-297.

Pinsky M., Montes H.R., Jr. & Palumbi S.R. (2010). Using isolation by distance and effective density to estimate dispersal scales in anemonefish. Evolution, 64, 2688-2700. doi:10.1111/j.1558-5646.2010.01003.x

Roberts C.M. (1997). Connectivity and management of Caribbean coral reefs. Science, 278, 1454-1457.

Rousset F. (1997). Genetic differentiation and estimation of gene flow from F-statistics under isolation by distance. Genetics, 145, 1219-1228.

Shanks A.L. (2009). Pelagic larval duration and dispersal distance revisited. Biological Bulletin, 216, 373-385.

Swearer S.E., Caselle J.E., Lea D.W. & Warner R.R. (1999). Larval retention and recruitment in an island population of a coral-reef fish. Nature, 402, 799-802.

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Talking science – bridging the gap between scientist and journalist

Christina Schallenberg, University of Victoria, Canada
SCHALLENBERG Christina

Communicating science to people outside of the scientific community can be a daunting endeavour. Most researchers can share a story or two about having been grossly misquoted. And yet, talking to journalists is still one of the most effective ways to make your research accessible to the wider public. With so-called climate skeptics rallying to “expose” climate change as a scam, it is perhaps more important than ever that researchers get their word across. We, as responsible scientists, can no longer sit back and enjoy the peace of our ivory towers; we have to communicate and make ourselves be heard. To this end, this article provides some hands-on hints on how to get more out of talking to journalists.

Why things sometimes go wrong

It’s instructive to first think about why things often get lost in translation when scientists talk to reporters. For one, not every journalist (or reader, for that matter) knows the difference between correlation and causality. As well, numbers need to be put into context. If you talk about probability and risk, make sure you explain what the numbers mean in real-life terms. Finally, the general public is often not familiar with the scientific method, i.e. the fact that progress includes following dead-ends at times and that conclusions are only valid until challenged by new research. It’s worth pointing out that new findings contradicting old beliefs do not indicate that the scientists are confused or misinformed, but that this kind of discovery is part of the scientific progress.

What the journalist needs from you

When talking to people from the media it helps to be aware of their information “needs”.  In order for them to tell a story, and to tell it well, they need more than a collection of dry facts. First of all, they do indeed need a story with a beginning, middle and end. It can be the story of how you happened onto a discovery, or a quirk in the progress of the research, or even a story of how and why you got interested in researching this topic. Frustrations, joys, highlights and surprises in your studies – they all spice up the story. So don’t be afraid to add a personal touch, it will entice the reader.

Secondly, journalists need catchy quotes from you. If you don’t provide them, they’ll find them elsewhere. So it’s in everybody’s best interest if you prepare a few sound bites that you “feed” the journalist. Think of colourful analogies, examples and metaphors. Provide a take-home message in lay language. And feel free to repeat these a couple of times, too, just to be sure that the reporter has time to catch them.

Third, make sure you answer the question “So what?” The reporter has to sell the story to her editor in order to get it published – an impossible task if this important question remains unanswered. So put your research into context, explain why it’s important and what it means in the greater scheme of things.
Fourth, journalists are interested in answers more than in questions. This doesn’t mean you should oversimplify an issue, but you don’t need to point out every possible “maybe” and uncertainty either. Keep in mind that you’re not talking to a fellow researcher. A story needs a red ribbon rather than a cluster of loose ends, so as a general rule you want to stick to the ribbon as much as possible. If there is more than one side to your story, explain why you favour your version and what the alternatives were.

Finally, and this has been a catch in the reporting on climate change, journalists are trained to look for conflict. This means that they will seek out someone who is of a different opinion than you in order to provide a “balanced” account, i.e. give more than one point of view on the story. You can help the reporter by pointing her to colleagues who disagree with you on certain topics, but who are nonetheless respected researchers. In other words: acknowledge this need and provide guidance as best you can rather than leave the journalist to her own devices.

The bottom line

Keep it simple! Use lay language and avoid jargon. It might even be a good idea to practice talking about your research to your nieces, nephews, aunts and uncles. If they can understand you, so will a reporter. Have a message prepared that you want to convey, and make sure it is short and precise (no more than 3 key points!). Think of examples and analogies to illustrate this message. Finally, a good image to keep in mind when talking about complicated matters: think of your research as a box with many layers of complexity. Ask yourself how many of these layers you really need to unwrap in order to make your point, and simply leave the rest.

