| Cyanobacteria, or "blue-green algae"ÂÂ, thrive in warm, nutrient-enriched, anthropogenically degraded watersheds worldwide. Under optimal conditions, cyanobacteria can form super-blooms, releasing potent cyanotoxins into lakes, rivers and estuaries. Once formed, these toxins can concentrate in food webs and spread downstream, killing animals and posing human health risks. Over the past 30 years, an increased distribution, severity and duration of these blooms has been noted worldwide. One of the most common and concerning is the hepatotoxin microcystin. Until recently, microcystin was considered to be a problem solely of freshwater and estuarine systems, primarily affecting livestock and pets. However, numerous reports have documented marine outflow of microcystin from impaired watersheds. In 2007, deaths of Southern sea otters, a state and federally protected threatened marine mammal, were linked to microcystin intoxication, and microcystin was identified in nutrient-impaired watersheds flowing into the Monterey Bay National Marine Sanctuary. Spatial patterns are apparent between microcystin-positive sea otters and contaminated river outflows, and at present, no local marine source has been identified. Sea otter exposure may result from contact with microcystin-contaminated freshwater runoff, or consumption of marine filter-feeders. Because humans consume many of the same prey items, our preliminary findings raise concern regarding potential unrecognized human health risks. |