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The influence of carbon dioxide concentration on bacterial grazing rates, nutrient strategies and composition of marine nanoflagellates in the Baltic sea

2012The influence of carbon dioxide concentration on bacterial grazing rates, nutrient strategies and composition of marine nanoflagellates in the Baltic sea.CRAIG Joel (United States)joelcraig@gatech.edu
Organisation:Christian Albrechts University, Kiel (DE)Supervisor :
Summary: Increasing atmospheric carbon dioxide concentration is increasing the dissolved CO2 in the ocean and leading to a lowering of pH, so called ocean acidification. As CO2 concentration increases in the future, this may affect the marine nanoflagellate community. Hypothesized changes include a shift towards more heterotrophic species (and thus an increase in community grazing rate), a shift towards a more heterotrophic nutrient strategy amongst mixotrophs, and possibly an increase in individual heterotroph grazing rate. If these changes take place involving bacterial grazing, this would have a profound effect on the microbial loop, increasing its importance and decreasing the nutrient flux to higher trophic levels. To test these ideas, 9 large mesocosms were placed in the Baltic Sea off the coast of Finland with varying levels of CO2, simulating a range of realistic atmospheric values over the next century. Bacteria were extracted from integrated depth samples taken over a six week experiment and colored for use in grazing trials. Autotroph and heterotroph abundance was measured at each time step. Colored bacteria were incubated with a sample of the mesocosm community and fixed at three time intervals. Individuals were identified and gut contents analyzed using florescence microscopy.
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