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Subterranean estuaries are connective zones between inland aquifers and the open sea where terrestrial freshwater and circulating seawater mix and undergo major biogeochemical changes. They are biogeochemical reactors that modify groundwater chemistry prior to discharge into the sea. We propose that subterranean estuaries of high-energy beaches are particularly dynamic environments, where the effect of the dynamic boundary conditions propagates tens of meters into the subsurface, leading to strong spatio-temporal variability of geochemical conditions. We hypothesize that they form a unique habitat with an adapted microbial community unlike other typically more stable subsurface environments. So far, however, studies concerning subterranean estuaries of high-energy beaches have been rare and therefore their functioning, and their importance for coastal ecosystems, as well as for carbon, nutrient and trace element cycling, is little understood. We are addressing this knowledge gap within the interdisciplinary research project DynaDeep by studying the combined effect of surface (hydro- and morphodynamics) on subsurface processes (groundwater flow and transport, biogeochemical reactions, microbiology). A unique subterranean estuary observatory was established on the northern beach of the island of Spiekeroog facing the North Sea, serving as an exemplary high-energy research site and model system. It consists of fixed and permanent infrastructure such as a pole with measuring devices, multi-level groundwater wells and an electrode chain. This forms the base for autonomous measurements, regular repeated sampling, interdisciplinary field campaigns and experimental work, all of which are integrated via mathematical modelling to understand and quantify the functioning of the biogeochemical reactor. First results show that the DynaDeep observatory is collecting the intended spatially and temporally resolved morphological, sedimentological and biogeochemical data. Samples and data are further processed ex-situ and combined with experiments and modelling. Ultimately, DynaDeep aims at elucidating the global relevance of these common but overlooked environments.

16.3.2021 – 27.3.2021, Kiel (Germany) – Kiel (Germany) MScMarineMeasure

A series of multibeam bathymetry surveys revealed the emergence of a large pockmark field in the southeastern North Sea. Covering an area of around 915 km2, up to 1,200 pockmarks per square kilometer have been identified. The time of emergence can be confined to 3 months in autumn 2015, suggesting a very dynamic genesis. The gas source and the trigger for the simultaneous outbreak remain speculative. Subseafloor structures and high methane concentrations of up to 30 μmol/l in sediment pore water samples suggest a source of shallow biogenic methane from the decomposition of postglacial deposits in a paleo river valley. Storm waves are suggested as the final trigger for the eruption of the gas. Due to the shallow water depths and energetic conditions at the presumed time of eruption, a large fraction of the released gas must have been emitted to the atmosphere. Conservative estimates amount to 5 kt of methane, equivalent to 67% of the annual release from the entire North Sea. These observations most probably describe a reoccurring phenomenon in shallow shelf seas, which may have been overlooked before because of the transient nature of shallow water bedforms and technology limitations of high resolution bathymetric mapping.

Optic technologies and methods/procedures are established across all areas and scales in limnic and marine research in Germany and develop further continuously. The working group “Aquatic Optic Technologies” (AOT) constitutes a common platform for knowledge transfer among scientists and users, provides a synergistic environment for the national developer community and will enhance the international visibility of the German activities in this field. This document summarizes the AOT-procedures and -techniques applied by national research institutions. We expect to initiate a trend towards harmonization across institutes. This will facilitate the establishment of open standards, provide better access to documentation, and render technical assistance for systems integration. The document consists of the parts: Platforms and carrier systems outlines the main application areas and the used technologies. Focus parameters specifies the parameters measured by means of optical methods/techniques and indicates to which extent these parameters have a socio-political dimension. Methods presents the individual optical sensors and their underlying physical methods. Similarities denominates the common space of AOT-techniques and applications. National developments lists projects and developer groups in Germany designing optical high-technologies for limnic and marine scientific purposes.

