World’s lakes are losing oxygen faster than oceans, climate change implicated: study
It’s not just oceans that are in trouble from climate change.
Oxygen levels in temperate freshwater lakes are plummeting worldwide, a new study suggests.
The climate-change-driven trend threatens everything from freshwater biodiversity to drinking water quality, researchers said in a study published Wednesday in Nature.
Researchers surveyed oxygen levels in lakes across the temperate zone and found a 5.5% decline at the surface and 18.6% drop in deep water since 1980, they said in a statement.
In lakes polluted with nutrients, surface oxygen levels were increasing when water temperatures crossed a threshold that favors cyanobacteria, which has the potential to produce toxins when burgeoning into harmful algal blooms, the researchers said.
The drop in oxygen could lead to increased fish kills, algal blooms and methane emissions, the researchers said.
“All complex life depends on oxygen,” said Kevin Rose, study co-author and a professor at Rensselaer Polytechnic Institute, one of the research entities. “It’s the support system for aquatic food webs. And when you start losing oxygen, you have the potential to lose species. Lakes are losing oxygen 2.75-9.3 times faster than the oceans, a decline that will have impacts throughout the ecosystem.”
The team analyzed a combined total of more than 45,000 dissolved oxygen and temperature profiles collected since 1941 from nearly 400 lakes in the temperate zone across the world.
The findings are significant because of the scope of potential effects, the scientists said. Besides biodiversity, the concentration of dissolved oxygen in aquatic ecosystems influences greenhouse gas emissions, nutrient biogeochemistry, and ultimately, human health.
“Oxygen is one of the best indicators of ecosystem health, and changes in this study reflect a pronounced human footprint,” co-author Craig E. Williamson, a biology professor at Miami University in Ohio, told The Associated Press.
While lake oxygenation has been studied before, this seems to be the first study to look specifically at lakes, AP said. And they turn out to have lost two to nine times as much oxygen as oceans, the new study’s authors said. It’s also the first to look at oxygen concentrations at both the surface and depths of lakes.
“I think one of the really interesting findings here is that the authors were able to show that there’s this pretty pronounced decline in dissolved oxygen concentrations in both the surface and (deep) parts of the lake,” Samuel B. Fey, a Reed College biology professor who studies lakes and was not involved in this study, told AP.
Lakes comprise just 3% of the planet’s land surface but are home to the bulk of the world’s biodiversity, making the changes worrisome because of what they point to about environmental change in general, as well as the potential direct impact on freshwater ecosystems, the researchers said.
“Lakes are indicators or ‘sentinels’ of environmental change and potential threats to the environment because they respond to signals from the surrounding landscape and atmosphere,” lead author Stephen F. Jane said in the researchers’ statement. “We found that these disproportionally more biodiverse systems are changing rapidly, indicating the extent to which ongoing atmospheric changes have already impacted ecosystems.”
With News Wire Services
