Brian Barton
Lichens are sensitive to air pollution and can act as bioindicators of environmental health. They are composed of fungi and algae and/or cyanobacteria, and their ability to absorb nutrients directly from the atmosphere makes them responsive to pollutants. Lichens can indicate the presence of nitrogen, sulphur dioxide, ammonia, nitrogen oxides, and heavy metals. They are also affected by global warming and can reflect the overall health of an ecosystem. Scientists can monitor changes in lichen communities, species composition, and health to gauge the potential decline or improvement of an ecosystem. While lichens are useful indicators, they have limitations, including their inability to provide immediate feedback on exact pollution levels.
| Characteristics | Values |
|---|---|
| Indicator species | Lichens are indicator species that provide information on the condition of their environment |
| Sensitivity to pollution | Lichens are sensitive to air pollution as they receive all their nutrients from the atmosphere |
| Air quality indicators | Lichens are good indicators of air quality and can tell the effects of air pollution on ecosystems |
| Nitrogen pollution | Lichens are sensitive to nitrogen pollution and can be used to monitor nitrogen levels |
| Sulphur dioxide pollution | Lichens are the most sensitive to sulphur dioxide pollution |
| Heavy metal pollution | Lichens can absorb heavy metals from the soil and act as bioindicators of heavy metal pollution |
| Other pollutants | Lichens are also sensitive to other acidic pollutant gases, photo-oxidants, and ammonia |
| Pollution tolerance | Some lichens are more tolerant of nitrogen than others |
| Species composition | A shift in lichen species composition can indicate the potential beginning of ecosystem decline |
| Health | A decline in the health of lichens can indicate potential ecosystem decline |
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What You'll Learn
Lichens are sensitive to nitrogen pollution
Lichens are miniature ecosystems made of fungi and algae and/or cyanobacteria. They receive all their nutrients and water from wet and dry atmospheric deposition, which includes nitrogen. Nitrogen deposition can increase the load of nutrients, and too much nitrogen can harm and kill the algae's chlorophyll, which is used to produce sugars that feed the fungi.
Some lichens will die in the presence of nitrogen, while others will thrive. Crustier lichens tend to be hardier than hairy lichens. For example, the golden shield lichen (Xanthoria parietina) can live in areas with high levels of nitrogen, especially ammonia. It is commonly found on trees and buildings near farmland and on sea cliffs where seabird droppings provide nitrogen.
Lichens are very sensitive to nitrogen pollution and respond to it in short time frames. Scientists monitor lichen communities to determine the sources and levels of pollution causing detrimental effects. If an increase in nitrogen-tolerant species is observed, in combination with a decrease in nitrogen-sensitive species, it may indicate an increase in atmospheric nitrogen deposition. This shift in species composition and/or their health can exemplify the potential beginning of ecosystem decline due to nitrogen deposition.
Nitrogen dioxide in the air can be a powerful pollutant and is harmful to human health in high concentrations. In UK cities, around half of the nitrogen dioxide air pollution comes from road traffic, while farms emit nitrogen pollutants from fertilisers, machinery, and livestock waste. Nitrogen dioxide gas can irritate the lungs and cause respiratory symptoms such as shortness of breath and coughing. It can also decrease the body's immune response to lung infections and trigger more frequent asthma attacks.
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They can indicate sulphur dioxide levels
Lichens are miniature ecosystems made of fungi and algae and/or cyanobacteria. They are very sensitive to air pollution and can indicate sulphur dioxide levels in the air. Sulphur dioxide is released into the atmosphere through coal burning and industry.
Usnea lichens, also called old man's beard, do not grow in areas where there is sulphur dioxide pollution. If you see one of these lichens while out walking, it is likely that coal has not been burnt in the area for a long time.
Lichens can be used to indicate sulphur dioxide levels because they are sensitive to this pollutant and will die in its presence. Some lichens are more tolerant of sulphur dioxide than others. By learning about common lichen species, you can judge the sulphur dioxide pollution levels in your area.
The presence of certain lichens can indicate whether there are high levels of sulphur dioxide in the atmosphere. For example, the oakmoss lichen is sensitive to nitrogen in the air and can be found on woodland branches where the air is clean. If oakmoss lichens are present in an area, it is likely that the levels of sulphur dioxide are low.
Overall, lichens are useful indicators of sulphur dioxide levels in the air. They respond quickly to environmental changes and are easier to study than other indicators such as butterflies, nematodes, frogs, and toads. By monitoring lichen communities and observing changes in their species composition and health, we can gain insights into the potential decline of ecosystems due to increased pollution levels.
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They are affected by heavy metal pollution
Lichens are miniature ecosystems composed of fungi and algae and/or cyanobacteria. They are highly sensitive to air pollution, making them excellent bioindicators of the health of the ecosystems in which they are found. Lichens are especially useful in biomonitoring efforts to assess the sustainability of ecosystems, including air quality.
Lichens are affected by heavy metal pollution. They can accumulate heavy metals inside their thallus, which can have adverse effects on their physiology. This accumulation can disrupt metabolic pathways and inhibit photosynthesis by degrading chlorophyll. Lichens' sensitivity to heavy metal pollution can be used to monitor environmental health and develop strategies to reduce pollution.
