It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Tuesday, January 09, 2024
Can Florida’s corals survive climate change? Fate of one small reef may hold the answer
2024/01/07
Cynthia Lewis, director of the Keys Marine Laboratory, points to staghorn corals that were recently bleached in an ongoing, unprecedented marine heatwave.
- Max Chesnes/Tampa Bay Times/TNS
When marine scientist Ian Enochs jumped into the water at Cheeca Rocks, a small reef in the Florida Keys known for vibrantly colorful corals, what he saw shook him to the core.
“Literally everything was white,” said Enochs, a research ecologist with the National Oceanic and Atmospheric Administration in Miami. “It does not look normal at all, it’s just like a different reef.”
It was July, still early in what would become the hottest summer on record in South Florida, and Enochs waswitnessing a mass event bleaching — a telltale trouble sign that corals are struggling in abnormally hot ocean waters. Keys reefs have been hit periodically by bleaching over the decades and recovered, the corals weakened but still alive. But prolonged bleaching can prove fatal. To Enochs, this looked severe and potentially lethal.
“The flesh, the tissue (of the soft corals) were just falling off of them,” Enochs said, “They were literally falling apart before our eyes.”
Now, as ocean temperatures cool, teams of scientists are engaged in an unprecedented effort to assess not only the heat wave damage but the future of South Florida long-ailing reef tract.
Cheeca Rocks, Enochs’ prime study spot for more than a decade, had been considered among the Keys’ healthiest reefs. In the months and years ahead, it will serve as a living — or dying — laboratory. The fate of its corals will help tell scientists like Enochs how and if reefs can survive climate change, which is driving sea temperatures to new highs. Record sea temperatures off South Florida
At Cheeca Rocks, Enochs’ team from NOAA’s Atlantic Oceanographic and Meteorological Laboratory on Virginia Key , recorded a temperature near 93 degrees Fahrenheit. In other parts of the Keys and up both Florida coasts, ocean surface temperature soared 4, 5 or more degrees above historic averages. It approached 100 in the some shallow areas. One sensor in the grass flats off Manatee Bay in Everglades National Park hit a staggering 101.1 degrees Fahrenheit. Consider that hot tubs typically range from 100 to 103 degrees.
“Globally, August 2023 set a record for the highest monthly sea surface temperature anomaly of any month in NOAA’s 174-year record,” the federal agency later reported.
Cheeca Rocks, a shallow nearshore reef popular with snorkelers, is particularly vulnerable to the hot weather and water. Butmuch of the South Florida reef tract — which stretches from off Palm Beach County down to the Dry Tortugas — saw impacts.
It was starkly evident to scientists and divers who frequent South Florida reefs. During bleaching, coral shed the algae that give them their dazzling colors and provide them important nutrients. The bleaching victims, with all or swathes of their hard exoskeletons turned pale white, stand out like bones.
It may take a year to see how much recovers and to assess the final toll. But it’s already clear that the record heat worsened what has been a precipitous decline for corals off South Florida. In just a half century, the undersea reefscape bordering the coast has profoundly and permanently changed. Two species of large and spectacular branching corals, staghorn and elkhorn, once formed dense forests and served as the primary reef builders in South Florida. Since the 1970s, scientists estimate 90% of those have disappeared. Losses have been even higher in the Caribbean.
Diego Lirman, a University of Miami associate professor in marine science, has monitored the region’s reefs for 30 years. When he started working in the field of disturbance ecology — research focused on forces that can wipe out existing systems — the typical reef boasted about 20% coral cover. Now, hard coral survives on just about 5% of the bottom. Soft corals, algae and other marine life have moved in instead, altering the marine food chain and reducing the shelter and prey that reefs provide to an array of marine life.
The forces of destruction that Lirman and other scientists have identified are many. Over the decades, Florida’s reefs have been hammered by humans with everything from pollution and dredging sediments to boat anchors, fishing lines and diver fins. In 1990, the 3,843-square-mile Florida Keys National Marine Sanctuary, which stretches from Biscayne National Park to the Dry Tortugas, was created to help protect reefs from continuing damage.
Anchor buoys were added and no fishing zones established around major reefs. Divers and snorkelers are taught not to touch corals and are typically now much more attuned to the fragility of the undersea world they have entered. Those steps have helped reduce coral damage loss from tourists, divers and anglers. Breeding heat-resistent corals
But battling climate change is a whole other level of challenge. Scientists believe rising sea temps have driven the increasing impacts from invasive smothering algae and helped spread coral-damaging diseases, from black-band and white-band disease to white plague and stony coral disease. It’s also made the ocean more acidic, which makes it harder for corals to built their hard skeletons. Weakened by repeated bouts of bleaching, some corals may not be healthy enough to survive all the mounting stressors..
