Cornell scientists warn of dire threats to native fish habitat from warming temperatures, browning water
By Zachary Matson
Brook trout habitat in all but a small portion of Adirondack lakes could disappear as climate change warms lakes and summertime oxygen loss is exacerbated by lake browning associated with the region’s recovery from acid rain, according to a new study by Cornell University researchers.
The researchers estimated that only 5% of Adirondack lakes may sustain suitable habitat for cold-water fish like Adirondack brook trout and Atlantic salmon when water temperatures and oxygen depletion peak in the summer months.
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The most resilient lakes are those deeper than 30 meters, far fewer than 1% of the region’s lakes, and the declining number of shallower lakes that are still relatively clear, less than 5% of Adirondack lakes, according to the study.
Stephen Jane, who led the research as a postdoctoral fellow with the Cornell Atkinson Center for Sustainability, said the combined effects of lake browning and warming temperatures are pushing fish into smaller and smaller slices of the water column during the stressful summer season.
“They are squeezed from above by warm temperatures and squeezed from below by low oxygen,” Jane said.
Warming air temperatures mean earlier ice breaks and later ice formation, lengthening lake stratification – the separation of a warm top layer from a cold bottom layer. Typically, mixing events in spring and fall replenish nutrients and oxygen throughout a lake’s water column. But as stratification lasts longer, dissolved oxygen by late summer is falling to levels that pose harm to fish and other aquatic life.
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When Adirondack lakes were highly acidified, organic matter did not readily dissolve into the water column, resulting in many clear lakes. As pH levels increased so did the solubility of organic matter, and water clarity declined. The lake “browning” was a sign of recovery from acid rain but is now an emerging threat.
The browning effect concentrates warming in a thin layer at the water’s surface, where Adirondack water temperatures are rising faster than other regions around the globe. The browning prevents light from penetrating deeper into the water column, leading to some cooling in deeper waters. Scientists are finding that temperatures in the deeper parts of many lakes are cooling.
In some cases that can increase trout habitat, but the new study outlines how many more lakes are past a threshold where the combined harms of browning and warming outweigh the potential benefits of expanding cool waters.
At the time of a massive survey of over 1,400 Adirondack lakes in the 1980s, about 23% of lakes were clear enough that habitat could benefit from some browning, according to the study.
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Now, less than 5% of lakes would benefit from continued browning, researchers found using the historical data, while more browning will exacerbate habitat loss in the rest of the park’s lakes.
“Cold water fish, especially in the Northeast are no strangers to loss of habitat,” Jane said. “The difference now is in the Adirondacks you have major drivers acting across the entire region, even in the absence of obvious human alteration of the environment.”
More research needed
Cornell researchers in Ithaca and at a longstanding field station at the Adirondack League Club near Old Forge continue to study brook trout and how to protect them in the Adirondacks’ changing waters.
The field station is working with Department of Environmental Conservation scientists on a study of different brook trout genetic strains, attempting to find which are best adapted to the warming conditions.
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Pete McIntyre, an aquatic biologist at Cornell and co-author of the habitat study, said the new research shows “a staggeringly large proportion of Adirondack lakes where there is very little habitat remaining for brook trout at the end of the summer.”
McIntyre, who is also a lead organizer of the new SCALE survey of hundreds of Adirondack lakes, said the habitat study demonstrates the importance of collecting data at varying intensity levels across the region.
The researchers used a handful of closely studied lakes to determine the patterns of warming, browning and oxygen loss and then relied on the 1980s study to project those trends across more than 1,400 Adirondack lakes. A new survey would enable scientists to verify those trends and develop a better understanding of where brook trout are present.
“There is no substitute for going out to large numbers of [lake] systems to get those biological assessments and verification of predictions,” McIntyre said. “Which lakes have lost fish species they definitely had in the 1980s?”
Tommy Detmer, another author of the study, splits time between Ithaca and the Adirondack field station, where he oversees ongoing research. Detmer said fisheries managers should work to protect the region’s most resilient lakes from other threats, like invasive smallmouth bass that prey on brook trout.
He said lakes that are buffered against the warming and browning threats that have not been invaded by competitor fish are critical to maintaining healthy trout populations in the region; many of those lakes are privately controlled.
“Those lakes that haven’t been invaded are of high-tier conservation value,” Detmer said.
Cornell researchers working at the field station this summer started tracking the minute movements of some brook trout, monitoring the fish as they move up and down the water column. Initial data demonstrates how the monitored fish refuse to enter a lake’s oxygen-deprived depths, mapping the brook trout’s squeezed habitat.
“There is a line that the fish won’t go below,” Detmer said. “We are already in future climate scenarios, it’s no longer something we are looking toward that might be a generation down the road.”
The headline reminds me of an old joke. “ Doc, will I be able to play the piano after my surgery? “ I see no reason you won’t be able to.” “Good, I’ve always wanted to.”
My point, after 70 years on a lake that never had salmon or brook trout, how many of the 90%, never supported brookies or salmon?
