Evaluation of spore wall chemistry as a novel biochemical proxy for UV·B radiation

Fraser, Wesley T. (2009). Evaluation of spore wall chemistry as a novel biochemical proxy for UV·B radiation. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000eb39

Abstract

The stratospheric ozone layer provides protection for Earth's land-based organisms against harmful ultraviolet (UV) radiation, but the past century has seen the ozone layer compromised as a result of human activity, resulting in commensurate variations in surface UV -B flux. Despite the importance of UV radiation to the well-being of life, reliable records of surface UV-B flux only exist for a short period of time (20-30 years). In order to gain a deeper understanding of the behaviour of ozone and UV-B flux in the past, an alternative method of determining UV-B is required. Changes in spore chemistry have been proposed as a palaeo-monitor of UV-B flux, which can then be related to stratospheric ozone abundance. By employing the rapid and inexpensive technique of FTIR microspectroscopy to investigate changes in spore chemistry, a large dataset spanning seven different spatial and temporal UV regimes has been generated in order to evaluate the feasibility of routine usage of a spore-based UV-B proxy. Exploring contemporary samples grown under controlled UV conditions and spores preserved in historical archives reveals that modem-day and recent spore chemistry show a positive relationship with known and calculated UV-B flux, with additional environmental factors such as cloudiness and vegetation canopy cover superimposed on these results. Examination of fossil spores obtained from sediments and experimentally matured specimens provides an insight into the chemical changes that occur in organic matter after incorporation into sediments, even under mild burial conditions. This thesis explores the potential of spore chemistry to act as a proxy monitor of past UV-B flux and is the first concerted attempt at applying FTIR spectroscopy to the investigation of spore chemistry in this way.