Rebirth of a Coral Reef
by Gary Carlson
The dive site of choice for the last year or so with my oft dive buddy Mickey Charteris is just off the furthest west point of the island of Roatan. It is a huge area rarely dove by those on a casual dive holiday (vacation) which exists far off shore at depths of 25 to 30 meters (80 to 100 feet). The area sees a lot of unpredictable current coming from the depths on either side of the island which carry food and nutrients across the plateau allowing for incredible growth and abundance of all local sea life. The current brings up water from the depths, it is rarely still, and the temperature is quite consistent.
Last summer around August we started noticing the brown plate corals starting to show signs of coral bleaching down in the 80 to 100 foot depths we had been diving. No sooner noticed than a coincidentally scheduled meeting on coral bleaching by Ian Drysdale of Healthy Reefs Initiative was called which we attended to find to our shock that we were in the middle of a major, and possibly terminal bleaching event. The lagoons and shallower dive sites not subjected to a lot of current were heating rapidly and were already far above the range of healthy coral.
Coral bleaching is coral’s defensive response to elevated water temperatures. Coral’s vibrant colors, covering most of the spectrum, are actually created by a symbiotic relationship the coral has with the algae zooxanthellae. Corals are completely dependent on the algae. They would not be able to survive without them since they can’t produce sufficient amounts of food. The zooxanthellae can provide up to 90% of all the nutrients necessary, in most cases all the carbon needed for the coral to build the calcium carbonate skeleton. Hard corals are reef builders and the symbiotic relation enables the coral to grow faster, which is not only partly responsible for the existence of coral reefs, but also vital and necessary to the coral itself.
Coral’s ideal temperature range is between 73 and 84 degrees Fahrenheit. Above this the all too valuable algae exits the situation. I am told where it actually goes is still a mystery of science, but leave it does, taking the coral’s color and life sustaining nutrients, and leaving behind a brilliant white skeleton. This is not death, yet. The coral can sustain itself over a period of four to six weeks at elevated temperatures without succumbing by excreting a clear mucus covering, but any longer and the inevitable cannot be avoided, and the coral dies.
In the bleaching meeting volunteers were being asked to take surveys to determine the extent of the bleaching in different areas on the reef and the actual impact. At this point, the second week in September we were in the bleaching event about four to five weeks, and rapidly reaching the point of no return. If you remember the hurricane season of last year almost wiped out the windward islands of the Caribbean, with the storms devastating Anguilla, Barbuda, the British Virgin Islands, St. Martin / St. Maarten, the US Virgin Islands, and Turks and Caicos, Dominica, Puerto Rico, just missing Mar a Lago. Although devastating, these summer storms are the coolers of the Caribbean Sea. Normally the hurricanes come along the seas north of South America, heading west nicking Nicaragua, bumping the Caymans, passing north of Roatan and pestering Belize, Mexico and Texas, while cooling the water around the Mesoamerican reef. Not this year. The two hurricanes of the western Caribbean, Harvey and Nate originated far north of Honduras, in the Gulf of Mexico.
Mickey and I headed to one of our favorite dive sites, Seaquest to check out the extent of the bleaching personally, and it was ominous. Death was in the water. The reef looked like it had a couple of inches of snow on it. Over 80% of the coral had bleached. The lagoon temperatures were in the 90’s! Even the fish were noticeably torpid and sluggish. It looked like all that was left to do was document the demise.
Then came the rains. On the 26th of September it rained almost an inch, and the surface of the sea chilled (relatively). Putting our heads together Mickey and I came up with the idea of documenting the (we hoped) coral recovery. The plan was to use Mickey’s photography equipment, his extensive knowledge of the reef, his incredible photographic skills, and his hours of editing, along with my diesel to photograph multiple corals every week to show the stages of recovery. The rains continued, adding to the rainiest wet season on record. Waves and water not seen in the last few years came back with a vengeance, crashing on the reef, cooling the waters, and making life suitable for the zooxanthellae algae and the coral to hook up again.
Below are two slide-shows showing the coral bleaching, and recovery of two different species of coral here on Roatan at the divesite Seaquest. Images and production – Mickey Charteris
Unfortunately this colony of Boulder Star Coral below did not make a complete recovery. The central portion succomed to the elements.
We are literally overjoyed to announce that there was an 85 to 90% coral recovery this year! It was slow coming back, but the reef has returned to being healthy, and the fish etc. are back to frolicking in our pristine waters.
However, we are watching the waters, the calendar, and the thermometer with some trepidation.