Kathy Echols1, Tamara Wood2, Chris Ottinger3, Barry Rosen5, Summer Burdick4,
1US Geological Survey, BRD, Columbia Environmental Research Center, Columbia MO, USA,2US Geological Survey, WRD, WRD District Office, Portland OR, USA,3US Geological Survey, BRD, Leetown Science Center, National Fish Health Research Laboratory, Kearneysville WV, USA,4US Geological Survey, Klamath Falls Field Station, Klamath Falls, OR, USA, 5US Geological Survey, Florida Integrated Science Center, Orlando, Florida, USA
Upper Klamath Lake is a large hyper-eutrophic lake, found on the east side of the Cascade Mountains in Southern Oregon. Conditions in the lake include high levels of nitrogen and phosphorus nutrients that facilitate large, continuous cycles of cyanobacterial blooms from late spring through the fall. These cyanobacterial blooms include species of algae that are known to produce toxins that adversely affect other aquatic organisms. This study was designed to evaluate the presence of these toxins over three summer seasons (2007 - 2009) and to determine if there is any risk to the two endangered fish in the system: the Lost River sucker (Deltistes luxatus) and the shortnose sucker (Chasmistes brevirostris). Juvenile fish of these species are rare and appear to have poor survival in this ecosystem. Water and algae samples were collected monthly in 2007; bi-weekly in 2008 and weekly in 2009 from late June through September. Collected water/algal samples were filtered, extrac ted and analyzed using an enzyme-linked immunoassay (ELISA) method for quantitation of microcystin toxins, in water and algae. In 2007, high levels of microcystin toxins (up to 17.4 ug/L) were found in algae late in the summer and evidence from fish pathology showed exposure and adverse effects from these toxins. In 2008, lower levels of total microcystin were found in water/algal samples; from a low of 0.17 ug/L to a high concentration of 6.1 ug/L. The high water concentration for total microcystin in 2009 was 83 ug/L. Published LD50s for fish are around 1,700 ug/kg for one microcystin toxin variant; so assuming that juvenile fish are consuming 1% of their body mass in toxic algae, the average exposure to fish from microcystin was assessed to be approximately 1.5-fold greater than the published effects levels of microcystins to fish in 2007 and 0.7-fold greater in 2008 and 1.4-fold greater in 2009. Thus, cyanobacterial toxins may be limiting survival of juvenile endang ered Lost River sucker and shortnose sucker in Upper Klamath Lake.