A novel Heterosigma akashiwo (Raphidophyceae) bloom extending from a South Carolina bay to offshore waters

In April 2003, a novel Heterosigma akashiwo bloom was observed that extended from Bulls Bay, South Carolina USA, to approximately 8 km offshore. The bloom was associated with a fish kill of approximately 10⁴ fish. The bloom coincided with salinities anomalously low for the region and optimal for H. akashiwo growth. The low salinities were related to the rediversion of freshwater a month earlier from the Cooper River into the Santee River, which partially feeds into Bulls Bay. H. akashiwo identification was confirmed using a species-specific real-time PCR assay modified for the direct amplification of target DNA from the bloom sample. Because this H. akashiwo bloom was associated with a fish kill, and exposure to bloom waters caused sublethal toxic effects on oysters, the resolution of the cause and potential recurrence of the bloom are of importance to fishery management.