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Trophic interactions in marine plankton: copepod responses to a diatom defence strategy (TRITON)
Start date: Feb 1, 2008, End date: Jan 31, 2010 PROJECT  FINISHED 

A laboratory study is proposed to gain new insights into the trophic interactions between certain unicellular marine algae, the diatoms, and their main predators, calanoid copepods. Some diatoms produce polyunsaturated aldehydes (PUA) when wounded, which interfere with the reproduction of copepods and thus represent a defence strategy of the algae. This relationship may significantly shape the planktonic food web, but so far experiments have considered only few copepod species.In addition, most studies lack knowledge on the PUA production potential of the diatoms used as food, due to missing biochemical analysis methods for PUA. In consequence, the results were ambiguous and discussed very controversially. Recently, methods have been developed to quantify P UA production of diatoms.Using this new technology, this study aims to identify:1) potentially different responses of important neritic copepod species to PUA producing diatoms with regard to their different life cycle traits,2) the effects of PUA producers on feeding copepod larvae, and3) the impact of algal physiology on this trophic relationship.Feeding experiments will be conducted alongside with PUA measurements to determine differences in the reproductive success of key copepod species of Dutch coastal waters when fed diatom diets. As toxin biochemistry of the algae is expected to vary with environmental conditions, diatom cultures grown under various defined conditions will be used in feeding experiments and compared with non-toxic controls. Thus, this study will integrate research across the sub-disciplines phytoplankton ecophysiology and zooplankton ecology in order to improve our understanding of complex trophic relationships at the base of the marine food web.
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