Warming temperatures to blame; fish habitat at risk
By Zachary Matson
Dissolved oxygen levels have been declining in Adirondack lakes in recent decades and new research shows that could be a big problem for fish.
Warming temperatures mean earlier ice breaks and later ice formation. Which causes lake stratification – the separation of a warm top layer from a cold bottom layer – to strengthen and last longer.
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Typically, mixing events in spring and fall replenish nutrients and oxygen throughout a lake’s water column. But as stratification lengthens, dissolved oxygen by late summer is falling to levels that pose harm to fish and other aquatic life.
A new research paper published this month analyzed deoxygenation trends in around 400 lakes worldwide, including over a dozen in the Adirondacks, and examined the volume of water and habitat where dissolved oxygen levels dropped below 5 mg/l. Below that level coldwater fish like trout and salmon can struggle to find suitable habitat.
The researchers from Cornell University and Rensselaer Polytechnic Institute estimated that across the studied lakes the proportion of the water column falling below the critical oxygen threshold had increased between 0.9% and 1.7% per decade.
“Assuming this applies to lakes generally, this is a massive amount of water,” said Stephen Jane, a postdoctoral fellow at Cornell’s Atkinson Center for Sustainability, the paper’s lead author.
Jane said some lakes will be less sensitive to the oxygen declines but that those with lower oxygen concentrations are likely to see more of the water column fall into low-oxygen conditions.
“Lakes are definitely having increases in the amount of water that is not suitable for coldwater species,” Jane said.
Paul Bukaveckas, a Virginia Commonwealth University professor who has studied Adirondack lakes since the 1980s, is finishing up a paper that uses data from the Hamilton County Water and Soil Conservation District. The data included temperature and oxygen measurements at different depths on 17 Adirondack lakes, known as profiles.
Bukaveckas found that the shape and size of lakes determined how harmed they will be by the declining oxygen levels. Large, deep lakes will retain more oxygen-rich waters than smaller, shallower ones. Imagine a trout searching for suitable habitat in a lake: surface waters warm more than desired, so they move to deeper waters, but those deeper waters are losing the oxygen they need to survive. The lake’s “Goldilocks Zone” is shrinking.
“It’s an issue of habitat compression,” Bukaveckas said. “They have less and less habitat available in the lakes.”
Adirondack lakes
Some shallow Adirondack lakes don’t stratify and have consistent oxygenation throughout, but they are also susceptible to warming.
The 25 years of Hamilton County data showed that dissolved oxygen levels had declined in a significant number of lakes. In the early 1990s, 73% of the studied lakes registered average summer dissolved oxygen levels above 5 mg/l. By 2021, 55% of the lakes exceeded the oxygen threshold. Bukaveckas projected that by 2045 around 45% of the studied lakes would meet the threshold.
That habitat compression will be more impactful on certain lakes. Bukaveckas compared two Hamilton County lakes to demonstrate the point: Piseco Lake and Lake Eaton. Piseco is around 130 feet deep, while Eaton reaches a maximum depth of 56 feet. Oxygen depletion is more acute in Lake Eaton, where the cold layer of water is much thinner than at Piseco. Average summer dissolved oxygen levels at Eaton dropped below 3 mg/l, according to findings Bukaveckas said in an interview.
The loss of oxygen can alter the chemical and biological characteristics of lakes and create an accumulation of methane, a powerful greenhouse gas. Oxygen depletion results in the formation of a toxic form of mercury, potentially enhancing the bioaccumulation of mercury in fish. It may also exacerbate harmful algae and cyanobacteria growth, which in turn can deplete oxygen.
The Adirondacks’ history of acid rain further complicates research. When 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 it also limited sunlight’s ability to warm deeper waters, potentially strengthening stratification and exacerbating oxygen losses.
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“We think that is driving or contributing to faster than average rates of oxygen loss,” said Kevin Rose, an RPI researcher who runs the lab where as a doctoral student Jane studied stratification and deoxygenation.
In a 2021 paper published in the journal Nature, Jane, Rose and other researchers demonstrated that a decline in dissolved oxygen was “widespread in surface and deep-water habitats” across the world’s temperate lakes from 1941 to 2017.
Researchers at Rose’s lab compiled and published a dataset of 28 Adirondack lakes focused on the concurrent impacts of climate change and acidification, including the oxygen and temperature measurements. The data, which ended in 2012, showed that Adirondack lakes were losing oxygen at faster rates than global averages, Rose said.
Rose is also one of the lead scientists organizing a large survey of around 300 Adirondack lakes focused on climate change. As part of that survey, known as SCALE, researchers want to collect temperature and dissolved oxygen profiles, and on a subset of the lakes deploy probes to collect high-frequency data throughout the ice-free season.
Rose said an initial $500,000 appropriated to plan for the survey is supporting work at a variety of research institutions. RPI is mining datasets to determine a representative list of lakes to study. Cornell is working on methods to survey lake biology using environmental DNA technology. The City University of New York is using its satellite imagery expertise to maximize remote sensing of impacts to Adirondack lakes. He said they could start survey work in 2023 if the funding is available, estimating three years of sampling around 100 lakes each year.
