Time filter

Source Type

Boer S.I.,Federal Institute of Hydrology | Heinemeyer E.-A.,Governmental Institute for Public Health of Lower Saxony | Luden K.,Governmental Institute for Public Health of Lower Saxony | Erler R.,Alfred Wegener Institute for Polar and Marine Research | And 3 more authors.
Microbial Ecology | Year: 2013

The number of reported Vibrio-related wound infections associated with recreational bathing in Northern Europe has increased within the last decades. In order to study the health risk from potentially pathogenic Vibrio spp. in the central Wadden Sea, the seasonal and spatial distribution of Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio cholerae were investigated at ten recreational beaches in this area over a 2-year period. V. alginolyticus and V. parahaemolyticus were found to be omnipresent all year round in the study area, while V. vulnificus occurrence was restricted to summer months in the estuaries of the rivers Ems and Weser. Multiple linear regression models revealed that water temperature is the most important determinant of Vibrio spp. occurrence in the area. Differentiated regression models showed a species-specific response to water temperature and revealed a particularly strong effect of even minor temperature increases on the probability of detecting V. vulnificus in summer. In sediments, Vibrio spp. concentrations were up to three orders of magnitude higher than in water. Also, V. alginolyticus and V. parahaemolyticus were found to be less susceptible towards winter temperatures in the benthic environment than in the water, indicating an important role of sediments for Vibrio ecology. While only a very small percentage of tested V. parahaemolyticus proved to be potentially pathogenic, the presence of V. vulnificus during the summer months should be regarded with care. © 2013 Springer Science+Business Media New York.

Dreyer A.,Eurofins | Dreyer A.,Helmholtz Center Geesthacht | Kirchgeorg T.,Helmholtz Center Geesthacht | Kirchgeorg T.,University of Venice | And 3 more authors.
Chemosphere | Year: 2015

Eleven particle-size-segregated samples were taken to investigate the particle-size distribution of perfluoroalkyl substances (PFASs) using two five stage impactors in parallel. Samples were extracted with methanol and detected by HPLC/MS-MS. Investigation yielded reproducible results for the parallel samples over the entire sampling period. Particle-size distribution varied between perfluorooctane sulfonate (PFOS) and other perfluoroalkyl sulfonates (PFSAs), perfluorooctane carboxylate (PFOA) and other perfluoroalkyl carboxylates (PFCAs) and n-methyl-perfluorooctanesulfonamido ethanol (MeFOSE). Whereas PFOA and MeFOSE were predominantly observed in smallest size fraction (<0.14. μm), maximum PFOS mass fractions were observed in the coarser size fractions between 1.38 and 3.81. μm. The reason for this different behaviour remained unclear and indicated a complex atmospheric PFAS processing and sampling which should be further investigated and optimized, respectively. © 2014 Elsevier Ltd.

Dahlmann G.,Federal Maritime and Hydrographic Agency | Kienhuis P.,RWS Laboratory
Handbook of Environmental Chemistry | Year: 2016

This contribution describes the development and some highlights of the internationally agreed standard procedure CEN/TR 15522-2:2012: "Oil spill identification - Waterborne petroleum and petroleum products - Part 2: Analytical methodology and interpretation of results based on GC-FID and GC-MS low resolution analyses" [1]. In particular, handling of changes caused by weathering of spilled oil is described here: PW plots (partial weathering plots) allow a proper and unequivocal identification of oil, despite those changes. CEN/TR 15522-2:2012 has been produced by Bonn-OSINet (Oil Spill Identification Network of experts within the Bonn Agreement). Researchers from all over the world have cooperated and contributed to its development. This method has been continuously improved and tested over the last decade. Cooperation of laboratories culminated in COSIweb (Computerized Oil Spill Identification), an online program which includes a huge database of more than 2,200 oil samples at the time of writing and an automatic evaluation system. This web-based resource provides the possibility to handle raw data produced anywhere in the world and to evaluate these data as if they were produced in a user's own laboratory. © 2016 Springer International Publishing Switzerland.