One hope is to breed more resilient corals. Scientists have been growing coral in labs and underwater nurseries for years but newer tools like genetic sequencing have provided perhaps the latest and and maybe last chance for eventually reviving dying reefs. The hope is to pinpoint the most heat-tolerant genetic strains — ones that if cultivated, regrown and replanted on offshore reefs might have the best chance to survive and thrive.
The complication is that some coral strains may do better with hot water but might prove less resistant to disease or other issues. So it’s essential to have a selection of strong corals for the future and threats to come, some of the perhaps still not identified.
“We know there is no such thing as a super coral,’ said Phanor Montoya-Maya, program manager for theCoral Restoration Foundation in Tavernier. “We need to ensure that every single genotype that is alive today has the chance to live beyond these conditions.”
That’s part of the mission at NOAA’s Experimental Reef Laboratory on the campus of UM’s Rosenstiel School of Marine, Atmospheric, and Earth Science. NOAA’s Enochs and UM’s Lirman co-lead the lab and $4.2 million project launched last month involving seven different academic and research institutions that amounts to an largest collaborative effort yet to assess the health and future of South Florida’s reefs.
At the lab, scientists can manipulate conditions from temperature to water quality to assess the strength of samples of various species and genetic strains of corals. Those samples can be fragmented to grow as new individual corals. Then those small corals can be moved to nurseries in Biscayne Bay or elsewhere or eventually replanted on natural reefs.
“We watch them grow,” Lirman said, “and we build our restoration stocks.”
Lab-grown corals alone can’t replace all that has disappeared but, if they’re hardy enough, they might be the seeds for stronger natural reefs. Reef scientists turned emergency responders
The unprecedented summer sea temperatures turned many marine scientists into emergency reef responders, with an array of agencies and universities scrambling to save what they could. There was nothing to do about natural reefs but they could try to save the string of managed underwater coral nurseries all along the coast where researchers are growing thousands of coral fragments — the stock for future restoration efforts.
The staff at the Coral Restoration Foundation realized they had to move quickly to save their own four field nurseries, risking pulling them out of the ocean and moving them to land tanks with controlled temperatures — at least until the ocean waters returned to normal. Other groups did the same, pulling corals from offshore and putting them into tanks, creating a sort of Noah’s Ark of genetic diversity to ride out the heat wave.
In one case in August, UM scientists also did the opposite — planting nursery and lab-grown corals on the seafloor two miles east of Key Biscayne. It was a study that boiled down to survival of the fittest. Those corals, previously collected from a range of reefs off South Florida, are being put to a critical real-world heat-stress test.
Some likely won’t make it. But if some do, it could help identify coral types more likely to endure future climate change.
“We don’t want to keep doing this just to watch our corals die,” said UM’s Lirman. “We need to learn from the survivors.”
As waters cooled in late November, Montoya-Maya and other foundation staffers were able to return about 1,500 to field nurseries in the waters off Tavernier.
They carefully transferred the corals from a tank into coolers on a boat After about a 30-minute boat ride, scientists jumped into the water to pass down the shelves bristling with nubs of healthy corals. The shelves, made out of PVC tubing and mesh, were then attached to nursery “trees” in waters from about 10 feet to 30 feet deep.
Overall, scientists say that it will be hard to tell how much coral will rebound and survive to next summer. They will have a better idea as they collect more data in the coming year. But if the losses at offshore nurseries are any indication, the toll could be severe. As the year came to a close, the Coral Restoration Foundation estimated they’d lost just over half their nursery corals.
Since this summer’s heat wave, Enochs and his team have been back to Cheeca Rocks as often as possible. They are monitoring areas that are recovering, keeping an eye out for both outbreaks of disease among the weakened corals and natural pathways toward healing.
Was the biggest bleaching event perhaps ever the final nail in the coffin for the Keys’ reefs? It’s too soon to tell but at Cheeca, Enochs retains some hope.
“Things are not great, but they could be worse,” said Enochs. “And the fact that they aren’t worse means there’s a way out of this.”
When imagining corals, the picture that comes to mind is usually a stationary one: a garden of rock-like structures covering sections of the ocean floor. Reef conservation efforts typically focus on preserving established coral and protecting them from known stressors such as pollution, overfishing and runoff from coastline populations.
