In situ food compositions reveal niche partitioning in small marine cladocerans and copepods in Daya Bay, South China Sea

Abstract

Marine cladocerans and small copepods (<0.7 mm) share similar food resources based on their size and feeding modes but little is known about the mechanisms allowing their coexistence. Using the high-throughput sequencing (HTS) method, the in situ eukaryotic diets of the small cladocerans Penilia avirostris and Pseudevadne tergestina and the calanoid copepod Parvocalanus crassirostris during spring and summer in Daya Bay, South China Sea, were analyzed and their dietary preference and potential niche overlap were described and compared. Approximately 195 operational taxonomic units belonging to metazoans, phytoplankton, protists, and fungi were detected in the gut contents of the 3 species. Overall, animal and phytoplankton prey contributed evenly to the sequences of gut contents of P. avirostris, with diatoms and cnidarians being the most important prey, whereas arthropods were the major prey resource for P. tergestina, with an extremely high percentage (86.2%). P. crassirostris contained a high percentage of phytoplankton prey, with dinoflagellates and diatoms as the major prey (24.3 and 12.9%, respectively). Both P. avirostris and P. crassirostris consumed a higher percentage of phytoplankton with the seasonal transition. Low niche overlap (0.001-0.19) among the 3 small crustaceans highlights their strong dietary niche partitioning and explains their coexistence in Daya Bay.