Indicators and how to select them for water/sediment quality management
As part of the Water Quality Management Framework, you will:
- select lines of evidence at Step 3, under a weight-of-evidence process
- initiate relevant water quality monitoring.
Each line of evidence across the pressures, stressors and ecosystem receptors in the PSER causal pathway is represented by broad indicator types, and amongst these types are indicators from which you can select specific parameters for measurement.
More than one indicator may be selected and measured within each indicator type for each line of evidence. For example, biodiversity is an ecosystem receptor line of evidence for aquatic ecosystems that could be measured using multiple taxonomic groups, including macroinvertebrates, fishes and macrophytes.
Here we describe indicators for aquatic ecosystems and provide links to indicator information for other community values.
Indicators for aquatic ecosystems
Indicator selection depends on many factors, including:
- types of pressures and associated stressors identified in the conceptual model
- management goals
- assigned levels of protection
- spatial scale (broadscale, site-specific)
- water type or medium (freshwater, marine water)
- compartment (water or sediment)
- ecosystem type (e.g. river or wetland)
- location (e.g. wet–dry tropics, temperate coastal rivers of south-eastern Australia).
Indicators for other community values
These key factors that will help you determine the lines of evidence and indicators to measure in a particular situation, based on the information you gathered in Steps 1, 2 and 3 of the Water Quality Management Framework.
Choose diagnostic indicators from different lines of evidence
The lines of evidence identified from the quality of evidence tables completed in Step 3 are a culmination of decisions based on the prioritised water or sediment quality issues likely to affect ecosystems. These issues are drawn from the likely pressures and stressors affecting, or having the potential to affect, ecosystems, and the ecosystem receptors in the system that are likely to respond.
From the lines of evidence you have identified, select the precise indicators and measurements to be made by considering:
- the most sensitive mode of action of the stressor and the most sensitive ecosystem receptors of that action (highlighted in the conceptual model completed in Step 1 of the framework)
- diagnostic value of the indicator
- practicalities of monitoring the indicator in the local environment, including capacity of the measurement program to detect a change to the effect size for ecosystem receptor indicators with prescribed statistical power.
For example, if agricultural development (pressures) has potential to result in nutrient enrichment of receiving waters, then measurement of nutrients (stressors) and plants (any form of algae, macrophytes) (ecosystem receptors) may be the obvious priority indicator types for selection and measurement.
While there are no real constraints on the indicators and parameters to be used within each line of evidence, you should chose diagnostic indicators under the circumstances of the issue of concern to be as effective as possible.
- Ecosystem receptor indicators
- Physical and chemical stressor guidance
- Matching indicators to issues for stressors in water and in sediment.
Account for spatial and temporal scales
Selection of stressors and ecosystem receptors needs to be targeted to the spatial and temporal scale of the potential response to the activity or pressure.
The Water Quality Guidelines recognise different indicator types for finer-spatial scale and broadscale assessments.
Indicator selection for broadscale assessments has been reviewed by Dafforn et al. (2016) and deserves special mention. Such assessments are typically conducted over wide geographical areas for first-pass determination of the extent of a problem or potential problem (broadscale land-use issues, diffuse-source effluent discharges or information for State of Environment Reporting), screening of sites, or to assess results from large-scale remediation efforts (ANZECC & ARMCANZ 2000).
For broadscale assessments, ecosystem receptor biodiversity line of evidence may typically apply rapid assessment techniques (e.g. AUSRIVAS). For stressors, you will need water quality, hydrological, climate and other environmental data gathered from recorders or samples collected from a network of monitoring stations at a suitable sampling frequency. Increasingly, data for pressure and stressor indicators at these large spatial scales, including remote locations, are being acquired from remote (including satellite) and proximal sensing (e.g. sea surface temperature and chlorophyll a, mapping of vegetation type and habitat loss).
Indicators and associated measurements should also be collected over carefully selected timescales so that the data will provide a time-integrated history of the system (Dafforn et al. 2016). Humphrey et al. (1995), for example, described a tiered approach to biological monitoring in Magela Creek, Northern Territory:
- Early detection of possible (mine-related) effects arising over the short term (within the wet season of concern) using in situ toxicity testing (freshwater snail reproduction).
- Early detection of possible effects arising as a summation of wet-season exposures using bioaccumulation of metals in freshwater mussels.
- Detection of both post–wet season and longer-term effects over years using natural fish and macroinvertebrate communities.
Choose indicators to suit the water, ecosystem and medium
Different indicators are available for:
- water type — inland waters (including freshwater) versus coastal marine waters
- different ecosystem types
- medium compartment (water or sediment).
- Water type, ecosystem types and medium compartment for default guidance, guideline values and indicators provided in the Water Quality Guidelines are shown in Figure 2. Where site-specific guideline values are derived, water, ecosystem and compartment types will be broadest and will generally align with those described against physical and chemical stressors in Figure 2.
Relevant indicator types are described in the Water Quality Guidelines for:
- stressors (refer to toxicants in water, in Physical and Chemical Stressors and Toxicants)
- toxicants in sediments
- physical and chemical stressors
- ecosystem receptors (refer to Ecosytem receptor indicators).
Seek regional-specific advice on indicators
The ecoregional schema developed for aquatic ecosystems in Australia and New Zealand will eventually provide important regional-specific advice on indicators through Your location. Where information is available, you will find proven indicators that have been successfully and routinely monitored for specific pressures for different ecosystem types in the region.
Use indicators as surrogates or measures of management goals
Indicators within the biodiversity line of evidence may be selected as surrogates or direct measures of the management goals, ecosystem attributes that are locally important to protect. Such indicators can inform management of the extent to which ecosystems are being protected or are tracking towards improved ecosystem condition.
Include ecosystem receptors to target higher levels of protection
Section 22.214.171.124 of the ANZECC & ARMCANZ (2000) guidelines provided recommendations on the number and mix of indicators that could be used in integrated monitoring for each of the ecosystem conditions.
For sites of high conservation value, the ANZECC & ARMCANZ (2000) guidelines recommended:
- direct toxicity assessment (DTA) to determine a safe dilution wherever effluents are to be discharged
- water and sediment PC stressors
- an ‘early detection’ biological receptor indicator for either water or sediment (whichever is deemed to harbour greater risks to aquatic organisms arising from the fate and persistence of waste substances)
- a quantitative biodiversity indicator
- a community metabolism indicator, if applicable and available.
Prediction and early detection of possible effects in sites of high conservation value are important so that substantial and ecologically important effects can be avoided. Such information may be provided via in situ toxicity testing or use of biomarker indicators.
For slightly to moderately disturbed systems, and wherever possible, indicator selections similar to those applied for sites of high conservation value were recommended.
For highly disturbed systems, water and sediment toxicants and PC stressors, together with biodiversity assessment at coarse taxonomic discrimination, may suffice for many water/sediment quality assessments.
ANZECC & ARMCANZ 2000, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra.
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USEPA 1992, Toxicity Identification Evaluation: Characterization of Chronically Toxic Effluents, Phase I, United States Environmental Protection Agency, Washington DC.
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