Ecologically or Biologically Significant Areas (EBSAs)
published:15 Jun 2015
The Saba Bank is a unique and highly significant area for the entire region. Biophysically it is a submerged atoll, the largest actively growing atoll in the Caribbean, and one of the largest atolls in the world, measuring 1,850km2 above the 50m depth contour. The area is significant in terms of its unique ecological, socio-economic, scientific and cultural characteristics. Its extensive coral reefs, fishing grounds and algae beds are among the most diverse and pristine in the Caribbean.The Saba Bank has been declared a protected area by the Dutch Government (15 Dec 2010) to protect its biodiversity and prohibit anchoring. Additionally an application to IMO has been submitted requesting Particularly Sensitive Sea Area (PSSA) status for the Bank to regulate ship traffic.
The Saba Bank (17o25' N, 63o30' W) is an undersea elevation with a flattened top—a bank—3 to 5km south-west of the island of Saba and 25km west of St. Eustatius (Figure 1). It is raised about 1000m above the general depth of the surrounding sea floor, and its shape is approximately square or slightly elliptical, the long axis trending ENE-WSW. With a length of 60 to 65km and a width of 30 to 40km, the total surface area is approximately 2200km2 (measured to the 200m isobath). The platform is somewhat tilted, with the north-western part of the surface being deeper than the south-eastern part. The largest part of the bank is between 20 and 50m depth, but a substantial eastern part (app. 225km2) is between 10 and 20m depth. On its western rim, depths are around 50m, while on the eastern and south-eastern edges, where a prominent coral ridge system (55km long) runs along the platform, depths vary between 7 and 15m (Van der Land 1974, MacIntyre et al. 1975). Saba Bank is a classic sub-surface atoll consisting of a submerged mountain with a margin or ring of actively growing coral reefs. As such it constitutes the largest atoll in the Atlantic Ocean Basin and one of the largest atolls on Earth (Land 1977, Purdy & Winterer 2001). For generations Saba Bank has been fished by the Sabans. This fishery was first documented early in the twentieth century by Boeke (1907) who also mentioned the existence of extensive coral growth. The Bank has intrigued a number of scientists since the early twentieth century who studied and debated its geology (Spencer 1904, Vaughan 1919, Davis 1926, Macintyre et al. 1975), but otherwise little attention was given to Saba Bank until the 1970s, when many Caribbean nations declared Exclusive Economic Zones (EEZ) and started to control their fisheries.
Wider Caribbean and Western Mid-Atlantic
The Saba Bank is completely within the Exclusive Economic Zone of the Netherlands. Part of the Bank is within island authority (within 12nm) but the Netherlands is responsible for issues related to international treaties such as the CBD. The Dutch government declared the bank a protected area on 15 December 2010 (see provided official declaration map in Figure 2) and is now actively patrolled by the Dutch coast guard. The Royal Netherlands Hydrographical Survey carried out extensive acoustic surveys using the collected data to create a high-resolution bathymetric map (Figure 1). The Bank is not part of a submission to the Commission on the Limits of the Continental Shelf.
