Food sources of scallops and other benthic organisms--are enrichedcarbon ratios in benthic consumers caused by benthic primaryproducers?

摘要

We used stables isotope analysis to investigate the sources of primary productivity (phytoplankton, kelp and benthic microalgae) and the trophic structure of benthic food webs in the region of the Mingan Islands, northern Gulf of St. Lawrence. Benthic consumers were rich in super(13)C, seemingly indicating a strong dependence on super(13)C-rich benthic primary producers (kelp and benthic microalgae) as opposed to super(13)C-depleted phytoplankton as a food source. However, suspension feeders, the scallop Chlamys islandica, taken along a depth gradient and individuals suspended in cages away from shore were even more enriched in super(13)C than individuals on the bottom near shore, suggesting that inputs from near shore benthic primary producers are not the cause of the enriched carbon ratio in these organisms. A review of previously reported isotopic ratios from arctic and temperate regions showed that deposit and suspension feeders are almost always enriched compared to the super(13)C-depleted ratio of phytoplankton, regardless of their distance from super(13)C-rich primary producers (measured as depth). Thus, our data for the Gulf of St. Lawrence are consistent with those reported else-where.