Lichen's Superpower: Air Pollution Bioindicator

Lichens are composite organisms that consist of a symbiotic relationship between a fungus and a chlorophyll-containing partner, either algae or cyanobacteria. They are sensitive to air pollution and can be used as bioindicators to determine the quality of air in a given area. Lichens are valuable bioindicators of ecological health because of their ability to respond to a wide range of environmental factors. They can be used to monitor nitrogen and sulphur dioxide levels, as well as heavy metal pollution. Lichens are also easy to study and respond quickly to environmental changes, making them ideal for assessing environmental and health risks.

Lichens are sensitive to air pollution as they absorb nutrients from the atmosphere

Lichens are organisms that consist of a symbiotic relationship between a fungus and a chlorophyll-containing partner, either algae or cyanobacteria. Fungi are incapable of photosynthesis as they do not possess chlorophyll, but algae and cyanobacteria do. By forming a symbiotic relationship, the fungus gains constant access to nourishment and can thus thrive. Lichens are found in both nature and human-made environments, including rocks, trees, barren earth, metal, and concrete.

Lichens are sensitive to air pollution as they absorb all their nutrients from the atmosphere. They have no roots or protective surface, so they cannot filter what they absorb, and if there are pollutants, they can quickly accumulate in the lichen and become toxic. Lichens are especially sensitive to nitrogen (N) and sulphur dioxide (SO2) in the air. 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 to feed the lichen and the fungi. Sulphur dioxide is a pollutant produced when coal is burned instead of wood, and changes in industry can also cause this. Sulphur dioxide has killed many lichens around the UK, but now that less coal is burned, they are beginning to return.

The presence of lichens can be used to monitor air quality. Scientists monitor the health of lichens and pair this bio-monitoring data with atmospheric deposition data from the National Atmospheric Deposition Association (NADP). This allows them to determine the sources and levels of pollution causing detrimental effects. The variety in lichen species is also taken into account when calculating and representing the air quality index. This is done by determining the degree of cover and vitality.

Lichens are widely recognized as bioindicators of environmental pollution because of their sensitivity to various pollutants, including heavy metals. Their health and distribution can be used to monitor air quality, and their ability to accumulate particles allows them to retain significant quantities of heavy metals. Lichens are excellent biological models for assessing environmental and health risks.

They can indicate the presence of heavy metals in the environment

Lichens are sensitive to air pollution and can indicate the presence of heavy metals in the environment. Lichens are miniature ecosystems composed of fungi and algae and/or cyanobacteria. They absorb nutrients and water directly from the air, and since they have no roots or protective surface, they cannot filter what they absorb. This means that pollutants can accumulate in lichens and quickly become toxic.

Lichens are used in biomonitoring efforts to assess the sustainability of ecosystems, including air quality. They can absorb and retain heavy metals, and their physiological responses to these metals can be observed and measured. For example, a study in South Korea examined lichens from two geographically distant regions and found that even small variations in ambient heavy metal concentrations could be detected in natural lichens. The degree of fatty acid oxidation in lichens was associated with increased copper concentrations, and arsenic exerted a significant impact on chlorophyll degradation and protein content.

The presence of heavy metals in lichens can be determined through various analytical techniques such as inductively coupled plasma–mass spectrometry (ICP–MS). By studying the physiological variables of lichens, such as chlorophyll damage, lipid oxidation, and protein content, scientists can identify the specific heavy metals present in the environment.

The ability of lichens to accumulate heavy metals depends on the element and its abundance in the environment. Some lichens can tolerate high concentrations of metals by sequestering them extracellularly, preventing excessive intracellular accumulation. For example, zinc, lead, and cadmium are typically accumulated extracellularly, while copper and nickel are accumulated intracellularly.

The type of lichen also influences its ability to accumulate heavy metals. Studies have shown that crustose lichens, such as Candelariella aurella and Lecanora muralis, generally accumulate higher levels of heavy metals compared to other types of lichens.

They can be used to monitor nitrogen and sulphur dioxide levels

Lichens are sensitive to air pollution and can be used to monitor nitrogen and sulphur dioxide levels. They obtain their nutrients from the air and do not have a protective surface, so they absorb anything in the air, including pollutants. This makes them excellent bioindicators of air quality.

Nitrogen is a crucial element for lichens to survive as it helps them produce necessary proteins and organic acids. However, too much nitrogen can harm and even kill certain lichen species. Nitrogen deposition can increase the load of nutrients, which can damage the algae's chlorophyll, depriving the fungi of necessary sugars for survival. Some lichens, such as the golden shield lichen, can tolerate high levels of nitrogen, especially ammonia. By observing the presence of nitrogen-tolerant species and the absence of nitrogen-sensitive species, scientists can infer the levels of nitrogen pollution in an area.

