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Caddisfly (order Trichoptera), a macroinvertebrate used as an indicator of water quality. [1] A bioindicator is any species (an indicator species) or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. [2]
The most common indicators are total coliforms, fecal coliforms, E. coli, and enterococci. [2] The presence of bacteria commonly found in human feces, termed coliform bacteria (e.g. E. coli), in surface water is a common indicator of faecal contamination.
If a species can survive in both unpolluted and heavily polluted water, g is very small because finding the species in a survey has little predictive value. In practice, only indicator species with a weighting factor g ≥ 4 are used. For example, a caddisfly, Agapetus fuscipes, has a g value of 16, while the zebra mussel's value is g = 4.
Numerous biotic indices have been created to account for the indicator species found in each region of study. The concept of the biotic index was developed by Cherie Stephens in an effort to provide a simple measurement of stream pollution and its effects on the biology of the stream.
Indicator bacteria can be cultured on media which are specifically formulated to allow the growth of the species of interest and inhibit growth of other organisms. Typically, environmental water samples are filtered through membranes with small pore sizes and then the membrane is placed onto a selective agar.
Nonpoint source pollution can be contrasted with point source pollution, where discharges occur to a body of water at a single location. The nonpoint sources of phosphates include natural decomposition of rocks and minerals, stormwater runoff , agricultural pollution , erosion and sedimentation , atmospheric deposition , and direct input by ...
Species specific - It can be difficult to draw comparisons between results unless the same indicator organism has been used in each study, as every species has an individual niche and associated ideal conditions. Even similar species (as defined by either taxonomy or niche) may have different reactions and different thresholds for change.
Environmental indicator criteria and frameworks have been used to help in their selection and presentation. It can be considered, for example, that there are major subsets of environmental indicators in-line with the Pressure-State-Response model developed by the OECD. One subset of environmental indicators is the collection of ecological indicators which can include physical, biological and ...