PLoS ONE

Abstract:

This paper provides a context for the results of recent biodiversity surveys of Saba Bank.

Recent biological surveys of corals, fishes, and algae emphasized habitat diversity and the relative richness of the marine flora and fauna. These assessments formed the basis for a management plan to protect Saba Bank’s biodiversity and a draft proposal seeking Particularly Sensitive Sea Area (PSSA) status for the Bank. The intention of the PSSA proposal is to protect the benthic habitat on Saba Bank from anchor damage. It is hoped that this collection will serve as a knowledge baseline and provoke further research in the area.

Findings:

Meesters et al, 1996: review of existing knowledge and quick field survey of Saba Bank.

• This study confirmed that Saba Bank is of great interest, both geologically and biologically.
• This study confirmed that the area is a regionally unique ecosystem, relatively pristine and remote from human influences, with high biological diversity and productivity.
• The study highlighted threats from overfishing and anchoring by large tankers.
• Meesters recommended further study of Saba Bank, improved legislative instruments, including international instruments, and enforcement to control current and future activities as well as capacity and awareness building.

This study formed the basis for the N.A government’s policy for Saba Bank. Lack of resources and capacity delayed implementation of this policy.

Dilrosun, 2000: first in-depth fisheries catch assessment that provided solid data about the state of the Saba Bank’s fisheries.

• This study concluded that no new fishing permits should be issued until a long-term fishery monitoring program was in place.
• The study emphasized the need for effective enforcement of existing regulations.

This study had immediate effects on Saba Bank policy; the island government of Saba declared a moratorium on fishing permits and a capacity building effort to strengthen the Coast Guard’s enforcement of existing regulations began.

Several studies were requested so as to demonstrate that the Saba Bank satisfies all the criteria that the International Maritime Organization requires for the area to become a Particularly Sensitive Sea Area (PSSA)

2006 Rapid Assessment Program (RAP) of Saba Bank: the aim was to produce appropriate and realistic conservation recommendations.

• This survey really demonstrated the richness of the Saba Bank’s biodiversity.
• Many new species were reported, and Saba Bank was found to have a uniquely diverse marine macro-algal flora.
• The expedition brought worldwide publicity for Saba Bank and helped to earmark Dutch development funding for further study of the Bank.

2007 high-resolution bathymetric GIS map of Saba Bank

• The map was produced using the Navy’s sonar data within a Geographic Information System (GIS) framework.
• The map formed the basis for further study of Saba Bank.

2007 Second Fisheries Assessment: the goal was to assess the crustacean and gorgonian fauna of Saba Bank.

• Two undescribed octocoral species were discovered
• Two different shallow water gorgonian habitats were distinguished

The number of anchoring tankers and the damage caused by them was documented through a vessel monitoring system and the report of a few cases.

Saba Bank Management Plan Draft

• In-depth description of Saba Bank’s biodiversity.
• More data on the use being made of the Bank.
• Better idea of the habitats present on the Bank.

A PSSA status proposal has been drafted and is currently being finalized.

New legislation to regulate international shipping in the waters of the Netherlands Antilles, needed in order to submit a PSSA proposal to the IMO, was passed. This legislation also makes it possible to declare the area an EEZ (another requirement for the PSSA proposal). The process is underway and is expected to be finalized in 2010. The anchoring prohibition will also be extended to the whole of the Bank in 2010.

Management Recommendations:

• Further study and monitoring of the Bank’s biodiversity and use will be required to guide the Bank’s management in a feedback loop.
• Interaction of biodiversity research and policy development is essential to developing effective management of biodiversity and public support.
• Carry out further research into the various habitats of the Bank, about which far too little is as yet known. To date, only a very small part of the huge area has been adequately sampled.
• Another priority is a study of marine mammals on Saba Bank to determine their presence and use of the bank. Anecdotal evidence suggests that humpback whales may use the Bank for calving, and sperm whales may find prey around the steep edges of the Saba Bank platform. Other areas of research that would contribute to more effective management include further studies of conch (Lobatus gigas) and lobster (Panulirus argus) populations, and sea turtles’ use of the Bank. Socio-economic studies would also be welcome. 

Structural change in both the habitat and reef-associated fish assemblages within spatially managed coral reefs can provide key insights into the benefits and limitations of Marine Protected Areas (MPAs). While MPA zoning effects on particular target species are well reported, we are yet to fully resolve the various affects of spatial management on the structure of coral reef communities over decadal time scales. Here, we document mixed affects of MPA zoning on fish density, biomass and species richness over the 21 years since establishment of the Saba Marine Park (SMP). Although we found significantly greater biomass and species richness of reef-associated fishes within shallow habitats (5 meters depth) closed to fishing, this did not hold for deeper (15 m) habitats, and there was a widespread decline (38% decrease) in live hard coral cover and a 68% loss of carnivorous reef fishes across all zones of the SMP from the 1990s to 2008. Given the importance of live coral for the maintenance and replenishment of reef fishes, and the likely role of chronic disturbance in driving coral decline across the region, we explore how local spatial management can help protect coral reef ecosystems within the context of large- scale environmental pressures and disturbances outside the purview of local MPA management. 

Background:

Located in the Dutch Windward Islands, Saba Bank is a flat-topped seamount (20–45 m deep in the shallower regions). The primary goals of the survey were to improve knowledge of biodiversity for one of the world’s most significant, but little-known, seamounts and to increase basic data and analyses to promote the development of an improved management plan.

