A Current Affair

In Tobago, Divers Learn To Go With The Flow

A gigantic brain boulder coral, Tobago.

''Current looks mild today, but don't let that fool you,'' the divemaster warns us. ''Things can change real fast, and we don't want anyone lost at sea.''

We make final preparations that include a check of the personal ''safety sausages'' considered standard equipment when diving these waters. As members of the Philippe Cousteau Foundation dive team, we are all highly experienced divers, but we also know that the shifting, unpredictable currents that sweep Tobago's northeast shore could easily carry an inattentive diver into the deep blue.

In addition to collecting water samples at intervals throughout the dive, we hope to locate and survey the world's largest living brain coral. Our boat drifts parallel to the cactus-covered cliffs of Little Tobago Island, a half-mile east of the notorious Keleston Drain. In the confused waters ahead, divers just a few feet from each other could be separated and swept into shoal waters to the west, caught in a circular eddy, or carried north toward the open Atlantic.

We backroll into 80-foot visibility and a cloud of marine life. Free swimming salps, tunicates and comb jellies transform the upper portion of the water column into a galaxy of pulsating, translucent shapes. The reef's prodigious population of brown chromis, creole wrasses and black durgons are hard at work dining on the bounty of zooplankton. Their erratic, darting behavior in turn draws predators such as jacks and rainbow runners into the melee.

The underwater terrain is a mirror image of the hillside above, but instead of cactus, the volcanic slope is covered with dense communities of octocorals. A living carpet of sea rods and sea plumes is interspersed by deepwater sea fans of up to 6 feet in breadth.

Sponges in a pallet of hues added to this copious diversity, standing alone or interlaced in the branches of large gorgonians. Atop one orange elephant ear sponge, the long, spindly limbs of a purple rope sponge look like writhing snakes sprouting from the head of a submerged Medusa. Stranger yet are the region's giant barrel sponges, which are sculpted into weird contorted shapes by the constant flow of water.

Pushed by a mild but insistent current, we move parallel to the rocky shoreline. Trumpetfish, damselfish, wrasses, hamlets, rock hinds and coneys take cover in the coral and sponge thickets, ever mindful of the black grouper and cubera snapper that patrol the edge of the drop-off. Though soft corals seem to dominate the local ecosystem, one species of hard coral - the brain boulder coral - takes center stage on this dive.

As we near the western point of the island, the current intensifies. We fly over a trio of massive brain corals, then confront a minivan-sized monster that is undoubtedly the object of our search. We duck into the leeward eddy created by this massive creature, which measures a full 16 feet in diameter.

Ahead lies the Drain. We band together and swim to the left. A circling eddy draws us in, then ejects us into the rush of west-moving flow. We surface more than a mile from our starting point.

Colliding Currents
Situated some 70 miles northeast of South America's Atlantic Coast, the island of Tobago sits in the pathway of not one, but two major oceanic currents. These bodies of moving water not only collide when they reach Tobago's coast, they also swirl and bottleneck between the many small islands and rock pinnacles that line the shore. The result is some of the most exciting and unpredictable drift diving in the Caribbean.

These same currents also play a pivotal role in shaping the region's unique underwater ecosystem. From the east, the North Atlantic Equatorial Current, prelude to the Gulf Stream, surges through the southern Caribbean, bringing the clear oceanic waters that hard corals require for survival.

From the south, the Guyana Current skirts the South American coast, then pushes north towards Tobago. During Venezuela's rainy season, July through September, floodwaters from the Orinoco River add their muddy flow to the mix. As this nutrient-laden water moves north, it triggers enormous plankton blooms that sustain a host of filter-feeding organisms ranging from sponges and soft corals to manta rays.

During the height of the Orinoco flow, it's not uncommon to have underwater visibility along Tobago's coast fluctuate wildly from perhaps 80 feet one day to as little as 30 feet the next. This seasonal ebb and flow of ''clean'' and ''dirty'' waters gives rise to a rich and diverse underwater landscape, where the typical hard corals of the Caribbean exist among a riotous overgrowth of soft corals and sponges.

Soft Coral Laboratory
The factors that make Tobago an exciting and challenging destination for sport divers also create ideal conditions for the study of coral health. The natural seasonal fluctuations in water quality that account for Tobago's underwater diversity may also provide clues to recent global changes that threaten the health of coral reefs everywhere.