Kollner M.,Leibniz Institute of Marine Science | Kollner M.,University of Kiel | Kollner M.,Federal Maritime and Hydrographic Agency | Visbeck M.,Leibniz Institute of Marine Science | And 3 more authors.
Journal of Marine Systems | Year: 2016

Diapycnal diffusivity estimates from two Tracer Release Experiments (TREs) and microstructure measurements in the oxycline and core of the oxygen minimum zone (OMZ) in the Eastern Tropical North Atlantic (ETNA) are compared. For the first time, two TREs within the same area at different depths were realized: the Guinea Upwelling Tracer Release Experiment (GUTRE) initiated in 2008 in the oxycline at approximately 320 m depth, and the Oxygen Supply Tracer Release Experiment (OSTRE) initiated in 2012 in the core of the OMZ at approximately 410 m depth. The mean diapycnal diffusivity Dz was found to be insignificantly smaller in the OMZ core with (1.06±0.24)×10-5m2s-1 compared to (1.11±0.22)×10-5m2s-1 90 m shallower in the oxycline. Unexpectedly, GUTRE tracer was detected during two of the OSTRE surveys which showed that the estimated diapycnal diffusivity from GUTRE over a time period of seven years was within the uncertainty of the previous estimates over a time period of three years. The results are consistent with the Dz estimates from microstructure measurements and demonstrate that Dz does not vary significantly vertically in the OMZ within the depth range of 200-600 m and does not change with time. The presence of a seamount chain in the vicinity of the GUTRE injection region did not cause enhanced Dz compared to the smoother bottom topography of the OSTRE injection region, although the analysis of vertical shear spectra from ship ADCP data showed elevated internal wave energy level in the seamount vicinity. However, the two tracer patches covered increasingly overlapping areas with time and thus spatially integrated increasingly similar fields of local diffusivity, as well as the difference in local stratification counteracted the influence of roughness on Dz. For both experiments no significant vertical displacements of the tracer were observed, thus diapycnal upwelling within the ETNA OMZ is below the uncertainty level of 5myr-1. © 2016 Elsevier B.V..

Determann J.,Alfred Wegener Institute for Polar and Marine Research | Thoma M.,Alfred Wegener Institute for Polar and Marine Research | Thoma M.,Bavarian Academy of science | Grosfeld K.,Alfred Wegener Institute for Polar and Marine Research | Massmann S.,Federal Maritime and Hydrographic Agency
Annals of Glaciology | Year: 2012

Ice flow from the ice sheets to the ocean contains the maximum potential contributing to future eustatic sea-level rise. In Antarctica most mass fluxes occur via the extended ice-shelf regions covering more than half the Antarctic coastline. The most extended ice shelves are the Filchner-Ronne and Ross Ice Shelves, which contribute ≈30% to the total mass loss caused by basal melting. Basal melt rates here show small to moderate average amplitudes of <0.5ma-1. By comparison, the smaller but most vulnerable ice shelves in the Amundsen and Bellinghausen Seas show much higher melt rates (up to 30ma-1), but overall basal mass loss is comparably small due to the small size of the ice shelves. The pivotal question for both characteristic ice-shelf regions, however, is the impact of ocean melting, and, coevally, change in ice-shelf thickness, on the flow dynamics of the hinterland ice masses. In theory, iceshelf back-pressure acts to stabilize the ice sheet, and thus the ice volume stored above sea level.We use the three-dimensional (3-D) thermomechanical ice-flow model RIMBAY to investigate the ice flow in a regularly shaped model domain, including ice-sheet, ice-shelf and open-ocean regions. By using melting scenarios for perturbation studies, we find a hysteresis-like behaviour. The experiments show that the system regains its initial state when perturbations are switched off. Average basal melt rates of up to 2ma-1 as well as spatially variable melting calculated by our 3-D ocean model ROMBAX act as basal boundary conditions in time-dependent model studies. Changes in ice volume and grounding-line position are monitored after 1000 years of modelling and reveal mass losses of up to 40 Gt a-1. © 2012 Publishing Technology.

Discover hidden collaborations