Recovery will take decades for some spots, most coral reefs in good shape
Catastrophic Hurricane Dorian, which tore through two major islands in the northern Bahamas last in October 2019, was not as meticulous in its devastation undersea as it was on land.
The Category 5 storm ripped out patches of coral reefs the size of small cars, leaving them down and out much like bowling pins. Dorian trucked mud from inshore and dumped it onto reefs, burying its base in silt over two foot deep.
After buffeting trees about in its ferocious winds, the hurricane angrily dashed casuarinas into the sea. They came to rest on the ocean floor after steamrolling corals and crushing other underwater sea life in their path.
In places where Dorian wreaked havoc, the impact was devastating. Some reefs will take decades to recover, if they do at all.
These places, however, are in the minority – good news for thousands of Bahamians who make their living from this critical economic driver, the turquoise waters of the ocean surrounding The Bahamas.
Most coral reef sites throughout Grand Bahama and Abaco are in pretty good shape, the Perry Institute for Marine Science (PIMS) reported Wednesday (October 30).
From October 8-22, PIMS led an expedition to revisit 29 previously surveyed reef sites along both islands, including multiple reefs that suffered a direct hit by the eye of Hurricane Dorian as a Category 3, 4 or 5, hurricane as well as those that experienced less powerful winds.
Partners on the expedition included representatives from The Nature Conservancy, Middlebury College, Angari Foundation and others.
The preliminary findings were surprising.
“Some reefs look totally different now than they did before. Still, it’s really a mixed bag. Some places I thought were going to be totally destroyed came out looking fine and other places that were really not hit that bad by wind and storm surge have reefs covered with silt and the corals are being smothered,” said Dr Craig Dahlgren, a marine ecologist and PIMS executive director who studies a wide range of topics related to tropical marine ecosystems.
“It’s going to take a while for us to fully understand why things happened the way they did. I think we’re going to have to go back and do more in depth studies on some of these areas to see how they might naturally recover and what we can do to help them recover. In some cases, the reefs have been fundamentally changed from what they were before.”
Underwater, land debris ranging from trees to metal roofing to construction materials and household contents littered the ocean floor in some places.
At other sites, sediment buried sections of reef, coral, sponges and other organisms in a thick coating of silt.
Other observations included broken corals, reef structure collapse, reduced fish populations and some coral bleaching off North Abaco. It’s too early to say whether they latter is as a result of the hurricane or may have been caused by elevated temperatures pre-Dorian.
“There have been a lot of other studies on coral reefs hit by hurricanes but nothing with such a good, timely data set going into the storm over such a large area. Then, to get back so quickly after the storm hit and to be able to assess so many of these places which were impacted by the storm differently, we are really able to see what the storm did and have a really good before and after picture for this one,” said Dr Dahlgren who from June 2018 to July 2019, led a team of researchers conducting extensive assessments of the health of reefs throughout Abaco and Grand Bahama.
The expedition would turn out to be fortuitous, providing a timely benchmark.
It was funded by the Devereux Ocean Foundation, Disney Conservation Fund, Atlantis Blue Project Foundation, the Angari Foundation and the R/V Angari.
“There were so many unexpected things that took place underwater. This is not a simple case of damage on land equating to reefs destroyed underwater,” Dr Dahlgren noted.
“It’s totally different in some cases and by understanding how or why some reefs fared better than others we can better predict and plan for future storm impacts and how we respond to them to help coral reefs and fish recover in a much more effective way.”
The two-week assessment also revealed a silver lining, said Dr Krista Sherman, senior scientist at PIMS with over a decade of research and conservation experience.
“On a positive note, all the coral nurseries survived, and out planted corals appear to be doing well,” she reported. This will help Abaco and Grand Bahama moving forward as the reefs are essential for supporting the local economy through fisheries and tourism.
Additional, reef sites surveyed within several marine protected areas including Peterson Cay National Park, Lucayan National Park, Pelican Cays National Park, Fowl Cays National Park and Walker’s Cay National Park sustained only minimal or minor storm damage.
Presently, all data from the expedition is being compiled and will be analyzed for a comprehensive report expected to be made available by early December.