Beschreibung: Publication date: Available online 19 January 2018 Source: Journal of Hydrology: Regional Studies Author(s): Alfonso Rivera, Lucila Candela Study region Global scale. Study focus This paper highlights the main outputs and outcomes of the Internationally Shared Aquifer Resources Management Initiative (ISARM, 2000–2015) of UNESCO on the global scale. We discuss the lessons learned, what is still relevant in ISARM, and what we consider irrelevant and why. We follow with discussion on the looming scenarios and the next steps following the awareness on transboundary aquifers (TBAs) as identified by ISARM. New insights for the region This analysis emphasizes the need for more scientific data, widespread education and training, and a more clearly defined role for governments to manage groundwater at the international level. It describes the links, approach and relevance of studies on TBAs to the UN Law of Transboundary Aquifers and on how they might fit regional strategies to assess and manage TBAs. The study discusses an important lesson learned on whether groundwater science can solve transboundary issues alone. It has become clear that science should interact with policy makers and social entities to have meaningful impacts on TBAs. Bringing together science, society, law, policy making, and harmonising information, would be important drivers and the best guidance for further assessments. ISARM can still make contributions, but it could be redesigned to support resolving TBAs issues which, in addition to science (hydrogeology), require considering social, political, economic and environmental factors. ISARM can increase its international dimension in the continents that still lag behind the assessment and shared management of TBAs, such as Asia and Africa.

Beschreibung: Highlights • Active hydrothermal vent ecosystems are extremely rare. • Vent ecosystems are recognized as vulnerable by international organizations. • Mineral resources at active vents would not contribute significantly to the global metal supply. • Effective networks that protect representative active vents cannot be ensured. • A prohibition on mining active vents is consistent with obligations for conservation. Abstract There is increasing interest in mining minerals on the seabed, including seafloor massive sulfide deposits that form at hydrothermal vents. The International Seabed Authority is currently drafting a Mining Code, including environmental regulations, for polymetallic sulfides and other mineral exploitation on the seabed in the area beyond national jurisdictions. This paper summarizes 1) the ecological vulnerability of active vent ecosystems and aspects of this vulnerability that remain subject to conjecture, 2) evidence for limited mineral resource opportunity at active vents, 3) non-extractive values of active vent ecosystems, 4) precedents and international obligations for protection of hydrothermal vents, and 5) obligations of the International Seabed Authority under the UN Convention on the Law of the Sea for protection of the marine environment from the impacts of mining. Heterogeneity of active vent ecosystems makes it extremely challenging to identify “representative” systems for any regional, area-based management approach to conservation. Protection of active vent ecosystems from mining impacts (direct and indirect) would set aside only a small fraction of the international seabed and its mineral resources, would contribute to international obligations for marine conservation, would have non-extractive benefits, and would be a precautionary approach.

Beschreibung: Highlights: • A High Resolution-LOPC and a FlowCAM were evaluated for ballast water monitoring. • Both instruments underestimated density compared to microscopy. • Size measurements can be affected by organism orientation and complex morphology. • Both tools might be particularly useful when working with a known community. Abstract: Many commercial ships will soon begin to use treatment systems to manage their ballast water and reduce the global transfer of harmful aquatic organisms and pathogens in accordance with upcoming International Maritime Organization regulations. As a result, rapid and accurate automated methods will be needed to monitoring compliance of ships' ballast water. We examined two automated particle counters for monitoring organisms ≥ 50 μm in minimum dimension: a High Resolution Laser Optical Plankton Counter (HR-LOPC), and a Flow Cytometer with digital imaging Microscope (FlowCAM), in comparison to traditional (manual) microscopy considering plankton concentration, size frequency distributions and particle size measurements. The automated tools tended to underestimate particle concentration compared to standard microscopy, but gave similar results in terms of relative abundance of individual taxa. For most taxa, particle size measurements generated by FlowCAM ABD (Area Based Diameter) were more similar to microscope measurements than were those by FlowCAM ESD (Equivalent Spherical Diameter), though there was a mismatch in size estimates for some organisms between the FlowCAM ABD and microscope due to orientation and complex morphology. When a single problematic taxon is very abundant, the resulting size frequency distribution curves can become skewed, as was observed with Asterionella in this study. In particular, special consideration is needed when utilizing automated tools to analyse samples containing colonial species. Re-analysis of the size frequency distributions with the removal of Asterionella from FlowCAM and microscope data resulted in more similar curves across methods with FlowCAM ABD having the best fit compared to the microscope, although microscope concentration estimates were still significantly higher than estimates from the other methods. The results of our study indicate that both automated tools can generate frequency distributions of particles that might be particularly useful if correction factors can be developed for known differences in well-studied aquatic ecosystems.

