The Blake Plateau cold-water coral province is a vast deep-sea reef habitat about 100 miles southeast of Charleston. At an expansive 6.4 million acres, with a coral-dense center of about 1.5 million acres, it is larger than the state of Vermont and was recently confirmed as the largest known deep-sea reef in the world.
The province's white coral "highways" provide shelter for small fish, crabs, shrimp and thousands of other species. It is a connected ecosystem that exists in a world of darkness, crushing pressure and frigid temperatures.
Corals like those that make up the mounds along the Blake Plateau provide important habitat for a variety of marine life, such as this squat lobster, seen perched on healthy Desmophyllum pertusum at a site explored in 2019 approximately 100 miles east of the Florida Atlantic coast.
"We've known that there were cold-water corals in this area for decades," said Erik Cordes, a professor at Temple University and a researcher involved in a yearslong, multi-partner mapping project of the watery province. "What we didn't know was the extent of the reef and the fact that it's one continuous reef system, not a few isolated patches of coral habitat."
Now, significant marine heat waves threaten the reef and the unique ecosystem it supports.
"Over these reefs, we've measured temperature increases in one day of 15 to 20 degrees Fahrenheit," Cordes said. "That feels like it's a fast temperature change to us. But in the deep sea, these corals are used to an incredibly stable environment."
Given the sheer size of the deep sea, and the fact that most of it still hasn't been properly mapped, the distribution of cold-water coral is still "poorly understood," according to a recently published study outlining the mapping project's findings. But they appear to be primarily restricted to waters between 39 degrees and 57 degrees Fahrenheit.
A temperature swing as wide as Cordes describes could easily push coral out of its comfort zone.
CORAL MOUNDS ON THE BLAKE PLATEAU: The black outlines represent subregions of the greater Blake Plateau Cold Water Coral Province. The red line represents a "Coral Protection Area" established by the South Atlantic Fishery Management Council. Note: Two subregions fall outside the current zone boundaries. (MDPI; Esri)
And the Blake Plateau corals aren't the only reef feeling the heat. Rising ocean surface temperatures contributed to the loss of about 14 percent of Earth's coral between 2009 and 2018, according to a report by the Global Coral Reef Monitoring Network.
Writ large, last year was the hottest on record for Earth, and NOAA reports there's a 99 percent probability that 2024 also will rank among the top five hottest years on record. The global temperature average was about 58.96 degrees Fahrenheit in 2023, about 0.3 degrees higher than the previous record set in 2016, according to a calculation from the European Union's Copernicus Programme. Most of the increase can be attributed to greenhouse gases.
“It was record-breaking for seven months. We had the warmest June, July, August, September, October, November, December,” Copernicus Deputy Director Samantha Burgess told the Associated Press. “It wasn’t just a season or a month that was exceptional. It was exceptional for over half the year.”
Global average temperatures in 2023 were about 2.66 degrees Fahrenheit above the pre-industrial era. And while formal climate recordings only go back into the 19th century, the AP reports that evidence from tree rings and ice cores indicates Earth is likely at its hottest point in more than 100,000 years.
According to the National Oceanic and Atmospheric Administration, the upper ocean heat content, which is a measure of the amount of heat stored in the top 6,500 feet of the ocean, also hit its highest point on record in 2023.
Stony coral, found at the top of the crest of Richardson Ridge during Dive 07 of the Windows to the Deep 2018 expedition. Rubble of this species also appeared to form the mounds found in this region.
Cordes said scientists haven't known about this reef long enough to be able to tell if there's been significant change in the amount of living coral on the reef over the years. But well-documented shallower reefs in the Gulf of Mexico that have experienced die-offs could offer a potential lesson on the Blake Plateau reef's past and future.
He added that the Blake Plateau reef still is in "really good shape." But that may not remain so as marine heat waves continue to permeate the coral.
"We expect that this reef has been here for at least hundreds of thousands of years," Cordes said, adding that he wouldn't be surprised if the shallower ends of the reef — around 1,300 to 1,640 feet below sea level — start dying off in the next few years.
"They've endured a lot of different kinds of changes but probably haven't seen changes at the rate we're seeing right now," he said. "The change is happening faster than we think they can adapt."
Though a shipwreck was not found during Dive 07 of the Windows to the Deep 2019 expedition, the site contained several rocky outcrops that hosted a variety of sponges, coral, other invertebrates and fish. Seen here is an alfonsino fish taking refuge under one of the ledges.
Deep sanctuary, for now
While its upper reaches are racked by marine heat waves, the deepest portions of the Blake Plateau coral province could offer a sanctuary from rising temperatures.
