Ecologically or Biologically Significant Areas (EBSAs)
published:12 Jun 2015
Saya de Malha Bank
The Saya de Malha Bank is the largest of three shallow banks forming the Mascarene Plateau,, located in the Western Indian Ocean along the underwater Mascarene Ridge that spans the distance between the Seychelles and Mauritius. The Mascarene Plateau, being remote, with emergent land and small islands only at its southern extreme, is not yet well-known globally, or well-studied, but there are strong indications of unique oceanographic features and habitats, including the largest seagrass beds and shallow-water biotope in the world, species endemism and significant aggregations of marine mammals and seabirds. Mauritius and the Seychelles have individual or joint jurisdiction over the waters and entire seabed of the plateau, though the waters over the Saya de Malha Bank are beyond national jurisdiction in the high seas.
The Saya de Malha bank sits in the path of the South Equatorial Current (SEC), that dominates the oceanography of the Western Indian Ocean (WIO), and together with its sister plateau to the south, the Nazareth bank, concentrates the flow of the SEC into a narrow passage between them at 12.5-13oS. The bank thus has a major influence on the oceanography of the WIO and regions to the west. Only a small proportion of the SEC passes north of the bank as a slow, broad current, and island wakes and eddies in the lee of the bank may result in higher oceanic productivity due to mixing and upwelling. The influence of these features on the connectivity of the marine fauna of the bank and plateau system, with other coralline islands in the Seychelles, and for the WIO in general, is presently unknown. Enhanced oceanic productivity caused by interaction of the banks with the SEC is likely important for ocean food webs, including for seabirds such as wedge-tailed shearwaters and white-tailed tropicbirds (Seychelles Basin) and pygmy blue whales (Balaenoptera musculus brevicauda), which use it as a feeding and breeding ground.
DISCLAIMER: The designations employed and the presentation of material in this map do not imply the expression of any opinion whatsoever on the part of the Secretariat concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.
The Saya de Malha Bank is the largest single bank in the Indian Ocean, larger than the Great Chagos Bank. The bank is considered flat, but considerable depth variation occurs across its top, with the shallowest being a crest less than 75 m deep to the north and east and with extensive areas shallower than 20 m, additional shallow patches west of this and at the north-west side, and depressions down to 300-400 m depth in the centre of the bank. The entire bank is clearly differentiated at the 500 m contour from the deep ocean surrounding it. With no exposed island mass, the waters over the bank are a globally unique mid-ocean shallow sea. The smaller northern bank, the Ritchie plateau, is separated from the main bank by a transform fault and is part of the granitic continental rock of the Seychelles bank and the ridge extending between them in a NW-SE direction. South of the Saya de Malha Bank, the Nazareth and Cargados Carajos banks are of Bsimilar construction, and only St. Brandon’s Island, at the southern end of the Cargados Carajos Bank, has any aerially exposed landmass. Current knowledge holds that the bank supports the largest contiguous seagrass beds in the world, with 80 to 90% of shallow surfaces being covered by seagrasses dominated almost exclusively by Thalassondendron ciliatum, from depths up to 30-40 m, with additional records of Halophila decipiens and Enhalus acoroides. Coral reefs appear limited to rocky patches and outcrops, and likely to the edges of the bank. A partial survey conducted in 2002 documented that seagrass covers roughly 80 to 90% of the bottom, with corals covering between 10 and 20%, and sandy areas covering the remaining 5% (Hilbertz et al 2002). Shallower portions of the banks support a diverse reef-fish community including parrotfish, surgeonfish and rabbitfish. Pelagic fishes such as flying fish, bonito and tuna as well as whales (beaked, pilot) and dolphins (spotted, spinner) have been observed in the deeper, nutrient-rich waters over the edges of the banks. The deeper water that surrounds the banks also are known to be a breeding ground for pygmy blue and sperm whales (Vierros 2009, Hilbertz et al 2002).
There is no human habitation on or near the bank as there is no emergent land. Thus the ecological integrity of the bank is very high, and an EBSA that includes the whole bank would meet the highest level of integrity possible. Nomination of a portion of the bank would result in slightly lower integrity of the nomination site, but coherent management under the Joint Commission of Mauritius and the Seychelles could ensure high enough integrity for sustainability of a site. Management: future management of the Saya de Malha bank will depend on the Joint Commission established by the Seychelles and Mauritius, and national priorities such as in fisheries. Management, surveillance and enforcement of a distant marine zone with no emergent land to host a management base will be challenging, but increasingly possible with the advent of remote sensing surveillance technologies, and existing operationalization of them in, for example, fisheries management and vessel surveillance. National legislation to enable management of this type of distant marine site would be necessary.
