Sunburst Lichens on Lake Superior -- the Power of Collaboration

April 10, 2015


Photographer: Rob Sheridan
Summary AuthorRob Sheridan

Lichens are pioneer organisms. They're the first to colonize bare rock, beginning the rock’s conversion to soil by trapping moisture and enhancing physical and chemical weathering. Lichens are difficult to classify because they're symbionts, made up of two unrelated species growing in synchrony, compensating for each other’s weakness but forming a much stronger whole. This collaboration brings a fungus together with a photosynthetic single-celled alga or cyanobacterium. The fungus provides structure for both partners while the photosynthesizer provides food for both, converting atmospheric carbon dioxide into glucose and structural molecules. Neither partner can survive without the other, but together they can survive where no other organism can.
Lichens are typically grouped by their gross appearance and color. Crustose lichens have a crusted look, foliose a leafy morphology, and fruticose a branched appearance. The orange colored lichens shown above, Sunburst Lichens (Xanthoria elegans), were found on the basalt rock rimming the north shore of Lake Superior in Minnesota. Most of the surrounding soil and lake sediment owes its formation to rock decomposition initiated by lichens. These slow-growing lichens are among the first organisms capable of inhabiting hostile, nutrient-poor habitats. Their bright color is thought to protect the green algae from excessive ultraviolet exposure. The green lichen is an early successor species, probably Rock-Posy lichen (Rhizoplaca subdiscrepans). Photo taken on August 25, 2014.

Photo Details: Camera: Apple iPhone 5s; Focal Length: 4.1mm (35mm equivalent: 30mm); Aperture: ƒ/2.2; Exposure Time: 0.033 s (1/30); ISO equiv: 100.