Description: nformation on recent diversity and biogeography of Arctic marine protists with adequate temporal and spatial resolution is urgently needed to better understand consequences of environmental change for marine ecosystems. Here, we introduce a molecular-based observation strategy for high resolution assessment of marine protists in space and time, even in remote areas such as the Arctic Ocean. The observation strategy involves molecular analyses (e.g. Next Generation Sequencing (NGS) or quantitative PCR) of samples, collected with a set of complementary methods such as a newly developed automated under-way sampling device, CTD-casts and moored sediment traps. This integrated approach allows generating detailed information on marine protist community composition or abundance with adequate resolution. Currently, the observation strategy is organized at four major levels. At level 1, samples are collected at high spatial and temporal resolution based on under-way sampling with the remote-controlled automated filtration system AUTOFIM (developed in the COSYNA-project), and sampling at fixed stations based on CTD-casts and moored sediment traps. Resulting samples can either be preserved for later laboratory analyses, or directly subjected to molecular surveillance of key species aboard the ship, e.g. via quantitative polymerase chain reaction (level 2). Preserved samples are analyzed at the next observational levels in the laboratory (level 3 and 4). This involves at level 3 molecular fingerprinting methods for a quick and reliable overview of differences in protist community composition. Finally, selected samples can be used to generate a detailed analysis of taxonomic protist composition via the latest Next Generation Sequencing Technology (NGS) at level 4. An overall integrated dataset of all results provides comprehensive information on the diversity and biogeography of protists, including all related size classes. In the future, the observation strategy for Arctic marine protists will be part of the Molecular Microbial Observatory envisioned for the Arctic observatory FRAM (Frontiers in Arctic Monitoring).

Description: Rising water temperatures and ocean acidification are the major threats for polar marine ecosystems and will affect phytoplankton communities. Phytoplankton plays a major role in primary production and biogeochemical cycles and forms the basis of marine food webs. Changes in the composition and distribution of phytoplankton will affect the whole marine ecosystem. To assess the effects of changing environmental conditions on phytoplankton communities we have to know their current diversity and distribution. There is a lack of Phytoplankton diversity studies in the Pacific sector of the Southern Ocean, especially in the Amundsen Sea. To resolve this gap this study will deliver basic data of phytoplankton diversity and distribution, which will help identifying the dominant phytoplankton phyla and provide information on the rare biosphere in that area. Environmental samples, taken on the RV Polarstern cruise ANT XXVI/3, were analyzed with molecular approaches, including ARISA (automated ribosomal intergenic spacer analysis) and 454-pyrosequencing. Furthermore pigment analysis and flow cytometry were conducted. First results indicate a clustering of the samples according to the different water masses and regions with comparable environmental conditions. The sequencing will deliver more detailed information about the structure and diversity of phytoplankton in the Pacific sector of the Southern Ocean.

Description: As climate change is expected to be extremely intense in the Arctic Ocean there is an utmost need to study food-web interactions to contribute to a better understanding of the direction and strength of biogeochemical and microbiological feedback processes. Climate change induced alterations will directly affect food-web structures and ecosystem functioning. Recent studies indicate that environmental changes like increasing temperatures as well as freshening of surface waters promote a shift in the phytoplankton community towards a dominance of smaller cells, especially of eukaryotic picoplankton. The response of oceanic ecosystems and marine carbon cycling to these changes is particularly determined by microbial loop activity. Heterotrophic bacteria, as part of the microbial loop and a crucial component of marine food webs, have a key role in controlling carbon fluxes in the oceans. Microbial activities, dynamics and diversity were studied in the area of the deep-sea long-term observatory HAUSGARTEN of the Alfred-Wegener-Institute (Fram Strait) in July 2009. The investigation area is located within a transition zone between the northern North Atlantic and the central Arctic Ocean, which separates the warm and cold water masses originating from the West Spitzbergen and the East Greenland currents. While bacterial abundance and chlorophyll a were tightly coupled, differences of the planktonic and bacterial community structures are most likely due to the heterogeneous hydrography. Warmer water masses comprise a higher genetic diversity of picoplankton, as it is also expected for bacteria. A shift towards a dominance of smaller plankton species can potentially affect the quality of organic matter and subsequently microbial cycling. Here we present data on bacterial abundance, biomass and protein production, hydrolytical enzyme activities and community structure within different size classes with respect to changing biotic and abiotic conditions in the Fram Strait.

