Description: The Coastal Observing System for Northern and Arctic Seas (COSYNA) was established in order to better understand the complex interdisciplinary processes of northern seas and the arctic coasts in a changing environment. Particular focus is given to the German Bight in the North Sea as a prime example for a heavily used coastal area, and Svalbard as an example of an arctic coast that is under strong pressure due to global change. The automated observing and modelling system COSYNA is designed to monitor real time conditions, provide short-term forecasts and data products, and to assess the impact of anthropogenically induced change. Observations are carried out combining satellite and radar remote sensing with various in situ platforms. Novel sensors, instruments, and algorithms are developed to further improve the understanding of the interdisciplinary interactions between physics, biogeochemistry, and the ecology of coastal seas. New modelling and data assimilation techniques are used to integrate observations and models in a quasi-operational system providing descriptions and forecasts of key hydrographic variables. Data and data products are publically available free of charge and in real time. They are used by multiple interest groups in science, agencies, politics, industry, and the public.

Description: We present the in situ use of an underwater mass spectrometer (UWMS) for the detection and quantification of active submarine methane seeps. The key benefit of using this novel technique is the rapid instrumental response, which allows an up to 750 times higher sampling frequency of dissolved gas concentrations compared to other methods. Among other major and trace gases, the increased data density and accuracy allows for the improved determination of methane point-sources. Methane is the most abundant organic compound in the atmosphere and its influence on global climate is the subject of current scientific discussion. One source of atmospheric methane with variable strength is the ocean’s seafloor e.g. through the destabilization of gas hydrates. These submarine methane sources are characterized by rising gas bubbles and/or the diffusive flux of gas into the water column. While ex situ sampling methods are limited by the time and costs, the primary limitation is the difficulty in capturing concentrations that are highly dynamic in time and space. Using an optimized UWMS (significantly improved in detection limit by a cryo-trap system) in the North Sea (Atlantic Ocean), we have obtained high-resolution 3D distribution patterns of dissolved methane in the water column. In addition to presenting novel methodologies using in situ mass spectrometry to detect, map and calculate the methane inventory above submarine sources, we will present a new configuration of instruments to determine the diffusive transportation rates at the sediment-water-transition-zone.

Description: Benthic oxygen and nitrogen fluxes were quantified within the years 2012 to 2014 at different time series sites in the southern North Sea with the benthic lander NuSObs (Nutrient and Suspension Observatory). In situ incubations of sediments, in situ bromide tracer studies, sampling of macrofauna and pore water investigations revealed considerable seasonal and spatial variations of oxygen and nitrogen fluxes. Seasonal and spatial variations of oxygen fluxes were observed between two different time series sites, covering different sediment types and/or different benthic macrofaunal communities. On a sediment type with a high content of fine grained particles (o63 mm) oxygen fluxes of �15.5 to �25.1 mmol m�2 d�1 (June 2012), �2.0 to �8.2 mmol m�2 d�1 (March 2013), �16.8 to �21.5 mmol m�2 d�1 (November 2013) and �6.1 mmol m�2 d�1 (March 2014) were measured. At the same site a highly diverse community of small species of benthic macrofauna was observed. On a sediment type with a low content of fine grained particles (o63 mm) high oxygen fluxes (�33.2mmol m�2 d�1 August 2012; �47.2 to �55.1 mmolm�2 d�1 November 2013; �16.6 mmol m�2 d�1 March 2014) were observed. On this sediment type a less diverse benthic macrofaunal community, which was dominated by the large bodied suspension feeder Ensis directus, was observed. Average annual rain rates of organic carbon and organic nitrogen to the seafloor of 7.44 mol Cm�2 y�1 and 1.34 mol N m�2 y�1 were estimated. On average 79% of the organic bound carbon and 95% of the organic bound nitrogen reaching the seafloor are recycled at the sediment–water interface. & 2015 Elsevier Ltd. All rights reserved