Nitrogen oxides, such as nitrogen dioxide, are powerful pollutants that can harm human health. They are formed when nitrogen is heated and combined with oxygen, such as in car engines. Nitrogen dioxide can cause respiratory issues and decrease the body's ability to fight lung infections. Farms also contribute to nitrogen pollution through fertilisers, machinery, and livestock waste.

Sulphur dioxide is another pollutant that significantly impacts lichens. It interferes with the cyanobacteria's ability to fix nitrogen and impedes lichen reproduction and spore germination. Sulphur dioxide is released from coal burning and industrial activities. In the past, it has killed many lichens in the UK, but with the reduction in coal burning, their populations are recovering. Usnea lichens, also called old man's beard, do not grow in areas with sulphur dioxide pollution.

While lichens are valuable for monitoring nitrogen and sulphur dioxide levels, they have limitations as bioindicators. Lichens can only provide average pollution data over long periods, making it challenging to source, control, manage, and improve air quality in real-time. Additionally, there are other pollutants that pose ecological and health threats that lichens cannot directly indicate.

Lichens are indicator species that reflect the condition of their environment

Lichens are miniature ecosystems made of a fungus and an algae and/or cyanobacteria. The fungus gains constant access to nourishment through its symbiotic relationship with algae or cyanobacteria, which have chlorophyll and can perform photosynthesis. Lichens are found in nature and in human-made environments, including rocks, trees, barren earth, metal, and concrete.

Lichens are sensitive to air pollution because they absorb nutrients directly from the atmosphere. They cannot filter what they absorb, so pollutants can accumulate in the lichen and become toxic. Nitrogen and sulphur dioxide are two pollutants that especially affect lichens. Nitrogen deposition can harm and kill the algae's chlorophyll, which is used to produce sugars that feed the lichen. Sulphur dioxide is a pollutant produced by burning coal and industrial activities. It can irritate the mucus lining of the eyes, nose, throat, and lungs.

Lichen communities can be monitored to determine the sources and levels of pollution. Compositional changes in lichen communities are correlated with changes in levels of atmospheric pollution. Scientists can pair bio-monitoring data with atmospheric deposition data to determine the sources and levels of pollution. The presence of certain lichen species can indicate the levels of nitrogen and sulphur dioxide in the environment. For example, the oakmoss lichen is sensitive to nitrogen and can be found in areas with clean air. The golden shield lichen, on the other hand, can live in areas with high levels of nitrogen.

Lichens are also used as bioaccumulators of pollutants. They can accumulate various pollutants such as metals, organic elements, and radioelements. Lichens can be sampled and analysed to determine the presence and levels of these pollutants in the environment. This makes them valuable tools for assessing environmental and health risks.

They are used to assess the sustainability of ecosystems, including air quality

Lichens are bioindicators of air pollution and can be used to assess the sustainability of ecosystems, including air quality. Lichens are organisms that consist of a symbiotic relationship between a fungus and a chlorophyll-containing partner, either algae or cyanobacteria. They are sensitive to air pollution because they absorb nutrients directly from the atmosphere, and pollutants can accumulate in the lichen, becoming toxic.

Lichens are used to assess the sustainability of ecosystems as they are sensitive to a wide range of environmental factors, including air pollution. They can indicate the presence of pollutants such as nitrogen, sulphur dioxide, heavy metals, and other organic and inorganic compounds. Scientists monitor the health and distribution of lichens to determine the sources and levels of pollution and their effects on the ecosystem. For example, the presence of certain lichen species that are more tolerant of nitrogen can indicate an increase in atmospheric nitrogen deposition, which can be harmful to other species.

The variety of lichen species in an area, as well as their degree of cover and vitality, are taken into account when assessing air quality. Different methods of lichen observation have been developed to detect and map the effects of air pollution. One method, known as the Dutch method, classifies lichens as "nitrophyte" or "acidophyte" based on their preference for high or low nitrogen and pH environments. This method has been used to map and monitor nitrogen and ammonia pollution patterns.

Lichens are also used in biomonitoring efforts to assess the sustainability of ecosystems, including air quality. For example, a study in Korea collected lichens from pristine environments to investigate their physiological responses to ambient heavy metal concentrations. By observing the physiological variables of lichens, scientists can determine which types of heavy metals affect these variables and use this information to assess the health of the ecosystem.

Overall, lichens are valuable tools for assessing the sustainability of ecosystems and air quality due to their sensitivity to a range of pollutants and their ability to accumulate and retain these pollutants over time.

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