We still have brook trout, but for how long ? The state of NY KEEPS DUMPING THOUSANDS OF TON’S OF SALT ON OUR ROADS!!!!!! DRILLED AND HAND DUG WELLS ARE POLLUTED. THE PONDS AND LAKES THAT HAD SO MANY FROGS ,HAVE NONE! YOU CAN’T EVEN HEAR A FROG CROAK. FOR THE LAST 5 YEARS WE HAVE BEEN TRYING TO CATCH A FEED OF WHITE BELLY BULLHEAD. IN SEVERAL PONDS,LAKES AND RIVERS. IF YOU CATCH ANY YOU’RE DOING GOOD!!!!! THE STATE KEEPS LETTING LUMBER COMPANIES CLEAR CUT THOUSANDS OF ACRES,THERE ARE NO TREES TO KEEP THE DIRT FROM GETTING INTO OUR STREAMS. PLACES ARE ONLY LEFT WITH ROCK AND DIRT. CONSERVATION DEPARTMENT IS A JOKE. FORESTER’S CAN’T DO THERE JOBS,ALBANY DICTATES EVERYTHING.CONSERVATION OFFICERS SPEND ALL THERE TIME LOOKING FOR HURT OR LOST OUT OF STATE PEOPLE.MORE RESCUED IN ADK PARK IN ONE YEAR,THAN ANY PLACE IN US. THAT CAME FROM A FOREST RANGER. ALSO,MOST OF THE LAND IN THE NORTHERN PART OF THE PARK CAN ONLY BE ACCESSED BY FOOT. NO PICK UPS, 4 WHEELERS,OR EVEN BIKES & SNOWMOBILES. BUT ITS OK FOR SKIDDERS,FELLER BUNCHES TO TEAR IT ALL TO HELL. PAY THE LOGGERS TO MANAGE IT LIKE IT WAS THERE’S .YOU WOULD SEE A DIFFERENCE. THERE ARE MILES OF ROAD THAT HAVE 3 OR 4 PEOPLE LEASING AN ACRE OF LAND WITH A CAMP OR NOTHING AT ALL.SO THEY PUT A GATE UP, WHICH STOPS ANYONE FROM DRIVING IN FOR MILES. WHICH ONLY LETS A HANDFULL OF PEOPLE USE THOUSANDS OF ACRES. UNLESS YOU WALK IN. ONE HELL OF A PARK!!!!
Michael, and Steve, you’re 100% correct. Thank you for stating the hypocrisy. It has always been this way. Sadly.
People – it’s only a study. Don’t shoot the messengers. Science is not the same as politics. Wise readers understand the difference.
Regarding the science; after Covid, we all know how that turned out. I judge an Adirondack lake or body ow water by the presence or absence of avian predators. Loons, hawks, kingfishers and eagles to name a few, have a fear better handle on the subsurface ecology of a body of water than the aquatic biologists at Cornell. The obvious difference, one group is filling their bellies and the other is filling their wallets.
Brook ‘trout’ are from the Salmon family , if memory serves. But the point is , inability to survive worsening conditions threaten the survival of one of nature’s most beautiful fish!
An article 24 years ago https://www.adirondackexplorer.org/stories/tragedy-of-the-trout said trout were extirpated from 95% of the lakes due to acid rain. Now this article says – because of the effects of decreased acid rain on the water we’re going to lose 95% of the trout. Again? Perhaps the trout are more adaptable than the scientists give them credit for? I guess that would not fit the doomsday scenario though.
The article does not say that. The reference to the Saranac lakes wild forest refers to invasive species brook trout extirpation which is 100% true. Please stop spreading misinformation.
As a avid remote wilderness area ADK brook trout fisherman it is easy to be skeptical of these academia studies . All one has to do is look at the data from the ADK lake survey done in the mid 1980’s. I have recently fished many Lakes and ponds in the ADKs that the 30 year old study found were uninhabited by brook trout. Today many of these bodies of water are full of brook trout. In the last several years we have found that the brook trout fishing has actually become much better than it was 20 years ago. More and larger, healthy brook trout.
I suspect that many of these ADK lakes and ponds historically may have never sustained brook trout. That may be the reason why there are only 9 or 10 lakes in the ADKs that have self sustaining heritage strain brook trout in them today. Also, I know that some lakes without repeated lime applications , most likely will become to acidic once again for cold water fish.
I am not a biologists, but I do have decades of paddle miles with catch and observation experiences on many remote lakes in the ADKs. And I think that is worth something.
I’m willing to listen, but I believe there will be more unneeded regulations coming because of these studies, that in the end will do nothing to help sustain brook trout for the long term. But it will increase the grant money for academia.
In my 45 years of pond brook trout fishing I’ve noticed the water color change.
Due to the Clean air act amendments of 1990 and other executive actions on sulfate emissions, acid rain and its effects have been decreasing over the past 30 years. Many of those ponds in the ALS survey have recovered to the point they either repopulated from tributaries or were restocked with DEC. This wasn’t some magic or conspiracy, the ponds are far healthier now than then. That being said, the Cornell article implies that there is trouble ahead from other changes in chemistry and a warming climate.
You clearly don’t fish that many ponds to make the assertion that only 9 or 10 ponds have wild heritage brook trout. There are well over 100 public access ponds that have wild brook trout, probably an equal number on private land. This is still an unacceptably low number.
Consumptive angling practices for salmonids are a thing of the past and fisheries biologists should have the ability to regulate catch rates based on scientific data. If that means further angling restrictions designed to maintain our native brook trout until we figure out how to stop spoiling their habitat and our own then so be it.
I think you are confusing ponds stocked with heritage strain or hybrid heritage strain brook trout with self sustaining naturally occurring genetically pure never been stocked heritage strain brook trout ponds.
I am not making the assertion about self sustaining heritage brook trout ponds that have never been stocked. It is NYSDEC fisheries biologists making this assertion.
It is a fact in the ADKs and Catskills there are maybe around 12 ponds with genetically pure self sustaining heritage strain brook trout in them.
It was great to see Zachary Matson at the Warrensburg DEC Trout Pond discussion today, Thanks Zachary and Adirondack Explorer for being there for all of us.