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Issue: Habitat scale influences - In-stream habitat - woody debris and sand slugs

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

Why we need to know about this issue

The health of in-stream habitats is vital to the functioning of aquatic ecosystems.

Indicators

• IW-13 Catchment sediment load 
  Catchment sediments can accumulate in streams and smother bed habitats and fill deep pools, which can significantly alter the physical habitat of instream environments. Sediments also supply nutrients and change the food web structure of an ecosystem. Sediment loads in inland water catchments is one measure of the quantity of soil being eroded into waterways.
• IW-18 Exceedance of suspended solids water quality triggers 
  Where the supply of sediment from upstream exceed a river's flushing capacity, this material will accumulate and smother stream bed habitats and fill deep pools. Sand and gravel are too unstable for growth of benthic organisms and loss of deep pools also means a loss of refugia and breeding grounds. Sediments also supply nutrients and change the food web structure of an ecosystem.
  Number of exceedences of water quality triggers for suspended solids is an indirect measure of this pressure.
• IW-24 Extent of sedimentation (incl sand slugs) 
  Extent of streams and water bodies affected by sedimentation is a direct measure of this pressure.
• IW-25 Number and extent of re-snagging programs 
  Areas containing snags have a high diversity of river biota. They provide habitat for many plants and animals, from the microscopic bacteria, fungi and algae, through to large native fish and platypus. Snags that stick out of the water provide roosting places for birds and other animals such as turtles. They are sources of food for invertebrates and trap leaves and other organic matter, which are also sources of food. Snags provide breeding sites. Snags can reduce the effects of flooding.
  De-snagging in the past has been carried out for ‘river improvement’. Restoring snags are now being considered as part of river restoration projects. Number and extent of resnagging programs would be indicative of improvements in the management of inland waters.
• IW-30 Macroinvertebrate condition 
  Macroinvertebrates are widespread, easy to sample, relatively immobile, and most importantly, their composition reflects the historical impact of environmental changes on the stream ecosystem for up to several months before sampling. They therefore provide an ‘integrated’ indicator of human impact on the stream ecosystem.

Related issues

• Inland Waters - Habitat scale influences- Wetlands 
• Inland Waters - Habitat scale influences- Riparian vegetation 
• Inland Waters - Habitat scale influences- Fish passage 
• Inland Waters - Catchment scale influences- Hydrological condition- Ecological aspects of river flow regimes