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Ozeanographie

Die Ozeanographie umfasst viele verschiedene Disziplinen, die sich mit den physikalischen, chemischen und biologischen Prozessen beschäftigen, die sich in den Ozeanen der Erde abspielen. Die Stabilisotopenanalyse ist ein leistungsfähiges Mittel, um diese Prozesse nachzuverfolgen, sowohl in der Gegenwart als auch in der Vergangenheit. Die Paläoozeanographie nutzt stabile Sauerstoffisotopensignaturen von Materialien, die in Eiskernen oder Sedimenten konserviert wurden, um die Geschichte der Meeresoberflächen- oder Tiefseetemperaturen nachzuvollziehen. Die Stabilisotopenanalyse von Sauerstoff und Wasserstoff kann auch die Hydrologie von ozeanischen Gewässern enthüllen, indem die Bewegung und Zirkulation von Gewässern, evaporitische Prozesse und meteorologische Einflüsse auf lokaler, regionaler und globaler Ebene verfolgt werden.

Nährstoffkreislauf und Ökologie der Weltmeere sind ebenfalls von Interesse; stabile Kohlenstoff-, Stickstoff- und Schwefelisotope sind leistungsfähige Werkzeuge, die eingesetzt werden, um Algenaktivität, Struktur von Nahrungsketten in oberflächlichen oder benthischen Gemeinschaften und Nährstoffflüsse während der Jahreszeiten zu untersuchen. Besonders nützlich ist die Stabilisotopenanalyse, um ungewöhnliche Grenzen von tiefen, hydrothermalen Systemen zu erforschen, wo ungewöhnliche chemosynthetische Organismen die Basis der Gemeinschaften sind, die unter diesen extremen Bedingungen gedeihen.

Publikationen zum Thema Ozeanographie mit unseren Geräten

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83 Ergebnisse:

Similar temperature responses suggest future climate warming will not alter partitioning between denitrification and anammox in temperate marine sediments.
Global change biology (2016)
Lindsay D Brin, Anne E Giblin, Jeremy J Rich

Removal of biologically available nitrogen (N) by the microbially mediated processes denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability. Although few studies have examined temperature responses of denitrification and anammox, previous work suggests that denitrification could become more important than anammox in response to climate warming. To test this hypothesis, we determined whether temperature responses of denitrification and anammox differed in shelf and estuarine sediments from coastal Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was further assessed in a 12-week laboratory microcosm experiment. Temperature responses, as characterized by thermal optima (Topt ) and apparent activation energy (Ea ), were determined by measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging from 3 to 59°C. With a few exceptions, Topt and Ea of denitrification and anammox did not differ in Rhode Island sediments over the seasonal cycle. In microcosm sediments, Ea was somewhat lower for anammox compared to denitrification across all treatments. However, Topt did not differ between processes, and neither Ea nor Topt changed with warming or carbon addition. Thus, the two processes behaved similarly in terms of temperature response, and this response was not influenced by warming. This led us to reject the hypothesis that anammox is more cold-adapted than denitrification in our study system. Overall, our study suggests that temperature responses of both processes can be accurately modeled for temperate regions in the future using a single set of parameters, which are likely not to change over the next century as a result of predicted climate warming. We further conclude that climate warming will not directly alter the partitioning of N flow through anammox and denitrification. This article is protected by copyright. All rights reserved.
Schlagworte: nitrogen , ocea , clim , gashead

Water circulation and governing factors in humid tropical river basins in the central Western Ghats, Karnataka, India.
Rapid communications in mass spectrometry : RCM (2016)
M Tripti, L Lambs, G P Gurumurthy, I Moussa, K Balakrishna, M D Chadaga

