This pollutant has killed many lichens in parts of the UK in the past, but now because we burn less coal, they are beginning to return. In high concentrations, sulphur dioxide can irritate the mucus lining of the eyes, nose, throat and lungs. Exposure to sulphur dioxide may cause coughing and tightness in your chest. People with asthma are more sensitive to sulphur dioxide pollution. 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 on your walk, it probably means that coal has not been burnt in the area for some time. You can find out more about surveying lichens to assess air pollution as part of an earlier Open Air Laboratories OPAL citizen science project that mapped lichens in the UK. Humans have many uses for lichens, including as a source of potential antibiotic, anti-fungal and anti-cancer drugs.
Lichens also can be used in perfumes and incense and as a clothes dye. Lichens are also important for other plants and animals. Their ability to grow in some barren places, like on the surface of a rock, allows for other things to grow in the organic material that lichens leave behind when they break down.
Can studying lichens tell us how fertilizers used on tea planttaions are affecting surrounding ecosystems? Researchers at the Museum are part of a global team investigating nitrogen pollution from tea estates in Sri Lanka and in the forests of the Himalayas.
Tea growers in Sri Lanka use fertilizers that contain nitrogen in the form of ammonia. This ammonia does not stay on the tea farm, and some of it inevitably flows into the surrounding ecosystems.
The nitrogen is carried into the atmosphere through winds and sits in the clouds, ready to rain on the nearby mountains and cloud forests.
Gothamie is part of a team setting up permanent plots in Sri Lanka to monitor the effects of nitrogen air pollution. They are using lichens as indicators. These plots sit high up in the mountain cloud forests, and the researchers are recording how the lichen community in these plots change over time.
To set up the experiment, they consider the local climate and known atmospheric nitrogen levels. They then release nitrogen in a controlled way onto the plots to test the effects of different nitrogen concentrations. Gothamie says, 'Every year the amount of nitrogen increases in the atmosphere, from the increase of fertilisers being used. This research will help them understand how increases in fertiliser use on tea farms will change the ecology of southern Asia. Get email updates about our news, science, exhibitions, events, products, services and fundraising activities.
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Lecanora conizaeoides. Though sulphur dioxide is very damaging to many lichens some are highly tolerant. In the 19th century when coal was a common fuel the resulting smoke was rich in sulphur dioxide and lichen 'deserts' were typical around industrial centres, with very few species or even none to be found in such areas. The crustose lichen Lecanora conizaeoides tolerates high sulphur dioxide concentrations and during the later 19th and early 20th centuries was common in or near many of the major industrial cities of Europe.
The later 20th century saw the reduction of coal fires as well as the implementation and enforcement of various clean air policies, all of which has led to a great decrease in sulphur dioxide levels in various cities. Such actions have led to an increase in the number of lichen species found in previously polluted urban centres, though in some cases the lichen 're-invasion' has been limited to nitrogen-tolerant species because of the high levels of nitrate or ammonium deposition.
Another consequence of reduced sulphur dioxide levels has been the decline in abundance of Lecanora conizaeoides , since various other species easily out-compete it.
During the many decades of higher levels of sulphur dioxide the competing species were kept at bay but now the once common Lecanora conizaeoides has become very rare in parts of Europe.
Presumably this lichen is now present in levels closer to its levels before the industrial revolution. Lecanora conizaeoides grows naturally on acidic substrates, making it an acidophile. During the 19th and early 20th centuries the higher sulphur dioxide concentrations will have artificially acidified substrates that, otherwise, would not have hosted this lichen.
Sulphur dioxide emissions in southern California are very low but oxidants can be present in high concentrations. Various strongly oxidising compounds are produced photochemically when sunlight acts on compounds emitted in vehicle exhausts and possibly the best known such oxidant is ozone.
Studies in southern California have shown that a number of lichens, common there in the early 20th century, have not been found there in recent years. Though there have been relatively few studies into the effects of strong oxidising compounds on lichens, several experimental studies have shown that ozone can be detrimental to lichens but, as with other pollutants, some species are more resilient than others.
Bolder with lichen-free zone below metal plaque click to enlarge. Many people will have seen the damaging effects that some metals can have on lichens. Throughout the world there are numerous commemorative metal plaques fixed to boulders that have been placed in sites exposed to the weather. Such plaques are often of bronze, an alloy of copper, and copper forms the basis of several fungicides.
The boulders, covered with lichens, may have been plucked from the wild and had plaques attached. Or, the boulders may have been extracted from beneath the earth and still been bare when the plaques were affixed. Once affixed the plaques are washed by rain. Compounds toxic to lichens leach out and are carried down the boulder in the runoff. The activity of acid phosphatase in lichen was mainly dependent on the photobiont.
GSH was confirmed to be highly correlated with SO2 stress, and was proposed to be a significant and prospective biomarker of the status of lichen antioxidant system and the oxidative damage in lichen.
The mycobiont was proposed to mainly resist the oxidative stress by SO2, while the photobiont was damaged more easily with energy depletion. Abstract Xanthoparmellia mexicana was successfully isolating and culturing from its two symbionts and, preliminarily re-symbiosising its thalli in vitro performed from pure cultured photobiont and mycobiont.
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