Examples Of Indicator Species

We define an indicator in biology as an organism that the presence, or lack thereof, provides a clear signal about the environmental conditions. Depending on the organism, its appearance can signal both a healthy ecosystem or an unhealthy one. These indicators can reveal information about many factors in an environment, including pollution levels, salinity, temperature and nutrient or food availability.

There are many examples of indicator species. Indicator species can be anything from bacteria to more complex organisms such as plants and animals. While everything has evolved to live within certain thresholds, so all organisms are indicators of something; many are considered particularly sensitive and provide a good indication of the initial changes in environmental conditions.

Lack of wood storks in everglade ecosystems in the United States indicate that the environment is not suitable to sustain abundant wading bird life. Wood storks once thrived in these wetland environments by feeding on small freshwater fish. Conservationists use wood storks as a model example for the health of the everglades. The success of water-management restoration on wood stork populations helps indicate whether or not efforts are improving the overall everglade conditions to sustain all bird, fish, animal and plant life.

The evolutionary changes of the peppered moth in Britain in the 1950s from white to black was an indication of the high levels of pollution in the region. The theory goes that due to the trees being heavily covered in black soot, this put selective pressure on the moths with darker melatonin pigmentations as lighter moths were easily seen by birds. The darker moths were more camouflaged and therefore, more reproductively successful. Later in the 1970s, researchers found lower rates of the darker moths, which was thought to be due to less coal pollution on the trees and therefore it was once again advantageous to be paler.

River otters feast mostly on crayfish and fish but also other invertebrates, amphibians and smaller mammals. As one of the common keystone species examples and apex predators, if there is a problem lower down in the food chain, otters are typically the first to start declining. The success of river otter reintroductions has been used to assess the health of freshwater ecosystems.

River otter health has also been used to determine mercury pollution in an environment. Bioaccumulation is when chemicals or heavy metals gradually accumulate in an organism. Since mercury bioaccumulates and river otters are at the top of the food chain, they will likely be the first to show signs of mercury poisoning.

Frogs have highly semi-permeable skin that must remain moist for them to breath. Their skin makes them bioindicators for the health of their environment as they are vulnerable to absorbing chemical pollutants in their habitat. Many frogs have life stages that utilize both terrestrial and freshwater ecosystems, which also makes them sensitive to environmental stressors such as a change in temperature and UV-radiation.

Some plant species have developed mechanisms for coping with salt in the soil such as salt exclusion and cellular osmotic adjustment. Plants that don't have these mechanisms will not be able to grow in areas with high salinity. Buck's horn plantain is a useful ecological indicator example of salt concentration in Australian soils as its leaves get redder as the salt in the soil increases.

Algal blooms can indicate a change in the environment. An increase in nutrients from sedimentation runoff can cause an algal bloom. Algal blooms may also correlate with natural seasonal changes in nutrient availability. The concentration of algae across an area is also a useful indicator of gradients in nutrient availability in a body of water.

Lichens are a combination of various fungi and algae or bacterial species. Different functional traits and responses of lichens occur based on air pollution and temperature. Therefore, the presence of different types of lichens is useful for determining the effects of urbanization on the environment. For example, medium to high levels of urbanization is correlated with lichens made of chlorococcoid green algae and those with foliose narrow lobes. In contrast, low-density urbanized areas feature more cyanolichens and Trentepohlia algae lichens with a crustose formation.