RATIONALE: The small river basins in the narrow stretch of the Arabian Sea coast of southwest India experience high annual rainfall (800-8000 mm), with a higher proportion (85 %) during the summer monsoon period between June and September. This is due to a unique orographic barrier provided by the Western Ghats mountain belt (600-2600 m) for the summer monsoon brought by the southwesterly winds. This study is the first of a kind focusing on the water cycle with an intensive stable isotopes approach (samples of river water, groundwater, rainwater; seasonal and spatial sampling) in this part of the Western Ghats in Karnataka and also in the highest rainfall-receiving region (with places like Agumbe receiving 7000-8000 mm annual rainfall) in South India. In addition, the region lacks sustainable water budgeting due to high demographic pressure and a dry pre-monsoon season as the monsoon is mainly unimodal in this part of India, particularly close to the coast. METHODS: The stable isotopic compositions of groundwater, river water and rainwater in two tropical river basins situated approximately 60 km apart, namely the Swarna near Udupi and the Nethravati near Mangalore, were studied from 2010 to 2013. The δ(18) O and δ(2) H values of the water samples were measured by isotope ratio mass spectrometry, and the d-excess values calculated to better understand the dominant source of the water and the influence of evaporation/recycling processes. RESULTS: The water in the smaller area basin (Swarna basin) does not show seasonal variability in the δ(18) O values for groundwater and river water, having a similar mean value of -3.1 ‰. The d-excess value remains higher in both wet and dry seasons suggesting strong water vapor recycling along the foothills of the Western Ghats. In contrast, the larger tropical basin (Nethravati basin) displays specific seasonal isotopic variability. The observation of higher d-excess values in winter with lower δ(18) O values suggests an influence of northeast winter monsoon water in the larger basin. CONCLUSIONS: The narrow coastal strip to the west of the Western Ghats displays unique water characteristics in both tropical river basins investigated. For the smaller and hilly Swarna basin, the dense vegetation (wet canopies) could largely re-evaporate the (intercepted) rain, leading to no marked seasonal or altitude effect on the water isotope values within the basin. The larger Nethravati basin, which stretches farther into the foothills of the Western Ghats, receives winter monsoon water, and thus exhibits a clear seasonal variability in rainfall moisture sources. The degree of water vapor recycling in these wet tropical basins dominates the isotopic composition in this narrow coastal stretch of South India. An insight into the soil water contribution to the river water and groundwater, even in the rainfall-dependent tropical basins of South India, is provided in this study. Copyright © 2015 John Wiley & Sons, Ltd.
Schlagworte: hydrogen , oxygen , geol , ocea , gashead

Pan-Arctic concentrations of mercury and stable isotope ratios of carbon (δ(13)C) and nitrogen (δ(15)N) in marine zooplankton.
The Science of the total environment (2016)
Corinne Pomerleau, Gary A Stern, Monika Pućko, Karen L Foster, Robie W Macdonald, Louis Fortier

Zooplankton play a central role in marine food webs, dictating the quantity and quality of energy available to upper trophic levels. They act as "keystone" species in transfer of mercury (Hg) up through the marine food chain. Here, we present the first Pan-Arctic overview of total and monomethylmercury concentrations (THg and MMHg) and stable isotope ratios of carbon (δ(13)C) and nitrogen (δ(15)N) in selected zooplankton species by assembling data collected between 1998 and 2012 from six arctic regions (Laptev Sea, Chukchi Sea, southeastern Beaufort Sea, Canadian Arctic Archipelago, Hudson Bay and northern Baffin Bay). MMHg concentrations in Calanus spp., Themisto spp. and Paraeuchaeta spp. were found to increase with higher δ(15)N and lower δ(13)C. The southern Beaufort Sea exhibited both the highest THg and MMHg concentrations. Biomagnification of MMHg between Calanus spp. and two of its known predators, Themisto spp. and Paraeuchaeta spp., was greatest in the southern Beaufort Sea. Our results show large geographical variations in Hg concentrations and isotopic signatures for individual species related to regional ecosystem features, such as varying water masses and freshwater inputs, and highlight the increased exposure to Hg in the marine food chain of the southern Beaufort Sea.
Schlagworte: carbon , nitrogen , ecol , ocea , poll , elem

A Southern Hemisphere record of global trace-metal drawdown and orbital modulation of organic-matter burial across the Cenomanian-Turonian boundary (Ocean Drilling Program Site 1138, Kerguelen Plateau)
Sedimentology (2016)
Alexander J. Dickson, Matthew Saker-Clark, Hugh C. Jenkyns, Cinzia Bottini, Elisabetta Erba, Fabio Russo, Olga Gorbanenko, B. David A. Naafs, Richard D. Pancost, Stuart A. Robinson, Sander van den Boorn, Erdem Idiz

Schlagworte: carbon , geol , ocea , gaschrom

H + -driven increase in CO 2 uptake and decrease in HCO3− uptake explain coccolithophores' acclimation responses to ocean acidification
Limnology and Oceanography (2016)
Dorothee M. Kottmeier, Sebastian D. Rokitta, Björn Rost

