EFFECTS OF CATIONIC SURFACTANT EXPOSURE TO A BIVALVE MOLLUSK IN STREAM MESOCOSMS

Effects of the cationic surfactant lauryl trimethyl ammonium chloride (C-12-TMAC) on growth, reproduction, cellulolytic enzyme activity, and larval colonization of Asiatic clams (Corbicula fluminea) were invest igated in experimental stream mesocosms. Clams from three different po pulations and of two known morphotypes were evaluated for growth in tw o 8-week experiments in fall 1989 and spring 1990. Growth was impaired at 185 mug TMAC per liter or greater for both seasons and was not mor photype dependent. Mortality, cellulolytic enzyme activity, and adult reproductive condition were not altered up to concentrations of 1153 m ug/L. However, larval clam (pediveliger) colonization was affected at concentrations of 43 mug/L. It is not known at this time to what exten t the effects on pediveligers would be manifested relative to recruitm ent to later life stages. These findings were compared to a published safety assessment for mono-alkyl quanternaries, of which TMAC is a mem ber. The findings reported here do not substantially alter conclusions from previous studies; however, clams appear to be among the more sen sitive taxa studied thus far.