Optic technologies and methods/procedures are established across all areas and scales in limnic and marine research in Germany and develop further continuously. The working group “Aquatic Optic Technologies” (AOT) constitutes a common platform for knowledge transfer among scientists and users, provides a synergistic environment for the national developer community and will enhance the international visibility of the German activities in this field. This document summarizes the AOT-procedures and -techniques applied by national research institutions. We expect to initiate a trend towards harmonization across institutes. This will facilitate the establishment of open standards, provide better access to documentation, and render technical assistance for systems integration. The document consists of the parts: Platforms and carrier systems outlines the main application areas and the used technologies. Focus parameters specifies the parameters measured by means of optical methods/techniques and indicates to which extent these parameters have a socio-political dimension. Methods presents the individual optical sensors and their underlying physical methods. Similarities denominates the common space of AOT-techniques and applications. National developments lists projects and developer groups in Germany designing optical hightechnologies for limnic and marine scientific purposes.

Meereswissenschaftliche Berichte No 97 2015 - Marine Science Reports No 97 2015, Optic technologies and methods/procedures are established across all areas and scales in limnic and marine research in Germany and develop further continuously. The working group “Aquatic Optic Technologies” (AOT) constitutes a common platform for knowledge transfer among scientists and users, provides a synergistic environment for the national developer community and will enhance the international visibility of the German activities in this field. This document summarizes the AOT-procedures and -techniques applied by national research institutions. We expect to initiate a trend towards harmonization across institutes. This will facilitate the establishment of open standards, provide better access to documentation, and render technical assistance for systems integration. The document consists of the parts: Platforms and carrier systems outlines the main application areas and the used technologies. Focus parameters specifies the parameters measured by means of optical methods/techniques and indicates to which extent these parameters have a socio-political dimension. Methods presents the individual optical sensors and their underlying physical methods. Similarities denominates the common space of AOT-techniques and applications. National developments lists projects and developer groups in Germany designing optical high-technologies for limnic and marine scientific purposes., Optische Technologien und Verfahren sind sowohl in der limnischen als auch marinen Forschung Deutschlands über alle Bereiche und Skalen etabliert und entwickeln sich rasant weiter. Die Arbeitsgruppe „Aquatische Optische Technologien“ (AOT) will Forschern und Anwendern eine Plattform bieten, die Wissenstransfer fördert, der nationalen Entwicklergemeinschaft ein synergistisches Umfeld eröffnet und die internationale Sichtbarkeit der deutschen Aktivitäten in diesem Forschungsfeld erhöht. Diese Zusammenfassung dokumentiert erstmalig die AOT-Verfahren und -Technologien, die von nationalen Forschungsinstitutionen eingesetzt werden. Wir erwarten, dass die Dokumentation einen Trend in Richtung institutsübergreifender Harmonisierung initiiert. Dies wird die Etablierung offener Standards, eine Verbesserung im Zugang zu Dokumentationen und gegenseitige technischer Hilfestellung bei (System-) Integrationen ermöglichen. Effizienz und Leistungsfähigkeit der AOT-Entwicklung und Anwendung auf nationaler Ebene werden von diesen Bestrebungen profitieren. Weitere Arbeitsgruppen und Entwickler werden ausdrücklich ermutigt, Kontakt aufzunehmen, um in einer späteren Auflage berücksichtigt zu werden. Das Dokument gliedert sich in mehrere Teile: Plattformen und Trägersysteme zeigt, wie optische Sensoren häufig eingesetzt werden, aus welchen Medien heraus und mit welcher Hintergrund-Technologie. Fokusparameter beschreibt die Größen, die mit Hilfe optischer Verfahren gemessen werden und zeigt, inwiefern diese Größen eine gesellschaftspolitische Dimension besitzen. Methoden stellt die einzelnen optischen Sensoren und die zu Grunde liegenden physikalischen Verfahren vor. Gemeinsamkeiten beschreibt die nationale Schnittmenge an AOT-Themen, -Verfahren und – Anwendungen. Nationale Entwicklungen listet eine Vielzahl von Projekten und Entwicklergruppen auf, die optische Hoch-Technologie für den limnischen und marinen Einsatz entwickeln. Aufgrund dieser Gliederung lassen sich im Text inhaltliche Wiederholungen nicht vermeiden, da z.B. bei der Darstellung der Parameter die verwendeten Methoden und deren Einsatz auf Geräteträgern angesprochen werden. Bei einer Aufzählung von Untersuchungsmethoden gilt dies entsprechend umgekehrt. Wir haben aus Gründen der Lesbarkeit und Eigenständigkeit der einzelnen Abschnitte diese Wiederholungen bewusst in Kauf genommen und ggf. Querverweise eingefügt.