Secchi disk, photometry, and phytoplankton data from Crater Lake: Long-term trends and relationships
Dahm CN, Larson DW, Geiger NS, Herrera LK. 1990. Secchi disk, photometry, and phytoplankton data from Crater Lake: Long-term trends and relationships. Pages 143-152. 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
"There has been a decrease in average Secchi disk transparency measurements in Crater Lake during the late 1970s and 1980s relative to earlier studies. The decrease is frequently most pronounced in the late summer. This period of time corresponds to epilimnetic water temperatures generally above 10 C and bloom of the diatom, Nitzschia gracilis. These blooms have occasionally exceeded one million cells per liter. Depth integrated estimates of primary production rates in the epilimnetic zone (0-30 m) for measurements from 1980-1983 are 50 % higher than those taken in 1967-1969. An inverse relationship between the log of total cell numbers of Nitzschia gracilis and Secchi depth was seen in the summer of 1983. Photometer data from July 16, 1969 and July 16, 1982 showed an increase in green and a decrease in blue and unfiltered light penetration in 1982 relative to 1969. The evidence from comparative measurements made recently and in the late 1960s points to an approximately 20 % decrease in over all epilimnetic water clarity in Crater Lake."
- Type
- Conference Proceeding Paper
- Authors
- Dahm, C; Larson, D; Geiger, N; Herrera, L
- Units
- CRLA
- Keywords
- Abundance (Biodiversity), Aquatic Sciences, Limnology, Monitoring, Nitzschia gracilis (diatom), Observations, photometry, Phytoplankton, Presence (Biodiversity), Taxa Links To References, Water characteristics, Water Clarity, Water Quality, water turbidity