Unraveling a municipal effluent's toxicity to Tripneustes gratilla sperm fertilization

Abstract

A tiered investigative approach was employed to characterize and identify substances responsible for the persistent toxicity of a primary-treated municipal effluent to gametes of the Hawaiian sea urchin, Tripneustes gratilla. Toxicity identification evaluation (TIE) procedures from the US Environmental Protection Agency were modified to account for the tolerance of T. gratilla gametes to various sample manipulations. Microtox rapid toxicity screening was applied in some aspects of the study after verifying a correlation between the pattern of toxic responses of T. gratilla gametes and that of the bioluminescent bacteria Vibrio fischeri. Toxicity identification evaluation phase I manipulations revealed a toxicity profile implicating surfactants as possible toxicants, and TIE phase II toxicity assessment of isolated fractions coupled with colorimetric surfactant analyses confirmed the possible role of surfactants in effluent toxicity. The toxic effects of standard reference surfactants on T. gratilla fertilization indicated a concordance with the effects of the more nonpolar effluent fractions. Treatability studies showed that biodegradation by activated sludge eliminated effluent toxicity to urchin gametes.