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the variations in fish abundance and diversity correlated with alLerations in substrate
structure m determined by Carpenter et al. (f981) for certain Philippine reefs.
The relationship of increased reef degradation to rising human population levels has
been noted (Gomez, 1980; McManus and Wenno, 1981; Wijsman-Elest et aL, I98f). Destruction
of corel reefs is most evident near populated and industriat areas. B-eca-use of pnecisely these
trends associated with modernization and population growth, many problems thet do not as
yet exist in severe proportions are an[icipated in the near future, such as the various forms
of pollution.
Siltation
Siltetion constitutes me of lhe most important problems in the East Asian Seas region.
As indicated in Gomez (1980), major causes of siltation are large-scale deforestation, bad
agnicu ltural practices, and mangrove denudation. Additional causes which may attain
significant proportions in localized areas are terrestrial mining, dredging, offshore mining, oil
drilling, road construction, land clearance for domestic or industrial purposes, construction of
coastal struetures, and harbour dredging.
In Indonesia' particularly heavy destruction by siltation is known to occur in the
northern coast of Java due in part to intensive agrieulture, and off Padang in western
Sumatra, and Padangbai in eastern Bali from the construction of piers (Soegiarto and Polunin,
1981). Damage from siltation in Kalimantan and Sumatra is believed lo be a relatively recent
phenomenon (Soegiarto' I975). Examples of resulting destructive effects are shoreline
changes, modifications or burial of reefs, and alterations in patterns of sedimenL deposition,
erosion and distribution (Segiarto and Polunin, l98I).
Erosion caused by the dredging of reef corals is documented for Sanur and Kuta, and
Balikpapan (Tsuchiya et el.r 1976 and Samuel, 1979, in Ongkosongo, 1981). Sedimentation in
Southwest Sulawesi is believed to have been aggravated by mangrove denudation, and appears
Lo limit coral growth (Wijsman-Best et 4., 1981). In Ambon, deforestation may be associated
with hiqh nates of siltation (McManus and Wenno, f981).
At present, active offshore mining for tin, titanium and sand occurs in Indonesia
(Cruickshank, I98I). Offshore tin mining has been a major industny in Indonesia and Thailand
for many years, with as many as sixteen major dredges qerating in the coasLal islands.
Depths worked are generally less than 15 m, with Lotal digging depths of less than J0 m.
Recent siltation problems in Malaysia are attributed to dredging of channels f or
navigation near harbours and poris, and sand mining associated with the dredging qerations
(Chua and Pathansali, 1977). Also noted is indiscriminete deforestation (Rashid, 1980).
Dredging resociated with offshore mining is active in the case of iron and bauxite
(Cruickehank, 1981). Offshore tin is a resource to be exploited.
Siltation from various causes is associated with the complete loss of several reefs in
the Straits of Malacca, especially around Pulau Pangkor and Pulau Sembilan (Lulofs, 1977 in
De Silva, 1979). Other damaged areas include reefs of some offshore islands of the east coast
of Peninsular Malaysia' especially around bays near sites of agricultural developnrent (De
Silva' 1978 in De Silva' 1979). Destruction from similar causes has also mcuned in Teluk
Juara m the east coast of Pulau Tioman, and in the southenn coast of Pulau Mensirip, both
m the east coast of Peninsular Malaysia (De Silva et $., f980).
Coral reefs in the Straits of Malacea are generally poorly developed beceuse of high
turbidity and sedimentation due to increasing land clearance (Liew and Hoare, f979). Reef
development is ryparently also confined [o relat,ively shallow depths because of reduced light
intensity end srnothering by sediment. In e fringing reef at Cpe Rachado, significantly lower
values of living coverage and diveraity were attributed to sedimentation effects (Goh and
Sasekumar, I981).
In the Philippines' siltation from the different causes enunerated above is a widespread
and chronic problem (Gomez et {., f98l). ln eddition to being a problem by itself,
preliminary observations indicete that its presence in relatively large amounts may constitute
an added burden [o corals already stressed for another factor such as temperature (Y+ and
Gomez' 1981). This fact may eause the organism to exceed its threshold limits for zurvival.