Ardron J, Dunn D, Corrigan C, Gjerde K, Halpin P, Rice J, Vanden Berghe E, Vierros M (2009) Defining ecologically or biologically significant areas in the open oceans and deep seas: Analysis, tools, resources and illustrations. GOBI/CBD. Ottawa, Canada. 29 September – 2 October 2009 ASCLME. 2008. Information captured for transboundary diagnostic analysis development: offshore ecosystems and oceanographic data collection. A powerpoint presentation. Backman, J., Duncan, R. A., et al., 1988. Proceedings of the Ocean Drilling Program, Initial Reports, 115: 1 – 11. Bertrand, J., 1988. Selectivity of hooks in the handline fishery of the Saya de Malha Banks (Indian Ocean). Fisheries Research, 6: 249-255. Brooke SD, Lim TY, and Ardron JA. (2010) Surveillance and enforcement of remote maritime areas. Paper 1: surveillance technical options. Marine Conservation Biology Institute, USA. Version 1.2; 39 Pages. Christiansen, S. 2010. Saya de Malha Banks – A potential MPA. WWF Briefing. Duncan RA (1990) The volcanic record of the Reunion hotspot. In: Duncan, R. A., Backman, J., Peterson, L. C, et al., 1990 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 115 FAO. 2010. Fisheries and aquaculture topics. Deep-sea high seas fisheries. Topics Fact Sheets. In: FAO Fisheries and Aquaculture Department [online]. Rome. Updated 10 February 2010. [Cited 6 December 2010]. http://www.fao.org/fishery/topic/4440/en Fisher, R. L., Johnson, G. L., and Heezen, B. Z. 1967. Mascarene Plateau, Western Indian Ocean. Bulletin of the Geological Society of America, 78: 1247-1266. Gallienne, C. P. and Smythe-Wright, D. 2005. Epipelagic Mesozooplankton Dynamics around the Mascarene Plateau and Basin, Southwestern Indian Ocean. Philosophical Transactions: Mathematical, Physical and Engineering Sciences, 363: 191-202. GOBI. 2009. Saya de Malha Banks—Case study. http://www.gobi.org/Our%20Work/rare-1 Grandcourt, E. M. 2003. The effect of intensive line fishing on the virgin biomass of a tropical deepwater snapper, the crimson jobfish (Pristipomoides filamentosus). Fishery Bulletin April 01, 2003: http://www.accessmylibrary.com/coms2/summary_0286-23362382_ITM. Last accessed 3 December 2010. Hilbertz, W., Gutzeit, F., Goreau, T. 2002. Saya de Malha Expedition March 2002. funded by the Lighthouse Foundation, pp. 1-107. http://www.lighthousefoundation.org/fileadmin/LHF/PDF/saya_de_malha.pdf (Last accessed 3 December 2010). International Seabed Authority. Atlas of the International Seabed Area and its Resources. http://www.test.isa.org.jm/client/html/viewer.html. Last accessed on 2 December 2010. Maguire, J. J., Sissenwine, M., Csirke, J., Grainger, R., and Garcia, S. 2006. The state of world highly migratory, straddling and other high seas fishery resources and associated species. FAO Fisheries Technical Paper. No. 495. Rome: FAO. 84p. Meyerhoff, A. A. and Kamen-Kaye, M. 1981. Petroleum Prospects of Saya de Malha and Nazareth Banks, Indian Ocean: Geologic Notes. AAPG Bulletin, 65. Milchakova, N. A., Phillips, R. C., and Ryabogina V. G. 2005. New data on the locations of seagrass species in the Indian Ocean. Atoll Research Bulletin, 537: 178-188. Nath, B. N. and M. S. Prasad. 1991. Manganese nodules in the exclusive economic zone of Mauritius. Marine Mining 10: 303-335. New, A. L., Stansfield, K., Smythe-Wright, D., Smeed D. A., Evans, A. J., and Alderson, S. G.. 2005. Physical and biochemical aspects of the flow across the Mascarene Plateau in the Indian Ocean. Phil. Trans. R. Soc. 363: 151–168. Obura, D, Church, J, Gabrié, C. 2012. Assessing Marine World Heritage from an Ecosystem Perspective: The Western Indian Ocean. UNESCO world Heritage Centre. Payet, R. 2004. Research, assessment and management on the Mascarene Plateau: a large Marine ecosystem perspective. Philosophical Transactions of the Royal Society A, 363: 295-307. Sanders, M. J. 1993. Fishery performance and the value of future entitlements under quota management: A case study of a handline fishery in the southwest Indian Ocean. Fisheries Research, 18: 219-229. Shor Jr., G. G. and Pollard, D. D. 1963. Seismic Investigations of Seychelles and Saya de Malha Banks, Northwest Indian Ocean. Science, 142: 48 – 49. UNCLCS. 2008. Joint submission by the Republic of Mauritius and the Republic of Seychelles. http://www.un.org/Depts/los/clcs_new/submissions_files/submission_musc.htm. Last accessed on 3 January 2011. UNEP-WCMC. 6 December, 2010. UNEP-WCMC Species Database: CITES-Listed Species Vierros, M. 2009. The Saya de Malha Banks. GOBI Illustration case study. http://openoceansdeepseas.org/Our%20Work/rare-1/at_download/pdf. pp. 1-6. Vortsepneva, E. and Spiridonov, V. 2008. Saya de Malha –an invisible island in the Indian Ocean. Review of historical surveys of environmental conditions and biodiversity. Report to the Lighthouse Foundation, Moscow, Russia, pp. 1-42. WWF 2011 The Saya de Malha Banks factsheet. WWF Madagascar Marine Programme
