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When it gets hot, I like to go jump in the river. The Oregonians think the river is too dangerous, too polluted. I was repeating this viewpoint minutes ago, while sitting in a kiddy pool in my back yard with one of the young reporters who lives downstairs. She told me that in late July there was a toxic algae bloom in the Tualatin River. The Tualatin flows into the Willamette at Lake Oswego.

Public Health officials advised boaters and swimmers to stay away from it, and put up signs to warn people to keep out and keep their animals away. The USGS reports that 8-9 dogs/year die of drinking blue-green algae infested water.

When the algae dies it releases toxins into the water. Everybody calls it algae, but in fact it is cyanobacteria, a strain called anabaena. The toxins released are anatoxin (a nerve toxin) and microcystin (a liver toxin). Anatoxin is also known as the "Very Fast Death Factor." Ingested anatoxins can paralyze your diaphragm within four minutes. Microcystin is a "potent hepatotoxin and probable tumor promoter". But the local authorites are trying to keep that hush hush. The symptoms of exposure that they give are: skin irritations, weakness, nausea and diarrhea, cramps and fainting, numbness, tingling, dizziness, difficulty breathing and "heart problems".

The chemical is a bicyclic alkaloid:

Neil Edwards writes:
"Anatoxin is a severe neurotoxin, and as such affects the functioning of the nervous system, often causing death due to paralysis of the respiratory muscles. It is known that it acts as a mimic of the neurotransmitter, acetylcholine and irreversibly binds the nicotinic acetylcholine receptor (NAChR). Normal neuromuscular action involves the release of acetylcholine, which binds its receptor, leading to the opening of a related sodium channel. The resulting movement of sodium ions produces the action potential causing the muscles to contract. At this point, an enzyme called acetylcholinesterase then cleaves the neurotransmitter, allowing the sodium channel to return eventually to its resting state, and hence the muscle can relax. Anatoxin also binds the NAChR to produce an action potential, but cannot be cleaved by the enzyme. The sodium channel is essentially locked open, and the muscles become over-stimulated and become fatigued and then paralysed. When respiratory muscles become affected, convulsions occur due to a lack of oxygen supply to the brain. Suffocation is the final result a few minutes after ingestion of the toxin.

The Oregonian reports that the "algae" forms into mats, and more than once described the stream's contents as having the consistency of chowder. Releases of water from Hagg Lake were more than tripled to 45 million gallons a day to flush the bloom out. They made a big deal of reporting that it is now safe for people to recreate in.

None of the sources I consulted had any theories about why the algae bloomed. I would suspect it happens in response to a combination of low flows, high temperatures, and abundant nutrients (probably someone's sewage or farm waste). Fresh fast cold streams don't get algal blooms.

SOURCES:
Sarah Dunlap, reporter
http://blog.oregonlive.com/breakingnews/2008/07/tualatin_river_algae_bloom_was.html
http://blog.oregonlive.com/breakingnews/2008/07/usgs_tests_for_toxic_algae_in.html

the organization that reported the algae:
http://www.tualatinriverkeepers.org/

the press release from human services is here:
http://www.katu.com/news/local/24739734.html

on anatoxin:
http://www.chm.bris.ac.uk/motm/antx/antx.htm

on microcystin:
http://www.ehponline.org/docs/2000/108p435-439gilroy/abstract.html
abstract text: The presence of blue-green algae (BGA) toxins in surface waters used for drinking water sources and recreation is receiving increasing attention around the world as a public health concern. However, potential risks from exposure to these toxins in contaminated health food products that contain BGA have been largely ignored. BGA products are commonly consumed in the United States, Canada, and Europe for their putative beneficial effects, including increased energy and elevated mood. Many of these products contain Aphanizomenon flos-aquae, a BGA that is harvested from Upper Klamath Lake (UKL) in southern Oregon, where the growth of a toxic BGA, Microcystis aeruginosa, is a regular occurrence. M. aeruginosa produces compounds called microcystins, which are potent hepatotoxins and probable tumor promoters. Because M. aeruginosa coexists with A. flos-aquae, it can be collected inadvertently during the harvesting process, resulting in microcystin contamination of BGA products. In fall 1996, the Oregon Health Division learned that UKL was experiencing an extensive M. aeruginosa bloom, and an advisory was issued recommending against water contact. The advisory prompted calls from consumers of BGA products, who expressed concern about possible contamination of these products with microcystins. In response, the Oregon Health Division and the Oregon Department of Agriculture established a regulatory limit of 1 µg/g for microcystins in BGA-containing products and tested BGA products for the presence of microcystins. Microcystins were detected in 85 of 87 samples tested, with 63 samples (72%) containing concentrations > 1 µg/g. HPLC and ELISA tentatively identified microcystin-LR, the most toxic microcystin variant, as the predominant congener.

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