The Fossil Record of UV-B in Juncus Seeds and the Relation with Climate Change

Dan Yeloff [Yeloff@science.uva.nl], University of Amsterdam, The Netherlands; Peter Blokker; Jelte Rozema; Bas van Geel, Institute for Biodiversity and Ecosystem Dynamics, The Netherlands; Dmitri Mauquoy; and Sue Bartlett.

            Fluctuating solar UV may play a role in the amplification of relatively small changes in solar activity, and cause major Holocene climate shifts. The content of UV-B absorbing compounds (UACs) in plant reproductive structures such as pollen, spores and seeds can indicate the intensity of solar UV-B radiation during the formation of these plant tissues. A high resolution time series of sub-mm size sub-fossil Juncus seeds from a peat bog in the Faroe Islands has been analyzed for their UV-absorbing compounds using Gas Chromatography-Mass Spectrometry. A 1000 year profile was obtained, with a 10-20 yr sampling resolution covering the Little Ice Age climatic deterioration. The UAC p-coumaric acid is not affected by the depositional environment, suggesting that analyses of this compound in sub-fossil Juncus seeds may be used to reconstruct past solar UV-B irradiance. To ascertain whether variations in p-coumaric acid in Juncus seeds represent a response to UV irradiance, and are not the result of local factors such as variations in cloud cover or interactions between plants growing on the peat bog, analyses of sub-fossil Juncus seeds from a peat profile on Sub-Antarctic Marion Island is in progress. This work has the aim of replicating UV-B reconstructions made in the Faroe Islands. In addition, a greenhouse experiment has been initiated exposing Juncus articulatus plants to ambient and increased UV-B intensity, with the aim of determining the exact relationship between the amount of received UV-B and the concentration of UACs such as p-coumaric acid.