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Issue: Response of biota - Bacteria and algae

This is an issue under the Inland waters theme of the Data Reporting System.

Why we need to know about this issue

Bacteria and algae are important components of freshwater biodiversity and ecosystems, breaking down organic matter, releasing oxygen through photosynthesis and providing a basis of the food chain. Excess nutrients in the water can cause algae to overpopulate into blooms. Large blooms may spread across the upper levels of surface waters. The algae below the surface layer is blocked off from sunlight and dies. The dead blooms continue to block sunlight from other aquatic organisms and, while no longer providing oxygen through photosynthesis because they are dead, their decay actively robs the water of oxygen and can change water chemistry in other ways. This in turn can kill everything else that depends on the freshwater habitat.

Cyanobacteria (blue-green algae) are natural components of Australian inland waters occurring frequently during droughts and in billabongs. Blooms can be highly toxic to people and animals. Certain species of blue-green algae produce toxins that may cause skin irritations, gastrointestinal disorders, influenza-like symptoms and, in extreme cases, permanent organ damage and death.

Indicators

• IW-12 Catchment nitrogen and phosphorus load 
  Increased nitrogen and phosphorus may lead to algal blooms. Quantities of nitrogen and phosphorus concentrating in surface water catchments are a measure of the likelihood of this pressure occurring.
• IW-18 Exceedance of suspended solids water quality triggers 
  Suspended solids are a source of nutrients, which, when added to aquatic environments can lead to algal blooms under the right conditions. Number of exceedences of water quality triggers for suspended solids is one measure of the likelihood that excess nutrients are being transported.
• IW-29 Blue Green Algae 
  Number and distribution of algal blooms is a direct indicator of this pressure on freshwater biota.

Related issues

• Inland Waters - Catchment scale influences- Land and vegetation condition- Nutrients and sediments - sources and loads 
• Land - Direct pressure of human activities on the land- Pollution to and from the land 
• Human Settlements - Pressures created by human settlements on the environment- Waste 
• Inland Waters - Habitat scale influences- Water Quality (for surface and groundwater)- Nutrients 
• Inland Waters - Catchment scale influences- Land and vegetation condition- Erosion