Biotic index
Encyclopedia
Biotic Index is a scale for showing the quality of an environment
by indicating the types of organism
s present in it. It is often used to assess the quality of water
in river
s. It is measured from 1 to 10 and corresponds to the four basic water quality (Excellent, Good, Fair or Poor). The concept of the Biotic Index was developed by William M. Beck in an effort to provide a simple measurement of stream pollution
and its effects on the biology of the stream
To assign a biotic index value to a specific water site, the tester first collects macroinvertebrates from portions of the sample area of the stream, river or lake and separate them into groups of similar-looking organisms. More extensive testing can be done by looking for certain microscopic organisms.
Then an identification key is used to help determine which category or group the organism belongs in and allows a numerical value be assigned to that organism. A worksheet is then used to calculate the final value or score of all the organisms found. Depending upon the worksheet's equations, the score determines the condition of the water quality.
1. They are abundant and found in water bodies throughout the world.
2. They are not extremely mobile.
3. They carry out part or all of their life cycle within the stream or river.
Macroinvertebrates limited mobility and extended presence in the water means that they are exposed on a continuous basis to water quality in that stream or river. In particular, many of these organisms breath dissolved oxygen that is in the water. They are also easier to see at the time of sampling.
Not all the macroinvertebrates found in samples are listed on the biotic index scoring sheets. This is because some do not rely on oxygen within the water for survival. Many are able to collect air from the atmosphere and hold a bubble alongside their body to use like a scuba diver uses a tank of oxygen.
For those macroinvertebrates that do rely on dissolved oxygen, some can only live in water that has a lot of oxygen. Others can live in water that doesn't have much oxygen dissolved in it at all. Generally, it is assume that the more pollution there is in the water, the less oxygen.
Classification=
The biotic index works by assigning different levels of tolerance to pollution to the different types of organisms.
The types of macroinvertebrates and other organisms found during sampling are broken into 4 groups:
1: Pollution intolerant: These organisms are highly sensitive to pollution. (IE: Stonefly or Alderfly Larva)
2: Semi-Pollution intolerant: These organisms are sensitive to pollution. (IE: Dragonfly Larva or Crawfish)
3: Semi-Pollution tolerant: These organisms will be found in clean and slightly polluted waterways. (IE: Snails or Black Fly Larva)
4: Pollution tolerant: These organisms will be found in polluted, as well as clean aquatic ecosystems (IE: Leechs or Bloodworms)
Some index worksheets combine groups 2 and 3 together giving only 3 groups. Each group has a number assigned to it and is multiplied by the number of organisms found in that group. This is why identifying the type of organism is important.
See also=
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....
by indicating the types of organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s present in it. It is often used to assess the quality of water
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...
in river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s. It is measured from 1 to 10 and corresponds to the four basic water quality (Excellent, Good, Fair or Poor). The concept of the Biotic Index was developed by William M. Beck in an effort to provide a simple measurement of stream pollution
Water pollution
Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....
and its effects on the biology of the stream
To assign a biotic index value to a specific water site, the tester first collects macroinvertebrates from portions of the sample area of the stream, river or lake and separate them into groups of similar-looking organisms. More extensive testing can be done by looking for certain microscopic organisms.
Then an identification key is used to help determine which category or group the organism belongs in and allows a numerical value be assigned to that organism. A worksheet is then used to calculate the final value or score of all the organisms found. Depending upon the worksheet's equations, the score determines the condition of the water quality.
Why Macroinvertebrates
Aquatic macroinvertebrates have some general characteristics that make them very useful to assess stream health.1. They are abundant and found in water bodies throughout the world.
2. They are not extremely mobile.
3. They carry out part or all of their life cycle within the stream or river.
Macroinvertebrates limited mobility and extended presence in the water means that they are exposed on a continuous basis to water quality in that stream or river. In particular, many of these organisms breath dissolved oxygen that is in the water. They are also easier to see at the time of sampling.
Not all the macroinvertebrates found in samples are listed on the biotic index scoring sheets. This is because some do not rely on oxygen within the water for survival. Many are able to collect air from the atmosphere and hold a bubble alongside their body to use like a scuba diver uses a tank of oxygen.
For those macroinvertebrates that do rely on dissolved oxygen, some can only live in water that has a lot of oxygen. Others can live in water that doesn't have much oxygen dissolved in it at all. Generally, it is assume that the more pollution there is in the water, the less oxygen.
Classification=
The biotic index works by assigning different levels of tolerance to pollution to the different types of organisms.
The types of macroinvertebrates and other organisms found during sampling are broken into 4 groups:
1: Pollution intolerant: These organisms are highly sensitive to pollution. (IE: Stonefly or Alderfly Larva)
2: Semi-Pollution intolerant: These organisms are sensitive to pollution. (IE: Dragonfly Larva or Crawfish)
3: Semi-Pollution tolerant: These organisms will be found in clean and slightly polluted waterways. (IE: Snails or Black Fly Larva)
4: Pollution tolerant: These organisms will be found in polluted, as well as clean aquatic ecosystems (IE: Leechs or Bloodworms)
Some index worksheets combine groups 2 and 3 together giving only 3 groups. Each group has a number assigned to it and is multiplied by the number of organisms found in that group. This is why identifying the type of organism is important.
See also=
- BioindicatorBioindicatorBiological indicators 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...
- Biological integrityBiological integrityBiological integrity is associated with how “pristine” an environment is and its function relative to the potential or original state of an ecosystem before human alterations were imposed. Biological integrity is built on the assumption that a decline in the values of an ecosystem's functions are...
- BiosurveyBiosurveyA biosurvey, or biological survey, is a scientific study of organisms to assess the condition of an ecological resource, such as a water body.-Overview:...
- Index of biological integrityIndex of biological integrityAn Index of Biological Integrity , also called an Index of Biotic Integrity, is a scientific tool used to identify and classify water pollution problems...
- Indicator speciesIndicator speciesAn indicator species is any biological species that defines a trait or characteristic of the environment. For example, a species may delineate an ecoregion or indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change...