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An international team of researchers, led by Scripps Institution of Oceanography, UC San Diego, including USGS Research Oceanographer Dr. Kim Yates investigated the state of hypoxia—or low oxygen levels—on 32 different coral reef sites around the world. The team found that hypoxia is already occurring in many locations and is expected to worsen with rising oceans temperatures.
Oxygen is essential for life, even in the world’s oceans. This is especially true in coral reef environments with are some of the most diverse ecosystems on Earth. Declines in oxygen occur in marine environments for numerous reasons, but not typically on coral reefs. An international team of researchers conducted a global study of oxygen conditions on coral reefs around the world. The paper, published in Nature Climate Change, reveals that 84 percent of reefs have already experienced weak to moderate hypoxia and 13 percent experienced severe hypoxia. While this current situation already reveals cause for concern for coral reef inhabitants, the team also ran predictive models that indicate these hypoxic conditions will likely worsen between now and the year 2100. In fact, the total number of hypoxic observations on these reefs are expected to increase under all warming scenarios, ranging from an increase of 13 to 42 percent under one scenario to 97 to 287 percent under a more extreme scenario. Deoxygenation of the ocean is expected to worsen as ocean temperatures continue to rise and intense heat waves become more frequent and severe. This is because warm seawater can hold less oxygen than cooler waters. These data provide a critical first step in establishing baseline reef oxygen conditions, classifying future hypoxic events, and predicting the future effects of hypoxia on coral reef ecosystems.
