Journal of Plankton Research Vol.25 no.2 pp.185-192, 2003
© Oxford University Press 2003
Effect of toxins of the ‘red-tide’ dinoflagellate Alexandrium spp. on the oxygen consumption of marine copepods
Department Of Biological Sciences, Ohio University, Athens, OH 45701, USA
Corresponding Author: hassett{at}ohiou.edu
Toxic algal species produce a variety of responses in copepod consumers ranging from avoidance to retching behavior to high mortality. Toxic algae have also been observed to induce rapid heartbeat in copepods, but little is known of other specific physiological effects. The following experiment tested the effect of exposure to a toxic diet on the oxygen consumption rates and citrate synthase activities of five copepod species that co-occur with the toxic dinoflagellate Alexandrium tamarense in the Gulf of Maine. Experimental animals were presented with diets of toxic and non-toxic Alexandrium isolates, as well as ambient food, for 24 h before measuring oxygen consumption rates. In addition, citrate synthase activities were determined on two copepod species exposed to toxic and non-toxic isolates of A. tamarense over a 3 to 4 day period. Calanus finmarchicus, Pseudocalanus spp. and Acartia hudsonica consumed Alexandrium and showed no response of oxygen consumption rates to the experimental treatments. Citrate synthase activities of A. hudsonica and Temora longicornis were also unaffected by Alexandrium toxin content. Finally, Metridia lucens had lower rates after exposure to both Alexandrium isolates. However, Metridia fed little on either Alexandrium isolate, and in a subsequent experiment short-term starvation produced a similar decline in oxygen consumption, which is likely to account for the declines observed in the prior experiment. Thus, it appears that the toxin content of Alexandrium has little if any short-term effect on the respiration rates of these copepods.