An early marine heatwave in Florida made international climate news over the summer when never seen before sea temperatures reached over 100 degrees in August of 2023, according to NOAA. An emerging El Nino partially caused the hot water, but climate change produced record heating across the planet's sea surfaces, including Florida’s Atlantic and Gulf coasts.
Hearts in Florida were broken as five-year efforts to reintroduce lab-grown elkhorn and staghorn corals in the Florida reef succumbed to coral bleaching and disease from global warming and agricultural and urban runoff.
The corals reproduce in August during the peak hurricane season. After this year's spawning, over ninety percent of the parent corals died due to heat stress, according to reporting by Jack Prator of the Tampa Bay Times.
Prator noted that coral reefs occupy only one percent of the sea bed surface but account for more than twenty-five percent of marine biodiversity.
Elkhorn and Staghorn provide crucial habitats for many marine species, including fish populations in Florida and the rest of the Caribbean, providing protein for humans.
The expiration of Florida corals, or functional extinction, is widespread, meaning they cannot reproduce to make a difference in the survival of Florida’s coral reef without human assistance.
Once bleaching occurs, many corals die and are soon covered by algae and sea grass. It is the final blow to coral colonies without intervention from scientists. Once the water temperatures cool enough in the Fall, some corals can regenerate if given enough time, and the reintroduction of herbivores will play a significant role in their recovery.
Inside Climate News wrote in August.
“There is a big concern among the coral reef scientific community that we are potentially walking into another global bleaching event, based on what we know and what history has taught us,” said Derek Manzello, coordinator of NOAA’s Coral Reef Watch Program. “This is a very serious event; Florida is just the tip of the iceberg.”
It will be months before scientists fully understand the scope of the problem, but they say they are seeing “thousands upon thousands” of miles of corals undergoing bleaching as a result of heat stress in Belize, Colombia, Costa Rica, Cuba, El Salvador, Mexico, Panama, Puerto Rico and the U.S. Virgin Islands, with Florida most impacted.
To help mitigate the damage of the algae crisis, the Mote Marine Laboratory in Sarasota, FL, has raised hundreds of thousands of native Caribbean King Crabs, also known as Spider Crabs. The mission is to create an army that can cover the dying and dead corals and consume the algae and grasses now covering the largest coral barrier reef in the United States. The release won't save the corals from bleaching, but it does give them a chance at survival in the short term by eliminating other threats.
Coral reefs have long been considered the first casualty of climate change and its effect on biodiversity. The collapse will kick in high gear once global temperatures reach 1.5 Celsius, per the World Economic Forum (WEF).
Ninety-nine percent of tropical reefs could be gone within the 2030s, the WEF warns. The best hope to protect oceans is to slash fossil fuels immediately. (A few years ago, the projection for the loss of tropical corals was in the 2050s.)
Scientists determined the impacts of the climate crisis in the 1990s, including the loss of most corals. The only thing they got wrong was the speed of the changes occurring. Everyone thought we had more time before we saw events of this sort. Tragic.
From a Mote Marine Study published in 2021:
Typically, this degradation is manifested by a dramatic shift in benthic community dominance from corals to fleshy seaweeds, representing a phase shift to an alternative ecological state 6–8 that negatively influences the growth, reproduction, recruitment, and survival of corals.10–12
Evidence of the long-standing competition between seaweeds and corals is exemplified by the coevolution of coral-fish symbiotic relationships in which corals damaged by seaweeds release chemicals to signal the aid of herbivorous fish.13 Overgrowth of seaweeds may also promote the proliferation of reef sponges in a ‘‘vicious circle’’ nutrient cycling between seaweeds and sponges to the detriment of corals.8,14
On Caribbean coral reefs, the explosion of seaweeds is caused by coastal eutrophication and the loss of grazers,15 the most dramatic example being the near extirpation of the long-spined sea urchin (Diadema antillarum) in the early 1980s, a catastrophe caused by an unknown pathogen.16
Overfishing herbivorous reef fishes and the die-off of shelter-providing branching corals17,18 have also resulted in a loss in fish grazing on reefs despite regulations to reduce their overfishing.18,19
In at least one instance, the void in the grazing niche space once held by fishes has been filled by small invertebrate herbivores released from competition and predation by fish.20
In many places, reefs have likely degraded beyond a threshold whereby natural recovery of corals is possible. This prospect has sparked numerous restoration efforts in which corals are transplanted from nurseries onto degraded reefs to bolster coral biomass and sexual reproduction of corals. Thus far, this approach has not returned reefs to their former state 21. Some argue that unless the overgrowth of seaweeds unencumbers the underlying reef habitat, reefs will remain largely depauperate of live coral and suffer degraded ecosystem function.10,21,22
We discovered a potential solution to this ‘‘seaweed dilemma based on our previous research with the Caribbean king crab (Maguimithrax spinosissimus), a large, cryptic, and primarily herbivorous crab native to the Caribbean and western Atlantic Ocean. This species consumes seaweeds at rates that exceed nearly all other fish or invertebrate grazers in the Caribbean;9,23,24 they even eat chemically and physically defended algae (e.g., Halimeda spp.) that other grazers avoid.9
The study conclusion:
In summary, our experiments provide compelling evidence of the positive ecological effects that Maguimithrax can have on coral reefs overgrown with seaweeds and demonstrate their utility as a driver of recovery by shifting reefs away from their current seaweed-dominated state. The generality of our results was validated by nearly identical results in two separate field experiments conducted at different locations and in different years.
Of course, coral can not migrate to avoid rising temperatures. But in some areas, researchers are bringing shade to them. It won't save coral by itself; thousands of miles of shading coral reefs would be needed, and that will not happen. Besides, it is not the sun that is killing coral. It is rising temperatures. The result will be a Marine food web collapse, per Science Alert reporting in 2015.
A quick note: in 2022, two hundred Spiny Sea Urchins were released in the Florida reef. The spiny creatures aid the reefs by eating the fleshy plant growth caused by pollution runoff. Forty thousand are being raised in the Florida Aquarium; they will be reintroduced to the reef, as well.
Some marvelous marine biodiversity tweets.