Atoll Research Bulletin

The reefs surrounding Bonaire have long been renowned for their high abundance and diversity of scleractinian corals and for their long-time status as a protected marine park. As part of a comprehensive study of the current status of Bonaire’s reefs, a quantitative benthic community survey was conducted at 7 locations across depths from 10 to 30 m in early 2008. This showed mean coral cover ranging from 23.7% ± 3.8 (SE) to 38.4% ± 4.4 (SE) on the island’s leeward shore and 1.6% ± 0.4 (SE) to 22.4% ± 3.6 (SE) on the windward shore. Percent cover of macrophytes and turf algae ranged from 41.7% ± 2.0 (SE) to 51.8% ± 3.0 (SE) on the leeward shore and 60.8% ± 4.1 (SE) to 82.7% ± 2.5 (SE) on the windward shore. Comparison of these results to earlier work from 1982 on the leeward shore and 1988 on the windward shore points to a significant, system-wide decrease in corals, increase in macroalgae and increase in the ratio of algae to corals. These observations point to significant degradation of reefs at a site often described as relatively ‘pristine’ in the Caribbean and highlight the sensitivity of coral reefs to anthropogenic and natural stresses even on well-protected islands.

Abstract:

The reefs surrounding Bonaire have long been renowned for their high abundance and diversity of scleractinian corals and for their long-time status as a protected marine park. As part of a comprehensive study of the current status of Bonaire’s reefs, a quantitative benthic community survey was conducted at 7 locations across depths from 10 to 30 m in early 2008. This showed mean coral cover ranging from 23.7% ± 3.8 (SE) to 38.4% ± 4.4 (SE) on the island’s leeward shore and 1.6% ± 0.4 (SE) to 22.4% ± 3.6 (SE) on the windward shore. Percent cover of macrophytes and turf algae ranged from 41.7% ± 2.0 (SE) to 51.8% ± 3.0 (SE) on the leeward shore and 60.8% ± 4.1 (SE) to 82.7% ± 2.5 (SE) on the windward shore. Comparison of these results to earlier work from 1982 on the leeward shore and 1988 on the windward shore points to a significant, system-wide decrease in corals, increase in macroalgae and increase in the ratio of algae to corals. These observations point to significant degradation of reefs at a site often described as relatively ‘pristine’ in the Caribbean and highlight the sensitivity of coral reefs to anthropogenic and natural stresses even on well-protected islands. 

Although marine turtles are conspicuous members of the Caribbean fauna, significant gaps remain in our knowledge of their distribution and status within the region. Nowhere is knkledge more fragmentary than for the Lesser Antilles which, following the definition of Bond (1978) , include those islands fro:> Saba and Anguilla south and east to Barbados and Grenada. Comprising 17 major islands and 16 banks, the Lesser Antilles lie in an arc some 630 km long, and provide nesting and foraging habitats for four species of marine turtles: the green turtle (Chelonia mydas) , hawksbill (Eretmochelys imbricata) , leatherback (Dermochelys cor iacea) and loggerhead (Caretta caretta) . Although the olive ridley (Lepidochelys olivacea) .occurs peripherally in the wider Caribbean region, it is considered a waif in the Lesser Antilles. Kemp's ridley (Lepidochelys kempi) has not been recorded from this region.

Reefs of the windward Netherlands Antilles (Saba, Saba Bank, St. Eustatius, St. Maarten) were assessed at 24 sites in the late 1999. The Atlantic and Gulf Rapid Reef Assessment (AGGRA) protocol was used with modifications to detect recent hurricane impacts. Live coral cover averaged 18%. The assemblage of >10 cm stony corals was primarily composed of small-sized colonies (mean diameter = 37 cm) of which the Montastraea annularis complex was the most abundant (30% of colonies). Overall, =1% of the individually surveyed colonies had been physically damaged by Hurricane Lenny but injury levels were higher in Saba (2.6%). Bleaching was noted in 23% of colonies at the time of the assessment with the greatest percentage occurring on St. Maarten (44%) and the lowest on Saba Bank (9%). Total (recent + old) partial mortality of reef-building corals averaged less than 18% although levels were higher (26%) in Colpophyllia natans. Coral recruitment densities were relatively consistent (mean = 5 recruits/m2) across sites. Commercially significant fish species (i.e. serranids, lutjanids, haemulids >5 cm) were present with mean densities of 4.5 individuals/100 m2. High biomass (mean = 5.8 kg/100 m2) of grazing, herbivorous fishes (acanthurids, scarids >5 cm, Microspathodon chrysurus) partially explains the relatively low macroalgal cover (mean = 7%) throughout this area. Saba’s fish community had a greater total biomass than those in the other three geographic areas (mean = 11 kg/100 m2 versus 7 kg/100 m2). While the coral reefs of St. Maarten show signs of disturbance (i.e., increased bleaching and sedimentation), those of Saba, Saba Bank, and southern St. Eustatius have been relatively little disturbed by coastal development and remain potential sources of marine life. Nevertheless, reef development in the windward Netherlands Antilles is limited by frequent hurricanes.

Abstract:

The Atlantic and Gulf Rapid Reef Assessment (AGRRA) sampling strategy is designed to collect both descriptive and quantitative information for a large number of reef vitality indicators over large spatial scales. AGRRA assessments conducted between 1998 and 2000 across a spectrum of western Atlantic reefs with different histories of disturbance, environmental conditions, and fishing pressure were examined to reveal means and variances for 15 indicators. Twenty surveys were compiled into a database containing a total of 302 benthic sites (249 deep, 53 shallow), 2,337 benthic transects, 14,000 quadrats, 22,553 stony corals. Seventeen surveys contained comparable fish data for a total of 247 fish sites (206 deep, 41 shallow), 2,488 fish transects, and 71,102 fishes. Shallow (≤ 5 m) reefs were dominated by A. palmata, a good proportion of which was standing dead, while deep (>5m) reefs were nearly always dominated by the Montastraea annularis species complex. Fish communities were dominated by acanthurids and scarids with seranids making up less than 1% of the fish seen on shallow reefs and 4% on deep reefs.

AGRRA benthic and fish indicators on deep reefs showed the highest variation at the smallest spatial scale (~<0.1 km), with recent mortality and macroalgal canopy height displaying the largest area and subregional scale (~1-100 km) variation. A mean live coral cover of 26% for the 20 survey areas was determined for the deep sites. Significant bleaching and disease-induced mortality of stony corals associated with the 1998 (El Niño-Southern Oscillation) ENSO event were most apparent in the western Caribbean and Bahamas subregions and the Montastraea annularis complex was the most heavily impacted.

The overall low number of sightings for larger-bodied groupers and snappers (~< 1/100 m2) as a whole suggest that the entire region is overfished for many of these more heavily targeted species. More remote reefs showed as much evidence of reef degradation as reefs more proximal to human coastal development. Characterizing present-day reef condition across the region is a complex problem since there are likely multiple sources of stress operating over several spatial and temporal scales. Not withstanding the many limitations of this analysis, the value of making multiple observations across multiple spatial scales that can approximate the “normal” state for the region today is still very high.