Background
The authors write that Singapore "is one of the busiest ports of the world and land area is very limited," so that "space needed for industrial activities depending on maritime resources [has been] created at the coast or in the sea, which has caused suspended matter to decrease light penetration in coastal waters. In addition, they note that "besides the creation of landfills and dredging activities for port extensions, the seawater may also become sediment-enriched by logging and subsequent terrigenous run-off along the nearby coastline." And they say that "all these activities may cause damage to coral growth and survival," citing the work of Dodge et al. (1974), Dodge and Vaisnys (1977), Rogers (1990) and McClanahan and Obura (1997).

What was done
Hoeksema and Koh studied the characteristics of mushroom corals (Scleractinia: Fungiidae) that had either been collected from the coastal waters of Singapore or merely photographed in situ, based on historical records and specimen collections maintained at Singapore's Raffles Museum of Biodiversity Research, which were provided by researchers in the 1860s, 1890s, 1970, 1986-1991 and 2006, with the goal of identifying all of the species that were present at each of the times of observation.

What was learned
The two researchers report that all of the records together yielded a total of 19 species, but that "four species represented in collections made before 2006 were not observed during the 2006 survey." In addition, they say that three of the four species "are usually absent on reefs close to river outlets and most abundant on offshore reefs (Hoeksema and Moka, 1989; Hoeksema, 1990,1993)," which suggests, in their words, that these species "are less capable to withstand sedimentation" and, therefore, that the "increase in sediment load at Singapore is a likely cause for their disappearance."

Changing gears slightly, Hoeksema and Koh state that "although Singapore's reefs suffered severe coral bleaching in 1998, some species (including Fungia spp.) were also known to have recovered quite soon," citing Chou (2001). Likewise, they say that "coral populations in the offshore Thousand Islands off Jakarta showed recovery after the 1983 bleaching event (Brown and Suharsono, 1990; Hoeksema, 1991)," and that "during a coral reef survey in 2005 species richness of mushroom corals in the same area showed no visible decrease in species numbers." Therefore, as they continue, "coral bleaching is not a likely cause for a decrease in fungiid species richness in Singapore."

What it means
As Idso et al. (2000) have long maintained, sediment delivery and associated chemical insults to reef environments -- such as are caused by the rising levels of nutrients and toxins in coastal waters due to runoff from agricultural activities on land and activities such as those cited in the introduction to this Journal Review -- are a much greater threat to earth's corals than are rising temperatures and atmospheric CO2 concentrations, which conclusion is essentially the same as what Hoeksema and Koh concluded: "The observed loss in mushroom coral species in Singapore is most likely linked to an increased sediment load of the water and the reefs as a result of land reclamation projects in the harbor of Singapore (Hilton and Chou, 1999) and deforestation of Singapore's hinterland (Brook et al., 2003)."

References
Brook, B.W., Sodhi, N.S. and Ng, P.K.L. 2003. Catastrophic extinctions follow deforestation in Singapore. Nature 424: 420-423.

Brown, B.E. and Suharsono. 1990. Damage and recovery of coral reefs affected by El Niņo related seawater warming in the Thousand Islands, Indonesia. Coral Reefs 8: 163-170.

Chou, I.M. 2001. Country report: Singapore. Report of the International Coral Reef Initiative.

Dodge, R.E., Aller, R.C. and Thomson, J. 1974. Coral growth related to resuspension of bottom sediments. Nature 247: 574-577.

Dodge, R.E. and Vaisnys, J.R. 1977. Coral populations and growth patterns: responses to sedimentation and turbidity associated with dredging. Journal of Marine Research 35: 715-730.

Hilton, M.J. and Chou, L.M. 1999. Sediment facies of a low-energy, meso-tidal fringing reef, Singapore. Singapore Journal of Tropical Geography 20: 111-130.

Hoeksema, B.W. 1990. Systematics and Ecology of Mushroom Corals (Scleractinia: Fungiidae). PhD Thesis, University of Leiden, 471pp.

Hoeksema, B.W. 1991. Control of bleaching in mushroom coral populations (Scleractinia: Fungiidae) in the Java Sea: stress tolerance and interference by life history strategy. Marine Ecology Progress Series 74: 225-237.

Hoeksema, B.W. 1993. Mushroom corals (Scleractinia: Fungiidae) of Madang Lagoon, northern Papua New Guinea: an annotated check-list with the description of Cantherellus jebbi spec. nov. Zoologische Mededelingen, Leiden 67: 1-19.

Hoeksema, B.W. and Moka, W. 1989. Species assemblages and phenotypes of mushroom corals (Fungiidae) related to coral reef habitats in the Flores Sea. Netherlands Journal of Sea Research 23: 149-160.

Idso, S.B., Idso, C.D. and Idso, K.E. 2000. CO2, global warming and coral reefs: Prospects for the future. Technology 75S: 71-93.

McClanahan, T.R. and Obura, D. 1997. Sedimentation effects on shallow coral communities in Kenya. Journal of Experimental Marine Biology and Ecology 209: 103-122.

Rogers, C.S. 1990. Responses of coral reefs and reef organisms to sedimentation. Marine Ecology Progress Series 62: 185-202.