The Seychelles government has been hailed as a champion of the Blue economy concept, which has been adopted to diversify the Seychelles economy, to ensure long-term food security, to implement and maintain sustainable management of marine resources and by doing these things broaden and increase jobs available to Seychellois. The Blue economy is therefore built on and entirely reliant upon the health of the Seychelles exclusive economic zone, i.e. the ocean belonging to the Seychelles. Aldabra is the flagship of the Seychelles marine ecosystems, representative of the many intrinsically linked ecosystems that are paramount in securing biodiversity and thus safeguarding ecosystem health and food security in the region. Although Aldabra is one of several such marine hotspots in Seychelles, it is by far the largest in the region and renowned at a global level.

What role does Aldabra play in ecosystem health?

• The most recent land-cover study of Aldabra estimated the mangrove area to be 1720 ha, distributed along the lagoon shores. Mangroves fulfill many important ecological, social and economic functions. Not least that they are primary producers and therefore play a central role in transferring organic matter from the land to adjoining waters. This matter forms the base of off-shore marine food chains. In addition, mangrove stands provide nursery and spawning areas for coastal fish and shellfish species, and are a useful stopover site for migratory birds, fish, and mammals. The Aldabra mangroves contribute directly to supporting fish stocks in the area and therefore are a key component when considering food-security.

• Aldabra Atoll hosts vast areas of seagrass beds both inside the lagoon and on the outer reef flats. Seagrasses provide one of the most productive ecosystems in the biosphere, supporting a number of ecological roles and making them powerful ecological engineers. Seagrasses stabilise the habitat, aid in water filtration and clarity and provide both food and shelter for a wealth of species. Species directly dependent on seagrass at Aldabra are the iconic green turtle, for which Aldabra supports the largest breeding population in the Western Indian Ocean, and also the rare dugong which was largely extirpated from Seychelles waters through hunting and habitat destruction.

• The Aldabra seaward reef complex is approximately 53km², the lagoon reef is 19.24km². The coral reefs of Aldabra Atoll are among the richest in the western Indian Ocean, with a recent study showing biomass of fishes in the Aldabra Group is the largest in the Seychelles and among the largest in the Indian Ocean with Aldabra being the only location where sharks were recorded in significant numbers. Based on Aldabra's geographic location and position in the South Equatorial current it is likely that the atoll acts as a seeding site to coral reefs further east with both coral and fish larvae being circulated across the oceans, much like seeds are dispersed on the winds. Because Aldabra has a well-balanced ecosystem it is more resilient to environmental impacts than other reef areas that are also under a variety of anthropogenic stressors such as over fishing. For example, Aldabra's parrotfish, rabbitfish and surgeonfish are present in their natural numbers so when an event such as the 2016 bleaching takes place and coral cover decreases, these fish are busy grazing away the algae that would quickly utilise the space used by the corals and therefore give the coral a better chance of growing back.

What does Seychelles Islands Foundation (SIF) do to ensure Aldabra continues to fulfill this regionally vital role in ecosystem health and safeguarding marine biodiversity?

SIF has been managing Aldabra as a special reserve since 1981 under the National Parks and Nature Conservancy Act. This means that Aldabra has been completely protected for 36 years with no extraction of resources, no destruction of habitat and enforced protection of the marine protected area. Throughout this time SIF has carried out extensive scientific research to understand the Aldabra ecosystems and their value to the Seychelles. Several large projects have been conducted including the habitat mapping of the seaward reefs, as part of the GEF Protected Areas Project, to inform Aldabra’s Marine Protected Area (MPA) expansion strategy. The results of which have guided the decision to extend the Aldabra MPA out to approximately 30km in all directions. One of the more fundamental strategies for enhancing knowledge and informing management decisions is the regular long-term monitoring of the reefs and SIF has set up a comprehensive marine monitoring programme that provides essential and regular information on the marine ecosystem components. The monitoring programme includes: annual assessment of the benthic habitat, assessing the reef composition and changes to reef components such as hard coral cover; assessing fish abundance and diversity; assessing coral juvenile abundance and composition; using temperature and tidal loggers around the atoll to asses temperature and sea level changes and using baited and unbaited remote underwater video footage to assess the effectiveness of the MPA zoning plan. All of these methods are conducted by the SIF research staff stationed on Aldabra, building capacity in marine science within the Seychelles community. There is still a great deal to learn about the importance of Aldabra within the region and the SIF research strategy will focus on this in coming years.

With ever increasing stressors impacting marine resources around the globe, the value of Aldabra reserve increases. The government of Seychelles has recognised this and under the Blue economy concept are further safeguarding this invaluable resource; a wise decision!

April J. Burt

Seychelles Islands Foundation

Forrás: www.nation.sc