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Suggested reading:

Why trust a reporter? What science writers are looking for and why it behooves you to answer their calls. By Edyta Zielinska. The Scientist 2010, vol 24(9), p40.

Am I making myself clear? A scientist’s guide to talking to the public. By Cornelia Dean. Harvard University Press, 2009. 288 pages.

Don’t be such a scientist: Talking substance in an age of style. By Randy Ohlson. Island Press, 2009. 216 pages.

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CO2 availability and phytoplankton trace metal requirements

Andrew L. King, Marine Environmental Biology, University of Southern California, USA
KING Andrew

Marine phytoplankton–single-celled photosynthesizing organisms that account for about half of global carbon fixation (Behrenfeld & Falkowski, 1997)–require a suite of nutrient elements including carbon (C), nitrogen (N), phosphorous (P), and, in the case of diatoms, silicon (Si). Of these elements, C is the highest molar constituent of phytoplankton and is utilized from the ocean in the form of carbon dioxide (CO2) and bicarbonate (HCO3-). Although HCO3- is present at relatively high concentrations, CO2 is the preferred substrate and comprises <1% of total dissolved inorganic C.

Over the next century, due to anthropogenic fossil fuel use, the partial pressure of atmospheric CO2 (pCO2) is predicted to rise from ~380 ppm (present day) to ~750 ppm (year 2100) (Solomon et al., 2007) resulting in a decrease in carbonate (CO32-) and seawater pH. The consequences of these changes on marine phytoplankton are currently not entirely understood but include potentially deleterious effects for calcifying organisms such as coccolithophores. On the other hand, higher CO2 availability has been shown to relieve CO2 limitation of nitrogen-fixing diazotrophs such as Trichodesmium  (Hutchins et al., 2009).

Most marine phytoplankton require CO2 as the substrate for the carboxylating enzyme Rubisco that fixes C into organic matter. Cyanobacteria are believed to have evolved some 3.5 billion years ago when oceanic pCO2 was ~100-fold higher than present (~4000 ppm) and were not limited by CO2 availability (Kump et al., 2009). As CO2 concentrations declined a few hundred million years ago, carbon concentrating mechanisms (CCM) were believed to have evolved (Badger & Price, 2003) and enabled phytoplankton to more efficiently transport and retain CO2 and HCO3-, and to convert HCO3- to CO2 via carbonic anhydrase, a metalloenzyme that uses trace metal zinc (Zn), and, in the case of diatoms, cobalt (Co) or cadmium (Cd) (Morel & Price, 2003). Under lower CO2 availability, the reliance on CCMs is believed to increase iron (Fe) requirements of the photosystem that provides metabolic energy (ATP and NADH) for CCMs (Raven 1990). There is therefore a biochemical connection between the supply of CO2 and the requirement for trace metals that are very low in concentration in the present day oceans.

The CO2-trace metal connection is evident in culture-based studies with the centric diatom Attheya (family Chaetocerotaceae) grown semi-continuously at 200ppm (approximate last glacial maximum), 370ppm (approx. present day), and 670ppm (year 2100 prediction) pCO2. Higher CO2 availability resulted in increases in growth rate and carbon fixation, and decreases Fe and Zn requirements (mmol metal:mol P; Figure 1; King et al., submitted). A study with the diatom Thalassiosira weissflogii also observed a decrease in μmol Fe:mol C from low to high CO2 (Shi et al., 2010). The supply and availability of trace metals in present day surface oceans are relatively low and ~30% of the world’s oceans are limited by Fe in high nutrient, low chlorophyll regimes. Fe is also relatively low in coastal upwelling and transition zones where Fe availability controls phytoplankton nitrate utilization (Hutchins et al., 1998). Under high CO2 conditions, a lower Fe requirement could possibly relieve phytoplankton Fe limitation currently observed in these regions and could result in higher carbon fixation and export (to the deep ocean and fish production).

