Abstract

An unusual marine benthic community has been found to have established adjacent to an inland urban drain.  The fauna found were the Common Sandpiper (Actitis hypoleucos), mudskippers (Periophthalmus gracilis), one Malayan Water Monitor Lizard (Varanus salvator), mud lobsters (Thalassina anomala) and crabs like Scylla olivacea, Varuna yui, Episesarma spp, Uca annulipes, Perisesarma eumolpe and Uca rosea (endangered).  The most visible and abundant species of crabs, Uca annulipes was selected for this study.  The population density, drain water salinity, sediment salinity and LC₅₀ were determined and compared with natural habitats of similar Uca populations in Singapore.  Population density (25 individuals m^-2 ) was found to be comparable to natural habitats of East Coast Park and Pasir Ris Park.  The mean drain water and sediment salinity at the junction where most Uca annulipes burrow were found was 6.57 ± 1.34 ‰ and 11.63 ± 2.33 ‰ respectively.  LC₅₀ of specimens from the study site was found to be 0.067 ± 0.313 ‰.  While the drain water and sediment salinities were significantly different from that of natural habitats, Uca annulipes captured from all locations did not exhibit any significant difference in salinity tolerance.  The results suggest that Uca annulipes are able to survive in environments with a wide range of salinities.  They could tolerate high salinities but were unable to tolerate prolonged periods of exposure to near-freshwater salinities.