Recent ocean acidification (OA) studies revealed that seawater [H1] rather than [CO2] or [HCO2 3 ] regulate short-term responses in carbon fluxes of Emiliania huxleyi. Here, we investigated whether acclimation to altered carbonate chemistry modulates this regulation pattern and how the carbon supply for calcification is affected by carbonate chemistry. We acclimated E. huxleyi to present-day (ambient [CO2], [HCO2 3 ], and pH) and OA conditions (high [CO2], ambient [HCO2 3 ], low pH). To differentiate between the CO2 and pH/H1 effects, we also acclimated cells to carbonation (high [CO2] and [HCO2 3 ], ambient pH) and acidification (ambient [CO2], low [HCO2 3 ], and pH). Under these conditions, growth, production of particulate inorganic and organic carbon, as well as carbon and oxygen fluxes were measured. Under carbonation, photosynthesis and calcification were stimulated due to additional HCO2 3 uptake, whereas growth was unaffected. Such stimulatory effects are not apparent after short-term carbonation, indicating that cells adjusted their carbon acquisition during acclimation. Being driven by [HCO2 3 ], these regulations can, however, not explain typical OA effects. Under acidi- fication and OA, photosynthesis stayed constant, whereas calcification and growth decreased. Similar to the short-term responses toward high [H1], CO2 uptake significantly increased, but HCO2 3 uptake decreased. This antagonistic regulation in CO2 and HCO2 3 uptake can explain why photosynthesis, being able to use CO2 and HCO2 3 , often benefits from OA, whereas calcification, being mostly dependent on HCO2 3 , often decreases. We identified H1 as prime driver of coccolithophores’ acclimation responses toward OA. Acidified conditions seem to put metabolic burdens on the cells that result in decreased growth.

Dynamics of δ15N isotopic signatures of different intertidal macroalgal species: Assessment of bioindicators of N sources in coastal areas
Marine Pollution Bulletin (2016)
Stéphanie Lemesle, Alexandre Erraud, Isabelle Mussio, Anne-Marie Rusig, Pascal Claquin

δ15N of annual (Ulva sp., Porphyra sp.) and perennial intertidal seaweed species (Chondrus crispus, Fucus sp.) collected on 17 sampling points along the French coast of the English Channel in 2012 and 2013 were assessed on their suitability as bioindicators of N pollution in coastal areas. A sine function applied for δ15N time series data showed for all the species the same seasonal trend with lowest δ15N values in April and highest in summer but with no significant interspecific differences of amplitude (α) and phase angle (ϕ). This model provides a useful tool for monitoring the inter-annual changes of N pollution. An interspecific variability of δ15N values was observed, probably due to their tolerance to emersion. An in vitro study for comparing the kinetic acquisition of the isotopic signal and N uptake mechanisms of each species underlined the influence of algal physiology on the δ15N interspecific variability.
Schlagworte: nitrogen , ocea , poll , elem

Pliocene-Pleistocene evolution of sea surface and intermediate water temperatures from the Southwest Pacific
Paleoceanography (2016)
Erin L. McClymont, Aurora C. Elmore, Sev Kender, Melanie J. Leng, Mervyn Greaves, Henry Elderfield

Over the last 5 million years, the global climate system has evolved toward a colder mean state, marked by large amplitude oscillations in continental ice volume. Equatorward expansion of polar waters and strengthening temperature gradients have been detected. However, the response of the mid- and high-latitudes of the southern hemisphere is not well documented, despite the potential importance for climate feedbacks including sea ice distribution and low-high latitude heat transport. Here, we reconstruct the PliocenePleistocene history of both sea surface and Antarctic Intermediate Water (AAIW) temperatures on orbital timescales from DSDP Site 593 in the Tasman Sea, Southwest Pacific. We confirm overall Pliocene-Pleistocene cooling trends in both the surface ocean and AAIW, although the patterns are complex. The Pliocene is warmer than modern, but our data suggest an equatorward displacement of the subtropical front relative to present, and a poleward displacement of the subantarctic front of the Antarctic Circumpolar Current (ACC). Two main intervals of cooling, from c.3 Ma and c.1.5 Ma, are coeval with cooling and icesheet expansion noted elsewhere, and suggest that equatorward expansion of polar water masses also characterised the Southwest Pacific through the Pliocene-Pleistocene. However, the observed trends in SST and AAIW temperature are not identical despite an underlying link to the ACC, and intervals of unusual surface ocean warmth (c.2 Ma) and large amplitude variability in AAIW temperatures (from c.1 Ma) highlight complex interactions between equatorward displacements of fronts associated with the ACC and/or varying poleward heat transport from the subtropics.
Schlagworte: carbon , oxygen , ocea , clim , mulitcarb