NL16 King fig1

Figure 1: A) Specific growth rate (d-1), B) primary productivity (μg C μg chl-1 h-1), C) Fe:P (mmol:mol), and D) Zn:P (mmol:mol) for Attheya sp. (CCMP207) grown semi-continuously at 200, 370, and 670 ppm pCO2

Although the rate and magnitude of predicted change in pCO2 over the next century is indeed troubling, it is important to consider past and present day CO2 variability in the oceans. For instance, coastal upwelling water masses off California and Oregon have been recently reported to be as high as ~800 ppm (Feely et al., 2008). Conversely, high productivity and drawdown of CO2 could result in transient periods of low pCO2. The varying availability of CO2 relative to changing supply of nutrients and trace metals are collectively expected to affect phytoplankton growth and success.

Acknowledgements:

This work was in collaboration with Dr. Feixue Fu, Dr. Dave Hutchins, Dr. Sergio Sañudo-Wilhelmy, and Dr. Karine Leblanc; funding for this research was provided by the National Science Foundation (DH and SSW).

References:

Badger MR, Price GD. (2003). CO2 concentrating mechanisms in cyanobacteria: molecular components, their diversity and evolution. J Exp Bot 54:609-622.

Behrenfeld MJ, Falkowski PG. (1997). Photosynthetic rates derived from satellite-based chlorophyll concentration. Limnol Oceanogr 42:1-20.

Feely RA, Sabine CL, Hernandez-Ayon JM, Ianson D, Hales B. (2008). Evidence for upwelling of corrosive "acidified" water onto the continental shelf. Science 320:1490-1492.

Hutchins DA, DiTullio GR, Zhang Y, Bruland KW. (1998). An iron limitation mosaic in the California upwelling regime. Limnol Oceanogr 43:1037-1054.

Hutchins DA, Mulholland MR, Fu FX. (2009). Nutrient cycles and marine microbes in a CO2-enriched ocean. Oceanography 22:128-145.

King AL, Sanudo-Wilhelmy SA, Leblanc K, Fu FX, Hutchins DA. (submitted). CO2 and vitamin B12 interactions determine bioactive trace metal requirements of a subarctic Pacific diatom.

Kump LR, Bralower TJ, Ridgwell A. (2009). Ocean acidification in deep time. Oceanography 22:94-107.

Morel FMM, Price NM. (2003). The biogeochemical cycles of trace metals in the oceans. Science 300:944-947.

Shi DL, Xu Y, Hopkinson BM, Morel FMM. (2010). Effect of ocean acidification on iron availability to marine phytoplankton. Science 327:676-679.

Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor, and H. L. Miller, Climate Change 2007: The Physical Science Basis.

Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007.

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IMBER Regional News

CLIOTOP

charts strategic plans for future impact

CLIOTOP co-chairs: Alistair Hobday, CSIRO Marine and Atmospheric Research, Hobart, Australia

Olivier Maury, University of Cape Town, Department of Oceanography, Cape Town, South Africa

Launch of the new CLIOTOP Web site !

CLIOTOP

The CLIOTOP (CLimate Impacts on Oceanic TOp Predators) program is one of the four IMBER regional programs linking scientists from a range of countries to tackle major scientific challenges. In contrast to the other programs, CLIOTOP is actually a global program with interest in all oceans regarding the management and conservation of exploited and non exploited open ocean top predators under the impact of climate change. The CLIOTOP program is implemented by co-chairs together with a scientific steering committee (SC), and by co-chairs and members of six working groups.

The CLIOTOP SC met formally for the fourth time at the Hellenic Centre for Marine Research, located in the seaside town of Heraklion on the island of Crete (Greece) October 9-10, 2010, just prior to the IMBIZO meeting. Over two days of intensive discussion the committee discussed logistics, organisational structure, and the science focus of the program. As people involved in international programs are aware, coordinating and motivating a collaborative research and outreach program is a challenging exercise. While much can be accomplished by email and phone calls, face-to-face meetings are an important part of establishing and continuing a functioning network of scientists. Meetings allow longer and concentrated consideration of issues confronting the program, and in particular, allow argument about points of view that can easily be misunderstood in other communication forms. The support of IMBER and previous CLIOTOP sponsor (GLOBEC) in supporting SC and working group meetings is critical to the ongoing success of this program. Holding program meetings back-to-back with international meetings is one way to maximize the value to participating scientists, and provide additional networking opportunities. On this occasion, four main issues faced the SC;

  1. sharpening the science focus;
  2. raising the profile of the science outputs;
  3. succession planning for the committee and working groups;
  4. initiating the organization of the Second CLIOTOP Symposium to be held end of 2012.
CLIOTOP SSC Oct 2010 Crete Greece

Participants of the CLIOTOP SSC meeting. From left to right: SungKwon Soh, Olivier Maury, Dan Costa, Joel Llopiz, Raghu Murtugudde, Ziro Suzuki, Alistair Hobday, Kevin Weng.

