Paralytic shellfish poisoning: the relationship between Alexandrium abundance and psp toxins on Kodiak Island, Alaska

Abstract

Paralytic shellfish poisoning (PSP) events have severe negative impacts on Alaska commercial shellfish fisheries as well as recreational and subsistence harvests. This study, designed to improve existing PSP monitoring programs, involved the use of a rapid sandwich hybridization assay to detect and quantify the relative abundance of Alexandrium catenella based on species-specific LSU rRNA targeted oligonucleotide probes. Blue mussel (Mytilus edulis) toxicity, expressed as saxitoxin equivalents, was determined using the ³H-Saxitoxin receptor binding assay. Shellfish toxicity was relatively low in both 2000 and 2001 compared to historically high values on Kodiak, but exhibited pronounced late spring and late summer peaks, in both years at four to seven sampling sites. Temporal and spatial variability in shellfish toxicity among sites, seasons, and years suggested dynamic, and possibly unpredictable, Alexandrium bloom events. Importantly, DNA probe data revealed a strong association between Alexandrium abundance and shellfish toxicity. The results also demonstrated that increases in Alexandrium abundance preceded elevated toxin levels in shellfish, indicating that this assay may prove useful as a monitoring tool to predict toxic events in shellfish before they are harvested. Water column nutrients and climate data were evaluated to determine if bloom-triggering mechanisms could be identified.