ALBERT

Description: Anaerobic oxidation of methane (AOM) was shown to reduce methane emissions by over 50% in freshwater systems, its main natural contributor to the atmosphere. In these environments iron oxides can become main agents for AOM, but the underlying mechanism for this process has remained enigmatic. By conducting anoxic slurry incubations with lake sediments amended with 13C-labeled methane and naturally abundant iron oxides the process was evidenced by significant 13C-enrichment of the dissolved inorganic carbon pool and most pronounced when poorly reactive iron minerals such as magnetite and hematite were applied. Methane incorporation into biomass was apparent by strong uptake of 13C into fatty acids indicative of methanotrophic bacteria, associated with increasing copy numbers of the functional methane monooxygenase pmoA gene. Archaea were not directly involved in füll methane oxidation, but their crucial participation,likely being mediators in electron transfer, was indicated by specific inhibition of their activity that fully stopped iron-coupled AOM. By contrast, inhibition of sulfur cycling increased 13C-methane turnover, pointing to sulfur species involvement in a competing process. Our findings suggest that the mechanism of iron-coupled AOM is accomplished by a complex microbemineral reaction network, being likely representative of many similar but hidden interactions sustaining life under highly reducing low energy conditions.

Description: Climate change has significant implications for biodiversity and ecosystems. With slow progress towards reducing greenhouse gas emissions, climate engineering (or ‘geoengineering’) is receiving increasing attention for its potential to limit anthropogenic climate change and its damaging effects. Proposed techniques, such as ocean fertilization for carbon dioxide removal or stratospheric sulfate injections to reduce incoming solar radiation, would significantly alter atmospheric, terrestrial and marine environments, yet potential side-effects of their implementation for ecosystems and biodiversity have received little attention. A literature review was carried out to identify details of the potential ecological effects of climate engineering techniques. A group of biodiversity and environmental change researchers then employed a modified Delphi expert consultation technique to evaluate this evidence and prioritize the effects based on the relative importance of, and scientific understanding about, their biodiversity and ecosystem consequences. The key issues and knowledge gaps are used to shape a discussion of the biodiversity and ecosystem implications of climate engineering, including novel climatic conditions, alterations to marine systems and substantial terrestrial habitat change. This review highlights several current research priorities in which the climate engineering context is crucial to consider, as well as identifying some novel topics for ecological investigation.

Description: Highlights • The Fram Slide Complex has been active from late Miocene to late Pleistocene. • Local processes were critical for slope stability in the Fram Strait area. • Toe erosion caused by normal faulting may have led to retrogressive failure. • Low gradient contourite drifts might smooth and stabilize submarine slopes. • Low tsunami potential from the Fram Slide Complex could increase in the future. Abstract The best known submarine landslides on the glaciated NW European continental margins are those at the front of cross-shelf troughs, where the alternation of rapidly deposited glycogenic and hemi pelagic material generates sedimentary overpressure. Here, we investigate landslides in two areas built of contourite drifts bounded seaward by a ridge-transform junction. Seismic and bathymetric data from the Fram Slide Complex are compared with the tectonically similar Vastness area ~ 120 km to the south, to analyze the influence of local and regional processes on slope stability. These processes include tectonic activity, changes of climate and oceanography, gas hydrates and fluid migration systems, slope gradient, toe erosion and style of contourite deposition. Two areas within the Fram Slide Complex underwent different phases of slope failures, whereas there is no evidence at all for major slope failures in the Vastness area. The comparison cannot reveal the distinct reason for slope failure but demonstrates the strong impact of variation in the local controls on slope stability. The different failure chronologies suggest that toe erosion, which is dependent on the throw of normal faults, and the different thickness and geometry of contourite deposits can result in a critical slope morphology and exert pronounced effects on slope stability. These results highlight the limitations of regional hazard assessments and the need for multi-disciplinary investigations, as small differences in local controlling factors led to substantially different slope failure histories.

