The impact of mixotrophic bacterivory on microbial food webs in changing lake ecosystems (LakeMix)
Ecology and Biodiversity of Plants and Ecosystems
Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
Final Report Abstract
In plankton ecology, mixotrophy is defined as the combined nutrition by photosynthesis and phagotrophy. Mixotrophy was previously regarded as an exotic exception among protists, which traditionally were split into photoautotrophic algae and heterotrophic protozoa. Today, we know that mixotrophy is common among a variety of protists. While photoautotrophic organisms tend to dominate during the spring blooms and in upwelling areas where nutrient and light conditions are favorable, mixotrophs appear to be particularly important in situations where dissolved nutrients are scarce, e.g. in oligotrophic environments. There, mixotrophs can be the most important predators of bacteria, accounting for more consumption than heterotrophic protists. Aquatic ecosystems are currently changing at a rapid pace due to climate change and other anthropogenic stressors. It is currently poorly understood how these changes will impact mixotrophic bacterivores and the bacterial communities on which they prey. In the D-A-CH project LakeMix, we have addressed how mixotrophic bacterivores selectively impact bacterial prey communities and how mixotrophs respond to environmental change. In controlled incubation experiments with selected mixotrophic chrysophyte flagellates, we showed that mixotrophs select for bacterial prey, likely depending on their specific trophic mode. We found that mixotrophic bacterivory can have a positive effect on the diversity of bacterial prey communities, and that some bacterial prey taxa are predictably avoided. Further, in a series of mesocosm experiments, we investigated the effect of warming, increased dissolved carbon and nutrient concentrations and altered light regimes on entire freshwater foodwebs. First results indicate that mixotrophs remain quantitatively important in plankton communities also under altered conditions yet are sensitive to top-down control by zooplankton. Several studies linked to LakeMix are still ongoing, and will further reveal how mixotrophic bacterivory is affected by environmental change, and how this in turn impacts freshwater ecosystems.
Publications
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Desiccation time and rainfall control gaseous carbon fluxes in an intermittent stream. Biogeochemistry, 155(3), 381-400.
Arce, Maria Isabel; Bengtsson, Mia M.; von Schiller, Daniel; Zak, Dominik; Täumer, Jana; Urich, Tim & Singer, Gabriel
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The soil microbial food web revisited: Predatory myxobacteria as keystone taxa?. The ISME Journal, 15(9), 2665-2675.
Petters, Sebastian; Groß, Verena; Söllinger, Andrea; Pichler, Michelle; Reinhard, Anne; Bengtsson, Mia Maria & Urich, Tim
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Dispersal provides trophic-level dependent insurance against a heatwave in freshwater ecosystems. Cold Spring Harbor Laboratory.
Vad, Csaba F.; Hanny-Endrédi, Anett; Kratina, Pavel; Abonyi, András; Mironova, Ekaterina; Murray, David S.; Samchyshyna, Larysa; Tsakalakis, Ioannis; Smeti, Evangelia; Spatharis, Sofie; Tan, Hanrong; Preiler, Christian; Petrusek, Adam; Bengtsson, Mia M. & Ptacnik, Robert
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Top-down structuring of freshwater bacterial communities by mixotrophic and heterotrophic protists. Cold Spring Harbor Laboratory.
Ivanković, Marina; Ptacnik, Robert & Bengtsson, Mia Maria
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Spatial insurance against a heatwave differs between trophic levels in experimental aquatic communities. Global Change Biology, 29(11), 3054-3071.
Vad, Csaba F.; Hanny‐Endrédi, Anett; Kratina, Pavel; Abonyi, András; Mironova, Ekaterina; Murray, David S.; Samchyshyna, Larysa; Tsakalakis, Ioannis; Smeti, Evangelia; Spatharis, Sofie; Tan, Hanrong; Preiler, Christian; Petrusek, Adam; Bengtsson, Mia M. & Ptacnik, Robert
