Scientists at the California Department of Fish and Game and the University of California, Santa Cruz, reported at least 21 sea otters, a federally listed endangered species, have been killed near Monterey, Calif., by the toxin microcystin, an article in the online journal of the Public Library of Science said.
A type of cyanobacteria called Microcystis, also known as "blue-green algae," produces the toxin.
"This study is significant because it is the first to establish a connection between freshwater contamination by microcystin and marine mammal mortality," Melissa Miller, a senior wildlife veterinarian with the state fish and game department, said. "This land-to-sea link has important implications for marine life and human health."
The study team found high concentrations of microcystin in lakes bordering Monterey Bay and in rivers that flow into the bay.
"The toxin itself is extremely stable," Raphael Kudela, professor of ocean sciences at UC Santa Cruz, said.
"In laboratory studies, we found that microcystin didn't degrade much even after three weeks in ocean water," she said.