Feeding performance of the marine calanoid copepod Temora longicornis

Abstract

The feeding response of zooplankton on the oceans primary production is a fundamental parameter in ecosystem models and the ocean carbon cycle. This study provided extensive information on the role of prey density and prey size selection on the feeding response of T. longicornis, one of the most dominant copepod species in the northern hemisphere. Ingestion rates of different types of phytoplankton prey varying between 6.1-58.5 μm equivalent spherical diameter (ESD) were determined by grazing experiments. Ingestion and clearance maxima for each prey size were estimated by fitting functional response models to the observations.

T. longicornis showed a concentration dependant ingestion and clearance rate for all tested prey sizes. Testing the clearance rate of T. longicornis for different sized prey showed that the estimated maximum clearance rate is dependant on prey size The resulting prey size-spectrum was dome-shaped, with an optimal prey:predator size ratio between 1:18.1 – 1:12.5 (in ESD:ESD), which was close to the group specific optimal ratio of suspension feeding copepods. Ingestion maxima where independent of prey size, although the prey concentration at which half the maximum ingestion rate was reached decreased with prey size. The study of copepod feeding as function of prey size provided the chance to compare the feeding performance of T. longicornis to other marine copepods and showed that T. longicornis has a relative high estimated maximum clearance rate for its size and an average estimated maximum carbon uptake.