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search.filters.applied.f.access: openAccess × Subject: marine ecosystem ×

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    Unravelling New Processes at Interfaces: Photochemical Isoprene Production at the Sea Surface
    (Columbus, Ohio : American Chemical Society, 2015) Ciuraru, Raluca; Fine, Ludovic; van Pinxteren, Manuela; D’Anna, Barbara; Herrmann, Hartmut; George, Christian
    Isoprene is an important reactive gas that is produced mainly in terrestrial ecosystems but is also produced in marine ecosystems. In the marine environment, isoprene is produced in the seawater by various biological processes. Here, we show that photosensitized reactions involving the sea-surface microlayer lead to the production of significant amounts of isoprene. It is suggested that H-abstraction processes are initiated by photochemically excited dissolved organic matter which will the degrade fatty acids acting as surfactants. This chemical interfacial processing may represent a significant abiotic source of isoprene in the marine boundary layer.
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    A protocol for the intercomparison of marine fishery and ecosystem models: Fish-MIP v1.0
    (Göttingen : Copernicus GmbH, 2018) Tittensor, D.P.; Eddy, T.D.; Lotze, H.K.; Galbraith, E.D.; Cheung, W.; Barange, M.; Blanchard, J.L.; Bopp, L.; Bryndum-Buchholz, A.; Büchner, M.; Bulman, C.; Carozza, D.A.; Christensen, V.; Coll, M.; Dunne, J.P.; Fernandes, J.A.; Fulton, E.A.; Hobday, A.J.; Huber, V.; Jennings, S.; Jones, M.; Lehodey, P.; Link, J.S.; MacKinson, S.; Maury, O.; Niiranen, S.; Oliveros-Ramos, R.; Roy, T.; Schewe, J.; Shin, Y.-J.; Silva, T.; Stock, C.A.; Steenbeek, J.; Underwood, P.J.; Volkholz, J.; Watson, J.R.; Walker, N.D.
    Model intercomparison studies in the climate and Earth sciences communities have been crucial to building credibility and coherence for future projections. They have quantified variability among models, spurred model development, contrasted within-and among-model uncertainty, assessed model fits to historical data, and provided ensemble projections of future change under specified scenarios. Given the speed and magnitude of anthropogenic change in the marine environment and the consequent effects on food security, biodiversity, marine industries, and society, the time is ripe for similar comparisons among models of fisheries and marine ecosystems. Here, we describe the Fisheries and Marine Ecosystem Model Intercomparison Project protocol version 1.0 (Fish-MIP v1.0), part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), which is a cross-sectoral network of climate impact modellers. Given the complexity of the marine ecosystem, this class of models has substantial heterogeneity of purpose, scope, theoretical underpinning, processes considered, parameterizations, resolution (grain size), and spatial extent. This heterogeneity reflects the lack of a unified understanding of the marine ecosystem and implies that the assemblage of all models is more likely to include a greater number of relevant processes than any single model. The current Fish-MIP protocol is designed to allow these heterogeneous models to be forced with common Earth System Model (ESM) Coupled Model Intercomparison Project Phase 5 (CMIP5) outputs under prescribed scenarios for historic (from the 1950s) and future (to 2100) time periods; it will be adapted to CMIP phase 6 (CMIP6) in future iterations. It also describes a standardized set of outputs for each participating Fish-MIP model to produce. This enables the broad characterization of differences between and uncertainties within models and projections when assessing climate and fisheries impacts on marine ecosystems and the services they provide. The systematic generation, collation, and comparison of results from Fish-MIP will inform an understanding of the range of plausible changes in marine ecosystems and improve our capacity to define and convey the strengths and weaknesses of model-based advice on future states of marine ecosystems and fisheries. Ultimately, Fish-MIP represents a step towards bringing together the marine ecosystem modelling community to produce consistent ensemble medium-and long-term projections of marine ecosystems.
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    Natural variability or anthropogenically-induced variation? Insights from 15 years of multidisciplinary observations at the arctic marine LTER site HAUSGARTEN
    (Amsterdam : Elsevier B.V., 2016) Soltwedel, T.; Bauerfeind, E.; Bergmann, M.; Bracher, A.; Budaeva, N.; Busch, K.; Cherkasheva, A.; Fahl, K.; Grzelak, K.; Hasemann, C.; Jacob, M.; Kraft, A.; Lalande, C.; Metfies, K.; Nöthig, E.-M.; Meyer, K.; Quéric, N.-V.; Schewe, I.; Włodarska-Kowalczuk, M.; Klages, M.
    Time-series studies of arctic marine ecosystems are rare. This is not surprising since polar regions are largely only accessible by means of expensive modern infrastructure and instrumentation. In 1999, the Alfred Wegener Institute, Helmholtz-Centre for Polar and Marine Research (AWI) established the LTER (Long-Term Ecological Research) observatory HAUSGARTEN crossing the Fram Strait at about 79°N. Multidisciplinary investigations covering all parts of the open-ocean ecosystem are carried out at a total of 21 permanent sampling sites in water depths ranging between 250 and 5500 m. From the outset, repeated sampling in the water column and at the deep seafloor during regular expeditions in summer months was complemented by continuous year-round sampling and sensing using autonomous instruments in anchored devices (i.e., moorings and free-falling systems). The central HAUSGARTEN station at 2500 m water depth in the eastern Fram Strait serves as an experimental area for unique biological in situ experiments at the seafloor, simulating various scenarios in changing environmental settings. Long-term ecological research at the HAUSGARTEN observatory revealed a number of interesting temporal trends in numerous biological variables from the pelagic system to the deep seafloor. Contrary to common intuition, the entire ecosystem responded exceptionally fast to environmental changes in the upper water column. Major variations were associated with a Warm-Water-Anomaly evident in surface waters in eastern parts of the Fram Strait between 2005 and 2008. However, even after 15 years of intense time-series work at HAUSGARTEN, we cannot yet predict with complete certainty whether these trends indicate lasting alterations due to anthropologically-induced global environmental changes of the system, or whether they reflect natural variability on multiyear time-scales, for example, in relation to decadal oscillatory atmospheric processes.