Microcystin, a potent liver toxin produced by freshwater bacteria, is entering the ocean and polluting the nearshore ecosystem, resulting in the deaths of at least 21 southern California sea otters. It also poses a health threat to humans. Microcystin poisoning can cause adverse effects in fish, animals, and humans.
In a recent study, the California Department of Fish and Game (DFG) and University of California Santa Cruz (UCSC) scientists have found evidence of microcystin poisoning of 21 sea otters. "The study is significant because it is the first to establish a connection between freshwater contamination by the toxin microcystin and marine mammal mortality," said Melissa Miller, lead author and senior wildlife veterinarian at the DFG Marine Wildlife Veterinary Care and Research Center in Santa Cruz. " This land-to-sea link has important implications for marine life and human health."
The complete study, "Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters," was published on September 10, 2010 by PLoS ONE. Miller presented the findings at the California and the World Ocean Conference in San Francisco on September 10, 2010. Coauthor Raphael Kudela, professor of ocean sciences at UCSC, said the team found high concentrations of microcystin in lakes (Pinto Lake) bordering Monterey Bay and in rivers flowing into the bay (Salinas, Pajaro, and San Lorenzo), Corralitos Creek, as well as in ocean water at the Santa Cruz wharf.
Miller's and Kudela's research concluded that the dead sea otters became poisoned by eating microcystin contaminated shellfish, such as clams. In the laboratory, the tests showed that tissues from the contaminated shellfish had up to 107 times higher concentrations of microcystin than was detected in adjacent seawater. More studies need to be done to know the extent of possible health risks as humans also may be at risk from microcystin poisoning if they consume shellfish harvested near river mouths, especially during or after periods of freshwater runoff.
Most of the microcystin poisoned sea otters were recovered near the mouths of rivers and harbors. Miller reported that while most of the cases (17) occurred within Monterey Bay, microcystin poisoned sea otters were also found along the Big Sur and South-central California coastlines. Therefore, microcystin tests are needed in both freshwater and nearshore ocean waters south of the Monterey Bay.
Since sea otters are mammals and we often recreate in their coastal habitat and share the same marine foods, their health problems can indicate toxins that could also pose health risks to humans who swim, surf, dive, kayak, or otherwise recreate in the ocean.
The UC Santa Cruz article, "Sea Otter Deaths Linked to Toxin from Freshwater Bacteria,"
by Tim Stephens is the source for these photos.
"California sea otters have been poisoned by the microcystin toxin. This sea otter pup is healthy."
(Photo by R. Wilder, Monterey Bay Aquarium)
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The toxic cyanobacteria Mycrocystis gives this water sample from Pinto Lake its bright geen color.
(Photo by R. Ketley)
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The fact sheet, "Microcyctis:Toxic Blue-Green Algae," prepared by T. Le for the California Office of Environmental Health Hazard Assessment (OEHHA) in February, 2009 states the following dangers of microcystins:
*People swimming in water polluted with microcystins have experienced irritation such as skin rashes, burns, and blistering of the mouth.
*Ingestion or inhalation of water containing this toxin may cause vomiting, nausea, headaches, diarrhea, pneumonia, and fever.
*Ingestion of significant levels of the toxin microcystin can cause liver damage and dysfunction in humans and animals.
*Children have a higher risk of exposure since they tend to unintentionally ingest more water than adults while swimming.
*Exposure may be from drinking water, recreational exposure, consuming contaminated shellfish, fish, and food supplements.
*Microcystin can remain in fish and shellfish 2 to 3 weeks.
*Dogs can ingest large amounts of microcystis cells when they clean their coats after playing in the water.
*Dogs, wildlife and livestock have died following exposure to this toxin
According to the California water board, "Algal blooms occur when an oversupply of nutrients trigger large increases in phytoplankton." Nutrient-rich fertilizer runoff is a source that can trigger the algal bloom that results in producing the liver toxin, microcystin.
For example, Caitlin McGlade and Spencer Hunt reported in the "The Columbus Dispatch" on July 30, 2010, that three dogs died and at least 9 people became ill after coming in contact with the toxic blue-green algae in Grand Lake St. Marys. The reporters stated, "the 13,000-acre Grand Lake St. Marys has long been considered one of Ohio's most polluted bodies of water, largely because of manure and fertilizer runoff from nearby farms. Cyanobacteria, more commonly called blue-green algae, feed off phosphorus in the manure and fertilizers." One of the toxins produced by cyanobacteria is the liver toxin, microcystin. In fact, one man became ill and was hospitalized after he washed a "thick,green sludge" off his dog's fur, unfortunately, the dog died a few days after exposure to microcystin.
Scientifically, "microcystis thrives when the nitrogen:phosphorus ratio is less than 15 parts nitrogen (N) to 1 part phosphorus (P). When the ratio of N:P is greater than 20:1, non-toxic algae predominate."
Preventing microcystis blooms includes all efforts to prevent nutrients from running off of lawns, pastures, and agricultural fields. The OEHHA fact sheet advises:
Residents need to carefully use fertilizers, prevent run-off when watering, replace lawns with native plants, reduce use of fertilizer and water. Agriculturalists can carefully control the use of fertilizers and prevent run-off. Water agencies can increase the flushing of waterways through releases of water from dams to increase the flow rate in rivers.
Therefore, water testing for microcystin needs to occur, as well as coordinated prevention efforts. According to the "Recurrent Blue Green Algae Blooms in California Waterbodies" map, shown in the OEHHA factsheet, locations of known recurrent algae blooms occur in many waters in San Luis Obispo County, including reservoir dammed lakes, creeks and river pools. Designating the SLO coastal waters as a marine sanctuary could provide such water testing and coordination, as occur in Monterey Bay, where there is a national marine sanctuary. Not only were funds provided to test the nearshore ocean waters, but also the freshwater sources that flow into the Monterey Bay National Marine Sanctuary.
