Giraudeau J.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) |
Grelaud M.,British Petroleum |
Solignac S.,University of Quebec at Montréal |
Andrews J.T.,University of Colorado at Boulder |
And 3 more authors.
Quaternary Science Reviews | Year: 2010
Abundance patterns of coccolith species in two Holocene marine cores retrieved off Norway and northern Iceland are indicative of millennial-scale modulations in the flow of the main (Norwegian Atlantic Current) and secondary (North Iceland Irminger Current) branches of the North Atlantic Drift to the Nordic Seas. Long-term trends in coccolith abundance changes reflect major Holocene steps in Atlantic Water transfer to the Nordic Seas at orbital scale with important constraints on the convective activity of the Nordic Seas that leads to the formation of the precursor water mass of North Atlantic Deep Water. Millennial-scale Holocene episodes of increased advection of Atlantic waters off Norway are associated with enhanced winter precipitation over Scandinavia, increased sea-salt fluxes over Greenland, and strengthened wind over Iceland, thereby suggesting a common atmospheric forcing: the location and intensity of the westerlies and the associated changes in mid- to high-latitude pressure gradients. Our biotic data indicate an opposite pattern of Atlantic water inflow at suborbital scale between the western (Denmark) and eastern (Iceland-Scotland) straits of the northern Atlantic throughout the Holocene. This, as supported by present observational and simulated data, further highlights the role of atmospheric oscillations in the recent history of the North Atlantic-Nordic Seas water mass exchanges across the Greenland-Scotland Ridge. Such atmospheric processes are thought to explain the observed coupling between periods of excess export of arctic sea-ice to the Nordic Seas and intervals of maximum inflow of Atlantic water to the Norwegian Sea throughout the last 11 000 years. © 2010 Elsevier Ltd. All rights reserved.
Schiebel R.,University of Angers |
Brupbacher U.,ETH Zurich |
Schmidtko S.,Leibniz Institute of Marine Science |
Nausch G.,Leibniz Institute For Ostseeforschung Warnemunde |
And 2 more authors.
Journal of Geophysical Research: Oceans | Year: 2011
Production and dispersion of coccolithophores are assessed within their ecologic and hydrographic context across enhanced spring chlorophyll production in the surface eastern North Atlantic. Within a 4 day period from 12 to 16 March 2004, a N-S transect from 47N to 33N was sampled along 20W. Water samples from defined depths down to 200 m were analyzed for coccolithophores from 0.45 m polycarbonate filters by scanning electron microscopy. At 47N coccolithophores flourished when euphotic conditions allowed new production at deep mixing, low temperatures, and high nutrient concentrations. Emiliania huxleyi flourished at high turbulence during an early stage of the phytoplankton succession and contributed half of the total coccolithophore assemblage, with up to 150 × 103 cells L-1 and up to 12 × 109 cells m-2 when integrated over the upper 200 m of the water column. Maximum chlorophyll concentrations occurred just north of the Azores Front, at 37N-39N, at comparatively low numbers of coccolithophores. To the south, at 35N-33N, coccolithophores were abundant within calm and stratified Subtropical Mode Waters, and E. huxleyi was the dominant species again. Although the cell densities of coccolithophores observed here remained below those typical of plankton blooms visible from satellite images, the depth-integrated total mass makes them significant producers of calcite and contributors to the total carbon sedimentation at a much wider range of ecological conditions during late winter and early spring than hitherto assumed. Copyright © 2011 by the American Geophysical Union.
Martin B.,University of Hamburg |
Eggert A.,Leibniz Institute For Ostseeforschung Warnemunde |
Koppelmann R.,University of Hamburg |
Diekmann R.,Thunen Institute For Seefischerei |
And 2 more authors.