Description: For the investigation of organic carbon fluxes reaching the seafloor, oxygen microprofiles were measured at 145 sites in different sub-regions of the Southern Ocean. At 11 sites, an in situ oxygen microprofiler was deployed for the measurement of oxygen profiles and the calculation of organic carbon fluxes. At four sites, both in situ and ex situ data were determined for high latitudes. Based on this data set as well as on previous published data, a relationship was established for the estimation of fluxes derived by ex situ measured O2 profiles. The fluxes of labile organic matter range from 0.5 to 37.1 mg C m−2 d−1. The high values determined by in situ measurements were observed in the Polar Front region (water depth of more than 4290 m) and are comparable to organic matter fluxes observed for high-productivity, upwelling areas like off West Africa. The oxygen penetration depth, which reflects the long-term organic matter flux to the sediment, was correlated with assemblages of key diatom species. In the Scotia Sea (not, vert, similar3000 m water depth), oxygen penetration depths of less than 15 cm were observed, indicating high benthic organic carbon fluxes. In contrast, the oxic zone extends down to several decimeters in abyssal sediments of the Weddell Sea and the southeastern South Atlantic. The regional pattern of organic carbon fluxes derived from microsensor data suggests that episodic and seasonal sedimentation pulses are important for the carbon supply to the seafloor of the deep Southern Ocean.

Description: The role of lakes in the global methane budget seems to be higher than previously thought. Numerous pockmarks have been described for the marine environment, but at freshwater fluid seeps the geological, chemical and biological processes operating are largely unknown. Based on different observations of intense gas flow through the water column at Lake Constance two joint research cruises were conducted in winter 2005/06 to systematically search and study these structures. Several large fields of pockmark like structures were found in the eastern part of the lake (side scan sonar, echo sounder). Water and gas was selectively sampled and based on these preliminary data a joint DFG-funded research project was arranged. The objectives are to (1) locate, describe and map pockmark areas at Lake Constance, (2) identify the pockmark formation mechanism, (3) quantify the methane flux and the temporal variability and (4) identify the source of methane.So far more than 450 pockmarks larger 〉 2 m have been identified by side-scan sonar. The pockmarks vary largely in size (dm-range to maximum diameters of 15m) and spatial distribution. At some places, they are irregular spaced, but now and then smaller decimetre sized pockmarks are evenly spaced along small lineaments. Often, large pockmarks are located at morphological highs, such as channel rims or little hills at the lake floor. There is no morphological evidence for a catastrophic gas release (solid discharge at the rim, or irregular sediment patterns near the pockmarks). The observed structures point to a constant gas release from a deeper reservoir.Two representative locations (water depth 12m and 85m) close to the former Rhine estuary have been selected for further geochemical examinations. After deploying a digital horizontal sonar system at the lake floor to allow for exact positioning, water and sediment samples were taken within the pockmark with niskin bottles from a rosette and multicorer. In addition, sediment samples and gas samples were taken by divers across the shallow pockmark. Gas concentration and isotope ratios of dissolved gas in water were measured using standard GC-FID and GC-irMS techniques. Methane concentration in sediment samples was measured directly after coring by means of by a diffusion-based methane sensor.Preliminary results of the isotope analysis of methane (δ13C, δD) and CO2 (δ13C) as well as the absence of higher molecular weight alkanes strongly indicate a bacterial formation of the gases rather than a thermogenic origin of the methane. The results of the analysis of free gas of the sediments indicate the methyl formation as dominant pathway. However, up to now available data suggest a certain difference in the gases located at the deep pockmark, the corresponding reference site and gas sampled at the shallow pockmark. In the sediments of the deep pockmark high methane concentrations were recorded, however with no significant differences between the pockmark and control cores. At the shallow pockmark sediment cores could be positioned more precisely. Here methane concentrations vary within meters in order of magnitude. Several autonomous devices for gas flow measurements using different approaches were deployed in March 2008 at selected gas emanating pockmarks. Data are not yet available but will hopefully presented