Feeding by the small calanoid copepod Paracalanus sp. on heterotrophic dinoflagellates and ciliates

Abstract

Feeding of the calanoid copepod Paracalanus sp. on natural populations of heterotrophic (h-) dinoflagellates and ciliates was examined during the summer in the Seto Inland Sea, Japan. Paracalanus sp. ingested h-dinoflagellates with clearance rates of 35 to 146 ml ind.-1 d-1, comparable to those for autotrophic (a-) dinoflagellates. Feeding rates of the copepod on h-dinoflagellates (0.35 to 0.93 μg C ind.-1 d-1) were close to, or in some cases exceeded, the basic metabolic demands (0.5 μg C ind.-1 d-1) of the copepod. Ciliates were also ingested by Paracalanus sp., but the corresponding clearance rates (23 to 60 ml ind.-1 d-1) were lower than those for h-dinoflagellates. These results, together with data on the abundance/biomass of Paracalanus sp. and h-dinoflagellates in the study area, indicate that the population of Paracalanus sp. can have a significant feeding impact on h-dinoflagellates.