Around the globe, industrial development and large-scale agriculture have increased the supply of nitrogen and other nutrients entering the world's oceans. When these nutrient levels reach critical levels, hard corals are threatened, and reefs may be covered by algae growths.

The waters of Tobago provide an excellent laboratory for studying not only the regional effects of nutrient loading related to the Orinoco flow, but also localized sources such as those now threatening the island's signature tourist attraction, Buccoo Reef.

Buccoo Reef is a large, horseshoe-shaped barrier reef situated on the island's southwestern coast. Generations of local children learned to swim in the sand-bottom lagoon that lies inside the reef's protective ring of elkhorn coral, and glass-bottomed boats provided tourists with a rare glimpse of the underwater world.

Several years ago, grasses invaded the lagoon, and the fringing corals were covered in damaging algae blooms. Passed over by the cleansing currents that sweep Tobago's other shores, Buccoo Reef was succumbing to what experts call ''non-point source'' pollution, and what everyone else identified as runoff from a nearby village.

The degradation of Buccoo Reef became the catalyst for a grass-roots conservation movement that is now sweeping Tobago. A new administration has committed governmental resources to the updating of stormwater management and wastewater treatment systems, while private sector businesses such as the island's new Hilton hotel and resort complex have invested in state-of-the-art treatment and recycling systems.

Another result of this heightened environmental awareness was the creation of the Buccoo Reef Trust. This new organization will study not only the microcosm of its namesake reef, but also islandwide and regional issues related to coral health and marine issues. One of the Trust's primary goals is the establishment of an environmental education center research station focusing on Caribbean marine conservation and sustainable aquaculture practices.

Diving Into DiversityIt was an invitation from Buccoo Reef Trust scientist Richard Langton that brought the Philippe Cousteau Foundation dive team to the island of Tobago. Working with the staff of the World of Watersports, Langton hoped to provide us with a firsthand look at Tobago's rich diversity and an understanding of the challenges the entire Caribbean faces in the years to come.

During the course of a week, our team experienced the island's legendary currents and soft coral gardens, explored offshore pinnacles, surveyed near-shore reefs, toured a recent shipwreck and visited Buccoo Reef. Like most visitors, we were very impressed by the famous dive sites in the Speyside region, but we also enjoyed several memorable dives on the volcanic spires that lie off the island's western shore.

Near the town of Charlotteville, we dived on a collection of rock columns known as the Sisters and a towering volcanic spire known as London Bridge, which features a huge natural arch and a frigate bird rookery. Bare and unremarkable above the surface, these massive underwater formations are cut with deep clefts and caves, and they are decorated by extensive stands of black coral and gorgonians.

Like oases in the desert, the spires draw every manner of swimming creature. Clouds of baitfish attract predators such as jacks, barracuda, wahoo, and tuna; large sea turtles, sharks and manta rays also may show themselves. Near the surface, rolling ground swells generate luminous nebulas of heavily aerated water following each assault on the pinnacles' upper segments, sometimes blocking them from view. Adding to the spell are the resident tarpon that cruise through this fog of swirling micro bubbles.

At the end of the week, we were asked to summarize our impressions of Tobago's underwater environment and its potential for dive tourism. The first thing we agreed on was the fact that one week was not nearly enough to experience all that Tobago has to offer. This is a destination that divers could return to time and again.

The prevailing currents and the exposure of some sites to oceanic chop and swell make it a destination better suited to intermediate and advanced divers, we felt, but there are also plenty of sites for the competent novice. As compared to the rest of the Caribbean, the underwater landscape is more about soft coral diversity and fish life than it is about towering walls and hard corals.

What we found equally impressive was the island's commitment to the underwater environment. Thanks to forward-looking programs such as the Buccoo Reef Trust, this is a destination that should retain its natural wonders for years to come.

To bolster diving in the region north of Pigeon Point, Tobago's tourist board and a group of local dive operators recently sent a 350-foot transisland ferry to the bottom near Buccoo Reef.

Renamed the MV Maverick, the ship rests at a depth of 100 feet, with her entirely intact superstructure rising to within 56 feet of the surface. At a depth of 83 feet, the entrance to the vessel's car-loading deck gapes like the massive mouth of the Holland Tunnel. Although most varieties of marine growth have not yet taken hold, the wreck has become a haunt for a multitude of fish, including a large but shy Goliath grouper.