Caribbean Compass Yachting Magazine November 2015

Expedition Examines
Grenadine Reefs’ Health
by Emma Doyle and Patricia Kramer
Think of sailing in the Caribbean and inevitably images of blue water come to
mind. Not just a single blue, but a whole spectrum of blues. A good sailor knows by
colour or hue where the coral reef lies below the water.
But is that reef alive or dead? Healthy or suffering from pollution? Or becoming
stressed due to high water temperatures associated with the current El Niño?
In November 2014, the Compass’s Eco-News column reported on an expedition to
assess coral reef health throughout the Grenadines. Taking part were park rangers
and wardens from Grenada and St. Vincent & the Grenadines, the Monitoring
Coordinator from Sustainable Grenadines Inc. and a coral reef scientist with the
Atlantic and Gulf Rapid Reef Assessment Program (AGRRA). The team sailed over
100 kilometres in six days aboard the catamaran Sky Flirt, whose owner, Jean-Marc
Sailly of Wind and Sea, kindly donated the vessel to support the expedition and to
promote coral reef conservation. During the expedition, the team visited each of the
six marine protected areas along the Grenada Bank to survey coral reefs, and they
established long-term monitoring sites to track coral reef health over time.
MARSLYN LEWIS/SUSGREN
The Grenadines coral reef monitoring team aboard the Grenada Marine Protected
Areas patrol boat
Why monitor coral reefs?
Coral reefs are like underwater cities and everything you see on the reef has a role to
play. Coral reefs have high biodiversity, but a few things, like corals, fish and algae, are
the major players in controlling overall reef health. The loss or decline of just one of these
groups can have a domino effect on the entire reef ecosystem. By tracking the status of
several key indicators, it’s possible to get a picture of overall coral reef health.
Within the Caribbean, the health of the Mesoamerican Reef (the world’s second
longest barrier reef stretching through Mexico-Belize-Guatemala-Honduras) is carefully
monitored, allowing coastal managers to better address transboundary issues
between country borders. This is important since most reef organisms don’t conform
to national borders. Coral reefs in long-established marine parks such as Exuma
Cays Land and Sea Park in The Bahamas (established in 1958), and Florida Keys
National Marine Sanctuary (1990) have also been particularly well studied.
The Grenada Bank supports the most extensive coral reefs and related habitats in the
southeastern Caribbean, yet there has been comparatively little monitoring of its coral
reefs. This is changing as the Grenada Bank is now home to a network of six marine
protected areas, all of which have among their objectives the protection of natural
resources, species and critical habitat, including coral reefs. To monitor progress in
achieving this objective, it’s possible to track several key indicators of coral reef health.
What to monitor?
Firstly, the coverage of live coral on the reef is important: the more live coral the
better, as coral provides habitat — shelter, food — for fish and other creatures. In
contrast, the coverage of a type of algal growth referred to as “fleshy macroalgae” can
be an indicator of poor reef health. Too much fleshy macroalgae can over-grow corals
and take up space where baby corals could otherwise establish themselves and grow.
So the less fleshy macroalgae, the better.
The number of black sea eggs on the reef is important (black spiny sea urchins or
Diadema antillarum) because they graze on these algae and help keep the reef clean.
Their numbers in the Caribbean were affected by a mass die-off caused by disease
in the early 1980s, and only now are they recovering in some areas.
When monitoring reef fish, there are two key groups: herbivorous fish, including
parrotfish and surgeonfish, that graze algae growing on the reef and help to keep it
clean; and predatory fish that are often commercially important, such as snapper
and grouper. A long history of fishing in the Caribbean has resulted in dramatic
declines in fish stocks. Reef fish continue to be threatened today by overfishing,
unsustainable fishing practices and destruction of habitat, and they are especially
vulnerable to targeted overfishing of spawning aggregations. Big, old, fat fish are
exponentially more productive, and by protecting them we can help their populations
grow and spillover the protected area boundaries to contribute to sustainable national
fisheries. The monitoring team assessed fish biomass, taking into account both
the number of fish found on the reef and their size.
Managers in the Grenadines are fortunate that some of these coral reef data have
been collected in the past, as far back as 1999 in the case of Tobago Cays. There are
more than 2,000 sites in coral reefs in the Caribbean region that have been surveyed
and provide some reference values for the Grenadines. So the 2014 Grenadines expedition
used the same methodology as used in these other studies, and since several of
the survey sites had been studied before, this enabled some comparison over time.
What did the expedition find?
The news about corals in the Grenadines is generally positive. Live coral cover in the
marine protected areas of the Grenadines is quite good at 25 percent, which is higher
than the Caribbean average of 17 percent, although lower than historic values. Among
the six study sites, the highest live coral cover was found at Carriacou’s Sandy Island/
Oyster Bed Marine Protected Area (35 percent). Meanwhile, the level of fleshy macroalgae
in the Grenadines study sites is on average 18 percent, which is pleasingly lower
than the Caribbean regional average of 31 percent. Particularly low cover of fleshy
macroalgae was found at Woburn/Clarkes Court in Grenada, which also happens to
have the greatest number of black sea eggs of all the sites, and at Tobago Cays Marine
Park, which has the largest biomass of herbivorous fish.
—Continued on page 46
NOVEMBER 2015 CARIBBEAN COMPASS PAGE 11