Beschreibung: The seasonal and interannual variability of chlorophyll in the Gulf of Mexico open waters is studied using a three‐dimensional coupled physical‐biogeochemical model. A 5 years hindcast driven by realistic open‐boundary conditions, atmospheric forcings, and freshwater discharges from rivers is performed. The use of recent in situ observations allowed an in‐depth evaluation of the model nutrient and chlorophyll seasonal distributions, including the chlorophyll vertical structure. We find that different chlorophyll patterns of temporal variability coexist in the deep basin which thereby cannot be considered as a homogeneous region with respect to chlorophyll dynamics. A partitioning of the Gulf of Mexico open waters based on the winter chlorophyll concentration increase is then proposed. This partition is basically explained by the amount of nutrients injected into the euphotic layer which is highly constrained by the dynamic of the winter mixed layer. The seasonal and interannual variability appears to be affected by the variability of atmospheric fluxes and mesoscale dynamics (Loop Current eddies in particular). Finally, estimates of primary production in the deep basin are provided.

Beschreibung: The manganese nodule belt within the Clarion and Clipperton Fracture Zones (CCZ) in the abyssal NE Pacific Ocean is characterized by numerous seamounts, low organic matter (OM) depositional fluxes and meter-scale oxygen penetration depths (OPD) into the sediment. The region hosts contract areas for the exploration of polymetallic nodules and Areas of Particular Environmental Interest (APEI) as protected areas. In order to assess the impact of potential mining on these deep-sea sediments and ecosystems, a thorough determination of the natural spatial variability of depositional and geochemical conditions as well as biogeochemical processes and element fluxes in the different exploration areas is required. Here, we present a comparative study on (1) sedimentation rates and bioturbation depths, (2) redox zonation of the sediments and element fluxes as well as (3) rates and pathways of biogeochemical reactions at six sites in the eastern CCZ. The sites are located in four European contract areas and in the APEI3. Our results demonstrate that the natural spatial variability of depositional and (bio)geochemical conditions in this deep-sea sedimentary environment is much larger than previously thought. We found that the OPD varies between 1 and 4.5 m, while the sediments at two sites are oxic throughout the sampled interval (7.5 m depth). Below the OPD, manganese and nitrate reduction occur concurrently in the suboxic zone with pore-water Mn2+ concentrations of up to 25 µM. The thickness of the suboxic zone extends over depth intervals of less than 3 m to more than 8 m. Our data and the applied transport-reaction model suggest that the extension of the oxic and suboxic zones is ultimately determined by the (1) low flux of particulate organic carbon (POC) of 1–2 mg Corg m−2 d−1 to the seafloor, (2) low sedimentation rates between 0.2 and 1.15 cm kyr−1 and (3) oxidation of pore-water Mn2+ at depth. The diagenetic model reveals that aerobic respiration is the main biogeochemical process driving OM degradation. Due to very low POC fluxes of 1 mg Corg m−2 d−1 to the seafloor at the site investigated in the protected APEI3 area, respiration rates are twofold lower than at the other study sites. Thus, the APEI3 site does not represent the (bio)geochemical conditions that prevail in the other investigated sites located in the European contract areas. Lateral variations in surface water productivity are generally reflected in the POC fluxes to the seafloor across the various areas but deviate from this trend at two of the study sites. We suggest that the observed spatial variations in depositional and (bio)geochemical conditions result from differences in the degree of degradation of OM in the water column and heterogeneous sedimentation patterns caused by the interaction of bottom water currents with seafloor topography.

