12725 – Limnological Studies of Crater Lake

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

Limnological Studies of Crater Lake


Report Number: 12725

Reporting Year: 1992

Permit Number: CRLA1992ADOX

Current Status: Checked in

Date Received: Jan 01, 1998

Principal Investigator: Gary Larson, Oregon State University, Cooperative Park Studies Unit, Corvallis, OR

Park-assigned Study Id. #: CRLA1992ADOX

Permit Expiration Date: Jan 01, 1998

Permit Start Date: Jan 01, 1998

Study Starting Date: Jan 01, 1982

Study Ending Date: Jan 01, 1992

Study Status: Completed

Activity Type: Other

Subject/Discipline: Other

Objectives: Develop a reliable data base for use in the future. Develop an understanding of the physical, chemical and biological features of the lake. Establish a long-term monitoring program. If changes in lake conditions are detected, develop studies to identify the cause(s) and if anthropogenic, recommend mitigation actions.

Findings and Status: Secchi disk readings were in the mid-30 m range in June, but decreased to the low20 m range in August and September. Picoplankton (cyanobacteria) may play an important role in the primary production of the lake. Kokanee salmon were abundant again this year, but in poor condition. Nitrate concentrations in Spring 42 were at levels similiar to those reported in previous years. Analyses of the data collected between 1982 and 1992 indicated that Crater Lake is a complex and dynamic system. Deep-lake mixing appears to be important to lake productivity. Cyclic patterns in primary production, chlorophyll, phytoplankton, zooplankton and kokanee salmon were observed. The clarity of the lake is high, and this appears to be associated with vertical partitioning of the water column by phytoplankton and zooplankton species to a depth of 200 m. The level of the lake dropped by about 3 m during the period from 1984 to 1992. No apparent long-term declines in lake clarity were observed.

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: 92000

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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