Temperature outperforms light and flow as a driver of oxygen in US rivers, according to a study.

For the plants and animals that live there, the amount of dissolved oxygen in a river is a matter of life or death. However, the amount of dissolved oxygen varies greatly from river to river depending on their particular temperature, light, and flow. Researchers at Penn State used a deep learning model to examine data from hundreds of rivers across the country in order to determine which factor has the greatest influence on the concentration of dissolved oxygen.

Wei Zhi, assistant research professor of civil and environmental engineering and the study’s lead author, claims that since fish and other aquatic organisms need dissolved oxygen to breathe, oxygen concentration is an essential indicator of water quality. The study was recently published in Nature Water.

According to studies, the amount of dissolved oxygen found in a river or stream is influenced by three main factors: flow, temperature, and sunlight. At the U., we wished to know: Which of these conflicting drivers was dominant on a continental scale?”.

“Research has shown that three major factors—flow, temperature, and sunlight—influence the amount of dissolved oxygen found in a river or stream.” We sought to identify which of these conflicting factors was dominating at the continental level in the United States.”

Wei Zhi, assistant research professor of civil and environmental engineering 

The speed at which a stream flows affects how quickly oxygen in the air can dissolve in the water; temperature affects how much oxygen the water can draw from the air; and the amount of sunlight shining into the water affects how much oxygen the plants in the water can produce on their own, says corresponding author Li Li, Barry and Shirley Isett Professor of Civil and Environmental Engineering at Penn State. However, contrary to popular belief, none of these three factors is as important as they are.

The amount of monitoring data collected in various rivers at various times makes it difficult to determine which of these factors is most crucial on a continental scale, according to Zhi. “Measuring dissolved oxygen levels in various rivers has not always been done consistently. For instance, some rivers were only measured in the summer of the 1980s, and others in the spring of the 2000s.

using data from 580 rivers spread across the contiguous U.S. over the past 40 years. S.—each with distinct temperature, flow, and sunlight conditions—the researchers trained a long-short-term memory deep learning model to determine the association between the weather conditions and dissolved oxygen.

According to Li, “it has historically been very challenging to predict the dissolved oxygen levels simultaneously on such a large scale.”. “However, using a deep learning and big data approach, we can achieve that. Deep learning models allow for the systematic analysis of patterns and drivers on a large scale.”.

At a continental scale, the model showed that temperature dominated light and stream flow in determining the dynamics of dissolved oxygen. The results showed that stream flow had little effect on dissolved oxygen levels, while light was the second-most crucial factor.

“In the United States, temperature is the main determinant of daily dissolved oxygen dynamics. S. rivers,” Zhi proclaimed. Temperature alone can make reasonably accurate predictions of oxygen concentration. In warming rivers, dissolved oxygen is decreasing, which has significant effects on ecosystem health and water security in the coming years.”.

More information: Wei Zhi et al, Temperature outweighs light and flow as the predominant driver of dissolved oxygen in US rivers, Nature Water (2023). DOI: 10.1038/s44221-023-00038-z

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