NOAA estimates that US coral reefs, including the ones we dive on regularly in the Florida Keys, contribute about $3.4Bn annually to the US economy. Worldwide some 500 million people depend on reefs for food and income. In addition, barrier reefs like Molasses reef and French reef that we dive on the Sea Dweller III here in Key Largo provide protection to the shore and reduce potential flood and storm damage.
Coral reefs today are suffering as a result of multiple threats. Some global and some local:
In the fairly recent past, Carysfort reef, north of Key Largo was a model of a healthy reef, with huge stands of Elk horn coral. This picture from 2012 shows some decline. It is estimated that some 90% of the coral on the reef has been lost today.
When we talk about coral, most often we are referring to Stony Corals which are the basic building blocks of the reef.
Stony Corals come in several types. Branching corals, like the Elkhorn coral on Carysfort reef. Brain corals, like the one on the right on Snapper ledge.
Or encrusting coral. This one is from Hens and Chickens, just south of Key Largo. Stony Corals live as a result of a symbiotic relationship between the coral polyp and an alga called “zooxanthellae”. It is this alga that gives the coral it’s natural color. The alga is a plant which photosynthesizes to produce sugars. The coral is an animal which consumes the sugars produced by the algae and excretes waste. The algae use the waste as a type of fertilizer to grow.
When the coral is stressed, by any of the mechanisms described above, the coral expels the algae. This results in what is called coral bleaching. This occurs most often when ocean temperatures rise above normal. This photograph from the Great Barrier Reef in Australia shows what the coral looks like when this happens.
Research from the Great Barrier Reef has shown that branching corals are more effected by bleaching than the massive corals like brain coral. Coral bleaching on its own does not necessarily kill the coral. It can and does recover but bleaching makes the coral more susceptible to disease which will kill it.
What can a scuba diver do?
Obviously the most important action that mankind can take to stop the loss of coral reefs is to reduce global warming. Unfortunately, the United States, unlike 195 other nations, decided to withdraw from the Paris Climate accord in 2017. There is hope however that sanity may prevail. Many state, local and business leaders are taking action to meet emission reduction targets despite the Federal government.
Another way that we can take local action to resolve a global problem is by reducing pollution. The Florida Keys is spending $939m to replace the old septic tank systems with wastewater treatment plants. This has already shown measurable improvement in the water quality on our reefs.
The third way is to try to replace coral by growing it in a protected nursery and transplanting it onto the reef. This photo shows the Coral Restoration Foundation (CRF) nursery in Key Largo where stag horn coral is being grown to be replanted onto our reefs. The CRF has a 5 year grant to replant Carysfort reef with stag and elkhorn coral.
.Science is working on several innovative approaches to reverse the loss of coral cover on our reefs. One is to introduce higher temperature resistant algae into the coral allowing it to thrive in warmer water. Another is to transplant corals from warmer waters such as the Arabian gulf where corals have a naturally developed tolerance to higher temperatures. Perhaps one of the most si-fi solution being worked on today is through genetic engineering of the algae to produce more temperature resistant strains. This uses state of the art gene editing using CRIPER/Csa9 tools.
“Molasses Reef is still a beautiful reef. But perhaps one day we can look forward to scuba diving on Molasses reef with additional branching corals transplanted from places like the Great Barrier Reef… like the ones in these photographs!”
Anything is possible, and there is hope if we take action and work together to save the reefs of Key Largo and the world!
Sea Dwellers Dive Center of Key Largo