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Toxic Algae Not New to Puget Sound, Favor Rising Temperatures

University and NOAA investigators have found seed-like cysts of the toxic alga Alexandrium at all depths in a sediment core taken from Sequim Bay in Puget Sound. The depths in which they found the seeds indicate Alexandrium dates back to the late 1800’s.

Correlations between cyst abundance, sea surface temperature, air temperature, and, for a shorter time period, toxins in shellfish, implicate local climate change as a factor in the increasing frequency and spatial extent of toxic Alexandrium blooms in Puget Sound since the 1950’s.

Alexandrium produces neurotoxins that accumulate in shellfish and cause Paralytic Shellfish Poisoning in human consumers.  Rigorous monitoring and shellfish harvesting closures by state agencies protect human health but cause economic losses to the shellfish industry.  The results of this NCCOS Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) and Oceans and Human Health Initiative (OHHI) funded project suggest that in a warmer future such blooms will increase.


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