Air Quality with Biomarkers: Lichens

Air Quality using Lichens as Biomarkers



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Lichens are composite organisms consisting of a fungus (the mycobiont) and a photosynthetic partner (the photobiont or phycobiont) growing together in a symbiotic relationship. The photobiont is usually either a green alga (commonly Trebouxia) or cyanobacterium (commonly Nostoc).

The morphology, physiology and biochemistry of lichens are very different from those of the isolated fungus and alga in culture. Lichens occur in some of the most extreme environments on Earth—arctic tundra, hot deserts, rocky coasts, and toxic slag heaps.

However, they are also abundant as epiphytes on leaves and branches in rain forests and temperate woodland, on bare rock, including walls and gravestones, and on exposed soil surfaces (e.g., Collema) in otherwise mesic habitats.

The roofs of many buildings have lichens growing on them. Lichens are widespread and may be long-lived; however, many are also vulnerable to environmental disturbance, and may be useful to scientists in assessing the effects of air pollution, ozone depletion, and metal contamination.

Lichens are informally classified by growth form into:


by benet2006


by Boriss Lariushin


by Jason Hollinger

Lichens as pollution indicators

Lichens are sensitive to air pollution, specially the air's acidity. Therefore, the presence or absence can be used to see how clean the air is. Shrubby and leafy lichens only survive in clean air, and when an area is really polluted you will not find anyone.

The goal of this application is to help to analyze, classify and measure the size of the lichens in order to study the quality of air in different areas of the cities.

Look for lichens on walls, stones and trees take pictures with your phone and submit the data using this EpiCollect Plus Lichens project. Then, you can help in measuring the size of the lichen in this web application!

NOTE: You have to install EpiCollect+ in your Android phone for submitting new lichens. Use an EURO coin to do the callibration, and submit the picture!

Based on the size of the lichen we will estimate the pollution according to this table (extracted from an article published by the United States Enviromental Protection Agency):

  • 100mm - 120mm: Excellent
  • 70mm - 90mm: Good
  • 40mm - 60mm: Fair
  • 00mm - 30mm : Poor

Note: Info extracted from United States Enviromental Protection Agency and Wikipedia.