Monitoring changes in the sulphur isotopic composition and concentration of transplanted pendulous epiphytic lichens

Wiseman, Renée Denise (1999) Monitoring changes in the sulphur isotopic composition and concentration of transplanted pendulous epiphytic lichens. Masters thesis, Memorial University of Newfoundland.

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Abstract

Little is known about the response of lichens to sudden changes in the concentration and source of sulphur in the atmosphere despite an interest in lichens as tools in environmental monitoring. A transplant study was performed to determine this response in two species of pendulous epiphytic lichens by monitoring changes in their sulphur isotopic composition and sulphur concentration. -- Branches covered with the lichens, Alectoria sarmentosa and Bryoria capillaris, were taken from the Bonavista Peninsula and transplanted into the Memorial University of Newfoundland (MUN) Botanical Garden, St. John's. Two separate transplant experiments were performed between June 1997 and September 1998. Experiment I involved monthly sampling from June 1997 to June 1998. Experiment II involved weekly sampling from June 1998 to September 1998. -- The initial sulphur isotopic compositions and concentrations of the local lichens from the Bona vista Peninsula and St. John's were significantly different, providing an ideal opportunity to observe significant changes. The lichens in the Bonavista area had high isotopic compositions (~+15⁰/₀₀) from seaspray sulphur and lichens in St. John's exhibited low isotopic compositions (~+5-6⁰/₀₀) from anthropogenic sources. -- The results from this study showed that the transplanted lichens, A. sarmentosa and B. capillaris, acquired sulphur isotopic compositions and concentrations approaching those of the atmosphere surrounding the MUN Botanical Garden over the one year study period. For all transplants at all sites, the sulphur isotopic composition decreased while the sulphur concentration increased. Experiment I determined that one year is an insufficient amount of time to allow the transplanted lichens to achieve exactly the same sulphur isotopic composition and sulphur concentration as the local lichens. It is estimated that a minimum additional six months would provide enough time for the lichens to completely equilibrate with their new surrounding environment. Experiment II showed that natural variation in isotopic composition and concentration occurred on a weekly basis and three months is insufficient to reveal any significant patterns. -- This investigation is the first attempt to monitor lichen response to changing atmospheric conditions using stable sulphur isotopes. It has provided essential information for further lichen studies and sulphur isotopic studies in particular. It also has important implications for environmental monitoring and assessment.

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