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At present the Saba Bank is increasingly being investigated by the scientific community, and Hoetjes and Carpenter (2010) present an overview of biodiversity research that has taken place on the Bank. The area is difficult to access by the scientific community due to its distance to the nearest harbour, the high waves, and the depth. Below a summary is given with respect to the different taxa that have been studied for the Saba Bank (Table 1). Research to date has been mainly focused on species diversity, and little is known about the functioning of the Bank. In 2011 a research programme was started to gain more knowledge on the ecological processes to better understand the Bank and protect it effectively. Included in this programme is research related to the carrying capacity for lobster and reef fish. Below the different species groups (in alphabetic order) are briefly discussed. The total number of species that were found in the references in Table 1 represent a sample of what is present and is limited by sampling effort. Generally, the higher the effort the more species will be found, although this increase will gradually level off to an asymptote. Most studies to date did not, however, reach this asymptote. Seabirds. Postma and Nijkamp (1996) found that seabird densities on the Saba Bank averaged two times higher than off the Bank. On the Saba Bank most seabirds appear to be concentrated around the 200 m isobath. The most common species recorded (April-May) were red-billed tropicbird (Phaeton aethereus) with 5% of the world population breeding on nearby Saba (www.birdlife.org), magnificent frigatebird (Fregata magnificens), sooty tern (Sterna fuscata), and bridled tern (S. aneaetheus). Other species were pomerine skua (Stercorarius pomarinus), and Wilson’s storm petrel (Oceanites oceanites). In the pelagic areas adjacent to the bank, the brown noddy (Anous stolidus), and Audubon’s shearwater (Puffinus lherminieri) were most common. Hard corals. Coral reefs are present along the eastern and south-eastern edges of the Bank and are rich in terms of cover and diversity of hard and soft corals. There is a lot of structural complexity (Figure 3) from thousands of years of growth of stony corals, which created a large array of different habitats (e.g., fore reef, back reef, lagoon) for other species (Toller et al. 2010). Individual coral colonies can be found over the whole Bank. The coral reef area can be quite broad, up to 2 km wide with a double reef in certain areas (e.g., Figure 3). This means that the total reef area of the Bank is very large and likely constitutes the largest coral reef area within the Dutch Caribbean. Fish. Some habitat types, such as mangroves and seagrass beds, are not present on the Saba Bank. Therefore fish species that occur solely in these habitats are absent from the Bank. Despite this, the Bank ranks 8th in terms of fish diversity in the Greater Caribbean, with an estimated number of fish species between 320 and 400 (Williams et al. 2010). Sharks and other predatory fish are quite common and seem to indicate an intact food chain. Mammals. Mammals have been sighted many times (Hoetjes and Carpenter 2010), but little effort has been made to carry out bias-free surveys from which population densities can be calculated. It is likely that a shallow area as large as the Saba Bank plays an important role in a mostly much deeper region. In 2012 the Dutch government is financially supporting cooperation with the French in sea mammal surveys in the area. The intention is to come to more regular monitoring of sea mammals in the region through international cooperation, and one of the intentions of the government is to establish an international whale sanctuary together with France, UK, and US, including the Saba Bank. Marine macroalgae. Littler et al. (2010) remark “Prior to this survey, the two most diverse areas for algae reported in the Caribbean had been Diamond Rock, Martinique and Pelican Cays, Belize, a mangrove, sea grass, and coral complex. Habitats on Saba Bank have far exceeded both of these places for species diversity. A major reason for this uniqueness and richness is the sheer size and habitat range of the seamount/atoll.” Thus, the Saba Bank appears exceptionally rich in marine algae. The algal fields of the bank are a source of food for many organisms. Sea turtles. The enormous diversity and abundance of marine algae and sponges means that there is ample food for these animals. Therefore it is assumed that the area is important as a feeding area for turtles. There were several confirmed sightings of hawksbills (Eretmochelys imbricata) during a survey in 2007. Leatherbacks (Dermochelys coriacea) and loggerheads (Caretta caretta) have also been seen on the Bank (Lundvall 2008). Sharks. Sharks appear to be reasonably common on the bank (Lundvall 2008). In 2010 a small expedition to the bank encountered several sharks on every dive. During dedicated surveys in 2006 and 2007 (Williams et al 2010), nurse shark (Ginglymostoma cirratum),Cuban dogfish (Squalus cubensis), reef shark (Carcharhinus perezii), tiger shark (Galeocerdo cuvier), and lined lantern shark (Etmopterus bullisi) were found. Soft corals. The species diversity of soft corals appears to be exceptionally high (Etnoyer 2007, Etnoyer et al. 2010), and already two new species have been found. Soft corals may benefit from the high-energy environment of the Bank, which makes it an excellent environment to develop local endemism. Forty eight species were found, but species-area accumulation curves suggest more than 50 species. Sponges. Many sponge species were found with a comparably small sampling effort (Thacker et al. 2010). The large area and wide variety of Saba Bank's reef habitats suggest that the Saba Bank provides an important reservoir of sponge biodiversity for the Caribbean. Sponge community health appeared to be very good compared to other localities in the Caribbean. Unique and potentially endemic sponge species were collected from each site, thus further exploration of Saba Bank might reveal additional species that are new to science. The widespread Caribbean reefs indicate that the sponge fauna of Saba Bank is broadly representative of the Caribbean as a whole. A robust population of giant barrel sponge (Xestospongia muta) is abundant on the Bank and appeared healthy with none of the signs of disease or bleaching reported from other Caribbean reefs. This species can grow for hundreds of years and has been called the “redwood of the sea” (McMurray et al 2008). Anchor chain damage to these sponges has occurred in the past, but is now prevented through a ban on anchoring.