Mangrove degradation and response to anthropogenic disturbance in Maowei Sea (SW China) since 1926 AD: Mangrove-derived OM and pollen
Organic Geochemistry (2016)
Xianwei Meng, Peng Xia, Zhen Li, Dezhen Meng

Mangrove forests, located at the interface between land and sea, have been impacted by an increase in intensive anthropogenic disturbance in developing countries or regions. In order to study the impact of human activity on mangrove forests, mangrove development was reconstructed over the last 130 yr, using the contribution of mangrove-derived organic matter (OM) and mangrove pollen as proxies, from two sediment cores from the Maowei Sea (SW China). It is a semi-enclosed bay that receives a large amount of terrestrial material from the Qinjiang and Maoling rivers, with average sedimentation rate of 0.63–0.64 cm/yr. The material accumulates mainly in the coast and its adjacent region, owing to weak water exchange through the channel. Sediment samples had C:N and δ13Corg values intermediate between mangrove leaves and flood plain sediments, indicating that OM sources could be apportioned as a mixture from only these two sources. Based on k-mean cluster analysis, mangrove development was divided into three stages since 1880 AD: (i) a flourishing period (1880–1926 AD), (ii) a phase of slow degradation (1926–1980 AD) and (iii) a time of rapid degradation (1980 AD to the present). The study indicates that anthropogenic activity, including reclamation of mangrove swamps for farmland and shrimp ponds, is the primary reason for mangrove degradation since 1926 AD, rather than climate change (temperature and precipitation).
Schlagworte: carbon , soil , ocea , poll , elem

Aerobic gammaproteobacterial methanotrophs mitigate methane emissions from oxic and anoxic lake waters
Limnology and Oceanography (2016)
Kirsten Oswald, Jana Milucka, Andreas Brand, Philipp Hach, Sten Littmann, Bernhard Wehrli, Marcel M.M. Kuypers, Carsten J. Schubert

Freshwater lakes represent a substantial natural source of methane to the atmosphere and thus contribute to global climate change. Microbial methane oxidation is an important control on methane release from these systems, where oxygen appears to be the most essential electron acceptor for this process. However, there is extensive geochemical evidence that methane is also oxidized under anoxic conditions in lakes, though the details about the exact mechanism have still not been resolved. Here, we investigated the fate of methane in the water column of meromictic Lake Zug. We provide evidence for ongoing methane oxidation at the oxic/anoxic boundary and also in the anoxic hypolimnion, both apparently mediated by aerobic methane-oxidizing bacteria. Gammaproteobacterial methanotrophs (gamma-MOB) dominated the indigenous methanotrophic community and were active under all investigated conditions—oxic, sub-oxic and anoxic. Methane oxidation was stimulated by the additions of oxygen or iron and manganese oxides under anoxic conditions. In the latter case, trace amounts of oxygen may have still been required for methane activation, yet these findings indicate that gamma-MOB in Lake Zug might be able to respire electron acceptors other than oxygen. We propose that gamma-MOB are actively removing methane also in anoxic lake waters, thus contributing to methane mitigation from these habitats.
Schlagworte: carbon , ocea , gashead

Feeding patterns of two sympatric shark predators in coastal ecosystems of an oceanic island
Canadian Journal of Fisheries and Aquatic Sciences (2016)
Clément Trystram, Karyne Rogers, Marc Soria, Sébastien Jaquemet

Stomach contents and stable carbon and nitrogen isotope analyses (δ13C and δ15N) were used to investigate the trophic ecology of two apex predators, tiger sharks (Galeocerdo cuvier) and bull sharks (Carcharhinus leucas), from Reunion Island to describe their dietary habits at both the population and individual levels. In this oceanic island, the tiger and bull sharks were more piscivorous and teutophagous than noted in previous research from other localities. The δ13C values suggested that bull sharks depended on more neritic organic matter sources than tiger sharks, confirming a coastal habitat preference for bull sharks. Moreover, the total length of the bull shark influenced δ13C values, with smaller individuals being more coastal than larger individuals. All indicators suggest that there is a higher degree of similarity between individual tiger sharks compared with the more heterogeneous bull shark population, which is composed of individuals who specialize on different prey. These results suggest tha...
Schlagworte: carbon , nitrogen , ecol , ocea , elem