Toxic diatoms in western Washington waters (U.S. west coast)

Abstract

Members of the planktonic diatom genus Pseudonitzschia H. Peragallo, P. pungens (Grun.) Hasle f. multiseries (Hasle) Hasle and P. australis Frenguelli, that may produce the marine biotoxin, domoic acid, have been recognized in western Washington waters. Their distribution is not well-known in this area, probably because they often have been misidentified. However, they appear to be relatively common and may be abundant, especially in late spring and summer. Domoic acid, a potent neurotoxin, was found at levels up to 154 µg g⁻¹ wet weight in razor clams, Siliqua patula Dixon, and Dungeness crabs, Cancer magister Dana, on the Pacific coast of Washington in late October 1991. It was also found in trace amounts in blue mussels, Mytilus edulis L., and oysters, Crassostrea gigas Thun., in the inland waters of northern Puget Sound in summer 1992.

The presence of these potentially toxic diatoms signals the need for regular phytoplankton monitoring and additional shellfish monitoring to ensure that seafood is safe for human consumption. Further, studies are needed on the physiological ecology of the diatoms to determine the causative factors leading to production of the toxin.