Indicator species and biotic index

indicator species

species whose presence absence or abundance reflects a specific environmental condition, habitat or community. Species may:

• provide info of overall health of ecosystem

• reflect a particular environmental condition such as pollution

• be indicative of a particular habitat type or biological community

How can indicator species show changes in the environment

• increase or decrease in abundance

• presence or absence

• change in behaviour

• change physically or chemically

common air pollution

• smoke - deposits soot on buildings and trees causing them damage. permeates in air making it difficult for living creatures to breathe

• carbon monoxide - gas produced by combustion of fossil fuels which is toxic to haemoglobic organisms

• sulphur dioxide - contributes to acid rain

air pollution indicators - lichen

Grow on exposed rocks and trees and need to be efficient at absorbing water. Air pollutants dissolved in rainwater can damage lichen and prevent growth

air pollution indicator - blackspot fungus

Grows well on roses in unpolluted areas because it is killed in presence of sulphur dioxide found in polluted air

types of water pollution

• nitrates

• acid rain

• heavy metals

• pesticides

• oil

• other chemicals

water pollution indicator - invertebrate species

Different invertebrate species are able to tolerate different levels of pollution

• mayfly and stonefly larvae prefer clean water

• freshwater shrimp can tolerate low levels of pollution

• water louse can tolerate high levels of pollution

• rat-tailed maggot can tolerate very high levels of pollution

water pollution indicators - mussels

mussels are suspension feeders and accumulate heavy metals and toxins in their tissues = used as indicator for monitoring the health of coastal environments

water pollution indicator - algae

Rapid growth of algae as results of excess nitrates and other nutrients in water = composition and total amount of algae species can indicate the amount of organic pollution

water pollution indicator - amphibians

amphibians have moist permeable skin which is easily affected by water quality changes = some chemicals may potentially cause physical abnormalities

biotic index

compares the relative frequency of indicator species and provides an overall environmental assessment of an ecosystem. A change in biotic index over time indicates a change in environmental conditions

high and low biotic index

High - abundance of pollution sensitive organisms = unpolluted

low - absence of pollution sensitive organisms = polluted h

how to calculate biotic index

multiply the population size of each indicator species by its pollution tolerance rating