The Mendocino County Public Health Department, along with the North Coast Regional Water Quality Control Board, have issued health warnings about toxic mats found in three local rivers: the East Fork of the Russian River, the Navarro River at Philo, and Standish-Hickey State Park Recreation Area. Toxic Algae Alert signs have been posted in all three locations to alert the public recommending that all swimmers and waders, particularly children and dogs, should avoid touching any algal material or scum along the riverbanks or in the water. The potentially toxic algal mats composed of cyanobacteria may be attached to the river bottom, floating in the water, or lying on the riverbanks. The algae colors range from bright to dull green, orange, or maroon.