Effects of Klamath River Mainstem Impoundments on Water Quality and Cyanobacterial Toxin Accumulation in River Biota

The Klamath Basin Restoration Agreement leads to the removal of the four lower dams on the Klamath Hydroelectric Project (KHP) by 2020.  The lacustrine habitat created by Copco and Iron Gate Reservoirs (lowermost projects of KHP) allows planktonic toxic cyanobacteria to exploit nitrogen and phosphorus imported from the upper river basin.  Annual toxin producing blooms of the cyanobacterium Microcystis aeruginosa have been documented in both impoundments, and the hepatotoxin microcystin greatly exceeds public health standards, accumulates in reservoir warm water species, and is exported to the downriver environment.  Microcystin bioaccumulation has been documented in yellow perch in the reservoirs, salmon juveniles reared in the Irongate hatchery below the reservoirs, and adult Chinook salmon and steelhead in the downstream river environment.   High levels of microcystin were found in Klamath River freshwater mussels even when ambient concentrations were very low indicating toxin biomagnification.  Yellow perch and freshwater mussels showed tissue levels exceeding World Health Organization tolerable daily intake levels.  Freshwater mussels are an important tribal trust species and indicator species.  Removal of these dams via removal of plankton supporting lacustrine habitat will reduce toxic algal related water quality impacts and reduce stress and toxin accumulation in freshwater biota of the Klamath River.