An indicator species is one whose existence, nonexistence, or comparative well-being in a given environment is an indication of the total health of its ecosystem. By examining the form and activities of an indicator species, researchers can establish how changes in the environment are expected to affect other species that are more difficult to study. Indicator organisms are also utilized to analyse food, water or other samples for the likelihood of contamination by microorganisms.
To be an indicator, the organism must execute several criteria,that include: The species should always be present in the sample every time the pathogens are present and the indicator should always be present in larger numbers than the pathogen. This enhances the probability of detecting the indicator. Also testing directly for the pathogen, can be more costly and time consuming and may give a negative result if the numbers of the pathogen are low. The indicator organism should be totally absent, or present in very small numbers in uncontaminated samples. The indicator organism should not increase more lavishly than the pathogen in the same environment. The indicator should react to disinfection or sterilization processes in the same way as the pathogen. For instance, the response of E. coli to water disinfection processes, such as chlorination, ozone, and ultra-violet irradiation, is same as that of Salmonella. In that case if the indicator organism is destroyed by the water treatment, the probability of Salmonella being destroyed also is high.
Indicator species can sign an alteration in the biological state of a particular ecosystem, and thus may be used as an alternative to analyse the health of an ecosystem. For instance, lichens or plants that are sensitive to heavy metals or acids rains may be indicators of air pollution. Indicator species can also be a sign of a distinctive set of environmental qualities or characteristics found in a specific place, such as a unique microclimate. Though, care must be taken in using indicator species that is evaluating an ecosystem based on the response of a single indicator species. Indicator organisms also serve as a signal of fecal contamination. The most common fecal microbes that were used in the past were nominated as fecal coliforms. Today, with more specific growth media available, testing for E. coli can be done directly. The occurrence of E. coli indicates the presence of fecal matter from warm blooded animals, and so the likely occurrence of disease causing bacteria, such as Salmonella, Shigella, and Vibrio. An additional indicator bacterial species that is used are of the fecal Streptococcus. These have been chiefly useful in salt water analysis, as they carry on longer in the salt water than does E. coli. In addition, the relative amount of fecal coliform bacteria to fecal streptococci can provide an indication of whether the fecal contamination is from a human being or from other warm-blooded animals. The use of indicator bacteria has long been of elementary importance in the analysis of drinking water.
Indicator species are an interesting research and analysing means. A conservation specialist can utilize an indicator species as a substitute for the monitoring of overall biodiversity, analysing the results of management practices by recording the rise or fall of the population of the indicator species. For instance, river otters have been utilized as indicators of clean, hygienic river systems. In the moist peak forests of Mexico, many mountains harbor a unique species of arboreal lizard. The wellbeing of these unique tree-dwelling lizard populations is utilized an indicator of the health and biodiversity of the natural communities in that province. Likewise, maidenhair ferns are well-known to grow in lushly in northern hardwoods all through New England, but a subspecies of maidenhairs that are discovered only in areas with tortuous mineral soil is an indicator of a specific substrate.
Indicator species are a valuable monitoring tool, and can assist us describe an eco-region, indicate the position of an environmental condition, discover a disease outbreak, monitor pollution or climate change. In a feeling, they can be utilized as an "early warning system" by biologists and conservation specialists. Indicator species must also be associated thorough a learning of what situation does it indicates, how can it be correlated, and how this one species fits into the remaining of ecosystem.
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