Limnology of Upper Klamath Lake, Oregon, with emphasis on benthos

Graduation date: 1969Aspects of the limnology and benthic ecology of Upper Klamath Lake, Oregon, are described emphasizing those features that identify its uniqueness. The lake is large, shallow, and characterized by nuisance abundances of Aphanizomenon flos-aquae and midge flies. Results of this study indicate that it does not stratify and dissolved oxygen is sufficient to support game fish except in localized embayments. Although temperatures exceed 70°F and pH is between 9 and 10 during late summer, the lake supports a good trout fishery. Light penetration is limited with extinction coefficients between 1.32 and 11.56. Turbidity was demonstrated to result from both the\ud massive blooms of Aphanizomenon and the resuspension of bottom sediments. Water mass movements of the order of 0.02 ft/sec or more was needed to resuspend bottom sediments. This resuspension\ud occurred almost daily and sediments were mixed throughout the column of water. An estimate of the oxygen demand of bottom sediments was 1.14 mg/sq. ft/day. Zooplankton, benthos, and fishes were collected, identified, and categorized by habitat type, Daphnia schodleri, Diaptomus, and\ud Cyclops are the most abundant zooplankters. The diatomaceous ooze that covers nearly 100 percent of the bottom of the lake is inhabited primarily by Oligochaete worms, leeches (Helobdella and\ud Glossiphonia), midge larvae, and snails in that respective order of abundance. A large variety of benthic organisms inhabit the many habitats found at the edge of the lake. Artificial substrate experiments carried out in the lake indicated that some species are limited in their distributions by a lack of proper substrate. Apparent substrate preferences were demonstrated to be influenced by size of the organism, time of incubation of the sampler, and possibly by\ud predation by leeches