Declining oxygen levels in lakes are threatening many prized fish species

A recent study reported changes in oxygen levels from 1941 to 2017, in 393 lakes in the US, Europe, New Zealand and Canada. During the years 1980 to 2017 oxygen levels fell by approx. 5% at the water surface and as much as 19% at greater depths. The decline in oxygen levels was found to be 2.75% to 9.3% higher in lakes than the decline reported in the world’s oceans. (Source: Widespread Deoxygenation of Temperate Lakes, June 2/21; Stephen F. Jane, Gretchen J.A. Hansen, Kevin C Rose)

Many of the world’s fresh water fishing species such as trout, salmon, perch and walleye live in deep lake waters. As the oxygen supply is depleted, deep water fish are being replaced with species that can survive in low oxygen levels. Invasive species such as white suckers and common carp have been increasing in significant numbers as a result.

Climate change is a major contributor given the fact that water can’t hold as much oxygen at warmer temperatures. Another major contributor is sewage and fertilizers entering lakes which enhances the growth of algae blooms. Algae consumes oxygen as it decomposes and is often toxic. One way to reduce this trend is to remove chemicals, nutrients and fertilizers using environmentally friendly wastewater treatment practices.

Aclarus Ozone wastewater treatment is a chemical free, superior disinfection process that also increases the dissolved oxygen content in the effluent water. This is better for people, the environment, and the world’s prized fresh water sport fish.