| Concise outline: Recent climatologic research in the Arctic shows a significant increase in mean seasonal temperatures leading to an ongoing reduction in Arctic sea ice cover. The increase in sea surface temperature is expected to enhance thermal stratification of the water column. In addition, increased precipitation and run-off will cause enhanced input of meltwater and sediments in marine waters, thereby also strongly affecting water column stability and turbidity. Stratospheric ozone depletion in the Arctic is anticipated to intensify for the decennia to come, resulting in enhanced ultraviolet radiation. These shifts in temperature and the light climate are likely to affect marine microbial communities, which are the main drivers of the biogeochemical cycles. Phytoplankton are very sensitive to changes in both temperature and the light climate, whereas bacterial and viral activity and community composition will be directly or indirectly (via the dissolved organic matter pool) affected. At the same time the enhanced sediment-input could directly affect the prokaryote community because shifts are expected in favour of species that specifically attach to suspended particles, such as the Crenarchaea. In a very recent pilot experiment we have demonstrated shifts in bacterial consortia as a result of prolonged manipulated irradiance exposure at an Arctic marine site (Kongsfjorden Spitsbergen). So far, extremely little is known about spatial and temporal diversity of Arctic marine microbial communities. Yet, serious consequences for the carbon flux can be anticipated. During two field campaigns in the Kongsfjorden (79N), Spitsbergen, in 2007 and 2008, two sister projects will be executed that both combine in situ measurements with microcosm studies in which the light climate and the concentration of suspended matter will be manipulated. In the first project (Subproject 1: CAMP) extensive reseach will be done on the composition, diversity and production of microbial communities in relation with environmental factors such as temperature, salinity and turbidity, by combining classical and molecular techniques. Furthermore, temperature, turbidity and light quality and quantity will be manipulated in microcosm experiments in which natural eukaryote and prokaryote microbial communities will be incubated. The consequences of these simulated aspects of climate change will be investigated on the molecular, ecological and physiological level. In the second project (Subproject 2: PACCA) specific attention will be given to the role of a group within the Archaea (the Crenarchaea) and the possible shifts of the prokaryotes as a result of changes in suspended matter Recent research suggests that a substantial part of these Crenarchaea are ammonia oxidisers. At the same time, Crenarcheal density in Arctic coastal waters seems positively correlated with the concentration of suspended particles. As a results, these particles appear to be ?hot-spots? of ammonia oxidation. Climate change in Arctic systems could therefore favour Archaea at the expense of Bacteria. The proposed research complies with IPY Theme I (Baseline information) and with Theme II (Climate change) and will give new insight in overall production as well shifs in species composition related with the predicted change in the Arctic climate. |
