The utility of molluscs as environmental indicators

Project Number
RI 7/09 SL

Project Duration
January 2009 - December 2013


In recent decades, El Nino and La Nina events have increased in intensity and frequency, occurring every two to three years. Scientists from NOAA explained in their 1998 report that higher global temperatures might be increasing evapotaion from land and adding moisture to the air, thereby intensifying the storms and floods associated with El Nino. In many locations, especially in tropics, La Nina (or cold episodes) produce the opposite climate variations to El Nino. For instance, parts of Australia and Indonesia are prone to drought during El Nino but are typically wetter than normal during La Nina. The weather conditions in Singapore are similarly affected. Biodiversity on this small island would be greatly affected when there are severe weather changes such as elevated temperatures drought or prolonged rainy spells. In addition, Singapore is a commercial hub with major shipping activities as well as intensive urbanization - such economic progress does not come without a price. It has beendocumented that our coastal waters and sediments are heavily contaminated with metals and anti-fouling paints. Three local species of muricid have been reported to exhibit as a result of tributyltin exposure. We propose to study the utility of molluscs as environmental indicators for noth heat stress as well as stress caused by pollutants using novel methods. Gastropod molluscs are ubiquitous animals in both marine and freshwater habitats, are relatively sedentary, respond well to handling and are easy to collect. Hence, they are ideal organisms to use as indicators. Quite a lot of work has been carried out in my laboratory on heat tolerances in the local littorinids as well as the Australian periwinkles. Aspects studies to-date include the strange 'head standing' behavior of periwinkles, enzyme stability in various species of periwinkles when subjected to heat stress and the effects of temperatures and density on the aggregation behaviours of periwinkles. Results of research in progress have shown that distribution and abundance of two species of littorinids (Echinolittorina malaccana & E. vidua) are affected by ambient temperature. We also discovered that the two species adopt different behavioural strategies to alleviate heat stress - this has never been reported before for these species. Funding is now sought in this present proposal to support further work to better understanding the protein expressions under headt stress in the two species. This will place Singapore science at the forefront of understanding aspects of cellular effects of climatic change. Bioaccumulation of pollutants in molluscs, especially bivavles and gastropods has been widely studied. In most of these studies, chemical analyses were carried out using whole body tissues of the molluscs which provides information on much linger-term exposure to pollutants. We propose to explore the use of the radula (feeding organ) as potential bioindicator of pollutant exposure. As the radula constantly renewed and fast-growing, it would provide a snap-shot of short term exposure which could be extremely useful in environmental impact assessment. Lastly, we propose to explore the potential of mucus as an indicator of pollutant contamination. As mucus can be obtained from live snails, there is no necessity of killing any specimens: any non-invasive method that can be used for environmental impact assessment is always a bonus in biodiversity conservation.

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