Answering questions on the impact of recycled water on wildlife using Gambusia holbrooki as a surrogate

The disruption of endocrine systems due to environmental contaminants potentially impacts on developmental, behavioural, regulatory, and reproductive systems of wildlife. A major source of exposure of wildlife (terrestrial and aquatic) to endocrine disrupting compounds is through contact with contaminated surface waters. Current testing routines in aquatic systems have not been designed specifically to assess endocrine disruption properties or, alternatively, methods tend not to be fully developed. An alternative approach is to use a response sensitive to these chemicals such as gonopodium length in the pest species Gambusia holbrooki as an indicator. This species was used as a surrogate for native aquatic species to assess endocrine disruption in wetlands that are used for the storage of stormwater or treated sewage effluent. These were compared with adjacent wetlands used for watering stock (farm dams) that were not contaminated with these pollutants. Deformities in the mosquito fish were found that were consistent with endocrine disruption caused by sex steroids and/or their mimics in the first in the sequence of each pollution type but not in farm dams. We concluded that the first wetland in the sequence of recycling stormwater or treated sewage effluent could cause detrimental effects to wildlife but not in subsequent wetlands in a sequence of water storage systems. Since all waters are moved through at least three wetlands before being used for irrigation, or released into the river system, the impact on wildlife is likely to be minimal beyond the first wetlands.