Projectdetails

The Arctic climate is changing at an unsurpassed rate. Recent data show dramatic increases 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. At the same time, bacterial and viral activity and community composition will be directly or indirectly (via the dissolved organic matter pool) affected. 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.

The aim of the proposed research is to investigate the effects of temperature and irradiance on phytoplankton, bacterial and viral activity and species composition. We will conduct a series of field surveys in the Arctic (Koldewey lab. Kongsfjorden, Spitsbergen), covering spring, summer and autumn periods. Microcosm experiments (in 12 L UV transmissive PMMA bottles) will be set-up in UV transparent incubators, and exposed to natural solar radiation in a matrix of temperatures (2: environmental, elevated), irradiance quantities (3: 90 %, 60%, and 30% of incident) and irradiance qualities (3: PAR only, PAR + UVAR, PAR + UVBR + UVAR). Here, climate change induced changes in meltwater input and water turbidity will also be addressed. In addition to standard physical (T, irradiance) and chemical parameters (a.o. nutrients, DOC, POC), phytoplankton growth, species composition and some photoacclimation parameters (e.g. xanthophyll cycling) will be followed in each microcosm for the duration of the experiments. Bacterial metabolic activity will be studied using production and respiration measurements on the community and on a single cell level by microautoradiography combined with catalyzed reporter deposition fluorescence in situ hybridization (MICRO-CARD-FISH). Fingerprinting techniques (DGGE) will be applied to assess the composition of the eukaryote and prokaryote communities. Sequence information will be used to develop oligonucleotide probes for more detailed MICRO-CARD-FISH analyses. Thus, we will perform a complex structure-function analysis of the microbial community.

Artikelen

• Et al., Prof. dr. A.G.J. Buma (2008). Diversity an dynamics of Antarctis marine micorbial eukaryotes under manipulated environmental UV radiation.. FEMS Microbiol.. pp. 352-366
• Et al., Prof. dr. A.G.J. Buma (2010). Variability of protistan an bacterial communities in two arctic fjords.. Polar Biol. pp. 1521-1536
• Et al., Prof. dr. A.G.J. Buma (2010). Seasonal succession and UV sensitivity of marine bacterioplankton at an Antarctis coastal site. FEMS Microbiol.. pp. 68-82

Proefschriften

• Dr. A.M.T. Piquet Mild climate, harsh times for polar marine microbes.. Rijksuniversiteit Groningen. promotiedatum 12-2-2010