The Saba Bank has a unique position in terms of geomorphology and biodiversity. The Bank is relatively isolated from land-based influences and intensive fisheries. Therefore, the chances of disruption of the ecosystem and its services by common sources of reef degradation, such as eutrophication, sediment runoff, and overfishing, may be small or even absent. Damage caused by other agents, such as temperature increases as a consequence of climate change, diseases, the sea urchin (Diadema antillarum ) die-off in 1983, hurricanes, and the introduction of invasive species such as the lion fish (Pterois volitans/miles),have occurred on the Saba Bank as well. There is growing scientific support that resilience of coral reef ecosystems to these region-wide disturbances may be better in areas that are relatively free from anthropogenic pressures (Mumby et al. 2007, Smith et al. 2008, Carilli et al. 2009). One of the biggest direct threats to the Saba Bank ecosystem is probably the anchoring of large tankers and cargo vessels. Their anchors and heavy chains may flatten large extensions of reef area that may require decades or longer to regenerate. With the designation of the area as a protected area (2010), anchoring has been forbidden. The Saba Bank still offers some of the most pristine coral reefs of the Caribbean. A research programme was started in 2011 by the Dutch Government (commissioned to the Institute of Marine Research and Ecosystem Studies, IMARES) to provide more knowledge on the ecological functioning of the Bank.
Information that is still missing It is still not clear how important the Bank is for seabirds and sea mammals, as there is no regular monitoring programme. Also, the carrying capacity for the lobster fishery is as yet unknown, but research has been started. Another point of attention is the biodiversity of the mesophotic reefs (40-150m). More research in this area has been planned for the near future. The Netherlands is taking steps to collect more information by stimulating monitoring and research, including the organization of a large international expedition to the area to collect relevant oceanographic and biological data. Other relevant information In view of the possible importance of the Saba Bank for other island reefs in the region (connectivity) it may well be possible to include the Saba Bank into a larger area meeting EBSA criteria. Because of its well documented biodiversity and protected status it is believed that it at this point in time may also be considered a separate area meeting EBSA criteria.
