Acropora palifera, a particularly dense coral which lives in shallow, wave exposed regions, especially on seaward reef slopes facing north to west.  It was abundant in 1979.  The grey shading in the inset compass diagram (scale is % cover of shallow substrate) shows that it covered between 20-40% of the shallow reefs in these areas.  In 1996 its abundance was noted to have decreased markedly (small black shaded part in the compass diagram) though it was still not 'rare'.  The cause was not known at that time, though it was commented that it may have been due to natural fluctuations.  Following further general collapse in abundance of corals two years later in 1998, it is now suspected that this fall was due to the occasional El Nino events through the 1980s.  Today it is almost extinct in Chagos, though some surviving branches may be found.  It lives in shallow water, so any deeper 'refuges' of corals probably do not harbour this important, wave, resisting species.

