Bacterivorous Ciliates in Marine Food Webs: Lipid Chemistry and Copepod Nutrition

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Bacterivorous ciliates are an important component of planktonic food webs. They can consume a large proportion of bacterial production, and convert material that is low in essential lipids (bacterial biomass and detritus) into lipid-rich ciliate biomass. How do consumers benefit nutritionally from these ciliates, and what role do they play in the biochemical transformation of ciliate carbon? To investigate the nature of ciliate lipids and their fate and importance in the marine food web Dr. Harvey and McManus will: - identify and quantify ciliate lipids, especially ones that may be useful as group-specific biomarkers in trophic studies. - examine sources of lipids in the ciliate diet and follow how ciliates assimilate and modify dietary lipids. - measure the assimilation and transformation of ciliate lipids by one of their principal consumers, copepods. This project combines biochemical measurements with feeding experiments. Detailed lipid analysis of a number of ciliate species will first provide additional data on the ubiquity of the unique compounds they have already observed. They will measure in detail the role of diet on lipid content and distribution of several representative bacterivorous ciliates. Finally, they will conduct in-depth feeding experiments to follow the incorporation and transformation of ciliate lipids by grazing copepods. These results will provide substantial new information on the role of bacterivorous ciliates in the marine food web, especially their importance in copepod nutrition.