Boeke J (1907) Rapport betreffende een voorloopig onderzoek naar den toestand van de visserij en de industrie van zeeproducten in de kolonie Curacao. Eerste gedeelte. The Hague, Belinfante. Carilli, J.E., R.D. Norris, B.A. Black, S.M. Walsh, M. McField (2009) Local stressors reduce coral resilience to bleaching. Plos One, 4(7): e6324. doi:10.1371/journal.pone.0006324. Davis WM (1926) The Lesser Antilles. Am Geol Soc Pub 2: 207. Dilrosun, F. (2000). Monitoring the Saba Bank fishery. Department of Public Health and Environmental Hygiene, Environmental Division. Curaçao, Netherlands Antilles, 56 pp. Etnoyer, P.J. (2007) Multivariate analysis of gorgonian habitats on Saba Bank, Netherlands Antilles. Report. 12 pp. Etnoyer PJ, Wirshing HH, Sa´nchez JA (2010) Rapid Assessment of Octocoral Diversity and Habitat on Saba Bank, Netherlands Antilles. PLoS ONE 5(5): e10668. doi:10.1371/journal.pone.0010668 Hoetjes PC, Carpenter KE (2010) Saving Saba Bank: Policy Implications of Biodiversity Studies. PLoS ONE 5(5): e10769. doi:10.1371/journal.pone.0010769 Land, J. Van der (1977) The Saba Bank - A Large Atoll In The Northeastern Caribbean. FAO Fisheries Report no. 200, 469-481. Littler MM, Littler DS, Brooks BL (2010) Marine Macroalgal Diversity Assessment of Saba Bank, Netherlands Antilles. PLoS ONE 5(5): e10677. doi:10.1371/journal.pone.0010677 Lundvall, S. (2008) Saba Bank Special Marine Area Management Plan 2008. 94 pp. Macintyre, 1. G., Kinsman, D. J. J.& German, R. C. (1975). Geological reconnaissance survey of the Saba Bank, Caribbean Sea. Carib. J. Sci. 15: 11-20 McKenna, S. (2006) Preliminary report of the Saba Bank RAP expedition. 8 pp. McKenna SA, Etnoyer P (2010) Rapid Assessment of Stony Coral Richness and Condition on Saba Bank, Netherlands Antilles. PLoS ONE 5(5): e10749.doi:10.1371/journal.pone.0010749 McMurray, S. E., J. E. Blum, and J. R. Pawlik. 2008. Redwood of the reef: growth and age of the giant barrel sponge Xestospongia muta in the Florida Keys. Marine Biology 155: 159–171. Meesters, E.H., H. Nijkamp, L. Bijvoet (1996) Towards sustainable management of the Saba Bank. A report for the Department of Public Health and Environment (VOMIL), Curaçao, Netherlands Antilles. KNAP Project 96-03. 42 pp. Mumby, P.J., A. Hastings, H.J. Edwards (2007) Thresholds and the resilience of Caribbean coral reefs. Nature, 450(7166), 98-101. McMurray, S. E., J. E. Blum, and J. R. Pawlik. 2008. Redwood of the reef: growth and age of the giant barrel sponge Xestospongia muta in the Florida Keys. Mar Biol 155: 159–171. Postma, T. A. C. And H. Nijkamp. 1996. Seabirds, marine mammals and human activities on the Saba Bank. Field observations made during the Tydeman expedition, April-May 1996. AIDEnvironment, report. 25 pp. Purdy, E. G. and E. L. Winterer (2001). Origin of atoll lagoons. Bulletin of the Geological Society of America 113(7): 837-854. Smith, L.D., J.P. Gilmour, A.J. Heyward (2008) Resilience of coral communities on an isolated system of reefs following catastrophic mass-bleaching. Coral Reefs, 27(1), 197-205. Spencer JW (1904) The windward islands of the West Indies. Trans Can Inst 7(1901 1902): 351–370. Thacker RW, Dı´az MC, de Voogd NJ, van Soest RWM, Freeman CJ, et al. (2010) Preliminary Assessment of Sponge Biodiversity on Saba Bank, Netherlands Antilles. PLoS ONE 5(5): e9622. doi:10.1371/journal.pone.0009622 Toller W, Debrot AO, Vermeij MJA, Hoetjes PC (2010) Reef Fishes of Saba Bank, Netherlands Antilles: Assemblage Structure across a Gradient of Habitat Types. PLoS ONE 5(5): e9207. doi:10.1371/journal.pone.0009207 Vaughan TW (1919) Fossil corals from Central America, Cuba, and Puerto Rico, with an account of the American Tertiary, Pleistocene, and recent coral reefs. Smithsonian Inst U S National Museum Bull 103. Williams JT, Carpenter KE, Van Tassell JL, Hoetjes P, Toller W, et al. (2010) Biodiversity Assessment of the Fishes of Saba Bank Atoll, Netherlands Antilles. PLoS ONE 5(5): e10676. doi:10.1371/journal.pone.0010676
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Areas described as meeting EBSA criteria that were considered by the Conference of the Parties
C1: Uniqueness or rarityHigh
The Saba Bank is the largest atoll in the Caribbean and among the 10 largest of the world. The Bank is unique in that it is far away from larger landmasses that cause many human-related stressors such as eutrophication and run-off. Recently, new species have been discovered that may be unique to the area: • Six possible fish species (Williams et al. 2010) • Possibly 12 new marine macro algal species (Littler et al. 2010) • Two new species of soft corals (Etnoyer et al. 2010) • New sponge species are expected (Thacker et al. 2010)
C2: Special importance for life-history stages of speciesHigh
The area is important for the survival of local fish populations, as several fish spawning aggregations have been observed along the edge of the Bank (Lundvall 2008). Size and geographic position of the Bank indicates that it has an important function as a source of larvae from fish and invertebrates (connectivity). The area is used as feeding ground for turtles, and sea mammals and several shark species have been observed.
