ALBERT

Description: Sources and Transformations of Anthropogenic Nitrogen along an Urban River-Estuarine Continuum Michael J. Pennino, Sujay S. Kaushal, Sudhir Murthy, Joel Blomquist, Jeff Cornwell, and Lora Harris Biogeosciences Discuss., doi:10.5194/bg-2016-264,2016 Manuscript under review for BG (discussion: open, 0 comments) The results of this manuscript report the analysis of the fate and transport of wastewater and anthropogenic nitrogen along the Potomac River Estuary, from Washington D.C. to the Chesapeake Bay. In conjunction with a mass balance approach, nitrate isotopes were used to estimate fluxes and trace the sources and transformations N along the estuary. This study shows that estuaries have a large capacity to transform N inputs, but with large seasonal variability due to hydrological extremes.

Description: Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra Inge Juszak, Werner Eugster, Monique M. P. D. Heijmans, and Gabriela Schaepman-Strub Biogeosciences, 13, 4049-4064, doi:10.1594/PANGAEA.860561, 2016 Changes in Arctic vegetation composition and structure feed back to climate and permafrost. Using field observations at a Siberian tundra site, we find that dwarf shrubs absorb more solar radiation than wet sedges and thus amplify surface warming, especially during snow melt. On the other hand, permafrost thaw was enhanced below sedges as a consequence of high soil moisture. Standing dead sedge leaves affected the radiation budget strongly and deserve more scientific attention.

Description: Diversity and mineral substrate preference in endolithic microbial communities from marine intertidal outcrops (Isla de Mona, Puerto Rico) Estelle Couradeau, Daniel Roush, Brandon Scott Guida, and Ferran Garcia-Pichel Biogeosciences Discuss., doi:10.5194/bg-2016-254,2016 Manuscript under review for BG (discussion: open, 0 comments) Endolithic (inside rock) microbial communities are dominated by cyanobacteria, among which the true boring cyanobacteria actively perforate the mineral and play a significant role in the erosion of coastal outcrops that may increase with ocean acidification. We interrogated the microbial communities associated with various intertidal substrates of Mona Island (PR) and brought the first evidence that there exists a mineralogical substrate preference among the pioneers true boring cyanobacteria.

Description: Anaerobic methane oxidation in an East African great lake (Lake Kivu) Fleur A. E. Roland, François Darchambeau, Cédric Morana, Sean A. Crowe, Bo Thamdrup, and Alberto V. Borges Biogeosciences Discuss., doi:10.5194/bg-2016-300,2016 Manuscript under review for BG (discussion: open, 0 comments) We studied methane consumption in a tropical Great Lake (Lake Kivu, East Africa). Lake Kivu has huge methane concentrations in its deep anoxic waters, but is a very poor emitter of methane to the atmosphere, which suppose a strong methane consumption in the water column. During this study, we put in evidence high aerobic and anaerobic consumption rates, whose relative importance varied with the season (higher aerobic rates in dry season, when the oxic compartment is wider).

Description: Coastal-ocean uptake of anthropogenic carbon Timothée Bourgeois, James C. Orr, Laure Resplandy, Jens Terhaar, Christian Ethé, Marion Gehlen, and Laurent Bopp Biogeosciences, 13, 4167-4185, doi:10.5194/bg-13-4167-2016, 2016 The global coastal ocean took up 0.1 Pg C yr −1 of anthropogenic carbon during 1993–2012 based on new biogeochemical simulations with an eddying 3-D global model. That is about half of the most recent estimate, an extrapolation based on surface areas. It should not be confused with the continental shelf pump, perhaps 10 times larger, which includes natural as well as anthropogenic carbon. Coastal uptake of anthropogenic carbon is limited by its offshore transport.