Description: Climate change is expected to be particularly intense in the Arctic Ocean having as well extensive consequences on Arctic pelagic ecosystems. Thus, evaluations of the impact on the base of the food web, on local phytoplankton communities, are required. Prerequisite of such an evaluation is comprehensive information about the present phytoplankton diversity and distribution. Recent investigations indicate that rising temperatures as well as freshening of surface waters in the marine environment promote a shift in the phytoplankton community towards a dominance of smaller cells. In such a scenario, picoplankton can comprise a large pool of biomass and can attain high abundances. Understanding the impact of climate related environmental change for this phytoplankton size class in the Arctic Ocean demands that we understand how environmental parameters influence their diversity, occurrence and distribution. In this perspective, samples to investigate picoplankton have been taken in the area of the “deep-sea long-term observatory HAUSGARTEN” of the Alfred-Wegener-Institute (Fram Strait) in July 2009 and analyzed by the application of ribosomal fingerprinting technology (ARISA), 18S rDNA clone libraries and Pyrosequencing. The investigation area between 2 - 6°E and 78 – 80°N is located within the frontal zone which is separating the warm and cold water masses originating from the West Spitzbergen Current and East Greenland Current, respectively. Based on the heterogeneous hydrographic condition differences in the picoplankton community according to the water masses is likely. Preliminary results on the investigation of the genetic diversity of picoplankton reflect these environmental differences. The findings reveal that the diversity within the warm water mass is higher compared to the one found in the colder water mass. Further the dominance of single species (Phaeocystis pouchetii vs. Micromonas pusilla) differs at the stations according to abiotic conditions. All in all, this study will provide a framework for a better understanding of the interactions between environmental conditions and corresponding pico-phytoplankton communities in arctic pelagic systems.

Description: Studies of phytoplankton ecology and biogeochemical parameters have been carried out with the ice breaking vessel RV Polarstern since the nineties at various locations in the central Artcic Ocean, the Greenland Sea and the Fram Strait, however, plankton abundance and composition were determined sporadically, and only few biogeochemical components were analysed. Since rapid environmental changes due to increasing temperatures, sea ice loss and ocean acidification in the Arctic Ocean are expected, a more comprehensive impression of the impact of the anticipated changes on pelagic biological processes and the consequences for organic matter cycling is desirable. To get more detailed investigations on the pelagic system the new research group PEBCAO was created. The aim of this group is to complement the measurements of bulk variables and samples on phyto- and protozooplankton abundances by a molecular assessment of the phytoplankton diversity, including the pico- and nanoplankton allowing to better quantifying the intrusion of invading species into the polar habitat. The point measurements during cruises will serve as ground-truthing data to create basin wide satellite images focussing on the quantitative estimation of various phytoplankton functional types, which can serve as an input for modelling approaches. Furthermore, investigations on changes in the composition of organic matter (OM) including molecular analysis of OM are carried out and together with abundance and activity of key species in zooplankton will improve the export estimates under climate change. One local focus of this group is the deep-sea long-term observatory HAUSGARTEN of AWI in the Fram Strait off Svalbard, where investigations on plankton ecology and particle flux have been carried out since the 1990. These observations can be used to identify how current observed changes are related in a historical context. Here we present first results of the multidisciplinary approach form the long term observations and the studies carried out during two Polarstern cruises (ARK 24_1&2 and ARK 25_1&2) in the summer of 2009 & 2010, respectively.

Description: Most of the iron fertilization experiments conducted in the Southern Ocean during the past two decades were carried out in high silicic acid waters and have induced phytoplankton blooms, dominated by diatoms. The iron fertilization experiment LOHAFEX, performed during the RV Polarstern cruise ANT XXV/3 from January to March 2009, was however carried out in a silicic acid depleted mesoscale eddy in the Atlantic sector of the Southern Ocean. The low silicic acid concentrations (〈2 µM) limited diatom growth and the phytoplankton assemblage was instead dominated by nano- and picoeukaryotes. In the present study we used molecular methods to investigate the composition and succession of small phytoplankton (0.2-5µm) during LOHAFEX. This involves on the one hand ARISA (automated intergenic spacer analysis) and on the other hand 454 next generation sequencing. The ARISA approach is based on the heterogeneity of the region between the 18S and the 28S rRNA gene and delivers a quick community structure overview. The 454 sequencing is a high throughput approach and provides high resolution information on the phytoplankton diversity, including the rare biosphere. During LOHAFEX the 0.2-5µm phytoplankton fraction shows a high diversity. The most prominent classes are the Prasinophyceae (dominated by Micromonas pusilla), the Haptophyceae (dominated by Phaeocystis antarctica) and the Dinophyceae (dominated by Syndiniales). The fertilized and non-fertilized samples show a similar community structure and no significant differences concerning the abundance of the dominant species. In all samples there are a large number of sequences belonging to the rare biosphere. The results support the general notion that the diversity of the picoplankton community was highly underestimated in the past. There is still a vast number of unknown organisms, hiding in the rare biosphere, to discover. According to other studies, our outcome shows that in the northern part of the Southern Ocean the picoplankton assemblage is dominated by Micromonas pusilla and Phaeocystis antarctica. Measurements during the experiment revealed an increase in total biomass, attributed to the addition of iron. In our samples there is no species or group in the picoplankton community that is favored by the iron addition and the relative abundances remain constant. In conclusion the iron addition has increased picoplankton biomass but the assemblage composition did not change significantly.