The occurrence and response to toxic cyanobacteria in the Pacific Northwest, North America

Abstract

Toxic cyanobacteria are of increasing concern in the Pacific Northwest region of North America. Toxic blooms have been documented in Idaho, northern California, Oregon, Washington, and British Columbia and have caused animal poisonings, lake closures, and public health concerns. Microcystins are the most commonly detected cyanotoxins in this region and have been found at water concentrations from <1 μg/L to 30 mg/L. Anatoxins have also been measured in water bodies throughout the region and have been implicated in the deaths of both domestic and wild animals. Environmental factors associated with the occurrence of toxic blooms have been studied in several western Washington lakes. In these lakes, toxic blooms occurred during conditions of high phosphorus, water temperatures, and water column stability. Migration of cyanobacteria from the sediments contributed to toxic blooms in one of the lakes. Although regulations have not been formally adopted by the states and province in this region, some local jurisdictions use the World Health Organization proposed drinking water guideline of 1 μg/L microcystin-LR to close lakes to recreational use and for drinking water supplies. Recommendations currently advocated by Oregon take into account genera-specific differences, as well as separate, less stringent guidelines for recreational water bodies not used for drinking water.