Calanoid copepods feed and produce eggs in the presence of toxic cyanobacteria Nodularia spumigena

Abstract

Feeding and fecundity of two calanoid copepod species (Acartia bifilosa and Eurytemora affinis) were studied in a food assemblage dominated by toxic cyanobacteria, to reveal whether mesozooplankton are able to obtain sufficient good quality food in different phases of a cyanobacteria bloom. Bloom conditions were simulated in a mesocosm by adding a high concentration of cultured hepatotoxic Nodularia spumigena to 100 μm filtered natural sea water. This seston was fed to copepods at days 1, 7, and 14 from the start of the mesocosm experiment, when it consisted of actively growing cyanobacteria (days 1 and 7) and increasing amounts of heterotrophic organisms and probably detritus (day 14). From bulk changes in chlorophyll and estimated ratios between chlorophyll and accessory pigments, it appears that both copepod species ingested large quantities of cyanobacteria in the first experiment but switched to ciliates when those became more abundant. Egg production of A. bifilosa was observed in all experiments, irrespective of the high concentration of nodularin in the mesocosm. The results demonstrate that the dominant copepod species of the Baltic Sea are able to feed, survive, and produce eggs in a plankton community dominated by toxic cyanobacteria.