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Cyanobacteria and primary succession

Nicole Stone and Dana Dudle
Biology Department and Science Research Fellows, DePauw University
Summer 2006

Primary succession is the process by which barren regions without soil, such as the abandoned limestone quarry within the DePauw Nature Park, are colonized. Cyanobacteria likely play an important part in the progression of such developing communities, through their abilities to stabilize organic material and sediment with their sticky sheaths, to help slow evaporation of water in dry environments, and to fix atmospheric nitrogen into a form usable by plants.  The goal of our research was to determine if cyanobacteria exist only in wet marshy areas covered with visible biocrust or if they exist in a broader range of conditions in the Quarry Bottom.  We investigated the distribution and abundance of cyanobacteria, comparing sites where colonizing plants are thriving with sites with no plants. 

We sampled 120 sites in the Quarry Bottom; 60 sites were chosen to represent an even distribution throughout the Quarry Bottom and 60 sites were chosen based on the presence of Apocynum cannabinum. We collected data on moisture levels and substrate conditions. We collected samples, cultured the samples in the lab, and monitored the cultures for growth of cyanobacteria over a period of one week.

Results and Discussion
Cyanobacteria was present in the cultures from most of the sites at the end of one week, but cyanobacteria and moisture levels were higher at sites with Apocynum cannabinum compared to sites without plants. Opportunities for future study include exploration of cyanobacteria’s nitrogen contribution and the potential benefit to vegetation, especially pioneer species such as Apocynum cannabinum that often live in close conjunction with biocrust containing cyanobacteria.