Coral Reefs
Coral reefs are the most spectacular and most well known of the marine environments of The Bahamas. Andros Island in the Bahamas has the third longest barrier reef in the world (229km). However, they make up a small area of the country compared to mangroves and sea grass areas. They are structurally complex and biologically diverse. As well as our beaches and clear blue waters, the reefs attract thousands of visitors a year to snorkel, dive and fish on them.
What are coral reefs?
Corals are tiny animals belonging to the phylum called Cnidaria (formally Coelenterata). Corals live in colonies consisting of many individuals called polyps, each one about the size of a pinhead. An entire colony many meters in diameter can start out as a single polyp. Each polyp feeds at night by reaching out with tentacles to catch prey such as small fish and planktonic animals. They secrete a limey (calcium carbonate) skeleton that is the basic structure of the reef. These skeletons group together over time to form coral heads, they come in a large variety of shapes and sizes.
Most corals have symbiotic relationship with single-celled algae called zooxanthellae. The plant-like algae live inside the coral polyps and produce food that is shared with the coral. In exchange the coral provides the algae with protection and access to light. Since the corals require warm water to extract calcium carbonate from the ocean to build the reefs and the zooxanthellae require sunlight for photosynthesis, the reefs are found in clear, shallow and tropical water.
While corals are the chief architects of reef structure, they are not the only builders. Coralline algae cement various corals together with compounds of calcium, and other organisms such as tube worms and molluscs donate their hard skeletons. Together these organisms construct many different types of reefs. The term ‘reef’ in The Bahamas refers to several different hard bottom habitats: hard bar, patch reef, channel reef, fringing reef and deep reef or wall.
Why are coral reefs important?
Not only are the coral reefs outstandingly beautiful to look at, giving pleasure to many, they are also extremely important to our community. They protect our shoreline, provide habitats for commercially important fisheries including lobster, grouper, snapper and jacks, provide food, produce sand, support the tourism industry and help scientists in new discoveries, particularly medicine. They are an extremely important resource that needs to be protected.
What are the threats to our reefs?
Because many coral reef organisms can tolerate only a narrow range of environmental conditions, reefs are sensitive to damage from environmental changes, many of which are caused by humans. Because of the important ecological and economic roles coral reef communities fulfill, an understanding of the stresses and dangers to the reefs is necessary. Fortunately, many of the human induced hazards to coral reefs can be remedied.
There are three main threats or stresses caused by humans: physical destruction, overharvesting of fish or invertebrates and changes in coastal environments that degrade water quality.
Physical destruction: - this occurs from dredging and development, the creation of navigational channels through reefs, and destructive fishing methods such as bleaching or dynamiting reefs. Every major development project has to submit an environmental impact assessment report (EIA) to the relevant authorities before approval is given. But it is also the small events that take their toll as well. Anchors constantly being dropped on corals, fish traps dragged across the corals can damage the coral so that it is susceptible to disease or predation and eventually die. All contribute to the destruction of the reefs.
Overfishing:- the removal of all of the lobsters, grouper and snappers is not only bad for the animals themselves, but deprives the reef of the services they perform. Spiny lobsters are the cleaners and garbage collectors. They eat anything; dead material, waste and leftovers, thus recycling this material and putting nutrients and energy back into the reef making it more productive. Groupers and snappers play a similar role. The larger fish eat smaller fish that eat corals and marine invertebrates. Without these large groupers and snappers the food chain cycle is broken and the coral growth will not occur. It is important that we protect the these species by establishing marine protected areas with no take zones, having closed fishing seasons for spiny lobster and grouper, size restrictions e.g. lobster and conch. It is important that animals are harvested at a sustainable level for both the animals and the reef to survive. Fisheries management is the responsibility of the Department of Fisheries.
Water quality:- apart from major disasters that occur for example oil spills from tankers, everyday activities affect the water quality. But everyday activities can affect the water quality over time; construction site sediment runoff, pesticides and fertilizers from golf courses, sewerage, toxins from boat paints, sea - going trash washed out from beaches and trash thrown overboard from boats, all can change the water quality. Coral reefs environments are very sensitive to chemicals, nutrients, sediments and anything else that may be found in the water from these pollution activities. It is not only our islands that contribute to this but other countries as well. Studies have shown that greenhouse gases from the burning of fossil fuels are increasing the ocean’s acidity making it harder for coral to grow and reproduce.
Coral bleaching:- this is when stressed coral loose their pigment and are most susceptible to disease and premature death. This occurs when sea temperatures rise above normal healthy limits. In 2005, researchers found that more than 47% of coral in underwater study sites around the US Virgin Islands died after abnormally warm seas. Researchers are warning that more than half of the world’s coral reefs could die in less than 25 years. It has also been noted that smaller species of coral (e.g. mustard hill coral) are replacing the larger species (e.g. boulder star coral). These smaller varieties do not grow high enough to protect the fish, lobster and other sea life that rely on the reefs. The Bahamian reefs are currently in a better condition than our Caribbean neighbors, but changes are being observed. We must all work together to do all we can to preserve them.
What can you do to help?
- Take time to learn about your marine environments and country in general
- Experience the underwater marine environment
- Support marine conservation measures
- Do not pollute the air
- Wage a war against litter
- Become a ‘green consumer’
- Get involved with local conservation organizations like BREEF and The Bahamas National Trust.