A new study reveals significant changes in the global freshwater oxygen cycle.
Rivers, streams, lakes, and reservoirs aren’t just beautiful features of the landscape, they’re vital to life on Earth. Like us, these inland waters need oxygen to function. But a new study led by researchers at Utrecht University reveals that over the past century, during the Anthropocene, we’ve been slowly suffocating them. Published in Science Advances, the study shows that the way oxygen is produced and used in freshwater systems has changed dramatically since 1900, largely due to human activity.
Oxygen is not only essential for aquatic life, it also plays a key role in critical nutrient cycles like carbon and nitrogen. When oxygen levels drop too low, a condition known as hypoxia, ecosystems begin to unravel. Fish die, food webs collapse, water quality declines, and these effects are already being felt around the world. This study makes it clear: what’s happening to our lakes and rivers isn’t just a local issue. We’re facing a global, human-driven crisis.
Behind oxygen depletion: accelerated oxygen cycle
A group of researchers, led by Utrecht Earth scientists Junjie Wang and Jack Middelburg, have developed for the first time a global model that describes the entire oxygen cycle of inland waters around the world. “With this model, we offer the most complete possible understanding of this cycle on a large scale, so that one can see oxygen-related problems coming, get to know the causes, and hopefully intervene in time,” Jack Middelburg explains.
Inland waters have become much busier places when it comes to oxygen. The team found that the global “oxygen turnover”—that is how much oxygen is produced and consumed—has increased. But here’s the twist: these waters are consuming more oxygen than they produce, making them a growing sink of atmospheric oxygen.
Cause
“More farming, more wastewater, more dams, and a warmer climate—they all change how our freshwater ecosystems function,” says Junjie Wang. With more nutrients flowing into rivers, lakes and reservoirs, algae grow faster, but when they die and decompose, they use up huge amounts of oxygen. “We found that the main causes lay in these direct human activities. First, it turns out that nutrient input through, for example, over-fertilization, is a major driver of this acceleration. Secondly, the longer travel time of freshwater to the sea through the construction of dams and reservoirs has proven to be just as important,” says Jack Middelburg.
At the same time, indirect human impacts like rising temperatures make oxygen less soluble in water, transport slower vertically across the water column, and speed up processes that burn through it even faster. “Until now, the consensus in the scientific literature has always been that the rise in temperature is primarily causing this acceleration. But our model shows that warming only contributes about 10-20% to this phenomenon,” Junjie Wang says.
The Anthropocene fingerprint
This study showed that the modern oxygen cycle in inland waters looks nothing as it did in the early 1900s. “Even though these waters cover just a tiny fraction of Earth’s surface, they now remove nearly 1 billion tonnes of oxygen from the atmosphere each year—overall half of what the entire ocean emits back,” says Middelburg.
“We can’t ignore inland waters in global climate and oxygen budgets anymore,” Junjie Wang adds. “They’re changing faster than we thought, and they’re crucial pieces of the Earth system puzzle.”
Reference: “Global inland-water oxygen cycle has changed in the Anthropocene” by Junjie Wang, Xiaochen Liu, Alexander F. Bouwman, Lauriane Vilmin, Arthur H.W. Beusen, José M. Mogollón, Wim J. van Hoek and Jack J. Middelburg, 4 April 2025, Science Advances.
DOI: 10.1126/sciadv.adr1695
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10 Comments
In 1969 I was told in school Lake Erie is dead and will take 300 yrs to recover. Man can destroy, for sure but it’s striking that there are no studies about anything good happening, anywhere? Isn’t it?
We can’t study hope. We can only study reality. And that means studying how we pillage and destroy aspects of nature, and then we try to gauge how nature will progress or recover. We are often wrong by degrees, but we shouldn’t start to assume that because we haven’t burnt the planet to a crisp yet that we can safely focus on how everything is still mostly great in spite of our folly as a species.
It’s striking that you seem to believe that. Are you being hyperbolic for effect or are you really subject to news algorithms that only feed you bad news?
I would argue that the amount of bad news is overwhelming but there is goodness all the time. That’s part of what makes the focus on bad news so frustrating. We talk about are dying waterways for example without any of the things we could do to address them other than dying off to stopping everything we currently do.
The ‘Anthropocene’ is NOT an officially recognized division of geologic time. Those who use it, after a panel of experts has rejected the proposal, demonstrate a disdain for procedures to insure that crackpots don’t influence the direction of science. Alarmists with an agenda, who put their views above that of scientists who have studied the issue, should have their claims considered with suspicion because they have demonstrated that they play by their own rules and apparently believe that their end justifies any means.
https://wattsupwiththat.com/2024/09/29/anthropocene-cockroach-of-the-geologic-time-scale/
A team of hundreds of scientists opposed Einstein’s theory of relativity. The anthropocene is real just like Pluto never stopped being an astronomical body or changed size when we relabeled it. we are creating plastic based geology and acidifying our oceans. Denial of the facts because the mainstream scientists rejected a label is pointless.
I have micro plastics in my brain and so do you. Because our entire ecosystem is contaminated by our industry and our human ability to reshape the world however the masses see fit.
Sure nature will bounce back from our nonsense, but it’s not going to be friendly to life or beauty or us. We have left unique and destructive fingerprints all over this rock.
“we are creating plastic based geology and acidifying our oceans.”
If you were a student in a chemistry lab and instructed to acidify an aqueous solution as a step in an experiment, you would be expected to reduce the pH below 7. That is, increase the ratio of hydronium ions to hydroxyl ions to greater than 1. There is no reason to believe that the claimed small change (~0.1 pH) that has occurred in buffered sea water in the last 100 years from the addition of weak carbonic acid will ever result in reaching a pH of even 7 — neutrality.
I’m left with the impression that you didn’t bother to read the link I provided. The issue is one of whether the proposed new epoch meets the definition used to define all the other epochs. It does not. Are humans having an impact on the environment? Yes. But that is a different issue from some people wanting to ignore the procedures for naming geologic stratigraphy to encourage political actions.
Exactly why your comment about using a commonly known period of time is such a joke. No one cares what you want to call a given period of time or how popular any given name is.
If you don’t want to discuss the science just because someone used a proper noun that triggers you find carefully curated content that removes your triggers. You can probably even get AI to help you.
You are absolutely wrong that no one cares. If that were the case, there would be no need for an international committee to decide on and approve names.
As with all words, there has to be general agreement on the meaning of words for communication to occur. Without agreement on meaning, with everyone attaching their own arbitrary and random meanings, one is presented with the Tower of Babel conundrum where nobody can communicate. Trying to redefine existing words just creates confusion about the meaning.
Not surprisingly, you missed the point of me objecting to the use of the word “anthropocene.” I said, ” Alarmists with an agenda, who put their views above that of scientists who have studied the issue, should have their claims considered with suspicion because they have demonstrated that they play by their own rules and apparently believe that their end justifies any means.” I am not personally “triggered.” I’m concerned about precise communication, which is necessary for science. It isn’t that I don’t want to discuss science, rather, I want to be sure that words used in discussing science have the same meaning to all participating and that they contribute to greater understanding and not just be words that trigger emotional responses like “more acidic” or “tipping point” do. Real science is concerned about repeatable measurements, definitions that are consistent, and conclusions that are logically defensible.
Given how we seem to be in non-stop emergencies of various kinds, we’re doing quite well on a whole.
Simply concentrating this summery. ” we’re Doomed and the current Trump administration is going to be the last . Get over it”