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Archive for December, 2001

Beneath the Blue-green Sea a Complex and Varied World Lies Waiting the Curious

12 1st, 2001

By Dave Gale

There is a kingdom in Abaco unseen by some who come here to stroll among loyalist-style homes, bask on sugary beaches, or cruise crystalline waters. To a snorkeler or diver, drifting weightless over Abaco’s 50-plus miles of coral reef, the experience of visiting this Diving Abaco's Reefunderwater kingdom seems almost like a chance to sightsee on another planet. Yet the reef, a single wall of which hosts a broader representation of earthly life than most continents, is actually a microcosm representing the very essence of our blue planet. It’s a kingdom where life and death struggles punctuate scenes of vast peacefulness, where sharks glide in seeming serenity while searching for prey, where the graceful waving of sea fans and plant life mask desperate struggles for survival. It’s a place where partnerships between species are a key to the survival of both entities; where deception is honed to an art form by animals pretending to be inanimate, and by fish pretending to be larger, more poisonous, or less aggressive than they actually are.

Coral reefs are formed when colonies of tropical marine plants and animals with limestone skeletons rise atop earlier generations to fashion the most visually diverse natural environments on earth. I’ve seen ads for hotels and dive shops boast that Abaco has the longest - or second, or third longest - barrier reef in the Western Hemisphere, the Caribbean, the world, and I’m confused. The Great Barrier Reef, stretching 1260 miles along Australia’s northeast coast, is indisputably the longest chain of coral reefs in the world, but which reef comes in second or even third is, I believe, hard to determine.

Claims to fame aside, there’s no argument that Abaco has a beautiful, healthy and lengthy reef. Experts say the Abaco complex is not truly a “barrier” reef, true barriers rising from the edge of the continental shelf. It lies somewhere between a “near-fringe” and a “bank-barrier,” but to keep it simple, I’ll just call it a barrier reef. The southern end begins just south of Elbow Cay’s “elbow,” at Hope Town, and runs northwestward almost continuously for about 50 miles to Walker’s Cay and a little beyond. That’s the northwestern tip of the Little Bahama Bank at the edge of the Gulfstream, which is as far as Abaco goes. There are gaps and channels along the way. The dazzling white beaches on many of the Abaco cays owe their existence to the beautiful barrier of prolific shallow reefs which grow right to the surface, creating the beaches in the first place, and then providing protection from the sometimes violent Atlantic Ocean.

Partnerships between reef animals are reflected by a partnership between the reef and the land itself. By acting as a buffer against heavy seas, the reef and island complex maks sea grass beds and coastal mangrove forests possible. Those, in turn, trap sediments, store nutrients, and serve as nurseries for reef residents.

Once believed to be plants, corals are actually carnivores related to anemones and jellyfish. They use stinging tentacles to snare microscopic organisms. Most of their nourishment, however, comes from the algae they host in their tissues. The corals’ enzymes cause the algae to leak carbohydrates. In return the algae get nitrogen from the coral, as well as a home.

The corals themselves thrive as a result of a unique partnership with algae. Once believed to be plants themselves, corals are actually carnivores related to anemones and jellyfish. They can use stinging tentacles to snare microscopic organisms, but most of their nourishment comes from algae hosted in their tissues. The corals’ enzymes cause the algae to leak nourishing carbohydrates. In return the algae get nitrogen, and a home, from the bodies of the coral.

A fringing reef develops directly from the craggy and jagged limestone, or iron-shore as it’s sometimes called, of a cay with very little bay area between the reef and the shore. Sandy Cay Reef in the Bahamas National Trust Pelican Cays Land and Sea Park has been described as a fringing reef. It’s the only major reef in Abaco that I know of, that is wholly inside the chain of protective cays which runs like a string of pearls along the Islands of Great and Little Abaco thereby forming Abaco Sound, also called “the Sea of Abaco.”

Going south from Hope Town, there is a large patch of reef to seaward of Lynyard Cay, then another at Little Harbour called The Boilers. There’s more reef just south of the settlement of Cherokee Sound at the beautiful Eight Mile Beach. But there’s little reef off the mainland from there to the southern-most tip of Abaco at Hole-in-the-Wall, and consequently, not many beaches either, except for Guinea Schooner Bay and Crossing Rocks.

Sunlight becomes them

On the so-called barrier, some of the reefs lie fairly close to shore and some are a mile or so away from the nearest cays. Some reefs are skinny, some are wide, but most are of dense coral reaching within inches of the surface. Coral heads are frequently hollow inside, for corals are tiny community animals, called polyps, that thrive on the sunshine and water movement which brings them the nutrients they require. The driving force behind the abundance of reef life is solar power; the marine food chain is based on the ability of plants to convert solar energy to food.

