EUTROPHIC WATERS OF SOUTHWESTERN AUSTRALIA

Water bodies in coastal areas of southwestern Australia are predispose d to eutrophication. The sandy soils of the catchments retain nutrient s poorly, streamflow is highly seasonal, most freshwater wetlands are small and shallow, and the estuaries are poorly flushed. Nearshore wat ers lack the conventional upwelling of other coastal regions in these latitudes. Consequences include increased macroalgal growth and phytop lankton blooms, especially of cyanobacteria, and loss of seagrasses. C hanges to fish and invertebrate populations result both from increased algal production and low oxygen concentrations. Algal toxins and outb reaks of botulism have caused waterbird casualties. Phosphorus is espe cially important in controlling plant biomass in freshwater wetlands a nd estuaries, and N in some wetlands and coastal embayments. In the ex amples reviewed here nutrients are derived mainly from fertilizer appl ications in catchments and rural industries, and from sewage and indiv idual discharges to coastal waters.