Marine Ecology | Year: 2015
Spatial and temporal distribution patterns of zooplankton are highly variable in the Northern Benguela Upwelling System. We studied the distribution of zooplankton (size class ≥ 0.33 mm) and used field data from four cruises that took place between March 2008 and February 2011, as well as simulation results of a regional ecosystem model. Remotely sensed sea surface temperatures (SST) and surface chlorophyll concentrations were analysed to investigate environmental influences on zooplankton biomass. The Intense Benguela Upwelling Index showed a distinct seasonal signal throughout the years and the highest upwelling peaks in August/September. Even though surface chlorophyll concentrations were very variable throughout the year, the highest concentrations were always detected in September, following the upwelling of nutrient-rich water. In field catches, zooplankton biomass concentration in the upper 200 m was highest above the outer shelf and shelf-break in December 2010 and February 2011, i.e. 6 months after the upwelling peaks. In contrast, zooplankton biomass simulated by the model in the surface water was highest in September. In March/April, biomass maxima were typically measured in the field at intermediate water depths, but the vertical distribution was also affected by extensive oxygen minimum zones. The ecosystem model reproduced this vertical pattern. Although general trends were similar, simulation data of zooplankton standing stocks overestimated the field data by a factor of 3. In upwelling systems, food webs are generally considered to be short and dominated by large cells. However, our field data indicate more small-sized zooplankton organisms above the shelf than offshore. © 2014 Blackwell Verlag GmbH.
Voelker A.H.L.,Instituto Portugues do Mar e da Atmosfera IPMA |
Voelker A.H.L.,CIMAR Associated Laboratory |
Colman A.,University of Chicago |
Olack G.,University of Chicago |
And 2 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2015
Only a few studies have examined the variation of oxygen and hydrogen isotopes of seawater in NE Atlantic water masses, and data are especially sparse for intermediate and deep-water masses. The current study greatly expands this record with 527 δ18O values from 47 stations located throughout the mid- to low-latitude NE Atlantic. In addition, δD was analyzed in the 192 samples collected along the GEOTRACES North Atlantic Transect GA03 (GA03_e=KN199-4) and the 115 Iberia-Forams cruise samples from the western and southern Iberian margin. An intercomparison study between the two stable isotope measurement techniques (cavity ring-down laser spectroscopy and magnetic-sector isotope ratio mass spectrometry) used to analyze GA03_e samples reveals relatively good agreement for both hydrogen and oxygen isotope ratios. The surface (0-100m) and central (100-500m) water isotope data show the typical, evaporation related trend of increasing values equatorward with the exception for the zonal transect off Cape Blanc, NW Africa. Off Cape Blanc, surface water isotope signatures are modified by the upwelling of fresher Antarctic Intermediate Water (AAIW) that generally has isotopic values of 0.0 to 0.5‰ for δ18O and 0 to 2‰ for δD. Along the Iberian margin the Mediterranean Outflow Water (MOW) is clearly distinguished by its high δ18O (0.5-1.1‰) and δD (3-6‰) values that can be traced into the open Atlantic. Isotopic values in the NE Atlantic Deep Water (NEADW) are relatively low (δ18O: -0.1 to 0.5‰ δD: -1 to 4‰) and show a broader range than observed previously in the northern and southern convection areas. The NEADW is best observed at GA03_e Stations 5 and 7 in the central NE Atlantic basin. Antarctic Bottom Water isotope values are relatively high indicating modification of the original Antarctic source water along the flow path. The reconstructed δ18O-salinity relationship for the complete data set has a slope of 0.51, i.e., slightly steeper than the 0.46 described previously by Pierre et al. (1994, J. Mar. Syst. 5 (2), 159-170.) for the tropical to subtropical Northeast Atlantic. This slope decreases to 0.46 for the subtropical North Atlantic Central Water (NACW) and the MOW and to 0.32 for the surface waters of the upper 50m. The δD-salinity mixing lines have estimated slopes of 3.01 for the complete data, 1.26 for the MOW, 3.47 for the NACW, and 2.63 for the surface waters. The slopes of the δ18O-δD relationship are significantly lower than the one for the Global Meteoric Water Line with 5.6 for the complete data set, 2.30 for the MOW, 4.79 for the NACW, and 3.99 for the surface waters. The lower slopes in all the relationships clearly reflect the impact of the evaporation surplus in the subtropics. © 2015 Elsevier Ltd.
