Environmental Engineering Reference
In-Depth Information
death or migration of different species. In most cases, it includes a decrease in the
reproductive capacity and a decrease in the normal metabolic rate of aquatic organisms.
Biomonitoring aims at identifying and quantifying such types of responses, with respect
to particular organisms and the evaluation of the suitability of water to sustain aquatic
life.
Different types of biological effects, caused by the whole complex of physical and
chemical characteristics of the aquatic environment, might be used for assessment during
the biomonitoring process, but some of the most commonly used ones include:
• Changes of the species' composition in the aquatic community;
• Changes of the dominant group of organisms in a particular habitat;
• A decline in the number of some species;
• A high mortality of sensitive life stages, e.g. eggs, larvae.
The biological assessment of an aquatic ecosystem include different types of methods,
which estimate and quantify the above-listed biological effects:
• Ecological methods
Presence or absence of indicator species-invertebrates, plants, algae;
Analysis of biological communities (biocenosis)-invertebrates;
Analysis of biocenosis on artificial substrates
• Microbiological methods
Detecting the presence of selected bacteria;
• Bioassay and toxicity testing;
Tests expose organisms (invertebrate, fish) to different contaminants in varying
concentrations in order to obtain their response.
With respect to biomonitoring techniques for the evaluation of the status of natural water
bodies, the ecological methods are by far the most widely used. Bioassays and toxicity
testing are methods applied widely in laboratory conditions. They are used to determine
the guidelines and criteria related to toxic or other biological effects caused by specific
contaminants, as well as the determination of maximum pollution limits (criterions) with
respect to acute or chronic toxicity.
The ecological methods for biomonitoring are using biotic indices as specific
assessment tools. The oldest one is the Saprobic index, developed at the beginning of the
20th century to assess the impacts of sewer discharges on river water quality in Central
Europe. It identifies four zones of gradual self-purification capacity of the river body,
where the identification of selected indicator species is made, in addition to the
determination of several chemical characteristics (as DO) and the characterization of the
general conditions of the water body. Contemporary biotic indices include a much wider
list of indicator organisms, typical for the specific climatic and geographical conditions.
In general, no single group of organisms can be used to assess all aspects of water quality
and when using biological approaches for water quality assessment, a combination of
techniques using different organisms usually gives a more accurate assessment.
Numerous tools for biological assessments and the evaluation of the health status of