With regard to science focus, the CLIOTOP program is in the synthesis phase of the science plan (phase II). This is not the concluding phase, but an intermediate step focusing on drawing together information from regions to address the driving question: “What were, are, and will be the effects of global changes on the structure and dynamics of pelagic ecosystems, the top predators which inhabit them, the potentially associated fisheries, and the feedbacks of the oceanic systems to the earth system”. Comparative approaches involving both raw data and models are seen as critical to achieving the CLIOTOP goals. One challenge that continues to confront the CLIOTOP science community is funding to support comparative approaches. Participating CLIOTOP scientists give freely their time and intellectual contribution, yet are often constrained by the national funding systems in which their research is supported. International funding programs are often targeted to particular activities and limited in scope, while domestic programs (and sometimes science employers) have a focus at a national scale. For many scientific issues, such a national scale focus may be appropriate, however, given the wide-spread distribution of oceanic top predators such as marine mammals, sharks, tunas, and turtles, an international perspective to problem solving is critical – as advocated by CLIOTOP.

This led to the SC recommending that working group chairs foster the conduct of comparative analysis of specific processes between oceans, regions and species. Co-chairs in several working groups have recognised that such global comparisons require the development of shared databases, gathering and standardizing data from different origins, and the SC encouraged other working groups to follow suit. The SC will work together with working group chairs to facilitate these data being accessible through the CLIOTOP-MDST (Model and Data Sharing Tool developed under the framework of WG4 –Synthesis & Modelling-). Another important contribution expected from working groups is to contribute to the development of the CLIOTOP-SIP (Synthetic Indicator Panel also to be led by WG4). To integrate the dynamics of the oceanic ecosystem including its physical, biogeochemical, ecological and socio-economic components and couple it to the rest of the Earth System, WG4 is setting up the CLIOTOP-ESM (Earth System Model) which will ultimately contribute to scenario development. Eventually, each WG is indeed expected to contribute to the CLIOTOP-SEE (Scenarios of Ecosystem Evolution).

Raising the profile of our science outputs is important, as we believe CLIOTOP will have much to offer the scientific and management arenas as a result of these initiatives. For example, the SIP will allow a range of environmental, biological and management indicators to be rapidly distilled for use by Regional Fisheries Management Organisations (RFMOs) charged with management of wide ranging ocean predators. The SEE will be important to those exploring scenarios of change, in the same way as the SRES scenarios were important to the climate modelling community. Finally, while time is at a premium for participating scientists, the SC emphasised the need for SC members and working groups to produce peer-reviewed papers illustrating the findings resulting from the comparative approach to understanding open ocean systems.

These scientific efforts are championed by the scientists involved, and so as terms on the CLIOTOP committees and working groups expire, succession planning to maintain and grow momentum is critical. For example, a number of scientists are nearing the end of their terms on the SC and discussion of suitable replacements was enhanced by the range of disciplines represented on the scientific committee. Retiring members include Molly Lutcavage (USA), Raghu Murtugudde (USA), Kathleen Miller (USA) and Shiham Adam (Maldives) and we are grateful for their critical contributions during their terms. The SC discussed the selection criteria for nominating replacements, considering geographic and gender representation, scientific excellence in the disciplines critical to CLIOTOP including fisheries, policy, social, economics, and oceanography. The nomination process is now underway, and a number of excellent candidates are under consideration. These will be in place by the next scientific committee meeting - scheduled for 2011, with Australia being a likely location. Planning the Second CLIOTOP Open Science Symposium, to be held in the second half of 2012 in a venue to be officially announced soon, will be a major focus for the SC in the months leading up to this meeting.

