According to a recent research paper published in the Proceedings of the National Academy of Sciences, cold-water fish are seeing a “squeeze” from climate change. They are beginning to lose their homes in temperate lakes.
Stephen Jane, the study’s principal author, and colleagues analyzed information from twenty-eight browning lakes in New York’s Adirondack area, where lacustrine brook trout live. (Elevated levels of dissolved organic carbon cause the browning due to warming.)
From 1994 to 2012, they found that oxygen levels dropped and surface temperatures rose in the lakes. This occurrence surpassed the growth of cold water habitat in 2021, resulting in significant habitat loss for these species.
“Constrained, squeezed, overheated, and buffered” were the four types of lakes classified by the researchers. Seasonal loss or severe limitation of appropriate habitat is a significant problem for trout in most of the lakes included in the research. These alarming numbers show that oxygen depletion in lakes is rapidly increasing.
Decades of browning have diminished oxy-thermal refugia in most Adirondack lakes, according to their analysis of large-scale survey data.
The authors conclude that cold-water fisheries may not be able to thrive in warmer lakes due to warming and browning. More thermal havens for cold-blooded creatures in deep water have opened up due to browning, which keeps heat at the top. Nevertheless, thermal refugia may become inhospitable if browning causes dissolved oxygen levels to drop too low. Dissolved organic carbon concentrations are strongly related to the availability of oxy-thermal habitats in late summer. The deoxygenation of bottom waters caused by browning is outpacing the spread of cool-water habitat in most lakes, forcing cold-loving creatures to live between layers of unsuitable water.
An existential danger to preserving cold-water species like salmonid fish populations is the oxy-thermal squeeze, which occurs as surface waters warm and bottom-water oxygen levels decline.