Coral ecosystems support biodiversity and provide food to at least 500 million people, particularly in developing countries as this image from a Fijian market demonstrates.

(Dr. Candida Savage)

At a Glance

Researchers conducted a one-year growth experiment at two Fiji marine protected areas.One island, Namena, had seabirds, the other did not.After one year, corals at the Namena had grown four times faster than at the island with no seabirds.

Guano, or bird droppings, is having a positive effect on coral growth, which highlights the importance of protecting seabirds, a new study says.

Researchers with New Zealand's University of Otago say nutrients in , which significantly boosts their growth, according to the study published this week in Scientific Reports.

"The findings have for catchment-to-reef connectivity and demonstrate that coral conservation should also consider catchment management in addition to marine protection," author Candida Savage of Otago's Department of Marine Science said in a press release.

Researchers with the university conducted a one-year growth experiment at two Fiji marine protected areas — one with breeding seabirds on the island of Namena and the other on the island of Cousteau, which is devoid of any seabirds. The researchers found that corals grew up to four times faster at Namena.

"Bird guano is known for its qualities as a fertilizer, however the impact it had on coral growth has been unknown until now. I was astounded at how much of a difference the presence of guano had in promoting coral growth," Savage said.

Comparison of staghorn corals grown for one year without the influence of seabird guano (three corals on left) with corals grown near a seabird colony (three corals on right).

(Dr. Candida Savage)

Of note is the efficacy of guano on coral growth as opposed to man-made fertilizers, which tend to degrade coral reefs.

Throughout the tropics, coral reefs have been highly impacted by the effects of global warming. A study last year found that a following marine heat waves in 2016 and 2017 had irreparably changed the world's largest reef system.

According to a press release sent to weather.com, researchers with Australia's James Cook University said the nearly 1,500-mile-long reef had experienced a "catastrophic die-off" which was "transforming the ecological functioning of almost one-third of the 3,863 reefs that comprise the world’s largest reef system."

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Similar reports of dying coral were coming from other reef systems throughout the world as tropical waters warmed.

Savage noted that given the importance of seabirds and their guano for the regrowth of threatened coral reefs, measures should be taken for their protection.

"Given that nearly one-third of seabird species are at risk of extinction globally and now that we know how beneficial seabird subsidies are for coral growth, we should consider catchment-to-reef management to protect our marine ecosystems," said Savage. "This could be in the form of protection of established seabird nesting grounds or promoting new seabird habitats by enhancing natural vegetation on land alongside protecting marine areas. If the birds are there, the benefits of their droppings will be too."