12793 – Longterm Limnological Monitoring

Investigator’s Annual Reports (IAR’s) for Crater Lake National Park

Longterm Limnological Monitoring


Report Number: 12793

Permit Number: CRLA1996AOZN

Date Received: Jan 01, 1998

Reporting Year: 1996

Principal Investigator: Gary Larson, National Biological Survey, College of Forestry, Oregon State University, Corvallis, Oregon

Additional investigator(s): David McIntire, Mark Buktenica

Park-assigned Study Id. #: CRLA1996AOZN

Permit Expiration Date: Jan 01, 1998

Permit Start Date: Jan 01, 1998

Study Starting Date: Jan 01, 1996

Study Ending Date: Jan 01, 1996

Study Status: Completed

Activity Type: Other

Subject/Discipline: Other

Objectives: 1. Develop a data base to compare present and future conditions of the lake.;2. Develop an understanding of lake components and processes.;3. Develop a long-term program for monitoring changes.;4. Determine if the lake has experienced recent changes. ;5. If changes detected, identy causes and recommend mitigation procedures if the changes are related to human activity.

Findings and Status: Water clarity, as measured with a secchi disk, was at record levels in August 1994, with a reading of 40.8 meters. However, secchi depth was extremely shallow in 1995. This is believed to result from increased turbidity associated with severe landslides that occurred following a large thunderstorm event on the south caldera. Clarity was at record levels again in 1996. The nitrate-nitrogen concentrations in Spring 42 were at similar levels in 1996 as observed before the sewage facility was removed from the rim in 1991. Daphnia was abundant in the lake in 1988, but was absent in all samples collected in 1994. It was again collected in 1995 although in low abundance. Daphnia was more abundant in 1996. Kokanee salmon biomass remained greatly reduced in 1995 and 1996 although the condition of fish improved compared to that in 1994.

For this study, were one or more specimens collected and removed from the park but not destroyed during analyses? No

Funding provided this reporting year by NPS: 245500

Funding provided this reporting year by other sources: 0

Full name of college or university: n/a

Annual funding provided by NPS to university or college this reporting year: 0


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