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Monday, November 17, 2008


Bioindicators are species used to monitor the health of an environment or ecosystem. They are any biological species or group of species whose function, population, or status can be used to determine ecosystem or environmental integrity. An example of such a group are the copepods and other small water crustaceans present in many water bodies. Such organisms are monitored for changes (biochemical, physiological, or behavioural) that may indicate a problem within their ecosystem. Bioindicators can tell us about the cumulative effects of different pollutants in the ecosystem and about how long a problem may have been present for, both which physico-chemical testing cannot.

Depending on the organism selected and their use, there are several types of bioindicators:

1. Plant indicators
2. Animal indicators
3. Microbial and chemical indicators, and
4. Macroinvertebrate bioindicators

Plant indicators

Plant Indicators—The presence or absence of certain plant or other vegetative life in an ecosystem can provide important clues about the health of the environment-(environmental preservation).

Lichens-(not a plant), found on rocks and tree trunks, are organisms comprising both fungi and algae. They respond to environmental changes in forests, including changes in forest structure-(conservation biology), air quality, and climate. The disappearance of lichens in a forest may indicate environmental stresses, such as high levels of sulfur dioxide, sulfur-based pollutants, and nitrogen-oxides.

The composition and total biomass of algal species in aquatic systems serves as an important metric for organic pollution and nutrient loading such as nitrogen and phosphorus.

Animal indicators, and toxins

Animal Indicators—An increase or decrease in an animal population may indicate damage to the ecosystem caused by pollution. For example, if pollution causes the depletion of important food sources, animal species dependent upon these food sources will also be reduced in number-population decline. Overpopulation, can be the result of opportunistic species growth. In addition to monitoring the size and number of certain species, other mechanisms of animal indication include monitoring the concentration of toxins in animal tissues, or monitoring the rate at which deformities arise in animal populations.

Microbial indicators and chemical pollutants

Microbial Indicators—Microorganisms can be used as indicators of aquatic or terrestrial ecosystem health. Found in large quantities, microorganisms are easier to sample than other organisms. Some microorganisms will produce new proteins, called stress proteins, when exposed to contaminants like cadmium and benzene. These stress proteins can be used as an early warning system to detect low levels of pollution.

Macroinvertebrate bioindicators

Macroinvertebrates are useful and convenient indicators of the ecological health of a waterbody or river. They are almost always present, and are easy to sample and identify. The sensitivity of the range of macroinvertebrates found will enable an objective judgement of the ecological condition to be made.

In Australia, the SIGNAL method has been developed and is used by researchers and community Waterwatch groups to monitor water health.

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