Use of PCR-DGGE to investigate the trophic ecology of marine suspension feeding bivalves

Abstract

Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) approaches have previously been used to characterize marine plankton communities, but have rarely been used to investigate the trophic ecology of marine organisms. Here we use PCR-DGGE to obtain complex dietary profiles (often >20 bands) of eukaryotic organisms ingested by various species of bivalves. Sequence-based identification of individual phylotypes revealed ingestion of diatoms, dinoflagellates and other groups of organisms consistent with their known feeding ecology. Simulta- neously profiling the seawater (plankton) allowed direct comparison to the dietary profiles. In Mytilus edulis, 50% of the detected plankton community was observed in the dietary profiles. Conversely, 34% of the phylotypes detected in the dietary profiles were not observed in seawater samples. Simi- larity-based cluster analysis of the dietary profiles from 6 sympatric species (4 epifaunal, 2 infaunal) of bivalves revealed a distinct, species-specific clustering pattern in 5 species, indicating a partial division of food based resources. Interestingly, both infaunal species investigated had dietary profiles that clustered not only at the species-specific level, but also as a distinct infaunal group. Trophic over- lap was also present as evidenced by multiple shared phylotypes across all species. Mimachlamys varia did not group in a species-specific manner, suggesting a more generalist feeding strategy. Together, these results demonstrate the utility of a PCR-DGGE approach to study the feeding ecology of marine bivalves. This method offers a fast and accurate way to investigate the trophic interactions of marine bivalves (and presumably other invertebrates) across both large spatial and temporal scales.