In this situation, less precise indicators of flow change can be sourced from assessments of the amount of flow captured in storages or abstracted for agricultural or urban use. This type of data is often not available. Unfortunately, nearly all of these indicators rely on the existence of good flow data for both current and pre-disturbance conditions. To assess these different changes, a number of indicators are required. Changes to natural flow caused by humans are varied and include changes to peak flows, base flows, no flow periods and seasonality of flows. Assessing the changes is therefore important.
In freshwater, changes to flow are often the main cause of aquatic ecosystem health degradation the Murray-Darling system is an example of this. Indicators of instream habitat include measures of the extent of scouring and bank erosion and the presence of woody debris (fallen trees, etc) that provide important habitat for many species. Indicators of riparian habitat include the width, continuity, extent of shading and species composition. Habitat indicators include both fringing (riparian) habitat and instream habitats. Therefore, it is important to include indicators of these factors in monitoring programs. In many aquatic ecosystems, the key influences on aquatic ecosystem health can be factors other than water quality, including habitat degradation and changes to natural flow patterns. In coastal embayments, indicators such as seagrass condition or condition of fringing coral reefs are sometimes used. The only commonly used biological indicator in estuaries is chlorophyll-a, which is a measure of phytoplankton population density. The SEQ Report Card website has more information on these indicators.įor estuaries, biological indicators are less developed. Commonly used biological indicators in freshwater include various measures of macroinvertebrate or fish diversity, benthic algal growth and benthic oxygen demand. Biological indicatorsīiological indicators are direct measures of the health of the fauna and flora in the waterway. To assess this, we need to assess the biological indicators.
For example, is it an organic waste that affects dissolved oxygen, or is it some type of toxicant? Although physico-chemical indicators can identify the cause of the problem, they only provide limited information on the extent that pollutants are actually impacting on fauna and flora. Physico-chemical indicators provide information on what is impacting on the system. They also include measures of toxicants such as insecticides, herbicides and metals. They include dissolved oxygen, pH, temperature, salinity and nutrients (nitrogen and phosphorus). Physico-chemical indicators are the traditional 'water quality' indicators that most people are familiar with. However, for aquatic ecosystems there are a range of generally accepted indicators that are commonly used in most monitoring programs.Īquatic ecosystem health indicators can be broadly divided into four categories:
It is highly desirable to put significant effort into selecting indicators. Often, the selected indicators will need to be a compromise between effectiveness and efficiency. This means that some effective indicators cannot be used routinely. The cost and effort to measure them should be reasonable, and preferably not require highly specialised skills. Examples of conceptual models can be viewed at:Īs well as being effective, indicators must also be efficient. Selection of effective indicators is best achieved by developing conceptual models of the ecosystem and using these to pinpoint indicators that provide the required information. An indicator is embedded in a well developed interpretative framework and has meaning beyond the measure it represents.įor an indicator to be effective it must provide a true measure of a component of the ecosystem.
0 kommentar(er)
