Gosford City Council Historical Water Quality Review & Analysis

INTRODUCTION 1-5
1.3.2 Biological Indicators
Biological indicators are algae, macrophytes, macroinvertebrates and fish, which display the effects
of the past and present exposure to contaminants or pressures.
Biological assessment (bioassessment) is used to provide information on biological or ecological
changes, which may be due to changes in water quality or physical habitats. Bioassessment and
biological indicators are used because traditional physical and chemical guidelines can be too simple
to provide a meaningful assessment of biological communities or processes. Bioassessment is also a
useful tool to assess achievements of environmental values and attain water quality objectives.
The ANZECC guidelines recommend stressors and biological indicators to be used for monitoring
and assessment of water quality, for different ecosystem types. The indicators are selected depending
on the object of the assessment i.e. broad scale assessment, early detection, or biodiversity or
ecosystem-level response. The guidelines provide concepts and monitoring frameworks that are
necessary to assess aquatic biological communities.
1.3.3 Physical and Chemical Stressors
Physical and chemical stressors include nutrients, biodegradable organic matter, dissolved oxygen,
turbidity, suspended particulate matter (SPM), temperature, salinity, pH, change in flow regime,
ammonia, cyanide, heavy metals, biocides and other toxic organic compounds. Physical and
chemical stressors are classified into two types, depending on whether they have a direct or indirect
impact on the ecosystem, as shown in Figure 1.2.
Figure 1.2 Types of Physical and Chemical Stressors
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