As many as 70% of rivers are losing oxygen and becoming hotter. Such a process, induced by climate change effects, is taking place in rivers significantly faster than in oceans.
Aquatic Life at Risk Due to Warmer and Oxygen-Deprived Rivers
The rising warmth and decreasing oxygen levels within the water could lead to serious issues for fish and other aquatic species in these ecosystems. According to the study, this phenomenon could result in acute deaths within southern US rivers.
For water-dwelling animals, dissolved oxygen is crucial to their survival. They typically absorb the oxygen through their gills or other ways. Massive die-offs of fish could result if the oxygen levels get too low. This, in turn, would foster decomposing bacteria growth and further reduce oxygen levels within the water and make the problem worse.
Li Li, a professor of civil and environmental engineering from Penn State and a co-author of the paper, explains that this is a wake-up call, adding that though there has been awareness regarding the warmth and oxygen-less among oceans, this was not expected to happen in shallow and flowing rivers. Professor Li also explains that this study is the first to examine deoxygenation and temperature alterations in oceans deeply. What the researchers discovered has crucial implications for aquatic system health and water quality on a global scale.
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River Temperature and Oxygen Levels
The study examined oxygen and temperature changes in 800 rivers. The researchers looked into 580 US rivers and 216 Central European rivers.
They discovered that 87% of these rivers were getting warmer in the last four decades. On top of this, 70% were losing their oxygen.
In terms of temperature, city rivers had it worst. However, agricultural rivers took the most severe toll when it came to oxygen loss, though warming for these rivers was the least extreme.
Based on their river data model, the researchers predict that the oxygen loss rate in the future will go up by as much as 1.6 to 2.5 times higher compared to the past.
Li explains that oxygen loss in rivers is a shock as rivers are not expected to lose significant amounts of oxygen compared to big water entities like oceans and lakes. The fact that rivers were found to lose oxygen was quite alarming, as this could put aquatic life at risk.
Coastal areas, including the Gulf of Mexico, have dead zones during summer. Recent research has revealed that this could also occur in rivers, as some rivers will be unable to facilitate life.
Impacts of Low Oxygen
Ocean zones with low oxygen may facilitate massive fish kills, leading to thousands of fish washing up dead ashore. Low river oxygen levels have also been observed to lead to massive fish floating dead over the surface.
Lower oxygen levels can also boost greenhouse gas release and toxic metal production.
The study also revealed that several fish species could die out fully due to warmer temperatures and river oxygen deprivation. This could happen over the next seven decades.
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