Interactions between the calanoid copepod Acartia hongi and the bloom-forming dinoflagellates Karenia bicuneiformis and K. selliformis

Abstract

Copepods are a major component of metazooplankton and important prey for fsh and invertebrates such as crabs, shrimps, and fatworms. Certain bloom-forming dinofagellates can kill copepods, but there is little research on the interactions between copepods and the bloom-forming dinofagellates Karenia bicuneiformis and K. selliformis. In this study, the survival and ingestion rates of the calanoid copepod Acartia hongi feeding on K. bicuneiformis and K. selliformis were determined as a function of prey concentration. On day 2, the survival of A. hongi incubated with K. bicuneiformis was 90–100% at all the tested prey concentrations, while that with K. selliformis was 0–20% at≥582 ng C mL−1. Compared to other harmful dinofagellates from the literature, K. bicuneiformis caused low mortality of Acartia; however, K. selliformis caused almost the highest mortality at similar dinofagellate concentrations. With increasing mean prey concentration, the ingestion rates of A. hongi feeding on K. bicuneiformis increased on day 1, but those on K. selliformis did not increase. Acartia hongi stopped feeding on K. bicuneiformis at mean prey concentrations of≥341 ng C mL−1 and K. selliformis at all prey concentrations on day 2. At the prey concentration of 1000 ng C mL−1, the ingestion rate of A. hongi feeding on K. bicuneiformis was moderate among the rates of Acartia spp. feeding on harmful dinofagellates; however, that on K. selliformis was the lowest. These results indicate that K. bicuneiformis and K. selliformis diferentially afect the survival and ingestion rates of A. hongi.