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ESSAS

2010 Annual Meeting

Margaret M. McBride, ESSAS Project Office, Institute of Marine Research, Bergen, Norway

Ken Drinkwater, Institute of Marine Research and Bjerknes Centre for Climate Research, Bergen, Norway

ESSAS

The 2010 ESSAS Annual Science Meeting (ASM), convened in Reykjavik, Iceland (30 August - 1 September), was hosted by Iceland’s Marine Research Institute (MRI) with 51 scientists from six countries participating. The meeting was divided into 5 half-day sessions to present ongoing research within ESSAS areas and that conducted by ESSAS working groups (WGs).

Session 1

Iceland Sea and East Greenland Sea Ecosystems ― reviewed work conducted by MRI as part of their Iceland Sea Ecosystem Project to investigate the recent changes in the capelin stock north of Iceland. Presentations covered aspects of physical oceanography, nutrients/phytoplankton, zooplankton, larval drift, and capelin ecology. Water exchanges between the Norwegian Sea and Iceland Sea was also addressed. During 2006-2008 capelin spawning was observed earlier and more to the west and north than previously, while adults were distributed more westerly and southerly during summer. The observed decline in capelin recruitment and the stock appears linked to changes in drift patterns of larvae and 0-group fish since 1995.

Session 2

West Greenland and Labrador Sea Ecosystems ― began with presentations of research being conducted off West Greenland by Danish scientists. A talk on work by the Greenland Climate Institute was followed by details on studies being conducted in Disko Bay and Nuuk Fjord. The importance of the spring phytoplankton bloom was noted in determining the extent of secondary production which feeds local populations of fish, birds, and marine mammals. Timing of the spring bloom varies annually depending on ice duration and meteorological conditions; a strong positive correlation exists between the open water period and the magnitude of annual primary production. Additionally, three Canadian scientists presented results on the physical oceanography and modelling, chemistry and zooplankton ― large phytoplankton in the Labrador Sea have decreased in abundance; smaller forms have become more important, while numbers of bacteria generally have not changed. A downward trend in pH (increasing acidity) has been observed in Labrador Sea over the last two decades; this might lead to pH levels low enough to dissolve shells of calcifying organisms before end of the century.

Session 3

Climate Variability and Fish Populations ― examined hypotheses of how climate variability affects fish populations. Need for both short-term comparative studies and empirical observations to resolve cause and affect issues between fish populations and climate was stressed. It was also pointed out that marine ecosystems are dynamically nonlinear with multiple feedback loops possibly allowing them continual alteration of their structure and operation in response to external stresses (climatic variations, fishing, habitat alteration, etc.). This has hindered progress toward understanding biological responses to climate variability. Examples, and possible mechanisms, for types of responses in marine ecosystems to climate variability from the Bering and Barents seas were also provided.

Session 4

Modelling Ecosystem Response ― showcased work by the ESSAS Modelling WG which has, together with PICES, been developing an end-to-end model to be applied to sardines and anchovies in the Pacific. Results and lessons learned from the ATLANTIS end-to-end model, as applied to the NE US shelf regions, were also discussed. Several regional modelling studies in the North Atlantic were presented, including pure physical oceanographic models, larval tracking models, and biophysical models ― some of which are being extended to include adult fish. Two presentations discussed modelled ecosystems under future climate scenarios.

Session 5

Gadoid-Crustacean Interactions in Sub-Arctic Seas ― presented research by the ESSAS WG on Climate Effects on Upper Trophic Levels, which is conducting comparative studies between different sub-Arctic seas to elucidate processes that lead to shifts between demersal fish (cod and pollock) and crustaceans (shrimp and crabs). Studies on snow crab suggest that colder temperatures generally lead to higher recruitment, whereas both predation and spawning effects showed no consistent relationship with snow crab recruitment between regions.

In conjunction with the 2010 ESSAS ASM the annual meeting of its Scientific Steering Committee was held (3 - 4 September) at MRI in Reykjavik.

More info...

