Effects of toxic Alexandrium minutum strains on the feeding and survival rates of pelagic marine copepods Acartia grani and Euterpina acutifrons

Abstract

Feeding and survival experiments with three different toxic strains of Alexandrium minutum (AL1V, AL2V, and AMINAR1) revealed that copepods Acartia grani and Euterpina acutifrons were able to consume all A. minutum strains to a similar extent at which they fed on the non-toxic and similar-sized Scrippsiella trochoidea (strain S. T.). Feeding of both copepod species showed a typical satiation response to increasing food concentrations. Ingestion rates of A. grani on the four dinoflagellate strains were always higher than those observed for E. acutifrons. Significant differences (P < 0.05) were found between these rates for the most toxic strain (AL1V) when comparing both copepod species. For carbon concentrations higher than 800 μg C copepod−1 h−1, ingestion rates of both copepod species on AL1V were higher than those found for S. T., and such behaviour could probably be linked to digestive dysfunction or to the use of part of the accumulated energy in detoxification processes. Survival rates and physiological condition index data suggest that A. grani is more sensitive to A. minutum PSP toxins than E. acutifrons. A long-term exposure experiment (288 h) resulted in 0% survival of A. grani when exposed to AL1V, whereas survival of E. acutifrons was greater than 50% for this strain. For the less toxic AMINAR1 strain, the survival rate of E. acutifrons was 80% compared to 95% survival feeding on S. trochoidea. Our results suggest that both A. grani and E. acutifrons can act, to a different extent, as A. minutum PSP-toxin vectors through the food web.