Coral Reefs of Southwest Tobago, then and now

To create a new record for The Maritime Ocean Collection, Anjani Ganase dived coral reefs in southwest Tobago. This is the first time she is observing these reefs through the eyes of a scientist. She compared what she saw with descriptions by Richard Laydoo from the Institute of Marine Affairs during the 1980s, about 35 years ago, in the book, A Guide to the Coral Reefs of Tobago

Diving in the southwest Tobago is a hotter and sunnier experience, compared with diving along the steep edges of the main ridge in the northeast. The brightly lit waters and whiter sand give the coral reefs a picturesque ambiance; but the coral reefs here also display a complex history of disturbance and some surprises.

Flying Reef

Along the southern coast, Flying Reef is exposed to the Atlantic Ocean with the strong currents which gives the reef its name. Flying Reef sits about 1 km off shore and runs parallel to the airport runway, but while planes were taking off to the east; divers would be swept to the west. Laydoo in 1984 described Flying Reef as a gentle sloping reef littered with sea fan and soft corals fluttering in the current. The most prominent feature here was the dominant star coral, reef builders that layered the seascape along with Elkhorn corals branching up towards the surface, while giant barrel sponges lined the reef base.

While the hard coral infrastructure is still present, diving on this reef today is a very different experience. Large sections of the reef framework appear to have been converted to rubble, and the hard coral has been replaced by macroalgae and sponges on much of reefscape

Bright yellow and purple sponges congregate around the bases of sea fans and soft coral plumes as well as the brain corals that still occur. Massive barrel sponges were still spotted along the deeper sections of the reef. Sponges in general make up a large portion of the reef community.

The fish life at Flying Reef however is still very impressive: it is the only reef where a black tip reef shark was spotted; adult Parrotfish were common, including the large Rainbow Parrotfish not seen anywhere else on the island and a rarity on many Caribbean reefs. Large schools of grunts and chub would gather around the existing coral mounds

Buccoo Reef

From Buccoo Bay, Buccoo Reef extends southwards arching its way to Pigeon Point. It is a unique reef system seen nowhere else in Trinidad and Tobago, and is special because it is a natural beauty, primarily because of the growth of the hard corals. The sheltered mangroves and lagoon persist because of the protection afforded by Buccoo Reef.

Another unique feature of Buccoo Reef is the presence of back reef and patch reefs occurring in the lagoon behind the reef. Laydoo described the presence of many reef patches as consisting of thickets of branching corals such as the fragile Staghorn as well as finger coral. Pockets of vibrant life occur within the lagoon. However, even back then, there were fields of coral rubble along the reef flat because of storm and anchor damage as well as over twenty years of walking on the reef. Thirty years after Laydoo’s observations, many of the patch reefs do not exist. Yet, the famous patch reef, known as Coral Gardens, composed primarily of star corals, still sparkles below the surface in a relatively healthy state.

The Buccoo’s seaward slope is a more depressing scene. Here is how Laydoo described the outer and eastern sections of Buccoo Reef:

“Generally, the reef crests, particularly at the Outer and Eastern reefs, are emergent or exposed at low tide. The fauna of the reef flats is composed mainly of elkhorn coral, finger coral, fire coral and sea carpet (palythoa).”

The section of reef where the Elkhorn corals once dominated is now a barren zone. It’s strange that the skeletal remains of Elkhorn still stand out against the blue water, as if they died yesterday; nothing significant has grown over them, only turf algae and some calcifying algae. It’s as if the reef has been suspended without regrowth or recovery. During the 1970s and 80s, Elkhorn corals across the Caribbean were wiped out by disease.

As we moved farther down the reef slope, the coral and marine life resemble what was described by Laydoo, with the boulder brain and star corals occurring in deeper water:

“the forereef, characterized mainly by large boulder-type formation of brain and star coral slopes gently to merge with the sandy seafloor”

Mount Irvine Reef

Mt Irvine with Brain Coral
Brain corals dominate a section of Mt Irvine Reef. Photo by Jonathan Gomez | The Institute of Marine Affairs

Continuing east, one bay over from Buccoo is Mt Irvine Bay. The eastern section of the Mt Irvine Bay near the headland is one of the most popular surf spots on the island but below the waves is a well developed coral reef.

As you round the point into Back Bay, the reef structure ebbs and the fish frequent the rocky outcrops; the submerged cliff and crevices form a natural refuge for schools of juvenile fish. Sections of Mount Irvine reef still resemble Laydoo’s descriptions with conspicuous colonies of boulder brain and star corals, but large sections of reef slope have become over run by swaying soft coral plumes.

The most fascinating feature of this reef is the structure itself. It was amazing to peer through the lattice of the reef framework. At 10 m depth at the top of the reef, I spied a network of tunnels and corridors extending at least another 10 m into the reef; a sort of reef underworld created by years and years of hard corals growing on top of each other. The fish used these secret passageways to escape my camera lens.

Arnos Vale Reef

Laydoo described the reefscape outside the bay consisting of submerged rocks and boulders with little hard coral growth. There may be something that naturally limits coral growth on these rocks, as they lack coral growth to today. Taking a closer look, you can find encrusting sponges, fire coral and sea fans coating surfaces of the rocks. The seascape is beautifully structured with rocky canyons and swim throughs where reef fish congregate.

Culloden Reef

Culloden Reef featuring Creole-Wrasse
A school of Creole Wrasse poses for the camera at Culloden Reef. Photo by Jonathan Gomez | The Institute of Marine Affairs

Culloden reef is located north of Arnos Vale. The reef spreads out seaward from the two headlands of the bay and, connecting in the middle, creates a horseshoe shape. This unique reef system developed a spur and groove formation as a result of moderate wave energy moving along the coastline.

This reef features spurs that spread out like fingers along the seafloor because of the growth and accumulation of hard corals. In between the spurs are narrow sand channels where dissipating wave energy moves sediment and rubble down the slopes to collect in these grooves. Laydoo remarked on the pristine conditions of corals that made up the spurs of Culloden Reef compared to other reefs on the island, with the presence of fish and shark life that gather in the grooves. He recommended that Culloden Reef be designated as a scientific reserve to be studied further.

Today the reef structure is still impressive and while some hard corals continue to grow along the spurs, there is now heavy competition with the sea fans and rods that overshadow and scour the star boulder corals. We did not find any sharks in the sandy grooves, instead a hoard of lionfish lurking under coral overhangs.

Laydoo, R. S. (1991) A Guide to the coral reefs of Tobago, Institute of Marine Affairs.

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