Toxicity of landfill leachate to sea urchin development with a focus on ammonia.

Sea urchin gametes and embryos serve as a model system to evaluate toxicity in the marine environment. In this study, the toxicity of complex chemical mixtures in leachate samples to sea urchin development was examined with a focus on ammonia, which was the main contaminant of concern in most samples. Two rapid tests, the submitochondrial particle function and bacterial luminescence tests, were also used. Ammonia is highly toxic to sea urchin embryos with an EC50 of 1.3 mg l(-1) for the embryos of the Australian sea urchin Heliocidaris tuberculata. Leachate ammonia levels were well above these EC50 concentrations. To assess the contribution of ammonia to leachate toxicity in sea urchin development, we compared the predicted toxic units (PTU) and observed toxic units (OTU) for ammonia for each sample. The PTU/OTU comparison revealed that the sensitivity of the sea urchin embryos to ammonia were altered (enhanced or decreased) by other chemicals in the leachates. This result emphasises the need for parallel chemical analyses and a suite bioassays for evaluating the toxicity of complex and variable chemical mixtures.