Lichens of Alaska's South Coast

"Lichens are specialized fungi that 'farm' algae as a food source. Unlike molds, mildews, and muchrooms that parasitize or scavenge food from other organisms, the fungus of a lichen cultivates tiny algae and/or blue-green bacteria (called cyanobacteria) within the fabric of interwoven fungal threads that form the body of the lichen (or thallus). The algae and cyanobacteria produce food for themselves and for the fungus by converting carbon dioxide and water into sugars using the sun's energy (photosynthesis). Thus, a lichen is a combination of two or sometimes three organisms living together.

Perhaps the most important contribution of the fungus is to provide a protective habitat for the algae or cyanobacteria. the green or green-blue photosynthetic layer is often visible between two white fungal layers if a piece of lichen thallus is torn off. Most lichen-forming fungi cannot exist without the photosynthetic partner because they have become dependent on them for survival. But in all cases, a fungus looks quite different in the lichenized form compared to its free-living form." less ↑