From the North Coast Regional Water Quality Board:
Benthic cyanobacterial blooms in California’s North Coast Region pose a health risk to the recreating public and are responsible for several dog deaths in the Eel, South Fork Eel, and Russian Rivers. To better understand benthic cyanobacterial growth and cyanotoxin production in these rivers, extensive monitoring was conducted by the North Coast Regional Water Quality Control Board from 2016 to 2019 using multiple monitoring approaches to determine: 1) what cyanobacterial genera are responsible for the formation of toxic benthic mats; 2) what cyanotoxins are being produced; 3) which cyanotoxins are associated with the various mat-forming cyanobacterial genera; and 4) what are the spatial and seasonal patterns to mat formation and cyanotoxin production.
The Regional Water Board identified several toxigenic cyanobacteria of concern (Anabaena Microcoleus [Phormidium], Oscillatoria) and a class of potent neurotoxins (anatoxins) that frequently occurred at high concentrations within benthic mats during the summer months until early fall.
The Regional Water Board recommends visual surveillance of toxigenic cyanobacterial mats as a primary tool for monitoring potential health risks in riverine systems, as well as Solid Phase Adsorption Toxin Tracking (SPATT) samplers to determine when cyanotoxins are present and increasing in concentration, and periodic laboratory cyanotoxin testing of benthic mats (using ELISA) to determine the potential health risks associated with river recreation.