Chesley Lake 1991 water quality assessment and management implications

Abstract

Chesley Lake is an eutrophic hardwater lake and experiences severe hypolimnetic anoxia. Anoxic hypolimnetic conditions were first noted in mid-May. The hypolimnetic oxygen depletion occurred at a maximum mass rate of 184.4 kg/day (AHOD: 280 mg/m2/day) in 1991. The hypolimnion, which extended from 8 to 18 m, was completely anoxic by the end of June. Bottom water nutrient and metals levels increased as a result. Total phosphorus concentrations increased in both bottom and surface waters as the season progressed reaching levels as high as 0.025 mg/L in mid-September. Soluble reactive phosphorus trends were similar, but levels increased from approximately 3.0 to 9.0 ?g/L during the August to September period. Marked seasonal increases were also observed (particularly in hypolimnetic waters) for ammonium, iron, manganese, hydrogen sulphide and turbidity. Hypolimnetic aeration could be a successful management technique used to reduce sediment nutrient regeneration and improve lake water quality and fish habitat.