Status of Coral Reefs of the World 2000

Status of Coral Reefs in East Africa
African coastline and splits north and south. The main reef system stretches for 770km from
the Rovuma River in the north, to Pebane in the south (17 o 20’S). Smaller isolated reefs are
dispersed along the 850km southern coast from Bazaruto Island to Ponta do Ouro
(26 o 50’S). Mozambique’s coastal population was estimated at just over 6.66 million people
(42% of the total) in 1997. Artisanal and commercial fishing, and tourism are the dominant
uses of coral reefs in Mozambique.
Tanzania
Two thirds of the 1000km coastline supports fringing and patch reefs on a narrow
continental shelf. The main areas of reef growth are along the islands of Unguja (Zanzibar),
Pemba and Mafia, and the mainland coast at Tanga, Pangani, Dar-es-Salaam Mkuranga, Lindi
and Mtwara. Tanzania’s coastal population was estimated at 8 million people in 2000, and
is concentrated in the districts around the capital Dar es Salaam. Coral reef use is varied,
with fishing and tourism supporting local and national economies.
Kenya
A continuous fringing reef dominates the southern 200km of Kenya’s coast. The fringing
reefs in the north are more patchy with influences from river discharges and influenced by
colder water from seasonal upwelling of the Somali current system. Kenya’s coastal
population in 2000 has been estimated to reach 2 million people, concentrated around the
main port of Mombasa. As with Tanzania, reef-based fishing and tourism are important
components of the coastal economy.
PRINCIPAL THREATS AFFECTING CORAL REEFS: 1998-2000
El Niño
There was a strong south-north gradient in the extent and impacts of the El Niño bleaching
event of 1998, which elevated normally warm local temperatures. Coral bleaching and
mortality started in the south in late February to early March 1998, and finished in May in the
north, directly corresponding to the ‘movement’ of the sun as it passed through the Inter-
Tropical Convergence Zone. There were dramatic losses of coral cover (summarised below).
After 1998, there were significant increases in fleshy, turf, calcareous and coralline algae
growing on the newly dead coral surfaces on all reefs, which in turn was influenced by an
abundance of herbivorous fish populations. The algae grew larger and more rapidly in areas
where there were large reductions in herbivore fishes due to over-fishing. These coral to algal
community shifts happened less in protected fish reserves. Non-reef building coelenterates
(cnidarians), including anemones, corallimorphs and soft corals were also heavily damaged
by bleaching and mortality on many reefs through East Africa. Changes in coral eating animals
were minor, but there were some increases in herbivore populations, such as on Mafia Island.
• South Africa: The bleaching threshold for corals was exceeded for both hard
and soft corals, but it was not excessive. Most corals on the reefs grow at 12m
or deeper, which may have protected them from warmer temperatures in surface
waters. Soft corals are more prevalent on shallow reef tops, with more
conspicuous bleaching.
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