41 Incidence of paralytic shellfish toxin in bivalve mollusc tissue from the oregon coast

Abstract

Saxitoxin and domoic acid sequestration by bivalve molluscs occurs periodically along the Oregon coast, presumably as a result of harmful algal blooms (HABs). Since 1958 and more continuously since 1979, the Oregon Shellfish Program (OSP) has assayed toxin levels in these molluscs as part of a monitoring program for paralytic (PSP) and amnesic (ASP) shellfish poisoning. We have created a working data base for all PSP sampling by the OSP between 1958 and 2001 and have examined the data for spatial and temporal trends in the appearance of toxin in shellfish, amount of toxin, and apparent duration of toxic events. In this report, we examine the data from the five stations with the longest record of continuous sampling (1979–2000) for evidence of correlation with El Niño events, upwelling, and/or a pattern of increasing frequency or intensity of toxic events. We also compare the pattern of appearance of toxin at open coast stations with the timing of first appearance of toxin in shellfish at adjacent estuarine stations. This is an important analysis because, in Oregon, shellfish closures due to PSP occur frequently in mussel beds on the open coast and the source of toxin‐producing organisms is unknown.