And coming soon...Ecosystem Studies of Sub-Arctic Seas (ESSAS) 2011 Open Science Meeting

Margaret M. McBride, ESSAS Project Office, Institute of Marine Research, Bergen, Norway

George Hunt, University of Washington, Seattle, Washington, USA

Ken Drinkwater, Institute of Marine Research and Bjerknes Centre for Climate Research, Bergen, Norway

ESSAS will convene its second Open Science Meeting (May 22 - 26, 2011 in Seattle, WA, U.S.A) entitled Comparative studies of climate effects on polar and sub-polar ocean ecosystems: progress in observation and prediction. In addition to showcasing progress made in understanding ecosystem processes in sub-Arctic Seas, the Meeting aims to identify important gaps in our knowledge and point the way for future work within ESSAS. The meeting will include nine separate theme sessions with three invited speakers per session, two of which will be in plenary. The themes are:

Comparative studies of polar and sub-polar ecosystems

Results from comparative studies of entire ecosystems or of ecosystem components (zooplankton, fish, and seabirds) between different polar or sub-polar seas, or between sub-polar seas and other types of ecosystems (e.g. temperate, tropical, etc.) will be presented.

New observations and understanding of eastern and western Bering Sea ecosystems

This session is meant to showcase the US Bering Sea Ecosystem Study (BEST) and the Bering Sea Integrated Ecosystem Research Program (BSIERP), new information from the recent PICES North Pacific Ecosystem Status Report, and studies that have been carried out in the Bering Sea by Russia, Korea, Japan, and China.

Modeling marine ecosystem dynamics in high latitude regions

This session will highlight different modelling approaches on the impacts of climate variability on high latitude marine ecosystems and their ability to support sustainable ecosystem services. Special emphasis will be placed on models that examine trophic interactions, link biogeochemical and ecological processes and estimate uncertainties.

Contributions of endogenous re-mineralization and advection to nutrient supplies in sub-polar marine ecosystems

This session will focus on the sources of macro- and micro-nutrients in sub-Arctic seas. How does the importance of various pathways to primary production vary with season, and how do they affect the fate of production? How do these differ between Atlantic and Pacific oceans? How are these processes influenced by the presence of sea ice?

New insights from the International Polar Year (IPY) Studies

This session seeks new and novel results from IPY field studies of physical, chemical, and biological investigations in both north and south Polar Regions, especially contributions from the ESSAS-sponsored IPY consortium, Ecosystem Studies of Sub-arctic and Arctic Regions (ESSAR).

National ESSAS Programs: Recent advances and contributions

Several large national programs under ESSAS have recently been completed or are underway in Japan, the US, Iceland, and Norway while other countries have conducted important research in ESSAS areas. This session will present the results from such programs with emphasis on syntheses of projects.

Socio-economic aspects of sub-polar and polar ecosystems

This session seeks to address marine socio-economic aspects of climate change and economic development, anticipated policy needs related to these issues, and the understanding and information needs (e.g. monitoring) required to forecast responses and to formulate policies. Comparative studies at a variety of spatial scales, as well as those that examine interactions and feedback mechanisms between humans and the environment are particularly welcome.

Interactions between Gadoids and Crustaceans: The roles of climate, predation, and fisheries

The aim of this session is to document and investigate the processes (e.g. predator-prey interactions, climate, and fishing) that lead to shifts between gadoid fishes, such as cod and pollock, and crustaceans, such as shrimp and crabs. Important in such investigations is determining the seasonal and interannual variability in the spatial overlap between gadoids and crustaceans.

Future Climate Change and Ocean Acidification: Their potential impacts in high latitude regions

This session will discuss the responses of high latitude regions to either future climate change or increasing acidification, or their combined response at time scales of a few years to a century or more. Of particular interest are physical, chemical or biological thresholds or tipping points that will lead to large-scale changes in an ecosystem.

In addition, the day prior to the OSM, four workshops will be held on (1) biological consequences of a decrease in sea ice in Arctic and Sub-Arctic Seas, (2) Arctic-Sub-Arctic Interactions, (3) zooplankton life histories: Developing metrics to compare field observations and model results in order to predict climate effects and (4) comparative analyses of gadid and crustacean dynamics across subarctic ecosystems.

Publication of the OSM results will appear in the ICES Journal of Marine Science. Specific theme sessions will also assess the possibility of special issues of other journals. This meeting is co-sponsored by ICES, PICES, NPRB, IMBER, NOAA, IOC and GOOS.

More info...

