In the Copco and Iron Gate reservoirs’ nitrogen-rich environments, however, Kann said the species Microcystis aeruginosa dominates, which the Centers for Disease Control (CDC) lists as a producer of cyanotoxins.

According to the CDC, cyanotoxins produced by Microcystis can promote tumors and produce hepatotoxins, which damage the liver.

Kann and Anderson both stated that the Iron Gate and Copco reservoirs contain warm, nutrient rich and calm waters in which the toxin-producing algae can grow.

“Even now there has never been an exposure risk in the Klamath River immediately upstream from Copco, but numerous public health exceedances occur in the reservoirs and downstream, all the way to the estuary,” Kann said. “Such downstream levels are a direct reflection of the algae and toxin leaving Iron Gate Reservoir.”

According to a 2009 report in the journal Toxicon, titled “Recreational exposure to microcystins during algal blooms in two California lakes,” there are “no regulations defining acceptable levels of cyanobacterial toxins in drinking or recreational waters” in the United States.

The report, based on a 2007 study conducted in Siskiyou County during the occurrence of cyanobacterial algal blooms (CyanoHABs) containing Microcystis, stated that 81 adults and children were tested during the month of August after recreational exposure to CyanoHABs in the Copco and Iron Gate reservoirs.

Representatives from Siskiyou County, the Karuk Tribe, the CDC and a number of laboratories were involved in the study.

“It is likely that healthy persons will not have adverse acute effects from periodic exposures to [Microcystis] in aerosols generated by water-based recreational activities in lakes with patches of toxin-producing blooms,” the report reads. “However, these healthy persons clearly are exposed to potent hepatotoxins.”

Although the number of self-reported symptoms after exposure were low, according to the report, “recreational exposure to CyanoHAB toxins remains a public health concern.”

While a number of local residents have disputed the toxicity of the algae and have used anecdotal evidence suggesting that contact has not been harmful, each summer, signs have been posted at the reservoirs warning of contact with it.

Kann has also participated in a number of studies that demonstrated an accumulation of Microcystin toxins in mussels and some fish species in the Klamath River, raising concerns over consumption of those animals.

While all sources state that Microcystis is present in the reservoirs and is toxic, the Toxicon report states that further study should be conducted to determine to what extent recreational exposure can affect people.

The causes of and effects from Microcystis’ presence in the reservoirs will also factor into the KHSA dam removal decision.