A new study published in Science Advances has raised alarm over the growing crisis of freshwater deoxygenation, with climate change and increasingly frequent heatwaves significantly reducing surface dissolved oxygen (DO) levels in lakes across the world. The research, led by Prof. SHI Kun and Prof. ZHANG Yunlin from the Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences, highlights the devastating impact on lake ecosystems, threatening biodiversity and the health of aquatic life.
Collaborating with researchers from Nanjing University and Bangor University in the UK, the team analyzed an extensive dataset of over 15,000 lakes worldwide over the past two decades. The study reveals a troubling trend: 83% of the lakes studied have experienced significant declines in surface DO levels, with the rate of deoxygenation in lakes outpacing similar declines in oceans and rivers.
The findings underscore the dual threats of long-term climate warming and short-term heatwaves. The research shows that climate warming reduces the solubility of oxygen in water, contributing to a staggering 55% of global surface deoxygenation. Additionally, eutrophication—nutrient enrichment often due to agricultural runoff—accounts for approximately 10% of oxygen loss in freshwater systems.
Another key finding of the study highlights the rapid effects of heatwaves on freshwater ecosystems. The researchers discovered that heatwaves cause a sharp, immediate decline in surface DO levels, with a 7.7% reduction compared to average climatological temperatures. These heatwaves exacerbate existing challenges, putting even more pressure on freshwater organisms that rely on stable oxygen levels for survival.
The study’s results serve as a stark reminder of the profound impact of climate change on freshwater ecosystems. With the global frequency and intensity of heatwaves projected to increase in the coming years, the study calls for urgent action to mitigate these effects and protect vital freshwater resources. Policymakers and environmental managers are urged to develop strategies that address both the long-term and immediate threats to freshwater deoxygenation, ensuring the sustainability of lake ecosystems and the species that depend on them.
These findings bring into sharp focus the growing vulnerability of freshwater ecosystems to climate change, highlighting the need for concerted efforts to combat both climate warming and heatwave impacts. As the study emphasizes, addressing this issue is critical to preserving the health of aquatic life and maintaining the balance of biodiversity in lakes worldwide.
