{"id":7313,"date":"2021-12-03T09:00:31","date_gmt":"2021-12-03T08:00:31","guid":{"rendered":"https:\/\/www.breeze-technologies.de\/?p=7313"},"modified":"2021-12-03T11:42:50","modified_gmt":"2021-12-03T10:42:50","slug":"lichens-as-an-indicator-of-air-quality","status":"publish","type":"post","link":"https:\/\/www.breeze-technologies.de\/de\/blog\/lichens-as-an-indicator-of-air-quality\/","title":{"rendered":"Lichens as an Indicator of Air Quality"},"content":{"rendered":"

Indicator species<\/span><\/i><\/a> are organisms that provide information on the condition of their environment. <\/span><\/i>Lichens<\/span><\/i><\/a> are one such example, and have been used by scientists for the purpose of determining the air quality in a given area. Read on to find out more.<\/span><\/i><\/p>\n

What are lichens?<\/span><\/h2>\n

Lichens<\/span><\/a> are organisms consisting of a <\/span>symbiotic relationship<\/span><\/a> between a <\/span>fungus<\/span><\/a> and a chlorophyll-containing partner, either <\/span>algae<\/span><\/a> or <\/span>cyanobacteria<\/span><\/a>. Fungi are incapable of <\/span>photosynthesis<\/span><\/a> as they do not possess <\/span>chlorophyll<\/span><\/a>, but algae and cyanobacteria do. By forming a symbiotic relationship, the fungus gains constant access to nourishment, and can thus thrive. Lichens are found <\/span>in both nature and in human-made environments<\/span><\/a>, including rocks, trees, barren earth, metal and concrete. They are sensitive to air pollution because they receive <\/span>all nutrients from the atmosphere<\/span><\/a>, which makes them valuable as indicator species. In particular, the two pollutants that mostly affect lichens are nitrogen (N) and sulfur dioxide (SO2<\/sub>).<\/span><\/p>\n

How does nitrogen affect lichens?\u00a0<\/span><\/h2>\n

Lichens<\/span> need nitrogen to survive<\/span><\/a> as it supports them to produce necessary proteins and organic acids. Additionally, cyanobacteria engage in what is called <\/span>nitrogen fixation<\/span><\/a>, where the element is converted to ammonia, a more stable and easier-to-use form. The nitrogen used by lichens can be gaseous (N2<\/sub>), or come in the form of nitric oxide (NO) or nitrogen dioxide (NO2<\/sub>). Certain lichen species are sensitive to ammonia, while others are not. Too much nitrogen can in fact <\/span>over-fertilize<\/span><\/a> certain lichen species and cause them to die. Excess nitrogen can also <\/span>kill the chlorophyll<\/span><\/a> of the alga, which deprives the fungi of the necessary sugars for survival.<\/span><\/p>\n

How does sulfur dioxide affect lichens?\u00a0<\/span><\/h2>\n

Lichens are sensitive to sulfur dioxide. The compound easily <\/span>dissolves in water<\/span><\/a>, which the organism can then absorb, and is prevalent in the air in its gaseous state as well. Sulfur dioxide interferes with the cyanobacteria\u2019s ability to fix nitrogen, and <\/span>destroys the chlorophyll<\/span><\/a> of the alga, thus inhibiting photosynthesis. The compound also impedes lichen reproduction and spore germination across certain species.<\/span><\/p>\n

How are lichens used to indicate air quality?\u00a0<\/span><\/h2>\n

In the United States, the health of various lichen species are <\/span>monitored and paired<\/span><\/a> with atmospheric deposition data to identify critical sources and overall levels of air pollution. <\/span>Atmospheric deposition<\/span><\/a> is the process of gases and particles from the atmosphere being transferred to earth. In this case, scientists are looking at nitrogen deposition levels to protect sensitive ecological systems.<\/span><\/p>\n

Lichens have also been used in <\/span>Germany<\/span><\/a> as a bioindicator for air pollution, as they are sensitive to a number of air pollutants. Specifically, lichens are the most sensitive to sulfur dioxide, but other acidic pollutant gases as well as heavy metals and photo oxidants. In Germany, two methods existed that used lichens as indicators: exposure of lichens and recording of lichen growth on trees under natural conditions. The recording of the trees follows a certain standard:<\/span><\/p>\n