A largely unmonitored but worrisome toxin produced by freshwater algae has shown up in shellfish in San Francisco and Tomales Bays, though its presence in West Marin was low, according to a study by University of California researchers published last month.
The toxin, microcystis aeriginosa, is produced by freshwater algae that blooms with the right mixture of water temperature, sunlight and nutrients. If consumed in large quantities, it can sicken both humans and marine mammals…