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Coral Reefs – Past, Present & Future

Instructor David Jefferiss

The future of the Coral Reefs in Key Largo by David Jefferiss
The current situation:

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:

  • Climate Change
  • Pollution
  • Over fishing
  • Disease
Carysfort Reef

Carysfort Reef off Key Largo

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.

Pickles Reef off Key Largo

Snapper Ledge

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.

Hens and Chickens Reef in the Florida Keys

Hens & Chickens Reef

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.


Bleached Corals Great Barrier Reef

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 CRF helping our reefs for scuba diving!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.


Molasses Reef - Key Largo

.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.

If we can be successful in these efforts who knows?

Corals on the Great Detached reef - Australia

Corals on the Great Detached reef – Australia

Great Barrier Reef - Australia

Great Barrier Reef – Australia

“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!

David Jefferiss
Sea Dwellers Dive Center of Key Largo

Key Largo Dive Sites

The Key Largo Dive Sites – Something for Every Diver!

You can drive from Miami and be Scuba Diving in an Hour!

Key Largo is the first island you drive to from the Florida mainland. About an hour drive south from Miami you will come to the bridge at Jewfish Creek, considered the “entrance” to the Florida Keys.  Once across this beautiful bridge you are in Key Largo, commonly called the “Dive Capital of the World”.  Many Key Largo dive sites are just minutes away from you at this point, and you have entered the Dive Capital of America”!

The “Florida Keys Reef Track” is the only coral barrier reef in the continental United States, and is the third largest coral barrier reef in the world.  According to Wikipedia, “the densest and most spectacular reefs are found to the seaward of Key Largo (in and beyond John Pennekamp Coral Reef State Park) and Elliott Key where the two long keys help protect the reefs from the effects of water exchange with the Florida Bay.  Florida Keys Reefs Map.

Key Largo Dive Sites are for every level!We can humbly confirm this from direct experience!  Scuba Divers that are “in the know” understand that Key Largo scuba diving is the best in the Florida Keys. All the Key Largo Dive Shops here reflect the diversity and abundance of marine life found in these protected waters. The Florida Keys National Marine Sanctuary

Key Largo Dive Sites for New Divers & Students

Most of our Reef Dive Sites are in relatively shallow water depths, making them very attractive to beginning divers as well as student scuba divers looking to complete their certification dives in clear, blue, shallow reefs with lots of marine life!  These shallow reefs provide the ideal environment for newly certified divers and student divers looking to complete their training on a reef. We go out to these Key largo dive sites daily, every day of the year, and can provide the scuba training any day of the year also!

“Key Largo Dive Sites are Perfect for Newly Certified or Student Scuba Divers”Student on Key Largo Dive Sites with Sea Dwellers!


Key Largo Dive Sites for Advanced Diving

Key Largo also offers advanced Dive Sites, and is home to several deeper wrecks including the world’s largest artificial reef, the 510 foot USS Spiegel Grove.  Another artificial Key Largo dive site is the US Coast Guard Cutter “Duane”, sitting upright in about 125 feet of clear blue water. These 2 plus a few others provide Key Largo dive sites for the seasoned scuba diver and for those who are interested in Advanced training.

Key Largo Dive Sites – Our Best – the “Dive Capital of the World”

Abundant marine life on these Key Largo dive sites!

The most popular reef in the Florida Keys, as well as anywhere in the Caribbean, is the Molasses Reef Dive Site. It is the largest, most lively reef and according to the REEF Foundation, some of the greatest abundance and diversity of marine life in the Caribbean.  This is confirmed, once again, unofficially by our scuba divers who absolutely love this Key largo dive site!

Bottom line, Key Largo is known for its shallow reefs and deep wrecks. The shallow reefs provide world class diving for scuba divers of all ages and the deep wrecks offer excitement for scuba divers of all levels of training. Divers find out quickly why the diverse Key Largo dive sites have enabled the Florida Keys to be known as the “Dive Capital of the World”!

– Your Sea Dwellers Dive Center Staff



Sea Dwellers Dive Center of Key Largo 99850 Overseas Highway Key Largo, FL 33037 1-800-451-3640