Water quality of the Chokosna, Gilahina, Lakina Rivers, and Long Lake watershed along McCarthy Road, Wrangell-St. Elias National Park and Preserve, Alaska, 2007-08

A study of the Chokosna, Gilahina, and Lakina River basins, along with Long Lake watershed in Wrangell-St. Elias National Park and Preserve, Alaska, revealed that while trace elements like arsenic, chromium, and nickel exceed potentially toxic levels for aquatic life, these concentrations are naturally occurring due to local geology rather than human activity. The research, conducted during the open water periods of 2007 and 2008, analyzed water chemistry, benthic macroinvertebrates, and periphytic algae across six stream sites. Notably, Long Lake exhibited high Secchi-disc readings (17.5 to 23 feet) and strong thermal stratification, with temperatures ranging from 16 to 5 °C in the upper layers and dissolved oxygen decreasing sharply below 26 feet. A logistic model simulating water temperatures at the Long Lake outlet—critical for sockeye salmon—showed no significant trends over a decade (1998–2008), though 2007 recorded the highest temperatures. The study highlights the natural dominance of dipterans in macroinvertebrate communities and suggests that Long Lake’s unique conditions may enhance periphytic algae diversity.

Brabets, T. P., Ourso, R. T., Miller, M. P., & Brasher, A. M. D. (2011). Water quality of the Chokosna, Gilahina, Lakina Rivers, and Long Lake watershed along McCarthy Road, Wrangell-St. Elias National Park and Preserve, Alaska, 2007-08. Scientific Investigations Report. https://doi.org/10.3133/sir20115185