Bioassessment using the wide range of biological indicators now available for various
purposes should be seen as a vital part of assessing changes in aquatic ecosystems.
The published guidelines recommend an integrated approach using a suite of indicators
for monitoring, including biologial indicators and methods.
Biological methods also provide key tools in assessing achievement of environmental values
and attainment of the associated water quality objectives. Biological assessment methods
can be used to directly measure the progress towards a management goal for an ecosystem
or biological outcomes.
For example if the aim of the water quality management is to maintain fish species diversity
by reducing toxic heavy metal concentrations in a lake then biological methods can be applied
to monitor the species diversity directly as well as monitoring the levels of toxic metals.
It provides a much more focused approach for assessing performance against goals and targets.
The biological methods integrate over time and for a complex range of contaminants and
also show an integrated reponse with other likely requirements, such as physical habitat
and ecosystem functioning (food chains etc.).
The guidelines for biological assessment are intended to detect important departures from a
relatively natural, unpolluted or undisturbed state — the reference condition.
An important departure is deemed to be one in which the ecosystem shows substantial effects,
including:
• changes to species richness, community composition and/or structure;
• changes in abundance and distribution of species of high conservation
value or species important to the integrity of ecosystems.
See Volume 1 page 3.2-1 for more details.
Having determined the level of protection required for an ecosystem, the management goals for
achieving that protection, and the environmental concerns, managers should identify
assessment objectives for protection of the water resource, select appropriate indicators
and apply the published protocols.
Three broad assessment objectives are described as follows:
1. Broad-scale assessment of ecosystem health (at catchment, regional or larger scales) -
Tools for rapid biological assessment (RBA) are being developed that, while not
providing detailed quantitative information, are cost-effective and quick enough to
generate adequate first-pass data over large areas. The data may be adequate for
management purposes or they may help managers to decide what type of further
information may be required and from where.
Broad-scale assessment can be useful for the following applications:
• rapid, cost-effective and adequate first-pass determination of the extent of a
problem or potential problem, e.g. as applied to broad-scale land-use issues,
diffuse-source effluent discharges or information for State of Environment
Reporting;
• screening of sites to identify locations needing more detailed investigation;
• remediation programs being conducted over broad geographical areas
(catchment, regional or larger scales).
The most developed RBA method is AUSRIVAS, a method using macroinvertebrate
communities in rivers and stream.
Rapid bioassesment protocols are also being developed for riverine benthic algae (diatoms)
and fish, as well as for macroinvertebrate communities in wetlands and estuarine sediments.
2. Early detection of short- or longer-term changes - Prediction and early detection of
possible effects are useful to any water quality management program so that substantial
and ecologically important disturbances can be avoided.
Early information enhances the options for management. For example, where an effect is
observed from a controlled discharge, it may be possible to adjust the rate of release
or of subsequent releases.
Predictive information and early detection in the field can result if specific and
sensitive programs are set up, incorporating study of sublethal responses of organisms.
If sampling sites for any indicator can be located in mixing zones effectively creating
spatial disturbance gradients, they will enhance early detection and predictive
capabilities.
3. Assessment of biodiversity - To determine effects upon the ecosystem as a whole and as
important end-points in themselves, measures of biodiversity, including ecosystem
processes and the conservation status of sites, should be key responses sought-after
in monitoring programs.
Biodiversity and conservation status are best measured using species-level data
gathered from quantitative studies.
Information gathered at higher levels of taxonomic resolution will serve these needs
if the data are correlated with biodiversity or conservation status at species level.
The biodiversity assessment objective may be important for the following applications:
• for sites of special interest where indicators are needed to measure biodiversity,
conservation status, and/or ecosystem-level effects for assessing ecological
importance of disturbance. Information gathered for such indicators is highly
complementary to that gathered for early detection indicators.
• through RBA programs, as a first-pass measure of biodiversity, conservation
status and/or ecosystem-level effects for assessing ecological importance of
disturbance, at sites and over a broader geographical region.
• in any situation where a management objective has been strongly linked to the
Ecologically Sustainable Development tenet of the ‘Maintenance of
biodiversity and ecological systems.
See Volume 1 page 3.2-4 for more details.
Indicators and Protocols
The desired or essential attributes required for the broad indicator types (or methods)
to meet the assessment objectives are listed in table 3.2.1 (Volume 1 page 3.2-7).
The biological indicators recommended for various issues and ecosystem types are
listed in Table 3.2.2 (Volume 1 page 3.2-11). The protocols to be used are listed
in Section 8.1.3 (Volume 2 page 8.1-21).
See the Decision Tree for Biological Assessment of Water Quality