title: Warming and Acidification Effects on Planktonic Heterotrophic Pico- and Nanoflagellates in a Mesocosm Experiment.
abstract: We studied the response of the heterotrophic flagellate (HF) community to the combined impact of warming and ocean acidification in a mesocosm experiment with a plankton community from the western Baltic Sea. We performed a quantitative analysis of the response at the level of total biomass and size classes and a semi-quantitative one at the level of individual taxa. Total biomass of HF was significantly lower under higher temperatures while there was no significant effect of CO2. The mean biomass of the picoflagellates did not respond to temperature while the three nanoflagellate size classes (class limits 3, 5, 8, 15μm) responded negatively to warming while not responding to CO2. The taxon-level results indicate that heterotrophic flagellates do not form a homogenous trophic guild, as often assumed in pelagic food web studies. Instead, the heterotrophic flagellates formed a "food web within the food web". There was a pronounced succession of flagellates leading from a dominance of bacterivores and colloidal matter feeders before the phytoplankton bloom to omnivorous feeders preying upon phytoplankton and heterotrophic flagellates during and after the bloom. This complex intraguild predation patterns probably dampened the response to experimental treatments.
authors.affiliation: School of Biology, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece; GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, Düsternbrooker Weg 20, 24105 Kiel, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Moustaka-Gouni
authors.affiliation: Department of Ichthyology & Aquatic Environment, School of Agricultural Sciences, University of Thessaly, 384 46 Volos, Greece.
authors.forename: Konstantinos A
authors.initials: KA
authors.lastname: Kormas
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, Düsternbrooker Weg 20, 24105 Kiel, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Scotti
authors.affiliation: Department of Nutrition and Dietetics, Alexander Technological Educational Institute of Thessaloniki, GR- 574 00 Sindos, Greece.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Vardaka
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, Düsternbrooker Weg 20, 24105 Kiel, Germany; Christian Albrechts University at Kiel, Germany. Electronic address: usommer@geomar.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Sommer
mesh_terms: D000818:Animals; D018533:Biomass; D057231:Climate Change; D017753:Ecosystem; D020387:Food Chain; D005858:Germany; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D010839:Phytoplankton / Q000502:physiology*; D012623:Seawater / Q000737:chemistry*; D015048:Zooplankton / Q000502:physiology*
keywords: Global Change; acidification; heterotrophic flagellates; microbial food-web; plankton.