Coral Reefs Could Rebound If Put On A 'Balanced Diet,' New Study Shows

As global ocean temperatures rise, corals face degradation from acidification and coral bleaching. But it turns out that a nutrient-rich, balanced diet could help corals stay strong during stressful thermal conditions, according to a recent University of Miami (UM) study. This is a major step towards ensuring that corals continue to flourish during future climate change.

Researchers from UM's Rosenstiel School of Marine and Atmospheric Science and the Centre Scientifique de Monaco fed corals two different types of nutrients to see which were most beneficial during elevated temperature conditions. This included inorganic nutrients of nitrogen and phosphorus, which are commonly found in oceans from agriculture runoff, and organic nutrients of zooplankton, which are tiny marine animals corals commonly feed on.

"We found that the coral's resilience to thermal stress totally depends on the kind of inorganic enrichment - if it's 'balanced' or not," Erica Towle, an alumna of the UM Rosenstiel School, said in a news release.

Yellow scroll coral, Turbinaria reniformis, from the Red Sea were placed in separate seawater tanks and fed these nutrients. They were also subjected to varying temperatures to see how the nutrients affected their response to thermal stress. Then, to test the' recovery, the seawater was returned to normal temperature conditions. From these experiments, researchers concluded that excess nitrogen by itself or with and zooplankton made high-temperature bleaching events worse. However, excess nitrogen paired with extra phosphorus and zooplankton increased the resilience.

"Excess nutrients from land sources and thermal stress will likely occur in concert in the future so it's important to assess them together," Towle explained in a statement. "Incorporating nutrient levels in thermal bleaching models will likely be very important for coral reef managers in the future as ocean waters warm."

The study, recently published in the journal Limnology & Oceanography, is the first to asses the balanced relationship between the three nutrients, thermal stress and coral health and could help scientists better protect coral reefs in the future.

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