Methodology/Principal Findings:

Our team of three divers used scuba to collect algal samples to depths of 50 m at 17 dive sites. Over 360 macrophyte specimens (12 putative new species) were collected, more than 1,000 photographs were taken in truly exceptional habitats, and three astonishing new seaweed community types were discovered. These included: (1) ‘‘Field of Greens’’ (N 17u30.6209, W 63u27.7079) dominated by green seaweeds as well as some filamentous reds, (2) ‘‘Brown Town’’ (N 17u28.0279, W 63u14.9449) dominated by large brown algae, and (3) ‘‘Seaweed City’’ (N 17u26.4859, W 63u16.8509) with a diversity of spectacular fleshy red algae.

Conclusions/Significance:

Dives to 30 m in the more two-dimensional interior habitats revealed particularly robust specimens of algae typical of shallower seagrass beds, but here in the total absence of any seagrasses (seagrasses generally do not grow below 20 m). Our preliminary estimate of the number of total seaweed species on Saba Bank ranges from a minimum of 150 to 200. Few filamentous and thin sheet forms indicative of stressed or physically disturbed environments were observed. A more precise number still awaits further microscopic and molecular examinations in the laboratory. The expedition, while intensive, has only scratched the surface of this unique submerged seamount/atoll. 

Findings:

Combining the findings of this study with that of other studies, the authors conclude that the coral assemblage on the Saba Bank is diverse and healthy; it is representative and typical of those found elsewhere in the Caribbean.

Coral Richness

• A total of 43 species were documented.
• There were no significant differences in coral composition amongst bottom types or depth classes.
• There was a significant difference between sites near and far from the platform edge. The number of coral species observed ranged from 0 and 1 in algal dominated habitats to 23 at a reef habitat on the Bank’s southern edge.
• Coral species richness was higher on reef dominated areas as opposed to algal dominated ones.

Coral Condition

• Bleaching was evident at 82% of the sites assessed with 43 colonies bleached.
• Only three coral colonies were observed to have disease.
• Five reef sites had stands of Staghorn Coral (Acropora cervicornis), a critically endangered species on the IUCN Red List.
• No physical damage consistent with anchor usage or sand scour from shipping activity was noted at any of the sites assessed.

Management Recommendations

1. Immediate action is necessary to protect the diverse coral reef habitats documented.
2. The five healthy stands of staghorn coral (A. cervicornis) and their surrounding should be given highest priority for full protection in the zoning use plan under development (in consultation with all stakeholders).
3. More information is needed on the Saba Bank to create a comprehensive zone use plan. For example, more sites need to be studied so as to get a more comprehensive coverage of the bank’s coral composition.

Abstract:

Biodiversity surveys were conducted on Saba Bank, Netherlands Antilles, to assess ichthyofaunal richness and to compare with published surveys of other Caribbean localities. The primary objective was to estimate the total species richness of the Saba Bank ichthyofauna. A variety of sampling techniques was utilized to survey the fish species of both the visually accessible megafauna and the camouflaged and small-sized species comprising the cryptic ichthyofauna. Based on results presented herein, the number of species known on Saba Bank is increased from 42 previously known species to 270 species. Expected species-accumulation curves demonstrate that the current estimate of species richness of fishes for Saba Bank under represents the actual richness, and our knowledge of the ichthyofauna has not plateaued. The total expected fish species richness may be somewhere between 320 and 411 species. The Saba Bank ichthyofaunal assemblage is compared to fish assemblages found elsewhere in the Caribbean. Despite the absence of shallow or emergent shore habitats like mangroves, Saba Bank ranks as having the eighth highest ichthyofaunal richness of surveyed localities in the Greater Caribbean. Some degree of habitat heterogeneity was evident. Fore-reef, patch-reef, and lagoonal habitats were sampled. Fish assemblages were significantly different between habitats. Species richness was highest on the fore reef, but 11 species were found only at lagoonal sites. A comprehensive, annotated list of the fishes currently known to occur on Saba Bank, Netherland Antilles, is provided and color photographs of freshly collected specimens are presented for 165 of the listed species of Saba Bank fishes to facilitate identification and taxonomic comparison with similar taxa at other localities. Coloration of some species is shown for the first time. Preliminary analysis indicates that at least six undescribed new species were collected during the survey and these are indicated in the annotated list. 

Saba Bank is a 2,200 km2 submerged carbonate platform in the northeastern Caribbean Sea off Saba Island, Netherlands Antilles. The presence of reef-like geomorphic features and significant shelf edge coral development on Saba Bank have led to the conclusion that it is an actively growing, though wholly submerged, coral reef atoll. However, little information exists on the composition of benthic communities or associated reef fish assemblages of Saba Bank. We selected a 40 km2 area of the bank for an exploratory study. Habitat and reef fish assemblages were investigated in five shallow-water benthic habitat types that form a gradient from Saba Bank shelf edge to lagoon. Significant coral cover was restricted to fore reef habitat (average cover 11.5%) and outer reef flat habitat (2.4%) and declined to near zero in habitats of the central lagoon zone. Macroalgae dominated benthic cover in all habitats (average cover: 32.5 – 48.1%) but dominant algal genera differed among habitats. A total of 97 fish species were recorded. The composition of Saba Bank fish assemblages differed among habitat types. Highest fish density and diversity occurred in the outer reef flat, fore reef and inner reef flat habitats. Biomass estimates for commercially valued species in the reef zone (fore reef and reef flat habitats) ranged between 52 and 83 g/m2 . The composition of Saba Bank fish assemblages reflects the absence of important nursery habitats, as well as the effects of past fishing. The relatively high abundance of large predatory fish (i.e. groupers and sharks), which is generally considered an indicator of good ecosystem health for tropical reef systems, shows that an intact trophic network is still present on Saba Bank