Only the outside or a coral is alive. Thus, only the outer layer of the conglomeration of various corals making up a coral head is alive. As the corals grow on a coral head, the dead structure underneath breaks away, leaving it hollow inside, like an upside down bowl. This is a natural cycle of death and rebirth. This is where night creatures spend the day and day creatures spend the night. An assortment of sea squirts, soft corals and sponges make crevices in coral a full-time home, as the coral protects creatures which lack rigid skeletons from predation.

As divers, we slip into coral caverns to see the sun’s rays slanting through the cracks and splits as it glints off of the dense schools of fry and copper sweepers often gathered inside. It’s seeing through the eyes of a fish looking out on the sunny world outside.

Abaco’s reefs are short on spectacular walls because the water deepens slowly as it slopes away from the reefs, but they make up for that with prolific to-the-surface reefs and an abundance of marine life. Abaco’s most popular diving is in relatively shallow water, so many of the places that are good for scuba divers are also good for snorkelers. The water clarity in the Bahamas is world famous and stems from various geological and ecological factors. The Bahamas has no rivers, hence no run-off. There is little rainfall – although that varies greatly from one island to the next. Agriculture is absent from most areas, so there is little run-off of mud and harmful agricultural products.

An abundance of sand settles back to the bottom quickly after being stirred up by storms, currents and man, while the abundant bright sun reflects from the white sandy bottom, enhancing the water clarity and the photosynthesis of the coral community. You will find good diving and snorkeling at almost any reef in Abaco. There are miles of undisturbed reefs rising in profusion from the sandy bottom, loaded with underwater life: a rainbow of fish, large and small; both eagle rays and sting rays; and other critters too numerous to list. And there are cleaning stations where the wrasses and the red and white striped cleaner shrimp groom the queued-up customers.

Disguises are many

For fish-watchers, an incredible number of species is further complicated by the fact that many species change dramatically in coloration, marking and even gender as they mature. The Nassau Grouper, for example, can change from male to female as it matures. Some species can alter their color and marking patterns to indicate distress; (note the antics of the octopus in the sidebar to this story.) Even the number of individual animals observed can sometimes be deceiving; species such as octopus and squid can produce clouds of ink in forms that mimic their own body shapes!

The role of both pattern and color are under study by marine experts, who suspect that large eye-like spots are used by small fish to deceive predators about their size, that stripes are similarly used to confuse enemies about their size and exact location, and that bright colors and speckles may indicate, often falsely, that an animal is poisonous, or at least bitter-tasting.

Don’t overlook the invertebrates. Corals are part of this group, and there are many varieties of the hard and soft corals – brain, elkhorn, staghorn, finger, star, pillar, lettuce, button-hole, fire — the list goes on. Also in that group are sponges, sea fans, anemones, gorgonians, octopus, shrimps, sea urchins, jellyfish, and all the crabs — sea-soldiers, bulldozer crabs and decorator crabs (who attach sponges to their shells for camouflage). All the shells — lima clams, conchs, tritons, tulips — all fall into this category, as well as feather-duster worms, Christmas tree worms and sea cucumbers.

Higher on the excitement list are the air breathers – the turtles, dolphins and whales. Turtles are amphibians that have to break the sea’s surface to breathe, while mammals, like dolphins and whales, surface for air, sometimes leaving the water altogether as they cavort. The air-breathers, like the fishes, depend on the reef ecosystem for their livelihood.

When viewing these awe-inspiring reefs, the trick is to relax on the water, floating and observing in slow motion. Ask yourself, your buddy or a book, what is that critter doing? What interaction is going on? How will the outcome fit into the total underwater picture? The more one observes and inquires about these behaviors, the more one understands them. The gratifying payoff is that snorkeling and diving never loose their appeal.

With a barrier reef system like this, shipwrecks are inevitable, and Abaco’s history is full of them. The 1860’s was the heyday of sailing ship commerce here, and records indicate an average of about one wreck per month at Abaco, although that awesome figure is now believed to have been more like one or two per year. Lighthouses and other navigation aids helped stem that dreadful tide of loss of life and cargo.

