Water quality : is the effluent from Australian mariculture operations a problem in mangrove communities?

Mangroves are a community under pressure from many sources. Most pressure comes from clearing, in-filling and erosive events. Increasingly there are questions about the effects of long term changes in the quality of the tidal waters that flow through the communities. Estuarine and coastal waters that flow through mangrove communities receive run-off from industrial, domestic and agricultural processes. As well the waters may receive high volumes of pollutants from short term accidental discharges. In considering the effects of water quality on the mangrove communities we are looking at either short term polluting events or long term alterations in the chemical constituents and contaminants that are found in the water that moves through the communities. These components may be taken up and stored in the sediment or the biomass in the communities or remain in the water column. The fates of these extra inputs are not clearly understood. Clearly defining what is meant by the term water quality as it applies to these concerns about mangrove communities is a difficult process. While studies on the effects of pollution events eg. oil spills are found in the literature, there has been little published research on the long term effects of changes in water quality on mangrove communities. There are particular examples where research is required. The difficulties are that the base-line studies to define the chemical and biological constituents of the water have not been carried out. Instantaneous measurements of water, biomass or sediment composition are not enough. What is needed are long term surveys covering as wide a range of chemical and biological parameters as possible.