“…This valve movement detection method was used to study both natural changes in the environment and the effect of pollutants, e.g. the effects of temperature (Hiscock, 1950), light (Bennett, 1954;Ameyaw-Akumfi & Naylor, 1987), tidal movements, salinity (Davenport, 1979(Davenport, , 1981Akberali & Davenport, 1982), food quantity and quality (Higgins, 1980) and a series of toxicants like trace metals (Salanki & Varanka, 1976;Davenport, 1977;Manley & Davenport, 1979;Kramer et al, 1989), pesticides (Salanki & Varanka, 1978) and other trace organics (Sabourin & Tullis, 1981;Slooff et al, 1983).…”