Several studies have investigated the physiological responses of lichens to ambient heavy metal concentrations. For example, a study in Korea's Gangwon Province and Jeju Island collected lichens to identify physiological variables that could indicate heavy metal exposure. An inverse relationship between protein content and chlorophyll damage was observed, with exposure to pollutants leading to a decline in chlorophyll content, which is necessary for photosynthesis and subsequent protein synthesis.
Another study by Gothamie Weerakoon of the Natural History Museum examined the effects of nitrogen air pollution on lichen communities in Sri Lanka's mountain cloud forests. The experiment involved releasing nitrogen in a controlled manner to understand how different nitrogen concentrations impact the lichen community over time. This research helps to understand how increased fertiliser use affects the ecology of southern Asia.
Overall, lichens are valuable tools for assessing heavy metal pollution and its impact on ecosystems. By studying their physiological responses to pollution, we can gain insights into the effects of human activities on the environment and develop sustainable practices to protect both ecological and human health.
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Lichens are used to monitor air quality
Lichens are sensitive to nitrogen and sulphur dioxide. Nitrogen deposition can harm and kill the algae's chlorophyll, which is used to produce sugars to feed the fungi. Some lichens will die in the presence of nitrogen, while others will thrive. Certain species are more tolerant of nitrogen than others. Scientists monitor lichen communities and if there is an increase in nitrogen-tolerant species and a decrease in nitrogen-sensitive species, this may indicate an increase in atmospheric nitrogen deposition.
In Germany, two methods used lichens as indicators: exposure of lichens and recording of lichen growth on trees under natural conditions. The Dutch developed a method of classifying lichens: “nitrophyte” lichen species thrive in high-nitrogen environments and on tree bark with high pH, while “acidophyte” lichen species prefer the opposite.
Lichens are also used to monitor nitrogen and ammonia pollution patterns across Europe. They respond to global warming and can indicate the presence of pollutants. They can also absorb heavy metals from the soil, helping to detoxify polluted areas. However, heavy metal accumulation can cause oxidative stress in lichens, leading to the production of reactive oxygen species and subsequent lipid peroxidation. It can also affect protein content, chlorophyll levels and overall metabolic activity.
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They are indicator species
Lichens are indicator species as they are very sensitive to changes in their environment, specifically air pollution. They are miniature ecosystems in themselves, consisting of a fungus and a chlorophyll-containing partner, either algae or cyanobacteria. Lichens receive all their nutrients from the atmosphere, and so their presence or absence can indicate the overall health of an ecosystem. They are also very good at indicating the presence of pollutants, acting as "sponges" that absorb and retain compounds present in the atmosphere.
Lichens are particularly sensitive to nitrogen and sulphur dioxide, but they are also affected by other acidic pollutant gases, heavy metals, and photo-oxidants. Nitrogen deposition can harm and kill the algae's chlorophyll, which is used to produce sugars to feed the fungi. Some lichens will die in the presence of nitrogen, while others will thrive. Certain species are more tolerant of nitrogen than others, and so scientists monitor lichen communities. If there is an increase in nitrogen-tolerant species and a decrease in nitrogen-sensitive species, this may indicate an increase in atmospheric nitrogen deposition.
The variety of lichen species is taken into account when calculating and representing the air quality index. The Dutch developed a method of classifying lichens: "nitrophyte" lichen species thrive in high-nitrogen environments and on tree bark with high pH, while "acidophyte" lichen species prefer the opposite. Lichens are also used to monitor nitrogen and ammonia pollution patterns across countries in Europe.
Lichens are also used to study the physiological responses of organisms to heavy metal exposure. Heavy metal accumulation can cause oxidative stress in lichens, leading to the production of reactive oxygen species and subsequent lipid peroxidation. This can negatively impact the protein content, chlorophyll levels, and lipid oxidation in lichens.
Lichens are useful indicator species as they are prevalent in around 8% of terrestrial ecosystems and are commonly found in a wide range of environments. They are also easier to study than other indicator species such as butterflies, nematodes, frogs, and toads. However, it is important to note that the information lichens provide is limited as they can only be used to monitor nitrogen and sulphur dioxide levels, while there are many other pollutants that pose ecological and health threats.
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Frequently asked questions
Lichens are organisms that consist of a symbiotic relationship between a fungus and a chlorophyll-containing partner, either algae or cyanobacteria.
Lichens are sensitive to air pollution because they receive all their nutrients from the atmosphere. They are especially sensitive to nitrogen and sulphur dioxide, but they can also indicate the presence of other acidic pollutant gases, heavy metals, and photo-oxidants.
Lichens act as sponges, absorbing and retaining compounds present in the atmosphere. They can indicate pollution through their presence or absence in an environment, as well as changes in their growth and health.
Scientists study the distribution and variety of lichen species in an area to determine the level of pollution. They also consider the local climate and known atmospheric nitrogen levels to establish baseline conditions.
Lichens can only be used to monitor nitrogen and sulphur dioxide levels, while there are many other pollutants that impact ecological and human health. As indicator species, lichens cannot provide immediate feedback on exact pollution levels, but rather averages over a longer period of time.