We’re in this together

Modern day shipping and human impact have left another legacy. Scientists say that all the world’s reefs are in danger as pollution visits everyone’s shores. Fortunately Abaco has thus far escaped major disasters, such as a tanker spills. Reef death, almost imperceptible except in such a spill, a hurricane or a wreck site, causes the beaches to erode. Some things are beyond our control, but we can impact pollution if we are willing to make the effort. We cannot talk about the beauty of the reefs without touching upon their fragility, slow growth and their importance to Abaco’s economy, and in the long run, man’s survival.

Harbour development, dredging, breakwaters and docks make changes to the natural shoreline, causing Mother Nature to compensate often to the detrement of the marine environment, the people nearby and sometimes even the developers. Septic tanks, not-so-septic tanks, restaurant and laundry effluent, and agricultural run-off add unwanted and/or harmful nutrients to the sea. The oxymoron “harmful nutrient” is used in the sense that increased nitrogen levels hurt growth and reproduction in corals while benefitting one of coral’s enemies – free-living algae, which can smother its neighbors.

The occasional storm naturally stirs up the bottom, causing particulate to become suspended in the water column. Nature gives it a chance to settle out, but boat wakes crashing on the shorelines, as well as downward waves from their passage in shallow water, especially from tugs and barges, tends to keep the waters stirred up, thereby choking some plant and animal life and decreasing sun penetration for photosynthesis.

The disposal or dumping of oil, fuel, chemicals, trash and plastics does great harm to the marine environment. Abaco’s increased population, precipitated by our strong tourist industry, has created added pressure. There is more demand for fish and conch locally, and the export of these and other marine products, both legal and illegal, could cause a collapse of certain species.

Other damage is caused by boat anchors carelessly dropped onto living corals. Illegal or unprofessional creation of artificial reefs, as well as salvaging or neglecting wrecks, also contribute to reef damage and coral death. The list is by no means complete.

What we can do

A few pointers for divers and snorkelers are in order: don’t touch corals, or wear gloves which might tempt you to touch them. Don’t stand on formations, and watch where your flippers are flipping. Use moorings whenever possible. If you must use an anchor, drop it only in a sandy spot near the reef.

Moorings, in addition to marking good diving and snorkeling sites, offer convenience to visitors and lessen the impact of anchors in the delicate corals. The Green Turtle Cay Foundation recently funded the installation of 18 moorings in the most popular dive sites in their area with help from local divers and Reef Relief of the Florida Keys. Reef Relief, founded in 1986, is a grassroots non-profit membership conservation organization dedicated to preserving and protecting the living coral reef ecosystem. As watchdogs of the reefs, the organization encourages the public to become involved in their protection. Reef Relief has developed a highly successful system of drilling into base rock, inserting cement in the holes and imbedding U-bolts. All the Green Turtle Cay moorings withstood hurricane Floyd.

Abaco’s own Friends of the Environment, with financial help from south Abaco’s business community, residents, second home-owners and visitors and physical help of Reef Relief and Froggies Out Island Adventures, has installed moorings on the Sandy Cay and Fowl Cay reefs. Skeet LaChance, who founded Dive Abaco in Marsh Harbour in the 1970’s, used a similar system a few years ago at Mermaid Reef off Marsh Harbour’s Pelican Shores. The Mermaid Reef can be accessed from the shoreline at a sandy spot along the Pelican Shores road, where a small sign has been placed. When bad weather disallows boat access to Abaco’s offshore reefs, this can be an enjoyable alternative, for there are myriad fishes and undersea life there in the shallow water. Abaco’s dive operators are usually very careful, for their businesses depend on good healthy reefs, as does the entire Abaco economy, either directly or indirectly.

The Bahamas National Trust has been instrumental in setting up parks and protected areas in the islands and has promised to increase their presence in Abaco. Dive operators tend to use the same sites so that the dive masters will become familiar with the area. Good business and safety dictate getting to know an area well in order to provide more enjoyable dives. Some make it more interesting for their divers by setting up feeding programs – a practice that has become controversial. Feeding, and thereby habituating underwater critters, may not be good for them. It’s tempting, but it may harm them in the short run, as well as endangering divers (see sidebar.) Long-term harm is harder to discern, but man’s interference with the natural scheme of things oftens backfires.

Snorkeling and diving on the reefs of Abaco is for the young, the elderly, and everyone in between. It’s entertaining, educational, relaxing, invigorating and often quite humorous. With your face underwater you can slip into another world. It’s time away from your cares. It’s good exercise. Families can play together and stay together. I know I will enjoy it for as long as I can breathe — and float. And I’ll never be bored.



       
 

©  Jim Kerr, Abaco Life Magazine
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