Identifying trophic variation in a marine suspension feeder: DNA- and stable isotope-based dietary analysis in Mytilus spp.
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Accurate field data on trophic interactions for suspension feeders are lacking, and new approaches to dietary analysis are necessary. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was integrated with stable isotope analysis to examine dietary patterns in suspension-feeding Mytilus spp. from seven spatially discrete locations within a semi-enclosed marine bay (Strangford Lough, Northern Ireland) during June 2009. Results of the two methods were highly correlated, reflecting dietary variation in a similar manner. Variation in PCR-DGGE data was more strongly correlated with the principal environmental gradient (distance from the opening to the Irish Sea), while values of δ 13C and δ 15N became progressively enriched, suggesting a greater dependence on animal tissue and benthic microalgae. Diatoms and crustaceans were the most frequently observed phylotypes identified by sequencing, but specific DNA results provided little support for the trophic trends observed in the stable isotope data. This combined approach offers an increased level of trophic insight for suspension feeders and could be applied to other organisms.
KeywordsStable Isotope Bivalve Stable Isotope Ratio Shell Height Suspension Feeder
We would like to thank S. Gallagher for reading early drafts of the manuscript, and the staff of CAMBio for their assistance and laboratory support. This work was supported by a Higher Education Authority of Ireland Strand III grant awarded to J.W.S. P.N. was supported through a Kurt Hansen Scholarship from the Bayer Science and Education Foundation.
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