Description: Anthropogenically induced environmental changes in the northeastern Adriatic Sea in the last 400 years (Panzano Bay, Gulf of Trieste) Jelena Vidović, Rafał Nawrot, Ivo Gallmetzer, Alexandra Haselmair, Adam Tomašových, Michael Stachowitsch, Vlasta Ćosović, and Martin Zuschin Biogeosciences Discuss., doi:10.5194/bg-2016-273,2016 Manuscript under review for BG (discussion: open, 0 comments) Shallow and sheltered marine embayments in urbanized areas are prone to the accumulation of pollutants, but little is known about the historical baselines of such marine ecosystems. Here we study foraminiferal assemblages, geochemical proxies and sedimentological data from 1.6 m long sediment cores to uncover ~ 400 years of anthropogenic pressure from mining, port and industrial zones in the Gulf of Trieste, Italy. From 1600 to 1900 AD, element concentrations and foraminiferal assemblages point to negligible effects of agricultural activities. The only significant anthropogenic activity during this period is mercury mining in the hinterlands of the gulf, releasing high amounts of mercury into the bay and significantly exceeding today's Italian sediment quality guidelines (SQG) and the standards on the effects of trace elements to benthic organisms (ERL and ERM). Nonetheless, the fluctuations in the concentrations of mercury do not correlate with changes in the composition and diversity of foraminiferal assemblages due to its nonbioavailability. Intensified agricultural and maricultural activities in the first half of the 20th century caused slight nutrient enrichment and a minor increase in foraminiferal diversity. Intensified port and industrial activities in the second half of 20th century increased the normalised trace element concentrations and persistent organic pollutants (PAH, PCB) in the topmost part of the core, with solely Ni exceeding Italian SQG, ERL and ERM. This increase caused only minor changes in the foraminiferal community because foraminifera in Panzano Bay have a long history of adaptation to naturally elevated trace element concentrations. Our study underlines the importance of using an integrated, multidisciplinary approach in reconstructing the history of environmental and anthropogenic changes in marine systems. Given the prolonged human impacts in coastal areas like the Gulf of Trieste, such long term baseline data are crucial for interpreting the present state of marine ecosystems.

Description: Mechanisms of Trichodesmium demise within the New Caledonian lagoon during the VAHINE mesocosm experiment Dina Spungin, Ulrike Pfreundt, Hugo Berthelot, Sophie Bonnet, Dina AlRoumi, Frank Natale, Wolfgang R. Hess, Kay D. Bidle, and Ilana Berman-Frank Biogeosciences, 13, 4187-4203, doi:10.5194/bg-13-4187-2016, 2016 The marine cyanobacterium Trichodesmium spp. forms massive blooms important to carbon and nitrogen cycling in the oceans that often collapse abruptly. We investigated a Trichodesmium bloom in the lagoon waters of New Caledonia to specifically elucidate the cellular processes mediating the bloom decline. We demonstrate physiological, biochemical, and genetic evidence for nutrient and oxidative stress that induced a genetically controlled programmed cell death (PCD) pathway leading to bloom demise.

Description: Spring phytoplankton communities of the Labrador Sea (2005–2014): pigment signatures, photophysiology and elemental ratios Glaucia M. Fragoso, Alex J. Poulton, Igor M. Yashayaev, Erica J. H. Head, and Duncan A. Purdie Biogeosciences Discuss., doi:10.5194/bg-2016-295,2016 Manuscript under review for BG (discussion: open, 0 comments) This research describes a detailed analysis of current distributions of spring phytoplankton communities in the Labrador Sea based on ten years of observations. Phytoplankton community composition varied mainly according to the contrasting hydrographical zones of the Labrador Sea. The taxonomic distinctions of these communities influenced the photosynthetic and biochemical signatures of near surface waters, which may have a profound impact on the carbon cycle in high latitude seas.

Description: Sedimentary response to sea ice and atmospheric variability over the instrumental period off Adélie Land, East Antarctica Philippine Campagne, Xavier Crosta, Sabine Schmidt, Marie Noëlle Houssais, Olivier Ther, and Guillaume Massé Biogeosciences, 13, 4205-4218, doi:10.5194/bg-13-4205-2016, 2016 Diatoms and biomarkers have been recently used for palaeoclimate reconstructions in the Southern Ocean. Few sediment-based ecological studies have investigated their relationships with environmental conditions. Here, we compare high-resolution sedimentary records with meteorological data to study relationships between our proxies and recent atmospheric and sea surface changes. Our results indicate that coupled wind pattern and sea surface variability act as the proximal forcing at that scale.

Description: Observing and modelling phytoplankton community structure in the North Sea: can ERSEM-type models simulate biodiversity? David A. Ford, Johan van der Molen, Kieran Hyder, John Bacon, Rosa Barciela, Veronique Creach, Robert McEwan, Piet Ruardij, and Rodney Forster Biogeosciences Discuss., doi:10.5194/bg-2016-304,2016 Manuscript under review for BG (discussion: open, 0 comments) This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea. These observations were used to validate two physical-biogeochemical ocean model simulations, each of which used different variants of the widely-used European Regional Seas Ecosystem Model (ERSEM). It was found that the ability of the models to reproduce the observed biodiversity was strongly dependent on the details of the biogeochemical model formulations and parameterisations used.