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IMBER Special sessions

  • 43rd International Liège Colloquium on ocean dynamics. More info...
  • ASLO 2011 Aquatic Sciences Meeting: Limnology and Oceanography in a Changing World. More info...
  • European Geosciences Union (EGU) General Assembly 2011. More info...
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Other meetings and announcements

24-26 October 2011

Toulouse, France

EUR-OCEANS conference

ocean deoxygenation and implications for marine biogeochemical cycles and ecosystems

More info...

14-18 June 2011

Kuala Lumpur, Malaysia

22nd Pacific Science Congress More info...

28 June-1 July 2011

Brest, France

Marine ESFRI Symposium More info...

20-25 March 2011

Ventura, California, USA

Gordon Research Conference

Polar Marine Science - Exploring Complex Systems in Polar Marine Science

More info...

22-26 May 2011

Seattle, Washington, USA

ESSAS Open Science Meeting 2011 More info...

26-30 September 2011

Aberdeen, Scotland

World Conference on Marine Biodiversity

(Conference will include marine supplier exhibition)

More info...

24-28 October 2011

Denver, Colorado, USA

WCRP Open Science Conference

Climate Research in Service to Society

More info...
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IMBER endorsed conference: AMEMRIII 'The Next Generation'

More info...

GO-SHIP Repeat Hydrography Manual

The 'GO-SHIP Repeat Hydrography Manual: A collection of expert reports and guidelines' is now available online. The manual provides detailed instructions for the high quality collection and analysis techniques of numerous ocean parameters, both physical and biogeochemical. Sixteen chapters covering CTD methods, discrete samples, and underway measurements have been reviewed and revised by more than 50 experts.

More info...

GO-SHIP

LOICZ Special event

LOICZ is organising a special event for early-career scientists and managers around its Open Science Conference in Yantai, China: the Young LOICZ Forum (YLF 2011).

Taking place 8-15 September, 2011, in Yantai, China, the YLF is a well-balanced combination of conference sessions and specific targeted activities for early-career scientists and young coastal managers, including training workshops and practical exercises. It brings together senior scientists, international organisations, and young scientists and coastal managers from various countries for both formal training and open discussions on relevant global environmental change topics. The training programme includes tutorials, exercises, and open-discussions to provide cross-disciplinary learning; original workshops provide both practical skills and scientific knowledge.

Special attention is given to career advice, including acquiring transferable and soft skills, training-through-research and one-to-one mentorship. A job shop offers the opportunity to network with and meet potential employers; field trips and social events will support cultural understanding. Other features are the YLF statement ‘The Future we Sea’ and a carbon offset activity.

More info...

LOICZ YOUNG
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Publications

  • Ocean Acidification Reference User Group, 2010. Ocean acidification: questions answered, Laffoley D. d'A. & Baxter J. M. (Eds.), 24 p, European Project on Ocean Acidification (EPOCA). The guide can be downloaded in five languages. More info...
  • The Ocean Acidification Reference User Group (RUG) has launched a new guide "Ocean acidification: questions answered". In this guide four new things are done. We answer some key questions many people are now asking about ocean acidification. We say how sure the international scientific community is about what is already happening to the ocean, we discuss what the future may hold for the ocean in a high carbon dioxide (CO2) world, and we explore the consequences for all of us of what is now happening. 
  • Questions Answered follows on from the highly successful multilingual guide Ocean Acidification: The Facts, which was launched in winter 2009 at the UN climate change conference at Copenhagen. Questions Answered is inevitably more technical in nature than The Facts as it begins to help champion the science and reasoning behind frequently asked questions.

By getting to the point and improving understanding around these critical issues, we hope that many more people will not only be better informed about ocean acidification, but will also act with greater consensus, greater ambition and greater urgency to tackle one of the most significant environmental issues faced by present and future generations.

  • The ocean in the high-CO2 world II, Biogeosciences, Special issue 44, Editor(s): J.-P. Gattuso, J. Orr, S. Pantoja, H.-O. Pörtner, U. Riebesell, and T. Trull. More info...
  • Hypoxia, Biogeosciences, Special issue 3, Natural and human-induced hypoxia and consequences for coastal areas: synthesis and future development. Editor(s): J. Zhang and D. Gilbert. More info...
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IPO best wishes for 2011

Should you wish to announce a publication in the IMBER Update, please send information to virginie.lesaout@univ-brest.fr
 Published by IMBER
 Editors: IMBER IPO
ISSN 1951-610X

www.imber.info