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

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. Simultaneously 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. Similarity-based cluster analysis of the dietary profiles from 6 sympatric species (4 epifaunal, 2 infaunal) of bivalves revealed a distinct, species-specifc 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 overlap 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.