Trophic Status of 19 Subarctic Lakes in the Yukon Territory

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Abstract
Limnological investigations were carried out on 19 Yukon River basin lakes in the summer of 1982 and on 10 of the lakes in March of 1983. Their surface areas ranged from 1.6 to 90 km2 and mean depths from 2.5 to 93 m. Regression analyses were carried out using various chemical and biological variables and results were compared with similar studies in other geographic areas. Based on range in total phosphorus concentrations (3.2–12.9 μg∙L−1), average chlorophyll levels (0.62–3.76 μg∙L−1), and average bacterioplankton numbers (7.8 × 105 to > 107∙mL−1), most lakes were oligotrophic, several were mesotrophic, and one was close to eutrophy. Particulate concentrations of phosphorus, nitrogen, and carbon indicated that most lakes were predominantly phosphorus limited, but in a number, nitrogen was also important in limiting phytoplankton production. The picoplankter Synechococcus sp. was the most abundant phytoplankton species, and common zooplankters were Cyclops scutifer, Daphnia spp., and Diaptomus pribilofensis.