Lichens are a sybiotic association of fungus (mycobiont) and algae (Pediastrum boryanum . The fungus engulfs the algae, then supplies carbs, nitrogen, and vitamins while the algae photosynthesizes. This unusual relationship enables the lichen to grow in environments where neither fungus nor algae would normally be able to solely survive. They are found on every continent, ranging all the way from the freezing Arctic to the sweltering grasslands of Africa. Even though they can live in such extreme conditions, they do require clean air. This is why they are excellent environmental indicator. An indicator species is an organism whose presence or absence reflects the overall health of an environment. Lichens flourish where there is good air quality; however, they cannot survive where the air is polluted and toxins loom. This is because they have no stomata, or pores, to shut to keep the toxins out; therefore, absorbing all of the pollutants in the air. Because they are such unique organisms, they accumulate different metal anions in the air than other organisms, like plants do, for example. Lichens attract toxic metal ions. An ion is a charged atom. If the ion has a positive charge, it is a cation. An ion with a negative charge is an anion. During the ion exchange process, Hydrogen, an anion, is released and metal cations move in. This process occurs when lichens are exposed to polluted air. When the lichens are dropped into any of the metal solutions, their cell wall releases the methylene blue ions, which are replaced by metal cations. Upon their detachment, the ions integrate into the solution, which in turn, colors it blue. The darker the solution, the more metal cations taken in by the lichen. Valence is a measure of how much an atom wants to combine with something else. If the valence of a metal ion affects lichen uptake, then the higher the cation, the…