Alison Chase, a senior policy analyst for the Natural Resources Defense Council, said it's possible that species residing within the higher ends of the reef might migrate to the cooler depths as heat waves worsen. The reef's deeper portions can be found around the 2,600- to 3,000-foot range.
"As the temperatures for our oceans continue to rise in a warming world, those areas are likely to provide crucial refuge for the deep-sea, reef-building corals and all the other life around it," she said.
An almost perfect inverse effect can be seen in Earth's mountainous regions. A 2021 study in the journal Ecology Letters documented how the natural ranges of certain species move up mountains to escape extreme heat on lower land. That effect is occurring 10 times faster in tropical mountainous regions than in more temperate mountainous areas.
Mission control is pictured during an ROV dive aboard NOAA Ship Okeanos Explorer.
There's just one problem: The deepest portions of the Blake Plateau are a relatively untapped aquatic cash cow. At those depths, valuable reserves of oil and minerals such as manganese can be found.
Much of the Blake Plateau cold-water coral province falls within a protected area established by the South Atlantic Fishery Management Council. Significant areas of the reef are located outside that zone, so researchers have been communicating with the council about expanding the protected real estate to include those areas, Cordes said.
Chase said the management council doesn't have control over non-fishing industries like oil and gas or deep-sea mining.
The area's existing protections from oil and gas interests are scheduled to expire in 2032, according to the NRDC. The debate over who gets access to the depths of the Blake Plateau likely will heat up as that deadline approaches.
A short documentary on the mapping of the Blake Plateau coral mounds. NOAA Ocean Exploration / Provided
Chase said establishing marine sanctuaries, expanding others and protecting the sea floor in that area from heavy industrial work would add essential safeguards to the deep-water refuge areas.
Any significant damage to cold-water corals can take hundreds or thousands of years to repair. Deep-sea corals only grow a few millimeters per year, according to NOAA. For comparison, a human fingernail grows an average of 3.5 millimeters per month.
S.C.'s fishing industry
The Blake Plateau cold-water coral province plays an essential role in supporting the marine life that South Carolina's fishing industry depends on. That's partly why the area is protected by the Fishery Management Council, which is based in North Charleston.
An oreo fish swims above mounds of Desmophyllum pertusum (previously called Lophelia pertusa) coral found at the top of the crest of Richardson Ridge off the coast of South Carolina on the Blake Plateau.
While many species of marine wildlife can migrate to the depths when warm water sweeps over the plateau, most have a breaking point. Just as limited oxygen at the top of a mountain may prevent the upward migration of land-based species, the crushing depths of the ocean can bar marine species from moving downward.
South Carolina's fishing industry depends on the aquatic species that call Blake Plateau's corals home.
Brooke Blosser, the land, water and wildlife project manager for the Charleston-based Coastal Conservation League, said those species can get stuck between the proverbial rock and a hard place.
"At 650 feet, you might have some fish species that do not exist at 2,000 feet, even though the corals can exist at both depths," she explained. "If the corals that are living at 650 feet are migrating down, or suffering as a result of those heat waves, then all of a sudden you're changing the habitat at that 650-feet mark."
One 12-inch deep-sea coral can support up to 2,000 animals, including crabs, shrimp and small fish, according to the Conservation League.
Wreckfish, also known as stone bass, and barrelfish also inhabit the depths of the Blake Plateau around an area off the coast of South Carolina called the Charleston Bump, and could become an alternative commercial species as fish populations in shallower waters decline, according to NOAA. While adult wreckfish can exist down to 3,300 feet, they depend on shallower environments during the early stages of their life cycle.
“Like a coral highway!” Lead scientists on NOAA Ship Okeanos Explorer were stunned to see extensive, dense populations of coral during the Window to the Deep 2019 dive.
Marine heat waves along the Blake Plateau can also have an indirect effect on the health of local fish species. The deep-sea corals can change organic material into nutrients that are sucked upward, where they support an entire ecosystem near the ocean's surface.
According to the Conservation League, bluefin tuna, swordfish and grouper all live in the surface zone above the Blake Plateau and indirectly depend on the nutrients that are sucked up from the depths below. The upper reaches of the system are also home to bottlenose dolphins, loggerhead sea turtles and whale sharks, all of which also feed on the species that consume the coral-filtered nutrients.
Blosser emphasized that the Blake Plateau cold-water coral province is a foundation upon which the Southeast Coast's marine ecosystem rests — and it, in turn, supports the fishermen who depend on the Atlantic to make their living.
