Welcome to the Reef
Down in Key Largo, about six miles offshore, there lies a reef of beautiful clear water, with many fish flitting around, sea fans waving in the current, and a happy me drifting about. This beautiful place is well known as Molasses Reef.
History of Molasses Reef
Molasses Reef is part of the Florida Keys National Marine Sanctuary, meaning that it is in a protected area; no fish, shells, or even rocks can be taken from here. The famous saying goes: “Take only pictures, leave only bubbles”. The reefs here in the Keys maintain this mantra due to their protected status. Part of the reason for this status is the sensitivity of the organism that makes up most of the reef, the coral. Molasses Reef was well known for its boulder corals that took up large areas of the reef and towered over you as you swam by them.
With its proximity to the warm, clear waters of the Gulf Stream, Molasses Reef is visited by divers worldwide. You may be wondering how Molasses Reef got its name, this goes back to an old legend about a huge barge that ended up running aground on the reef. This barge was rumored to be filled with large barrels of molasses, hence the reef’s name.
Life on the Reef
The reef was incredible. I had never seen a parrotfish up close before, and they happily scraped away at the coral skeletons to get to the algae growing on top and leave behind fresh calcium carbonate sand when they had digested their fill. A Green Moray Eel sat perfectly still hiding beneath an outcropping, with only the eerie opening and closing of its jaw as it stared at us.
Naturally, the best part was the nearly seven-foot-long nurse shark hanging out beneath another coral ledge, chilling on the floor even as I swam over and bawled my eyes out at how serene and beautiful she was. She was a patient shark, that’s for sure, I was only 2 feet above her head for several moments and she just hung out while we took a billion pictures of her.
The life here on the reef was evident, fish could be spotted everywhere you looked. Even on the rocks and corals you could see Christmas tree worms popping back into their holes to hide from us as we swam by. Sea fans moved in time with the current, and they were. On this small section of reef, I’m sure there were hundreds of species we didn’t even get to see.
Parrotfish and Bioerosion
One of the coolest events we saw here at the reef was the parrotfish. We saw lots of Stoplight Parrotfish and Midnight Parrotfish munching on the algae covering some of the corals in the reef. These parrotfish perform an important role on the reef called bioerosion. Bioerosion is the process by which an organism will erode away hard substrates like limestone rocks, wood, or even coral skeletons. The parrotfish shown here are scraping algae, which is their main food source, off the coral by using their beak-like mouth. During this process, they will also scrape off bits of calcium carbonate from the coral skeleton and eat it with the algae. The calcium carbonate is then digested by the parrotfish and pooped out as fresh new sand for the reef. Parrotfish provide about 1,000 pounds of fresh sand to reefs in one year of their life, making them crucial to the health of the reef. For our living corals, this process is what keeps any excess algae from overgrowing the polyps and causing issues with photosynthesis.
Marked with Death
While the reefs in the Keys are a wonder to look at, filled with beauty from every angle, you can only imagine what this or any other reef around here must have looked like 50 or even 10 years ago. While the colors of the reef were still spectacular, there was something off about the place. There weren’t quite as many fish as you might expect around, the coral wasn’t quite as bright here. Some even looked dead, covered with the algae or encrusting sponges that take over when a coral’s life ends.
For a biologist, seeing this side of the reef puts a damper on the joy. While seeing a reef for the first time in person is quite literally one of the best experiences of my life, knowing what is changing is tragic. This being a protected area, there should be no touching the corals or taking anything from the reef, but this area isn’t managed 24/7 so there’s no telling what goes on after hours. Stepping on or touching coral can damage the small polyps that cover the skeleton, and stress them to the point that they may get diseases or even bleach themselves.
Coral bleaching is the expulsion of symbiotic zooxanthellae from the coral tissue, leaving it colorless. The corals will expel the zooxanthellae when stressed, and while for a short period they can regain them and be healthy again, after too long they will die and leave behind only the calcium carbonate skeleton. While bleaching can be caused from various forms of stress, the most common is from temperature changes, here specifically warm temperature changes. Corals are also known to be very sensitive to stress caused by other things like fuel spills, land runoff, and pollution. Climate change is another major impact on the health of corals, warmer waters and the increase in carbon dioxide levels will stress the coral and cause them to get diseases due to changing pH levels and higher temperatures than they are comfortable with.
What Can We Do?
Facilities like Mote Marine Laboratory are working in the Keys to help restore the reefs and grow new corals from fragments to help the reef recover. These scientists are also applying medications to the corals with diseases and investigating ways to help prevent coral bleaching and stressing from happening. You can help keep corals healthy too! Some ways you can help are by limiting your carbon footprint, reducing your waste, wearing reef-safe sunscreen, and making sure if you are visiting reefs to keep off the reef to prevent damage to the tissues and skeletons of the corals. Many of our coral reefs are already damaged, but we can help keep what’s remaining beautiful and promote future coral growth by working together to stop these stressors from continuing to impact our amazing coral reefs.
