When visiting the Panaroma Route in Mpumalanga, taking in the many highlights such as the Pinnacle Rock and God’s Window, one cannot help but notice the vibrant splashes of orange, green and white on the rocks in the area, almost like the rocks were painted. The splashes are in fact lichens growing on the rock. Lichen have always been a fascinating phenomenon to me. People often refer to lichen as a fungus or a plant, such as moss, growing on a rock or a tree, but they are in fact both at the same time. Lichens are actually a unique symbiotic relationship between a fungus and an alga or a cyanobacterium. A symbiotic relationship is a relationship between two organisms where both benefit from the relationship and neither is harmed by it. The fungus provides a protective environment and absorbs nutrients and moisture that creates and almost aquatic micro-environment for the alga or cyanobacterium to inhabit. The alga or cyanobacterium provides food through photosynthesis that feeds both organisms involved.
Most of us have an idea of what fungus and algae are, so I will stick to explaining a bit more about cyanobacteria. Like all bacteria, they are unicellular, prokaryotic organisms. This means that they consist of a single cell and that their cells lack the structure that our cells have in that they don’t have a nucleus or sub-cellular organelles. The cells basically consist of DNA and ribosomes floating in the cytoplasm that is bound by a membrane. What sets cyanobacteria apart from other bacteria is their ability to produce oxygen through photosynthesis, similar to plants. This ability makes them crucial contributors to the Earth's atmosphere and is one reason they are often referred to as "blue-green algae”. They are among the oldest known organisms on Earth, with a fossil record dating back more than 3 billion years.
Photosynthesis is, in short, the process by which organisms that contain chlorophyll (mostly plants) use sunlight, water and carbon dioxide to create oxygen and energy, stored in organic compounds such as sugar (if anybody is interested in a better understanding of photosynthesis, please let me know and I will be happy to unpack that in another article). Through this process, cyanobacteria played a significant role in the history of the planet by contributing to the oxygenation of the atmosphere, paving the way for the development of aerobic life forms.
Lichens are known for their ability to colonise harsh and inhospitable habitats, such as rocks, tree bark, and even exposed soil. They are ecologically important for the following reasons:
1) Lichens are sensitive to environmental conditions, including air quality and pollution, making them useful as bioindicators. Monitoring the health and abundance of lichen populations can provide insights into air quality and environmental changes.
2) Lichens can colonise and break down rocks, contributing to the initial stages of soil formation in barren environments. They release organic acids that weather rocks, and their decaying tissues contribute organic matter to the developing soil. This process is crucial for the establishment of plant communities in such areas.
3) The complex structure of lichens provides microhabitats for various microorganisms and invertebrates.
4) Some lichens, particularly those containing cyanobacteria, have the ability to fix atmospheric nitrogen into a form usable by plants.
5) Lichens are an important food source for various animals, including certain antelope species and insects.
6) Lichens have been used traditionally for medicinal purposes and also have industrial applications, such as use in dyes and antibiotics.
Next time you see the beautiful “splashes of paint” on tree bark, rocks or even bare soil, take a moment to consider the 3 billion years of evolution that it represents in a few square centimeters and the ecosystem that depends on it. To me, truly one of the most fascinating natural phenomena that we encounter on a daily basis.
Published by Dr. Helen Prinsloo
