CORDIO Status Report 1999.pdf

Table 1. Diversity of scleractinian corals from Indian reefs.
Reef area Reef type Hermatypes Ahermatypes
Genera Species Genera Species
SE coast (Palk Bay and Gulf of Mannar) Fringing 28 84 9 10
Gulf of Kutch Fringing/patchy 20 34 3 3
Andaman and Nicobar islands Fringing 47 100 12 35
Lakshadweep islands Atolls 27 69 4 9
Submerged banks Patchy 5 5 – –
Central west coast Patchy 8 8 – –
Total 51 156 21 44
2,300 km 2 , but the extent of coralline shelves below one
optical length (detection limit of satellite-borne sensors)
could be several times higher, especially the shelves of
the Andaman and Nicobar reefs. In the Indian reefs, a
total of 200 species of coral, belonging to 73 genera can
be found (Table 1).
Today, resource harvest from Indian reefs – be it
food fish, mining of coral blocks, collection of debris, or
collection of seashells – is only for sustenance of the
reef-dependent population. In the early eighties, reefs in
the Gulf of Kutch were utilized for commercial mining
of coral sand (up to 1 million tons per year). Though
commercial mining has come to an end, clandestine
removal of coral debris is still a practice in some reef
areas in the Gulf of Mannar.
At present, tourism to reefs per se is not wellorganized
in India, and where it occurs it is usually
carried out with other objectives, mostly religious. For
example, some reef areas in Gulf of Mannar and Gulf of
Kutch are located near shrines (Rameswaram temple,
Pirotan Dharga). Only in the Lakshadweep islands,
thanks to the access-on-permit policy, can the extent of
tourism be judged correctly. The tourism industry there
operates on a low volume, high value approach, and
amounts to less than a thousand visitors per year.
THE BLEACHING EVENT
The 1998 bleaching event affected all Indian reef areas
to varying degrees. The Andaman and Nicobar reefs
appear to have suffered the most (up to 80% mortality),
followed by the Lakshadweep (43–87%) and the Gulf of
Mannar (an average of 60%) reefs. The reefs in the Gulf
of Kutch seem to have fared well, with mortality levels
much below 30%. Of all Indian reefs, these are the most
northern and they occur in extreme, arid conditions.
The area also experience a large seasonal temperature
range (15–30°C) and quite often prolonged spells of
desiccation due to high tidal amplitudes (several meters).
Adaptation to these extreme conditions could have
rendered the corals of the Gulf of Kutch more tolerant
to bleaching and its associated effects (e.g. UV-impact)
than corals of other reefs.
The effects on other reef organisms is unknown,
since quantitative data on their condition prior to
bleaching are scarce. Post-bleaching surveys did not,
however, show any abnormal or substantial reduction in
the abundance of any reef dwellers, including fish.
Surprisingly, after the bleaching event, the 1998 tuna
catch in the Lakshadweep islands was exceptionally
high. The exceptional catch is difficult to relate to the
bleaching event, but the increasing sea surface temperatures
could have favoured migration of tuna; they are
known to follow warm currents. The socio-economic
effects of coral bleaching are difficult to evaluate, since
neither reef fisheries nor tourism are organized industries.
In fact, a large part of the local population has not
even realized that bleaching is an ecological disaster.
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