In situ diet of the copepodCalanus sinicus in coastal waters of the South Yellow Sea and the Bohai Sea

摘要

Copepods are a key trophic link between primary producers and predatory animals at higher trophic levels in the marine ecosystem. Knowledge of thein situ composition of the copepod diet is critical for the accurate evaluation of trophic relationships and energy transfer in marine food webs. In this study, we applied a PCR-based cloning technique developed previously to investigate thein situ diet ofCalanus sinicus, an ecologically important large-sized calanoid copepod that dominates in the shelf waters around China, Japan and Korea. Analyses of the 18S rDNA sequences obtained from the copepod diet revealed the diverse food composition ofC. sinicus from two stations (Y19 in the South Yellow Sea and B49 in the Bohai Sea). A total of 43 operational taxonomic units (OTUs) were detected, which belonged to 13 diverse lineages: Bacillariophyta, Dinoflagellata, Dictyochophyceae, Chrysophyta, Katablepharidophyta, Pelagophyceae, Apusozoa, Hydrozoa, Ctenophora, Echinodermata, Tunicata, Chaetognatha and marine fungi. The results indicate that during an algae bloom,C. sinicus can graze on the bloom causative species. When the abundance of phytoplankton in ambient water is relatively low,C. sinicus can choose eggs, larvae, or organic particles/detritus of various metazoans, especially hydrozoans and ctenophores, as alternative food sources. Our result suggests thatC. sinicus is an omnivorous species, and its prey choice may depend on the food availability in the ambient waters.