Limnological response of Crater Lake to possible long-term sewage influx
Larson DW, Dahm CN, Geiger NS. 1990. Limnological response of Crater Lake to possible long-term sewage influx. Pages 197-212. In Drake ET, Larson GL, Dymond J, Collier R (ed): Crater Lake: An ecosystem study. Corvallis, Oregon. June 18-22, 1988. San Francisco. 69th Annual Meeting of the Pacific Division/American Association for the Advancement of Science
"Average Secchi disk readings in Crater Lake, Oregon, diminished from 38 m and 37 m in 1937 and 1969, respectively, to 29 m in 1978. This trend has persisted: a Secchi disk reading of 21.8 m in August 1984 is the lowest on record. This reduction in lakewater visibility is attributed to biostimulation of phytoplankton population in the lake’s 0-40 m stratum. Investigators reported finding no phytoplankton at these depths in 1940, whereas recent surveys (1978-1984) have routinely found densities greater than 700,000 cells per liter. The biostimulation possibly stems from caldera springs contaminated by inadequate sewage and wastewater treatment facilities in Crater Lake National Park. One spring in particular, which emerges along the lake’s caldera wall directly below tourist facilities, discharges at the rater of 2 liters per sec and has nitrate concentrations of between 150 and 320 ug per liter. These levels are 5-10 times higher than those measured for ground water emerging below undeveloped localities in the park. Crater Lake appears to be nitrogen-deficient; summertime concentrations of inorganic nitrogen are usually less than 1 ug per liter throughout the 0-200 m stratum. Concentrations of dissolved phosphorous are generally 15-20 times greater. Consequently, the influx of nitrogen from sewage-contaminated ground waters may be substantial over the long run and indeed significant insofar as the availability of nitrogen to phytoplankton populations id concerned."
- Type
- Conference Proceeding Paper
- Authors
- Larson, Douglas; Dahm, Clifford; Geiger, N
- Units
- CRLA
- Keywords
- Abundance (Biodiversity), Aquatic Ecology, Aquatic Sciences, Clarity (Water), Limnology, Nitrogen (N), Phytoplankton, Pollution, Presence (Biodiversity), Sewage, Taxa List Only, Wastewater, wastewater drainage, Water Quality