According to a recent study, fish may be gasping for breath as oxygen levels in the world’s freshwater lakes plummet owing to climate change. “The Earth is becoming increasingly hot. As a result, the lakes’ ability to hold oxygen decreases. And every living thing requires oxygen “According to Peter Leavitt, a biologist from the University of Regina who co-authored the paper. “There are fewer opportunities for fish to breathe. And that has repercussions for almost everything in the lake.”
The study looked at variations in oxygen levels in 393 temperate lakes between 1941 and 2017 and was led by Stephen Jane, a Ph.D. student at Rensselaer Polytechnic Institute in Troy, New York. They were largely from the United States and Europe, though there were a couple from New Zealand and three from Canada:
- The IISD Experimental Lakes Area research station near Kenora, Ont.
- Lakes near the Dorset Environmental Science Centre in Muskoka, Ont.
- The Qu’Appelle River system lakes in southern Saskatchewan.
The researchers discovered that oxygen levels dropped by roughly 5% near the surface and 19% in deep waters from 1980 to 2017, according to a study published last week in the journal Nature. The reduction in oxygen levels in lakes is 2.75 to 9.3 times greater than the reduction in oxygen levels in the world’s seas, raising concerns about the health of aquatic life among experts.
The fact that water can’t contain as much oxygen at higher temperatures contributes to lower oxygen levels in lakes and seas. Surface waters mix less with deeper waters as they warm, impeding the downward flow of oxygen. Another concern with lakes is that, as a result of climate change and extra nutrients like sewage and fertilizers, algae grows more, dies, and decomposes, sinking and absorbing oxygen.
Wascana Lake in Saskatchewan, according to Leavitt, was one of the lakes losing oxygen the fastest, ranking in the top 15 of 393 lakes studied. Wascana Lake was sampled in 2011 and only common white suckers were identified, according to Wascana Centre, the urban park where the lake is located. Since then, the population of common carp has grown. Neither fish is a game fish.
Recent alterations to lakes can also be seen in Muskoka, Ontario, where the local watershed council was not engaged in the current study but did start monitoring algae in a few lakes as part of a trial project in 2019.