Excess nutrients
Because Australia is an old continent, natural nutrient levels are low compared to Europe and North America. Nutrients are important for plants and animals growth. However, when excessive amounts of nutrients are present, algal blooms and nuisance plant growths can occur in waterways. This can lead to:
- reduction in habitat and light availability for plants and animals
- decreases in the available oxygen in the water
- obstruction of waterways, affecting recreational use and fish migration
- odours and an unsightly appearance
- the production of toxins which threaten aquatic ecosystems and human uses of water (for some cyanobacteria blooms).
Elevated nutrient levels in waterways, reservoirs and wetlands can be caused by wastewater treatment plant discharges, urban stormwater runoff, irrigation drainage, agricultural runoff, intensive animal industries, soil erosion and forestry activities.
Nutrients enter the marine environment through creeks, rivers and estuaries. Excessive nutrient inputs from catchments to the coast can lead to imbalances to marine ecosystems. For example the Gippsland Lakes receive high levels of nutrient inputs, which has lead to some of the outcomes listed above.
Information on nutrients is available on the Murray Darling Basin Commission's website.