A group of researchers and advocates met to discuss the survey plans in Saratoga Springs in 2021. Rose and Peter McIntyre, a Cornell scientist, summarized the four overarching research questions of the project. The questions focused on carbon cycling, lake biodiversity and harmful algal blooms.
“Oxygen and temperature was question No. 1,” Rose said.
Very disheartening to think of how much the lakes in the Adirondacks have declined in the last 50 years.i remember in the 70’s when a mere 10-15 minutes of fishing could produce a beautiful fish for dinner, whether a trout stream or a bass/pike in a lake. Then acid rain changed everything, that lakes i had fished for decades suddenly the millions of frogs were just gone!! the fish were gone, the roar of croaking was quiet, the loons left. It has taken yet more decades to have a few fish and frogs reappear, now global warming is taking even that away.
Only people over 50 will remember when there used to be toads everwhere in the summer, so many turtles in spring in some areas you had to stop and sometimes move a few to drive by. when an hour’s fishing in a trout stream could easily fill a creel with 18-24 inch trout. walk along any water and frogs croaking, leapord frogs squeeking as they jumped. today’s reality is fish a stream all day for trout, you might not even catch a trout or see a frog or toad, or a single squeek of a jumping leapord frog. The lakes and rivers are very dead, sterile in most areas, there is maybe 99% loss of everything and much smaller size. It very much saddens me that my grandchildren and even children never will know the joy of real fishing.
I used to love fishing, but now to sit for hours with no fish to be caught and to know what used to be, it feels scary to know how little is left of life here. To never see fire newts when there were thousands walking in spring.
Racheal Carlson was right and it has come to be “a silent spring”, rich companies get to sell whole sale poisons and nothing is done, no matter what the enviromental cost. Atrzine scares the hell out of any knowledgeable person, but a milion pounds is poured on America, for maybe 4-5% more corn harvest! we spread millions of pounds of poison on our lawns, so that a dandilion will not bloom? or a crab grass not grow? or that insects should not crawl? That children get to run in a sterile lawn soaked in insecticide, herbicide, fungicide and we wonder why children get cancer?
We have dumped massive amounts of poison for close to 6 decades on our growing food, on our lawns. herbicides along every road, railroad, fences, powerlines, you get the idea, insecticides on our lawn, garden, around our house, even inside our house, your children crawl in poison since they first crawled, then they eat it, breath it, they even drink it from the milk, water or the very plastic bottle it is inside. 8 billion hungry mouths and growing…eating, poisoning, and sh*tting in our only bed!!
Zachery thank you for an article that gets word to more people, but sadly not enough people, not loud enough and profits are first.
Outdoorsman of the Adirondacks have lived and seen the effects that result and 90% of the population is so removed from nature they see nothing, Companies care about profit and spread lies and disinformation to ensurer they get profits like “Bayer” and “DeSantose” or “Scott’s lawn products”, they are ensuring your children will have much higher likelyhood of cancer, that animals will die off. oops i am off to get my can of “Lysol” and “Raid” to spray my house, my grandkids are moving!
Nathan,
I totally agree! Chalking up widespread species and diversity decline to climate change is literally a chemical smokescreen. Compare the billions poured into climate change research and remediation to the perhaps millions dedicated to environmental chemical hazards to ecosystems – much of which is carried out by Big Chemical themselves. Dubious at best.
Another unrelated consideration is simply the homogenization of the globe. Inattentiveness to spreading disease and organisms around the world is causing great – often unseen and unnoticed – damage to ecosystems. There is very little currently preventing this. White-nose syndrome, Emerald Ash Borer, Dutch Elm Disease, Chestnut blight, are only a few well-known ecosystem destroyers that have occurred in my lifetime. Continental isolation helps species to diversify and become more robust. Turn the globe into one big ecosystem and it is much more easily damaged because of lack of diversity.
The last 500 or so years of humans traipsing around the Earth may have become its undoing by weakening species diversity. Add unrelenting climate change and chemical destruction to the equation and the sum does not look hopeful.
Great replies.I agree completely. I just dont think enough people are listening and if they are what really do we do about it. Take the Adirondacks for instance. The governing bodies are still doing studies on the effects of salt on roads, loss of habitat in all areas. allowing atv”s in the forests, larger and larger ones, building more high end condos and housing for the rich and famous, calling logging “forest conservation” and believing it. With this mind set just in the adirondacks how would we get any message across to the masses?
Sure the wildlife and habitat will die, No need for more studies. All the studies show the death of our planet.
I dont know what to do to get this one park to understand another way of doing business. I do know this way is not working.
I think we all see the writing on the wall. We have past the tipping point. I am old enough to have done my own “study” on the health of the planet as I can tell you all have too, With no grant money, just my 65 plus years, my conclusion is it is terminal. And not far off.
I know, a radical conclusion. I am one of the few that will say it. I havent given up but I wont go on with my head in the sand thinking things will get better.
I didn’t see anywhere close to comment, but what an incredibly beautiful baby! Many congratulations to you both! And if I may make a suggestion, get a frontpack, and use it as much as possible. My daughter is nearly 21, and I still treasure the many times I carried her that way, both turned in to my chest, and later, facing out to see the world. It’s one of the most wonderful child inventions ever. I wish y’all both a world of happiness with Bryer.