However, new research near Miloliʻi in the southwestern part of Hawai’i Island shows that identifying and protecting marine ecosystems, both down-current and up-current of coral reefs, specifically areas where coral larvae are more likely to survive and thrive, is crucial to future coral conservation and restoration efforts—especially as reefs face increasing pressure from the devastating effects of climate change.
The research, completed by Arizona State University scientists and their collaborators, appears in the current issue of Proceedings of the National Academy of Sciences.
Additionally, the ʻĀkoʻakoʻa Reef Restoration Program, a regional effort that fuses cultural leadership, multi-modal education, advanced science and government engagement, backed the research.
Carlson says this type of collaborative work—partnerships combining local, indigenous knowledge and Western science – is crucial to mapping out a future that ensures the survival of coral populations.
“There’s a lot of indigenous knowledge about coral spawning and fish populations in West Hawaiʻi. In this study, we addressed an open question: how connected are coral populations between embayments along this coastline?” said Carlson. “What we essentially found is that the major factors in helping the coral keiki, known as larvae, settle down and survive are the nearshore current and the structure of the reef.”
The study shows that the larvae more often settle in and inhabit areas with large boulders and uneven surfaces, or “chunky features,” said Carlson, who is also a Chancellor's Postdoctoral Fellow at the UC Davis Bodega Marine Lab. Adult coral will spawn millions of larvae into the water column and those larvae prefer to settle in places with large knolls and boulders.
This discovery is good news: these kinds of seafloor features have been mapped via ASU’s Global Airborne Observatory, a highly specialized aircraft that uses several types of remote sensing technologies to track both underwater and land-based habitats. This means that the researchers have the capability to help find and map priority reefs for conservation and restoration.
“This is foundational research in several important ways,” said Asner, the study’s senior author. “First, it gives us an understanding of the connectivity of different parts of reefs along our coastline and tells us the level of connectivity in the context of the birth, settlement, and growth of corals miles apart. Second, our unique remote sensing capabilities can identify reef sites where coral restoration could be most viable in the future. Finally, these findings provide a critical building block for future restoration efforts by our ʻĀkoʻakoʻa team and collaborators.”
The group’s goal is to preserve and restore vitality to Hawaii’s coral reefs and coastline health.
"We as lineal descendants of the Miloliʻi area have always relied on the reef for our ʻOhana (families). Our reef is our sustenance and is of enormous cultural value to us." said Kaʻimi Kaupiko, president of the non-profit organization Kalanihale, which manages the Miloliʻi Community-based Subsistence Fishing Area (CBSFA) where the study took place.
Asner said the intertwined nature of reefs along Hawai‘i’s coastlines is crucial to consider in reef protection strategies. Narrowing in on one area without consideration for the reproductive corridors of corals, he said, would be akin to worrying about planting trees in a certain place and not thinking about the forest as a whole. This sentiment is echoed by Martin, who said reef connectivity is an underutilized tool in reef restoration efforts globally.
“In Hawai‘i and worldwide, we're trying to figure out where we should place protections and restore areas to help reefs,” Martin said. “This study is highly technical, but it needs to be part of that conversation and part of that work because if you aren’t protecting the up-current reefs, you are cutting off important reproductive areas.”
Martin said reef restoration could, for example, expand a protected area of reefs beyond just the spots that have more dense coral coverage on the ocean floor: protection efforts would also be needed in the upcurrent path that the coral larvae traveled through before they settled in a new location.
Asner adds that this research could very well help conservation efforts expand to much greater distances than have been achieved previously.
“These kinds of studies of connectivity, flow, and movement are needed because the west Hawaiʻi island coastline is longer than the whole circumference of any other island,” Asner said. “We have a lot of degraded reefs along our coastline, so knowing where and how to help baby corals thrive is fundamental to the ʻĀkoʻakoʻa restoration effort.”
"Our students participated in the coral study, and that also helped us to connect the dots between cultural knowledge and Western science,” said Kaupiko. “The study supports our CBSFA by showing that our area is ecologically connected, and thus it needs to be managed and protected as one connected reef and coastline."
Through the long-standing community collaborations that have shaped the ʻĀkoʻakoʻa program, this coral reef work reflects both cultural knowledge and scientific research. This type of approach is crucial in places like Hawai‘i, where a deep connection between coral reefs and people calls for research that serves them both.
By Sandra Leander and Kateyn Reinhart
A new coral colony is established on a rock. A colony of the native Hawaiian coral Pocillopora meandrina settles and grows along the South Kona, Hawaiʻi Island reef.
Coral polyps: Close-up view of the Hawaiian coral Porites compressa growing on a reef in South Kona, Hawaiʻi.
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