In September and October 2014, there was an unprecedented bloom of Alexandrium in Quilcene Bay that contaminated shellfish with potent biotoxins. The area where the bloom took place has historically been biotoxin free. The regulatory limit for human consumption is 80 μg saxitoxin equivalents per 100 g shellfish tissue. At the peak of the event, the Washington State Department of Health detected toxin in shellfish at a concentration of 12,688 μg STX equiv. / 100 g. The cause of the particularly toxic bloom is yet to be determined.
Species of Alexandrium produce resting cysts that overwinter in benthic sediments on the seafloor. The following season, the cysts germinate and can provide the inoculum for more blooms. Out of concern that the Quilcene Bay bloom formed a new "seed bed" (i.e., a concentrated area of cysts in benthic sediments) that could increase bloom risk this summer, PS-AHAB researchers initiated an emergency cyst mapping effort that was conducted on the University of Washington's R/V Barnes from January 17-20, 2015. The work was supported in part by the NOAA ECOHAB Program and Penn Cove Shellfish.
Previous cyst mapping efforts conducted as part of this project found zero or very low concentrations of cysts in the area; the highest concentration observed was 10 cysts per cc wet sediment in Quilcene Bay in 2013. in 2015, we found an order of magnitude greater concentration of cysts; up to 120 and 180 cysts per cc wet sediment in Quilcene Bay and Dabob Bay, respectively.
Please note that no relationship has yet been identified between locations with high cyst abundances and shellfish toxicity in Puget Sound, and the number of cysts required to initiate a bloom has not yet been determined. These questions, and others, form the basis of research currently being conducted by the PS-AHAB research team. Nevertheless, our results warrant increased vigilance for monitoring cells and toxins during the 2015 season and beyond in this area.