Jun 29, 2021 05:18 PM
https://www.wired.com/story/lakes-are-lo...in-danger/
INTRO: Kevin Rose and his team loaded their sensors into a boat and began rowing. It was late summer at Lake Giles, a small glacial lake in northeast Pennsylvania [...] Though the lake seemed full of life, the water had been changing. ... the lake was running low on dissolved oxygen, a key indicator of its health. As they lowered a sensor into the water, the reading presented another abysmal zero.
This is a condition researchers call “anoxia,” and it’s a big problem. It can harm cold-water fish species and contribute to algae blooms that do even more damage to the lake. As Rose and his team rowed back to shore, they wondered whether their experience at Lake Giles was an anomaly. Now, 15 years later, they know it’s not. Thanks to the help of more than 40 collaborators who collected and analyzed data from a broad array of sources, Rose and his team published a study earlier this month in Nature showing the widespread deoxygenation of lakes around the world.
[...] The researchers found that the oxygen decline in freshwater was happening at a rate up to 9.3 times greater than in oceans, and that climate change and a lack of water clarity had changed the physical and chemical makeup of those lakes too. That matters, because not only do we get much of our drinking water from lakes and use them for recreational activities, but they support an extensive variety of species. “These substantial declines in oxygen potentially threaten biodiversity, especially the more oxygen-sensitive species,” says Rose.
[...] In their analysis, the team found that although surface temperatures have been rising, deep lake waters have remained cool, but increasingly lost their oxygen due to a phenomenon called stratification. If you have ever walked into a lake from the shore and found that the waters are substantially colder the further out you go, you have experienced it. Colder water is denser, so, like oil separating from water, it remains deep in the lake, while the surface water maintains its warmth.
But as lakes’ surfaces have gotten warmer, the difference between the temperatures of their warm and cool parts has grown wider. So has the difference in their densities. That means more stratification. Once those two layers stop mixing well, oxygen from the surface is no longer being pulled into the deeper waters. Hotter temperatures also make the oxygen less soluble and less likely to be absorbed into the water... (MORE - details)
INTRO: Kevin Rose and his team loaded their sensors into a boat and began rowing. It was late summer at Lake Giles, a small glacial lake in northeast Pennsylvania [...] Though the lake seemed full of life, the water had been changing. ... the lake was running low on dissolved oxygen, a key indicator of its health. As they lowered a sensor into the water, the reading presented another abysmal zero.
This is a condition researchers call “anoxia,” and it’s a big problem. It can harm cold-water fish species and contribute to algae blooms that do even more damage to the lake. As Rose and his team rowed back to shore, they wondered whether their experience at Lake Giles was an anomaly. Now, 15 years later, they know it’s not. Thanks to the help of more than 40 collaborators who collected and analyzed data from a broad array of sources, Rose and his team published a study earlier this month in Nature showing the widespread deoxygenation of lakes around the world.
[...] The researchers found that the oxygen decline in freshwater was happening at a rate up to 9.3 times greater than in oceans, and that climate change and a lack of water clarity had changed the physical and chemical makeup of those lakes too. That matters, because not only do we get much of our drinking water from lakes and use them for recreational activities, but they support an extensive variety of species. “These substantial declines in oxygen potentially threaten biodiversity, especially the more oxygen-sensitive species,” says Rose.
[...] In their analysis, the team found that although surface temperatures have been rising, deep lake waters have remained cool, but increasingly lost their oxygen due to a phenomenon called stratification. If you have ever walked into a lake from the shore and found that the waters are substantially colder the further out you go, you have experienced it. Colder water is denser, so, like oil separating from water, it remains deep in the lake, while the surface water maintains its warmth.
But as lakes’ surfaces have gotten warmer, the difference between the temperatures of their warm and cool parts has grown wider. So has the difference in their densities. That means more stratification. Once those two layers stop mixing well, oxygen from the surface is no longer being pulled into the deeper waters. Hotter temperatures also make the oxygen less soluble and less likely to be absorbed into the water... (MORE - details)