Areas described as meeting EBSA criteria that were considered by the Conference of the Parties
C1: Uniqueness or rarityHigh
The Saya de Malha Bank is the largest bank of its type in the Indian Ocean, including the largest seagrass beds in the world, and it and neighbouring banks form a large contiguous shallow marine habitat that supports production in the surrounding ocean.
C2: Special importance for life-history stages of speciesHigh
Breeding grounds for the pygmy blue whale Balaenoptera musculus brevicauda.
C3: Importance for threatened, endangered or declining species and/or habitats No information
Uncertain as data are not very comprehensive. Although limited information exists on species associated with the Saya de Malha Banks, it is known that the seagrass meadows serve as nursery habitat for juvenile fishes, as feeding grounds for green sea turtles (listed as endangered by CITES), as grazing areas for larger predators and marine mammals, and as foraging areas for terns (Hilbertz et al 2002). In addition, a Russian expedition in 2008 reported an estimated five percent rate of endemism and identified more than 150 species of invertebrates (Vortsepneva and Spiridonov 2008).
C4: Vulnerability, fragility, sensitivity, or slow recovery No information
Unknown, though climate change is expected to be a significant threat for the carbonate-dominated food webs of the shallow banks.
C5: Biological productivityHigh
Ocean-platform interactions result in raised productivity on and downstream of the bank through mixing and seabed-water column interactions. Both satellite data and field measurements support the hypothesis that the Saya de Malha Banks form an area of high productivity (Vierros 2009, Gallienne and Smythe-Wright 2005). New and others (2005) documented higher nitrate levels on the eastern side of the banks (Figure 2). Elevated levels of chlorophyll, which correlates to relatively higher levels of net primary productivity, can be observed in satellite imagery of the region (New et al. 2005).
C6: Biological diversity No information
Not surveyed well enough to assess.
C7: Naturalness High
The remoteness of the Saya de Malha Banks provides them with a higher degree of naturalness than most other seagrass communities in the world, the vast majority of which are in nearshore environments. Hence, by their remoteness, they are removed from most land-based sources of anthropogenic stress. Due to the shallowness of the banks, the area generally is avoided on shipping routes as a navigational hazard (Christenson 2010). The banks are not entirely free from human-induced disturbance, however. Mauritius maintains a fishery for emperor fish (Lethrinus mahsena), a commercially valuable species. Handline fishing boats have been exploiting fisheries of the Saya de Malha Banks since the early 1960s (Bertrand 1988). The collateral impacts of this relatively small fishery are not known, but are probably not great. There are no known high seas fisheries for deep-water snapper and deep-water shrimp (Maguire et al 2006). In addition, earlier exploration for petroleum reserves and mineral deposits in the area resulted with no positive identification (Backman and Duncan 1988, ISA 2010, Meyeroff and Kamen-Kaye 1981, Nath and Prasad 1991). Straddling stocks do exist on the Mascarene Ridge, including the Saya de Malha Banks, where Mauritius maintains pelagic fisheries of dame berri (Lethrinus mahsena) and capitaine (L. nebulosa) (Maguire et al. 2006). Greater protection of the Chagos archipelago is reportedly displacing fishing activity from South Asian countries to the Saya de Malha Banks.
The Mauritian experts indicated that they supported the description of Saya de Malha Bank as an area meeting EBSA criteria purely for scientific—rather than for management—purposes. Rights and permissions Some text is from a UNESCO World Heritage report: Assessing Marine World Heritage from an Ecosystem Perspective: The Western Indian Ocean, by David Obura, Julie Church, Catherine Gabrié.