Plastic pollution disrupts recovery of threatened coral reefs

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A University of Hawaiʻi at Mānoa graduate's new research reveals that plastic pollution poses a significant, unseen threat to endangered coral reefs. The study found that chemicals leaching from plastics disrupt the two most critical processes for reef survival: the reproduction of adult corals and the settling of their larvae.

The work by Keiko Wilkins, who recently earned her PhD from the UH Mānoa Marine Biology Graduate Program, is among the first to demonstrate these hidden dangers, which may help explain why some reefs are failing to recover after mass-bleaching events.

"When people think of threats to coral reefs, microplastics are often unnoticed," said Wilkins. "Not only do corals eat microplastics, microplastic-associated chemicals may have hidden impacts. My research highlights this issue, urging us to see plastic pollution as a complex stressor to our reefs."

Unseen threat

Coral reefs in Hawaiʻi and around the world are vital ecosystems facing extreme pressure from climate change. Wilkins' work, conducted at the Kewalo Marine Laboratory, was published in two parts.

• The first study showed that plastic leachates-chemicals released from plastics into the water-significantly reduced fertilization rates in corals.
• The second study demonstrated that these same chemicals negatively affected the ability of coral larvae to settle onto reefs, a step essential for replenishing coral populations.

"Keiko's research is timely and essential in supporting efforts at the protection of coral reefs and all who depend on them," said Bob Richmond, director of the Kewalo Marine Laboratory and Wilkins' advisor. "Her results provide proof of the unseen, damaging effects of plastic pollution and the need to urgently address this problem if we are to leave a legacy of vital coral reefs for future generations."

Scholarship support, real-world impact

Wilkins conducted much of her research with support from a highly competitive NOAA Nancy Foster Scholarship. This allowed her to collect coral samples in protected areas, including the Papahānaumokuākea National Marine Sanctuary and the Hawaiian Islands Humpback Whale National Marine Sanctuary.

The scholarship also supported her outreach and education efforts, through which she has connected with communities and schools across American Sāmoa to share her findings and raise awareness about the health of our oceans. She is now investigating how many microplastic particles are being ingested by corals in these regions.