Climate dependent diatom production is preserved in biogenic Si isotope signatures

Climate change is likely to have the greatest impact on high-latitude ecosystems which are sensitive to climate fluctuations due to the relatively short growth season of diatoms. Biogenic silica (BSi) derived from diatoms provides a direct measure for tracking these processes although the knowledge gained from the amount of BSi preserved may be limited. In this study we report an application of a method based on Si isotope analyses of diatoms derived from a Gulf of Bothnia sediment core to reconstruct diatom production during the last two hundred years. During this time period large scale anthropogenic disturbances, such as the damming of rivers, can be observed. There is a relationship between measured Si isotope values of BSi, e.g. the silica incorporated into diatom frustules, in Bothnian Bay sediments and air temperature. This relationship suggests that the diatom Si isotope composition can be used to trace temperature variations over time. This method can be applied to other diatom dominated aquatic systems, i.e., a large part of the world's ocean and coastal seas, in order to improve our knowledge of impacts of temperature variations and thus also climate change and anthropogenic disturbance