NASSAU, Bahamas – A new, rapidly spreading outbreak of Stony Coral Tissue Loss Disease (SCTLD) has infiltrated nearly 40 miles of Grand Bahama’s southern coastline, killing a wide range of coral including some that are already endangered.
“Corals are the engineers that build the entire marine ecosystem. Without them the ecosystem collapses. The reefs lose their function. It makes a fundamental change in the ecosystem from what we’ve seen in the past,” said Dr Craig Dahlgren, a marine ecologist with the Perry Institute for Marine Science (PIMS) who led the research investigation last month.
“The greatest infection rates and greatest amount of mortality were close to Freeport, close to the port. For some species, 90 percent of the corals were either dead or dying. It was very widespread at that point. In those severe cases, there is little you can do to help those corals.”
Silent and deadly, if the outbreak goes unchecked scientists believe the fallout could prove worse than the 1930s marine disease which wiped out sponging beds across the country and led to the crash of the Bahama Islands then number one industry, sponging.
Although corals typically face a number of threats, including nearly a dozen different diseases, SCTLD poses the single greatest hazard since roughly half of the coral species in the Bahamas are susceptible. Other diseases usually infect maybe two to three species. SCTLD is also more lethal and spreads faster.
The report for Grand Bahama submitted to government agencies on March 16, linked the introduction of the disease to The Bahamas with cruise ships and large commercial vessels.
“It is more likely that SCTLD reached Grand Bahama through vessel traffic into and out of Freeport. Most likely ballast water from large commercial vessels (cruise ships or cargo ships) coming from Miami or another infected area are the culprit and may present the greatest threat to spread of the disease,” the report read.
“Since its introduction, however, the disease has spread over vast areas on shallow reefs, probably due to alongshore currents.”
The ballast water ships carry for stability can contain thousands of aquatic or marine microbes, plants and animals, which then gets transported across their route. Untreated ballast water released at the ship’s destination could potentially introduce a new invasive marine species.
According to the International Maritime Organization (IMO) hundreds of such invasions have already taken place, sometimes with devastating consequences for the local ecosystem.
Had the waterborne disease been reported sooner, scientist, marine biologists and environmental protection agencies could have done a better job of removal and containment, potentially saving more reefs around Grand Bahama.
At least one dive shop claimed to have seen impacted coral as early as July 2019. However, it wasn’t until late December and January of this year that information began trickling into the relevant authorities.
Back in October, PIMS, the non-profit organisation committed to protecting oceans through timely research, conducted reef surveys to assess the impact of Hurricane Dorian to the marine environment.
Scientists surmise only a very tiny percentage of corals in Grand Bahama had likely been touched by SCTLD at that time, since no signs of the disease was visible on the reefs surveyed. However, no surveys were conducted near the port area.
Dorian may have played a role in transporting the disease through water movement, advancing SCTLD progression to corals already weakened by storm-related stress.
“We are already behind. We need to act now,” said Dr Dahlgren, an internationally recognised expert in a wide range of areas related to tropical marine ecosystems.
Over four days, from March 12-15, a team of researchers conducted rapid assessment of 25 Grand Bahama reefs. That number included 18 shallow reefs spread between High Rock in the east and Bootle Bay in the west, one site in Lucayan National Park and one in Peterson Cay National Park.
Seven deeper reefs were also assessed – one in Lucayan National Park, two between Lucayan National Park and Peterson Cay National Park, and four sites between the Grand Bahama Waterway and the entrance to Bell Channel.
“The highest concentration of dying and dead corals appeared to be around the port. That’s why I think that transmission in ballast water from shipping, whether it’s Florida or some other place which has the disease already, is the likely culprit of why it got there, versus if it came in on ocean currents. We would have seen a very different pattern if that had happened,” said Dr Dahlgren. (CMC)
