A review of possible causes of nutrient enrichment and decline of endangered sucker populations in Upper Klamath Lake, Oregon
Water-Resources Investigations Report 93-4087
- Gilbert C. Bortleson and Marvin O. Fretwell
Upper Klamath Lake, and the connecting Agency Lake, is a large (140 square mile) lake in south-central Oregon. The lake has a recent history of long-duration, near-monoculture, blue-green algal blooms of Aphanizomenon flos-aquae. Typically, the algal bloom causes nuisance and detrimental conditions, including a deep-green "pea soup" appearance, from mid-May to late October. Accompanying the blooms are foul odors, extremely high pH, widely varied dissolved-oxygen concentrations of supersaturation or near depletion, occasional but extensive fish kills, and elevated levels of toxic ammonia. In 1988, the Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris), long-term inhabitants of Upper Klamath Lake, were placed on the Federal endangered-species list. The endangering of the sucker species in recent years is hypothesized to be caused by degraded lake-water-quality conditions.
Upper Klamath Lake has been eutrophic since it was first discovered. However, increases in algal abundance and changes in algal type over relatively recent years are evident, and can be correlated with agricultural development of the basin. The most common cause for an increased abundance of algae in lakes is increased enrichment of nitrogen and phosphorus compounds.
Ten possible causes for this excessive enrichment in nutrients are described. Three of these hypotheses are suggested for immediate testing because of large-scale changes in nutrient loading that may have occurred as a result of man’s activities. These three hypotheses relate nutrient enrichment to (1) conversion of marshland to agricultural land, (2) agricultural drainage from the basin, and (3) reservoir regulation. Eleven possible hypothetical causes for the decline in sucker populations also are described. The decline in sucker population may be related to excessive nutrient enrichment (eutrophication) of the lake.
Additional publication details
- Publication type:
- Publication Subtype:
- USGS Numbered Series
- A review of possible causes of nutrient enrichment and decline of endangered sucker populations in Upper Klamath Lake, Oregon
- Series title:
- Water-Resources Investigations Report
- Series number:
- Year Published:
- U.S. Geological Survey
- Publisher location:
- Portland, OR
- Contributing office(s):
- Oregon Water Science Center
- vii, 24 p.
- United States
- Other Geospatial:
- Upper Klamath Lake
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