Home / Meetings / IMBER OSC 2014 / Sessions & Workshops / Paradigm shift in plankton ecology: the central role of mixotrophic protists in future oceans

Paradigm shift in plankton ecology: the central role of mixotrophic protists in future oceans


  • Aditee Mitra
    Centre for Sustainable Aquatic Research, Swansea University
    Swansea, UK
  • Diane Stoecker
    Horn Point Laboratory, University of Maryland
    Cambridge, USA
  • Hae Jin Jeong
    Ecology & Bioenergy Laboratory, Seoul National University
    Seoul, Korea
  • Elizabeth Fulton
    Marine and Atmospheric Research, Commonwealth Scientific and Industrial Research Organisation
    Hobart, Australia

Description of the workshop

Planktonic primary production is a cornerstone process in planetary biogeochemical cycling with associated interactions with climate change. Traditional descriptions of the planktonic food-web link inorganic nutrients to autotrophic phytoplankton, to the heterotrophic zooplankton and then eventually to fisheries production, with the microbial loop channelling nutrient regeneration through bacteria and microzooplankton. Recent work, stemming from a Leverhulme funded International Network, challenges this traditional paradigm, arguing that open water marine ecology is heavily dependent upon the activity of protists that are mixotrophic (i.e., single-celled organisms capable of photosynthesis as well as phagotrophy). Mixotrophy is not confined to a single protist group rather it is employed by a variety of “phytoplankton” and “microzooplankton” groups, occurring widely in oceanic and coastal as well as fresh water systems. Mixotrophic “phytoplankton” dominate primary production most of the time; for example, thriving in summer temperate waters (which support the bulk of fisheries production), and in oligotrophic systems (which cover the bulk of the oceans). The combination of predatory activity, anti-grazing and varied nutritional capabilities, potentially renders mixotrophs supreme bloom forming organisms. At the extreme, mixotrophs can form harmful algal blooms responsible for severe socio-ecological damage such as fish kills.

Increases in eutrophication, driven by anthropogenic inputs especially due to growing human populations, and increases in the stability of the water column, predicted under climate change, may equally favour mixotrophic dominance due to their ability to flourish in high nutrient eutrophic systems as well as low nutrient, ecologically mature systems. Therefore, by shifting the flow of materials and forming blooms, mixotrophs can affect the structure and function of other parts of the food web and human societies. In terms of socioeconomic impacts they can cause direct losses through impacting water quality and contaminating shellfish cultures and fisheries, indirectly they can shift energy pathways and thence affect the relative composition and flows of ecosystems specifically in relation to fisheries which would have immense societal effects. All these processes and events represent a major shift in the way that we see the functioning of food-webs and biogeochemical cycling in marine ecosystems from the coastal zones to mid- oceans. This has important implications for both the natural environment and human society. This workshop will bring together researchers from across disciplines to explore the implications for this paradigm shift in our perception of planktonic ecosystems upon marine science and society. The vision behind this workshop is to spread the science to a much wider audience, to embed the concept of the importance of mixotrophic protists in open water ecology, into mainstream marine ecology and biogeochemistry, and to socio-economics (specifically in view of the role of mixotrophs in HABs and in trophic upgrading to support fisheries).


Session Programme

Oral Presentations

Monday 23 June, 09:00-10:30

Chair: Diane Stoecker

Time  ID Presenter Title
09:00-09:30   Mitra, Aditee Workshop background and Aim for the day
09:30-09:50 W6.1.O1 Jakobsen, Hans The role of pH feedback on phytoplankton community development in nutrient amended mesocosmos
09:50-10:10 W6.1.O2 Berger, Stella How does increased CO2 and iron availability affect mixotrophs, ciliates and mesozooplankton in a coastal marine system?
10:10-10:30   All Discussion (led by Diane Stoecker)

Monday 23 June, 11:00-12:30

Chair: Hae Jin Jeong

Time  ID Presenter Title
11.00-11:20 W6.2.O1 Bouvet, Antoine Phytoplankton communities in the Western Arctic Ocean during the sea ice melt record of 2012
11:20-11:40 W6.2.O2 Lee, Sung Yeon Mixotrophy in the phototrophic dinoflagellate Symbiodinium voratum
11:40-11.50 W6.2.O3 Martin-Jézéquel, Véronique Mixotrophy of harmful diatoms? The case of organic nutrition in the genus Pseudo-nitzschia
11:50-12:30   All Discussion (led by Hae Jin Jeong)

Monday 23 June, 14:30-16:00

Chair: Beth Fulton

Time  ID Presenter Title
14:30-14:50 W6.3.O1 Ghyoot, Caroline Modelling Phaeocystis globosa mixotrophy under phosphate limitation
14:50-15:10 W6.3.O2 Våge, Selina Successful strategies in size-structured mixotrophic food webs
15:10-16:00   All Discussion (led by Beth Fulton)

Monday 23 June, 16:30-18:00

Chair: Aditee Mitra

Time  ID Presenter Title
16:00-18:00   All Discussion – how to facilitate a better appreciation of planktonic mixotrophy

Poster Presentation

Monday 23 June, 13:30-14:30, Workshop Poster Session

ID Presenter Title
W6.P1 Martin-Jézéquel, Véronique Mixotrophy of harmful diatoms? The case of organic nutrition in the genus Pseudo-nitzschia