Lichens, seen frequently in the Pine Barrens, are composite, symbiotic organisms. They are made up of members of two to three different kinds of organisms: fungi, algae and/or cyanobacteria (bacteria with chlorophyll). Each colony is a relatively self-contained miniature ecosystem where additional random microorganisms can also be found.
The dominant partner is the fungus. Since fungi are incapable of making their own food they usually support themselves as decomposers or parasites. However, in the lichen relationship, they are partners with organisms that can manufacture their own food by photosynthesis (as seen in all plants). The algae and cyanobacteria benefit from this relationship by being protected from the environment by the filaments of the fungus. These filaments absorb moisture and nutrients from the surface they are anchored to.
In this unusual “marriage,” the lichen usually takes the scientific name of the fungus involved. However, algae and cyanobacteria have their own scientific names by which they are known when living alone. Lichens can also be classified as fruticose (branching), foliose (leaf-like), crustose (crust-like) and squamulose (pebble-like), depending on their structure or growth style. There are about 20,000 known species of lichen, making them major components of biological diversity.
Reproduction is varied and sometimes chancy because so many different organisms are involved. Reproduction is usually asexual, often resulting from breakage of some sort. These particles are then relocated by wind or water or carried on the body of a passing animal. They can also form purposeful units of algae wrapped in threads of fungus (Soredia). The fungal partner can also produce spores, which must then “stumble” across an appropriate photosynthetic partner or die alone.
Lichens can be found in environments that are too harsh or limited for most other organisms. They are often considered pioneer organisms, forming colonies on bare rocks or sterile soils. Because some lichen partnered with cyanobacteria produce nitrogen, they can even enrich soils. They can also shut down metabolically when conditions are unfavorable. They are able to survive intermittent extremes of heat, cold and drought. However, with the right amount of light, moisture, clean air and freedom from competition, lichens can be found on almost any undisturbed surface and even hang artistically from branches in rain forests.
Lichens also come in a variety of colors that are determined by specialized photosynthetic pigments, and will gaily decorate the surfaces of anything on which they find themselves growing. Without the specialized pigments, their colors range from bright green to greenish gray.
As special adaptations for life in extreme habitats, lichens produce more than 500 unique biochemical compounds that control light exposure, repel herbivores, kill attacking microbes and discourage competition from plants. These unique compounds have created many pigments, herbicides, insecticides and antibiotics that have made lichens very useful to people in ancient or traditional cultures. Reindeer or caribou feed on certain lichens, which can also be used as a human survival food.
Lichens are like little sponges that absorb everything they are exposed to, including air pollution. This makes them extremely vulnerable. When they start to disappear, they are an early warning of harmful conditions. Lichens abound in the Pinelands, so be on the lookout and view them with a renewed sense of awe and appreciation. Their existence is strange and wonderful and should never be taken for granted.