Warm lakes a threat to fish
Cornell study: Salmon, trout, whitefish at risk
ALBANY — Climate change is causing the bottom of most Adirondack lakes to become unlivable for trout, salmon and whitefish during the summer, according to Cornell University researchers.
In a study, the researchers also found that lake browning, caused by dissolved organic matter from forests, is also making those lakes unsuitable for the cold-water species. Only about 5 percent of Adirondack lakes may continue to maintain sufficiently cold and oxygenated water to support those species if current trends persist, the study said.
“After a few more decades of browning, most Adirondack lakes will become either too warm or too deoxygenated to support trout populations,” Peter Mcintyre, a Cornell aquatic conservation ecologist who worked on the study, said in a prepared statement. “This is a radical departure from the past, when trout fisheries in numerous lakes were celebrated by locals and tourists alike.”
Increased browning, despite a significant decrease in new acidic pollutants over recent decades, stems from a century of acid rain, according to the university. Additionally, climate change has increased organic matter runoff by causing more frequent extreme precipitation events, such as heavy rainfall, and lengthening growing seasons, the university said.
Water with a tea-like color typically contains organic compounds that absorb sunlight, resulting in the trapping of heat at the surface of the lake and preventing the rays from spreading to the depths of the water. In the summer, cold-water species dive deeper to find cooler temperatures, yet they still require ample oxygen.
The study, co-led by Cornell University, found that only 1 percent of Adirondack lakes were deeper than 30 meters, which distinctly avoided oxygen depletion from browning and warming. Researchers identified another 4 percent of lakes as clear, where the expansion of cold water surpassed the spread of low oxygen zones. Therefore, researchers concluded that in 95 percent of the lakes, further browning would
harm cold-water species.
The study received funding from Cornell University’s Cornell Atkinson Center for Sustainability, the United States Geological Survey’s Northeast Climate Adaptation Science Center and the David and Lucile Packard Foundation. It involved placing sensors in 15 Adirondack lakes to measure dissolved oxygen and temperature, while also studying browning rates in a set of lakes using decades of historical data.
Kyle Glenn of Trout Unlimited’s northeastern
branch, said his nonprofit has been aware of brook trout migrating from Adirondack lakes to nearby streams in search of colder water. After replacing culvert pipes that blocked the trout from passing through, he said the group has observed the fish using the unobstructed streams.
“Once the temperatures get too high, I think we will see some serious problems down the road in the ponds and lakes,” Glenn said. “The streams ultimately end up being the final refuge for some of these fish.”