Final conference, Rome October 11, 2016 Microbial community dynamics in the Arctic Kongsfjorden: changes in abundances, activity and composition Maurizio Azzaro1, Gabriella Caruso1, Carmela Caroppo2, Stefano Miserocchi3, Filippo Azzaro1, Franco Decembrini1, Renata Zaccone1, Marcella Leonardi1, Rodolfo Paranhos4, Angelina Lo Giudice1, Giuseppe Zappalà1, Gabriele Bruzzone5, Francesca Crisafi1, Renata Denaro1, Rosabruna La Ferla1 1Institute for Coastal Marine Environment, U.O.S. Messina, Spianata S. Raineri 86, 98122 Messina, Italy; 2Institute for Coastal Marine Environment, U.O.S. Taranto, via Roma 3, 74123 Taranto, Italy; 3Institute of Marine Sciences, U.O.S. Bologna, Via Gobetti 101, 40129 Bologna, Italy. 4Federal University of Rio de Janeiro, Av. Prof. Rodolpho Rocco 211, Rio de Janeiro CEP 21941-617, Brazil. 5Institute of Intelligent Systems for Automation, U.O.S. Genova, Via E. De Marini, 16149 Genova, Italy. Abstract Recent climate changes in Arctic regions have caused retreat of glaciers, increases in meltwater outflow and massive inputs of suspended sediment load to the coastal marine environment (Malone et al., 2016). Moreover, climate warming in the Arctic can potentially affect large-scale microbial processes including population dynamics and trophic level interactions. Viral, prokaryotic and phytoplanktonic communities play a key role in relevant processes such as carbon fluxes and nutrient regeneration and can be viewed both as sentinels and amplifiers of global change. Monitoring of environmental changes, especially those related to ice melting, requires the availability of advanced technologies, able to promptly record phenomena occurring at different spatial and time scales. Moreover, the development of new sampling technology in extreme environments can be used in areas not reachable by vessels or subject to oil spill. In the context of ARCA project the main aims of our research unit were: i) to assess the variability of planktonic abundance and activities over short time scales in a site of the study area; ii) to design and built an automatic sampler for extreme polar environments; iii) to search for cold-adapted OIL/PAH(Polycyclic aromatic hydrocarbons)-degrading bacteria in the Arctic region. To achieve the first objective, in June 2015 a study was performed at a coastal station (MDI) of the Kongsfjorden (Svalbard Islands) influenced by the freshwater runoff from land and glaciers (Fig. 1). The survey repeated a previous experiment carried out in September 2013 (Azzaro et al., 2014; Azzaro et al., 2015; Azzaro et al., 2016; Caroppo et al., 2016) at the same site, with the novelty of focusing on the sea surface microlayer and the bottom boundary layer. During this study, lasting 10 days, changes both in abiotic and biotic parameters were detected. In particular, the variability over short time scales of planktonic abundances (virio-, bacterio- and microphytoplankton) and microbial activities, was assessed in relation to environmental variables. The following results were obtained: lower biotic and abiotic variability in June 2015 compared to September 2013; prevalence of viruses over bacteria; a greater abundance of autotrophic than heterotrophic components and increased presence of temperate-warm species -including harmful and toxic species- compared to the previous survey; higher microbial activity levels in June 2015 than in September 2013, resulting in an increased efficiency of the Biological pump. The second aim was addressed to the development of new technological devices for the study of extreme polar environments. In particular, a first prototype of an automatic multisampler was tested in the Kongsfjorden (Zappalà et al., 2016a,b). It constitutes a practical low-cost system to obtain data with good spatio-temporal resolution both for the initial characterization and for the study of possible natural or anthropogenic disturbance in water quality. The developed multisampler has been successfully applied