Description: https://datadryad.org/stash/dataset/doi:10.5061/dryad.10rk4

Description: The surface chemistry of aquatic organisms determines their biotic interactions. Metabolites in the spatially limited laminar boundary layer mediate processes, such as antifouling, allelopathy and chemical defense against herbivores. However, very few methods are available for the investigation of such surface metabolites. An approach is described in which surfaces are extracted by means of C18 solid phase material. By powdering wet algal surfaces with this material, organic compounds are adsorbed and can be easily recovered for subsequent liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS) investigations. The method is robust, picks up metabolites of a broad polarity range and is easy to handle. It is more universal compared to established solvent dipping protocols and it does not cause damage to the test organisms. A protocol is introduced for the macroalgae Fucus vesiculosus, Caulerpa taxifolia and Gracilaria vermiculophylla, but it can be easily transferred to other aquatic organisms.

Description: For assessing the tsunamigenic potential, the mechanical strength, composition and fabric of forearc slope and accreted sediments from the Nankai Trough offshore SW-Japan have been investigated (NanTroSEIZE; IODP expeditions 315, 316, 333). Triaxial testing of shallow whole round samples (maximum depth of 130 mbsf) at confining pressures of 0.4-1.0 MPa, room temperature, strain rates of approx. 10-3 to 10-6s-1, and up to 64% axial strain (Stipp et al., 2013) revealed mechanically and structurally weak samples from the upper and middle forearc slope of the accretionary prism and strong samples from the accretionary prism toe (Stipp et al., 2013). In order to constrain these results, three additional experiments on samples from greater depth (211-221 mbsf) at confining pressures of 3.0-8.0 MPa, room temperature, strain rates of approx. 10-5s-1, and up to 54% axial strain were carried out. For these tests a digitally controlled servo-hydraulic triaxial appartus with a maximum load of 100 kN was used. Correspondingly to the shallow samples, these experiments show a deviatoric peak stress after only a few percent strain (〈10%) and a continuous stress decrease after this maximum combined with a continuous increase in pore pressure indicative of structurally weak behavior for the two forearc slope samples. The sample from the prism toe area, however, displays a continuous stress increase together with a decrease in pore pressure towards high strain indicative of structurally strong behavior. Synchrotron texture and composition analysis of the experimentally deformed and undeformed samples using the Rietveld refinement program MAUD indicates an increasing strength of the illite and kaolinite textures with increasing depth down to 523 m below sea floor corresponding to a shape preferred mineral alignment due to compaction (Schumann et al., 2014). Experimentally deformed samples have generally stronger textures than related undeformed core samples, and they show increasing strength of the illite and kaolinite textures with increasing axial strain. Mechanically weak samples have a bulk clay plus calcite content of 31-65 vol.-% and most of their illite, kaolinite, smectite and calcite (001)-pole figures have maxima 〉1.5 mrd (multiples of a random distribution). Mechanically strong samples, which were deformed to approximately the same amount of strain (up to 40%) have no calcite and a bulk clay content of 24-36 vol.-%. Illite, kaolinite and smectite (001)-pole figure maxima are predominantly 〈1.5 mrd. The synchrotron textures indicate that the mineral fabric as a whole (clay and also calcite grains) becomes preferentially oriented in the mechanically weak samples. Reorientation of the mineral grains is an important cause of strain weakening and contraction, persisting to high compressive strains. In contrast, the strong samples from the accretionary prism toe keep their microfabric up to fairly high compressive strain, allowing for strain hardening and dilation. This soft sediment hardening tends to involve increasingly large volumes of sediment into the imposed deformation, permitting strain dissipation as long as the sediments are homogeneous. Deformation will tend to localize into structurally weak sediments if they occur within the lithological sequence. Such weak sediments, which soften further with increasing strain, predominate in the cover units of the forearc slope and around the existing megasplay fault. They may either provoke mechanical runaway situations allowing for earthquake rupture, surface breakage and tsunami generation, or slope destabilization and resulting submarine mass wasting.

Description: Fish stocks have made surprising comebacks in the North and Baltic seas. But much remains to be done. Beginning in January, new EU laws will impose more sustainable practices with stricter quotas and by-catch rules.