EVALUATING THE HAZARD OF DODECYL ALKYL SULFATE TO NATURAL ECOSYSTEMS USING INDIGENOUS PROTISTAN COMMUNITIES

The effect of the surfactant dodecyl alkyl sulphate (C(12)AS) on the s tructure and function of lotic protistan assemblages was examined usin g the Experimental Stream Facility (ESF) operated by the Procter and G amble Company. Population- and community-level responses to C(12)AS we re monitored on introduced substrates placed in the channels 28 days p rior to dosing (mature communities) as well as those placed in the cha nnels on day 0 of dosing (immature communities), to allow for a broad assessment of the effect of the chemical on processes contributing bot h to community development and maintenance. C(12)AS appeared to elicit a subsidy response from the native protistan assemblage which may hav e resulted from both positive and negative responses at trophic levels above and below the assemblage. Protistan responses to the surfactant tended to occur more rapidly and be more sensitive than those documen ted for invertebrates and fish. C(12)AS elicited a modest response (i. e. a 20% change) from several reliable parameters including community respiration (reduced dissolved oxygen at 289 mu g per L), protozoan sp ecies richness (increased at 63 mu g per L) and protozoan community co mposition (increased dissimilarity at 1254 mu g per L). Responses to C (12)AS exceeded expected exposures in the real world by a factor of si x or greater thereby indicating that the hazard of exposure to C(12)AS to stream communities is low The results of this study support the us e of mesocosms as decisive tools for evaluating the hazard posed by co nsumer product chemicals to natural communities and ecosystems.