## What is Trent biotic index?

Ecological indices are expressed as numbers or scores that have been derived or transformed from quantitative data. For example, the Trent biotic index of water quality is derived from a mix of the presence or absence of certain indicator species and the number or diversity of taxa (or groups) or organisms present.

### What is a biotic index number?

A biotic index is a scale for showing the quality of an environment by indicating the types and abundances of organisms present in a representative sample of the environment. It is often used to assess the quality of water in marine and freshwater ecosystems.

#### Who created the biotic index?

The biotic index (BI) proposed by Beck (1955) has the following formula: BI = 2 (n class I) + (n class II), where n is the number of species.

How do you calculate biotic index?

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1. Example of Biotic Index Calculation. Using Macroinvertebrate Information.
2. If you find:
3. Mayflies. Caddisflies. Stoneflies. Scuds. Midge larva.
4. Multiply each by the Biotic Value:
5. Biotic Value. Mayflies. 25 x 10 = 250. Caddisflies. 15 x 10 = 150.
6. TOTAL = 820. Divide total by 10. This is the Biotic Index Value: 820/10 = 82.

What does a high BMWP score mean?

A high BMWP Score -or Biotic Index -as it is sometimes called, means the invertebrate is very sensitive to pollution, therefore, for the invertebrate to be present – the water must be clean. An example of an animal that has a very high Biotic Index is a Mayfly nymph (its biological name is Ephemeroptera).

## How do you find the biotic index?

### What is a good EPT percentage?

Just count the number of EPT taxa, divide by the total number of taxa, and multiply by 100. So… The higher the EPT index, the better! 15% is quite low, but 30% or more is quite high.

#### What are the limitations or drawbacks of the biotic index?

1. Time-consuming. 2. Difficult to interpret by non-biologists.

What does a high biotic index mean?

A high biotic index indicates the presence of many pollution-sensitive organisms, denoting an unpolluted environment. A low biotic index indicates a polluted environment, due to a relative abundance of pollution-tolerant organisms.

How is BMWP score calculated?

The BMWP index is calculated by adding up the individual tolerance scores of aquatic macroinvertebrates at family taxonomic level present at a sample site.

## How is BMWP and Aspt calculated?

The ASPT is calculated by dividing the Biological Monitoring Working Party (BMWP) score (Table 2) calculated by adding the individual scores of all indicator organisms present by the number of families present.