Giant Elkhorn corals (Acropora palmata), such as this colony from about three meters depth in St. John, are some of the most beautiful and important corals that have become lost as many reefs reefs in the Caribbean have degraded. This colony was photographed in 2015 and it was killed by Hurricanes Irma and Maria in September 2017. However, CSUN marine biologist’s latest study finds some resilience among the coral reefs of St. John. Photo by Peter Edmunds.

Peter Edmunds was prepared for the worst. Back-to-back Category 5 hurricanes had torn through the Caribbean in September 2017, and the California State University, Northridge marine biologist was not sure what he would find when he visited the fragile coral reefs near the island of St. John after the storms.

What he found is that decades of degradation of the reefs by the increasingly harmful effects of climate change had created a coral community that was resistant to the devastation usually associated with severe storms like Hurricanes Irma and Maria that hit the Caribbean and eastern United States in fall 2017.

CSUN marine biologist Peter Edmunds heading out to his field site in St. John, U.S. Virgin Islands, to begin the field sampling that provided the kind of data at the core of the paper. Photo by Chelsey Wegener.

“The coral communities have become resistant to adversity,” Edmunds said. “Basically, once you have lost everything, you’ve got nothing left to lose.

“The expectation was that the hurricanes were going to be devastating for the reefs of St. John,” he said. “After a year of monitoring and analyzing the data, we found that the impacts on the stony coral communities were minor. This isn’t necessarily good news for the reef. What is means is that the reef and its corals have become so degraded that the hurricanes did not affect them as much we anticipated.”

Edmunds findings, “Three decades of degradation lead to diminished impacts of severe hurricanes on Caribbean reefs,” were published this weekend in Ecology.

“This study highlights the value of long-term research to understanding the complexities of ecological change,” said Dan Thornhill, a program director for the National Science Foundation’s Long-Term Ecological Research program, which funded Edmunds’ research. “Surprisingly, two back-to-back Category 5 hurricanes had small effects on coral reefs in the U.S. Virgin Islands. But this resilience resulted from decades of environmental decline and a shift from coral to seaweed. Corals are now so uncommon in this region that even major disturbances only have small impacts on their abundance.”

Edmunds has spent 31 years mapping and documenting the state of the coral community off the island of St. John in the waters of the Virgin Islands National Park, part of the U.S. National Park Service. Decades-worth of research in the area gave Edmunds the knowledge to effectively assess just how badly the 2017 hurricanes impacted the coral community.

“This study underscores the importance of committing to decades of ecological monitoring and natural history,” he said. “Without that legacy, that knowledge, it is not possible to do justice in measuring the effects the hurricanes had on the reef. If we had just turned up in St. John in 2017 and measured the reef in the summer and then again in November, we would not have been able to put the effects of the most recent hurricanes in context. One year of research is not enough to lead to conclusion the that the reefs are becoming resistant to the impact of the storms.”

Edmunds is quick to point out the reef of the 1980s or 1990s “probably is never coming back.” But, he said, information he has gathered can contribute to the management of the resiliency of the marine ecosystem.

“We have a reef in St. John that seems to have become resilient to these disturbances,” he said. “Much of modern coral reef management focuses on promoting resilience to disturbances so that reefs might persist in the future. The point is that just saying you want to increase resilience is not sufficient. Paving something over with cement makes it resilient, but it doesn’t preserve the living community that has ecological value. We need to do more than just manage for resilience, we need to promote the success of specific corals that have great value to reef condition, such as the massive boulder and branching species. To achieve this outcome, you need high-resolution ecological information on the state of the reef and how it is changing.”

“The important message is that these record-breaking hurricanes have not caused catastrophic damage to the degraded reefs of 2017, and therefore it is all the more urgent and important to protect what is left,” he said. “There should be absolutely no sentiment whatsoever that after these hurricanes, there is nothing left to protect in a park. That is massively incorrect.

“(The study) allows us a far more objective appraisal of the real risks to these ecosystems and their current state,” he said. “Massive hurricanes may not be the biggest threats present-day Caribbean reefs are facing. The most serious threats are the insidious and dangerous effects of gradual warming sea water, ocean acidification, and coral diseases.”

College of Science and Mathematics, Coral Reefs, Department of Biology, Environment, Featured, Marine Biology, St. John