Koppelmann R.,University of Hamburg |
Kullmann B.,University of Hamburg |
Lahajnar N.,University of Hamburg |
Martin B.,University of Hamburg |
Mohrholz V.,Leibniz Institute For Ostseeforschung Warnemunde
Journal of the Marine Biological Association of the United Kingdom | Year: 2013
Many Thecosomata (Gastropoda) produce an aragonite shell and are potentially threatened by the increasing ocean acidification. Information about these species is very important for future monitoring of the fate of this group. This paper investigates the distribution, species composition and trophic role of Thecosomata along a transect from the coast into the open ocean off Walvis Bay, Namibia, in September 2010 and January/February 2011. Twenty species were detected, but three taxa (Limacina bulimoides, Limacina inflata and Desmopterus papilio) dominated the community with more than 80% of the total standing stock. Diel vertical migration was observed for both Limacina taxa with higher concentrations in surface waters during night. Desmopterus papilio revealed almost no day/night differences. The highest diversities and abundances were detected at the slope and offshore stations, indicating the oceanic preference of this group; some taxa aggregated at the shelf-open ocean interface. δ15N measurements confirmed the first trophic level of this group; however, significant differences were detected between seasons with higher values in February 2011. This can be related to differences in seston values as the primary food source. Possible biogeochemical causes for these differences like an exhaustion of the nitrate pool or denitrification processes under suboxic conditions are discussed. © Marine Biological Association of the United Kingdom 2013.
Frundt B.,Leibniz Institute For Ostseeforschung Warnemunde |
Muller T.J.,Leibniz Institute of Marine Science |
Schulz-Bull D.E.,Leibniz Institute For Ostseeforschung Warnemunde |
Waniek J.J.,Leibniz Institute For Ostseeforschung Warnemunde
Progress in Oceanography | Year: 2013
Data from almost thirty years of time series observations from a deep-sea mooring Kiel276 (33°N, 22°W), which was operated in the northeast Atlantic Ocean between 1980 and 2009, are studied to reveal information on the long term changes in the upper thermocline. This includes daily records of temperature and currents at two depths (240. m and 500. m). Until 1988, our analysis shows decreasing temperature in the entire thermocline followed by a slight increase at both depths; from 2000 on, extensive warming began at the shallower depth (240. m) and eight years later at the deeper (500. m) level. A northward displacement of the North Atlantic Subtropical Gyre is indicated by both current measurements and calculated kinetic energy between 1991 and 1998 resulting in an altered current regime in terms of absolute velocity and current directions in the last ten years compared to the first twenty years. Coherences of the currents with large scale climatic patterns such as North Atlantic Oscillation and El Niño/ Southern Oscillation evidence the atmospheric impact even at 500. m water depth. © 2013 Elsevier Ltd.
Schneider B.,Leibniz Institute For Ostseeforschung Warnemunde |
Gulzow W.,Leibniz Institute For Ostseeforschung Warnemunde |
Sadkowiak B.,Leibniz Institute For Ostseeforschung Warnemunde |
Rehder G.,Leibniz Institute For Ostseeforschung Warnemunde
Journal of Marine Systems | Year: 2014
A fully automated measurement system for recording of the surface water CO2 partial pressure, pCO2, was deployed on VOS (voluntary observation ship) "Finnpartner/Finnmaid" in 2003. Since 2009, an amendment of the system also allows for the continuous detection of the surface water partial pressure of methane, pCH4. The ship commutes regularly at 2-3day intervals between the Gulf of Finland (Helsinki) and the Mecklenburg Bight (Lübeck) in the southwest of the Baltic Sea.The pCO2 data in the central Gotland Sea showed a pronounced seasonality that was mainly controlled by the biological production and decomposition of organic matter in combination with stratification/mixing of the water column. CO2 consumption in spring/summer caused pCO2 that were by up to 300μatm below the atmospheric level. In contrast, the pCO2 exceeded the atmospheric values during autumn/winter when deep mixing transports CO2-enriched water to the surface. To identify the central Baltic Sea as a sink or source for atmospheric CO2, an air-sea CO2 gas exchange balance was established for three selected years (2005, 2008 and 2009). During each year the surface water acted as a net sink for atmospheric CO2 with uptake rates ranging between 0.60 and 0.89molm-2yr-1. The rates correspond approximately to the enhanced carbon burial in sediments during the last century and suggest a link between eutrophication and CO2 uptake.The data of the surface methane concentration are used to focus on situations were extraordinarily high methane concentrations were observed. Temporary methane peaks were observed south of the Island of Gotland, which could clearly be attributed to frequent upwelling events.Between spring 2012 and 2013, Finnmaid went at a few occasions to St. Petersburg in the east of the Gulf of Finland. Methane concentration of up to 130nmolL-1 where found close to the River Neva mouth but decreased rapidly to the west. The plume of methane-enriched waters was observed farthest to the west during the winter period. This was attributed to air-sea gas exchange that was most effective during summer but inhibited during winter because of the ice coverage. © 2014 Elsevier B.V.