C3: Importance for threatened, endangered or declining species and/or habitatsHigh
The area is very large (app. 2200 km2) and provides substrate and food for corals, sponges, algae, fish, turtles, seabirds, and possibly whales, which have been observed over the Bank. It is an important feeding ground for red billed tropicbirds from Saba and harbours approximately 5% of the world population (www.Birdlife.org). Whales have been observed in the area, and sharks were encountered on each dive during a 2010 expedition. A large and healthy population of a sponge species that can grow to the age of hundreds, possibly thousands, of years (McMurray et al. 2008), is also present.
C4: Vulnerability, fragility, sensitivity, or slow recoveryHigh
Coral reefs are very sensitive to human impact (nutrients, run-off, overfishing, anchoring) and harbour many protected species. Recovery of damaged areas may take decades or longer. The total reef area is very large (more than 60km long and in places more than 1km wide). The non-reefal area forms an important habitat for one of the richest areas of marine macro algae in the Caribbean (Littler et al. 2010), and a large and exceptionally healthy population of barrel sponges (Thacker et al. 2010). The whole area is important as a feeding area for threatened species such as turtles and, indirectly, sharks.
C5: Biological productivityHigh
The area has been known as an important source of reef fish, conch, and lobster already since the early 20th century (Boeke 1907) and is still well known by fishers from Saba, St. Eustatius, and other islands for its exceptionally high productivity (Dilrosun 2000). Coral reefs are also among the most productive ecosystems on Earth.
C6: Biological diversityHigh
The Bank’s biodiversity has been studied very recently by a team of researchers, and a number of new species were found. The area was cited as one of the richest in the Caribbean in terms of biodiversity containing: • at least 150-200 macro algae species, among which possibly 12 new species (Littler et al. 2010), • between 320 and 410 fish species with possibly 6 new species (Williams et al. 2010), • at least 43 coral species (McKenna and Etnoyer 2010), • at least 48 soft coral species with 2 new species (Etnoyer et al 2010), • more than 84 sponges (Thacker et al. 2010), including a large, healthy population of large barrel sponges that can grow for hundreds of years.
C7: Naturalness High
The area is surrounded by very deep water and is far away from larger land masses, thus hardly influenced by well-known disturbances, such as excess of nutrients, runoff, coastal development, and overfishing. In comparison with other Caribbean areas, the Bank stands out because of its naturalness and pristinity.
http://www.kennisonline.wur.nl/Eleni/BO-11-011.05 (Dutch) describing the Netherlands’ research program in the Caribbean Netherlands. Saba Bank, Treasure beneath the sea. 2002. Video documentary. Department of Environment and Nature, Netherlands Antilles. Available on request. Data from expeditions available from authors of publications. Data from 2010 and 2011 expedition available from IMARES.