Bad news for fishing: Research shows that climate change is drawing oxygen from lakes

A new study shows that due to climate change, the oxygen content in the world’s freshwater lakes has dropped, and fish may be out of breath.

“The earth is warming. At the same time, lakes are less able to hold oxygen. Every living thing needs oxygen,” said Peter Leavitt, a biologist at the University of Regina, co-author of the study. “There are fewer things for fish to breathe. This has a knock-on effect on almost everything in the lake.”

The research was led by Stephen Jane, a doctoral student at Rensselaer Polytechnic Institute in Troy, New York, and studied the changes in oxygen levels in 393 temperate lakes between 1941 and 2017. They are mainly in the United States and Europe, but also include three sets of a couple in New Zealand and Canada:

  • Lake near the Dorset Environmental Science Center in Muskoka, Ontario.
  • The IISD Experimental Lakes Research Station near Kenora, Ontario.
  • Located in the Qu’Appelle river system lake in southern Saskatchewan.

How serious is the problem?

Researchers found that from 1980 to 2017, the oxygen content near the surface dropped by about 5%, and the oxygen content in deep water dropped by 19%. Published in the journal Nature last week.

The decrease in oxygen content in the lake is 2.75 to 9.3 times Decrease in oxygen in the world’s oceansThis has also caused scientists to worry about the health of aquatic organisms.

The fact that water cannot hold as much oxygen at higher temperatures is the main factor causing the decline in oxygen levels in lakes and oceans. When the surface water warms, their mixing with deep water will also decrease, thereby disrupting the downward flow of oxygen.

As part of the algae monitoring program, a sampling device was placed in a lake in Muskoka, Ontario. (Muskoka Basin Commission)

For lakes, there is another problem: with climate change and excess nutrients such as sewage and fertilizer, algae grow more, then die and decompose, sinking and consuming oxygen in the process.

Levitt said Lake Wascana in Saskatchewan is one of the lakes with the fastest oxygen loss, ranking in the top 15 of the 393 lakes studied.

“So we lose about 10% every ten years. This is a big number,” Leavitt said.

Generally speaking, the place where the deepest part of the lake loses oxygen the fastest is also the habitat of the most prized and largest fish specimens in sport fishing.

“If you are losing oxygen in deep water and forcing them into warm water, it is not good for them at all,” Levitt said.

In some cases, they will be replaced by species that are more tolerant of low oxygen levels, including invasive species.

According to the Wascana Center in the city park where the lake is located, sampling in Lake Wascana in 2011 only found common white suction cups. And since then, carp The number has been increasing. Both types of fish are not prey.

Recent lake changes are also evident in the Muskoka area of ??Ontario. The local watershed committee did not participate in this new study, but as part of a pilot project in 2019, it did start to monitor algae in a few lakes.

The proliferation of algae causes low oxygen problems in the lake. When the algae dies, it sinks to the bottom and rots, consuming oxygen in the process. (Muskoka Basin Commission)

Rebecca Willison, who is in charge of the project, said that in Muskoka and Ontario, more algae blooms are reported.

“Much of this may be the result of the changing conditions of climate change that we are seeing,” she said. She said that with the hot and dry weather, algae appeared in large numbers in lakes that had never been seen before, including those with low nutrient content, and continued until later this year.

Some of these blooms may be toxic, prompting the authorities to order people not to drink or swim in them. “This must have a big impact on their enjoyment of the lake,” she said.

How to reduce the impact

Levitt said there are some potential ways to reduce the effects of the drop in oxygen in the lake.

The quickest solution is to install pumps or other equipment to promote water circulation.

“But they are expensive, and they only work well on fairly small systems,” he said.

Watch | Research shows that due to climate change, the oxygen content in freshwater lakes is decreasing:

Climate change has caused Canadian lakes to lose oxygen at a faster rate than the world’s oceans. 2:02

The medium-term solution is to reduce excess nutrients flowing into the lake by changing land use, farming, and wastewater treatment practices.

“There is always a technological advantage to doing things in a less polluting way,” Levitt said. “But it does require some innovation, which may be a challenge at the social level.”

It also takes time to see the effect-he estimates that it may take 20 to 30 years. But it will still be rewarded, he said.

“I want people to think more broadly about what they want their children’s environment to be like 30 years from now.”

Willison said that people living on coastlines can help by increasing the number of native plants and natural vegetation on their land.

“The more we can maintain this natural state, the better and more resilient our environment can respond to any changes that may occur.”

However, Leavitt suggests that even these solutions will only have a temporary impact. “The long-term solution is – well, we need to regulate greenhouse gases.”

As part of the algae monitoring program, volunteers Jake Knowles and Emily Crowder took samples from Lake Muskoka. (Muskoka Basin Commission)

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