Nausch G.,Leibniz Institute For Ostseeforschung Warnemunde
Chemie in Unserer Zeit | Year: 2011
Eutrophication, i.e. the increased supply of nutrients (nitrogen and phosphorus) due to human activities in the catchment area and the adverse follow-ups are still a major concern for the Baltic Sea. The article describes nutrient inputs to the Baltic Sea over time, the development of nutrient concentrations and gives a recent evaluation of the eutrophication status of the Baltic Sea. Finally, protection measures in the past and at present are documented. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
PubMed | Leibniz Institute For Ostseeforschung Warnemunde
Type: Comparative Study | Journal: MicrobiologyOpen | Year: 2014
Epsilonproteobacteria have been found globally distributed in marine anoxic/sulfidic areas mediating relevant transformations within the sulfur and nitrogen cycles. In the Baltic Sea redox zones, chemoautotrophic epsilonproteobacteria mainly belong to the Sulfurimonas gotlandica GD17 cluster for which recently a representative strain, S. gotlandica GD1(T), could be established as a model organism. In this study, the potential effects of changes in dissolved inorganic carbon (DIC) and pH on S. gotlandica GD1(T) were examined. Bacterial cell abundance within a broad range of DIC concentrations and pH values were monitored and substrate utilization was determined. The results showed that the DIC saturation concentration for achieving maximal cell numbers was already reached at 800 mol L(-1), which is well below in situ DIC levels. The pH optimum was between 6.6 and 8.0. Within a pH range of 6.6-7.1 there was no significant difference in substrate utilization; however, at lower pH values maximum cell abundance decreased sharply and cell-specific substrate consumption increased.
PubMed | Leibniz Institute fur Polymerforschung Dresden e.V. and Leibniz Institute For Ostseeforschung Warnemunde
Type: Journal Article | Journal: Analytical and bioanalytical chemistry | Year: 2016
The contamination of aquatic ecosystems with microplastics has recently been reported through many studies, and negative impacts on the aquatic biota have been described. For the chemical identification of microplastics, mainly Fourier transform infrared (FTIR) and Raman spectroscopy are used. But up to now, a critical comparison and validation of both spectroscopic methods with respect to microplastics analysis is missing. To close this knowledge gap, we investigated environmental samples by both Raman and FTIR spectroscopy. Firstly, particles and fibres >500m extracted from beach sediment samples were analysed by Raman and FTIR microspectroscopic single measurements. Our results illustrate that both methods are in principle suitable to identify microplastics from the environment. However, in some cases, especially for coloured particles, a combination of both spectroscopic methods is necessary for a complete and reliable characterisation of the chemical composition. Secondly, a marine sample containing particles <400m was investigated by Raman imaging and FTIR transmission imaging. The results were compared regarding number, size and type of detectable microplastics as well as spectra quality, measurement time and handling. We show that FTIR imaging leads to significant underestimation (about 35%) of microplastics compared to Raman imaging, especially in the size range <20m. However, the measurement time of Raman imaging is considerably higher compared to FTIR imaging. In summary, we propose a further size division within the smaller microplastics fraction into 500-50m (rapid and reliable analysis by FTIR imaging) and into 50-1m (detailed and more time-consuming analysis by Raman imaging). Graphical Abstract Marine microplastic sample (fraction <400 m) on a silicon filter (middle) with the corresponding Raman and IR images.