Draft:Lichens as bioindicators

Lichens are composite organisms that form when algae or cyanobacteria live in the filaments of fungi in a mutualistic relationship. Lichen, which lack roots, obtain most of their necessary elements from the air; the elemental levels in lichen can reflect the composition of ambient air. As a result, many studies of lichens have emphasized their role as bioindicators of air quality, as well as climate change, pollutants such as phosphate from industrial fertilizers, and heavy metal contamination.

Overview
Lichens are some of the most widely used bioindicators of terrestrial environments. Lichens have been recognized as sensitive bioindicators of various pollutants, including heavy metals, which accumulate in the bodies of lichens over time. Furthermore, the absence, or presence, of certain species of lichens in a given area can indicate the ecosystem's overall health; changes in an area's lichen population or composition can be an early warning sign of environmental damage. Lichens' responses to environmental change can include biodiversity of species, morphology, physiology, accumulation of pollutants within the lichen, and others. These responses for the framework of monitoring with lichens of effects ranging from acid rain to atmospheric pollutants to climate change.

There are several characteristics of lichen that make them an extremely successful biondicator: the ubiquity of lichens; the lack of a protective outer cuticle allows them to absorb both pollutants and nutrients from, predominantly, aerial exposures; perennial growing for year-round monitoring.

In the 1960s sulfur dioxide, a product of fuel combustion, was identified as a factor that affected the growth, health, and distribution of lichens; this prompted a boom in lichen biomonitoring studies world-wide.

Biomonitoring
Lichens biomonitoring is a process by which pollutants are measured in the tissue of a lichen, and then these levels are used to assess the pollution in the larger environment.

Pollutants
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