Beschreibung: Since January 2014, the reformed Common Fisheries Policy (CFP) of the European Union is legally binding for all Member States. It prescribes the end of overfishing and the rebuilding of all stocks above levels that can produce maximum sustainable yields (MSY). This study examines the current status, exploitation pattern, required time for rebuilding, future catch, and future profitability for 397 European stocks. Fishing pressure and biomass were estimated from 2000 to the last year with available data in 10 European ecoregions and 2 wide ranging regions. In the last year with available data, 69% of the 397 stocks were subject to ongoing overfishing and 51% of the stocks were outside of safe biological limits. Only 12% of the stocks fulfilled the prescriptions of the CFP. Fishing pressure has decreased since 2000 in some ecoregions but not in others. Barents Sea and Norwegian Sea have the highest percentage (〉60%) of sustainably exploited stocks that are capable of producing MSY. In contrast, in the Mediterranean Sea, fewer than 20% of the stocks are exploited sustainably. Overfishing is still widespread in European waters and current management, which aims at maximum sustainable exploitation, is unable to rebuild the depleted stocks and results in poor profitability. This study examines four future exploitation scenarios that are compatible with the CFP. It finds that exploitation levels of 50–80% of the maximum will rebuild stocks and lead to higher catches than currently obtained, with substantially higher profits for the fishers.

Beschreibung: The impact of storm surge on a barrier island tends to be considered from a single cross-shore dimension, dependent on the relative elevations of the storm surge and dune crest. However, the foredune is rarely uniform and can exhibit considerable variation in height and width at a range of length scales. In this study, LiDAR data from barrier islands in Texas and Florida are used to explore how shoreline position and dune morphology vary alongshore, and to determine how this variability is altered or reinforced by storms and post-storm recovery. Wavelet analysis reveals that a power law can approximate historical shoreline change across all scales, but that stormscale shoreline change (~10 years) and dune height exhibit similar scale-dependent variations at swash and surf zone scales (〈1000 m). The in-phase nature of the relationship between dune height and storm-scale shoreline change indicates that areas of greater storm-scale shoreline retreat are associated with areas of smaller dunes. It is argued that the decoupling of storm-scale and historical shoreline change at swash and surf zone scales is also associated with the alongshore redistribution of sediment and the tendency of shorelines to evolve to a more diffusive (or straight) pattern with time. The wavelet analysis of the data for post-storm dune recovery is also characterized by red noise at the smallest scales characteristic of diffusive systems, suggesting that it is possible that small-scale variations in dune height can be repaired through alongshore recovery and expansion if there is sufficient time between storms. However, the time required for dune recovery exceeds the time between storms capable of eroding and overwashing the dune. Correlation between historical shoreline retreat and the variance of the dune at swash and surf zone scales suggests that the persistence of the dune is an important control on transgression through island migration or shoreline retreat with relative sea-level rise.

Beschreibung: Highlights • Large seafloor depressions with diameters of up 10 km across have been mapped on the southern Chatham Rise, New Zealand. • Seismic reflection data show scarce indications for vertical fluid flow but no clear link between fluid flow and depressions. • Methane gas or methane hydrates appear to be absent on the southern Chatham Rise. • Seismic evidence suggests that vertical fluid flow was likely fuelled by polygonal faulting and silica diagenesis • The depressions are the results of erosion and sediment drift deposition of bottom currents associated with the Subtropical Front. Abstract Several giant seafloor depressions were investigated on the Chatham Rise offshore New Zealand using mainly bathymetric and seismic data, supplemented by sediment cores and reported porewater geochemistry data. The depressions have diameters of up to 11 km and occur on the southern flank of the Chatham Rise in water depths between 600 and 900 m, i.e. roughly underneath the location of the strongest thermal gradients of the Subtropical Front (STF) and characterized by eastward flowing currents. With up to 150 m of relief the depressions cut into post-Miocene deposits. Some of the depressions are partially filled with drift deposits that have similar seismic characteristics as the surrounding sediments and consist of alternations of silty muds and silts. Seismic profiles also show completely filled depressions that no longer have a bathymetric expression. Despite several pipe structures indicating vertical fluid flow, neither active fluid seepage nor indications for past fluid seepage are present at the seafloor of the Chatham Rise. Also, both pore water geochemistry and geophysical data do not show indications for an existing or past gas hydrate system in the area. Instead, seismic data suggest widespread polygonal faulting and the presence of silica diagenetic fronts. The release of mineral-bound water during silica diagenesis or fluid expulsion during sediment compaction can explain the presence of vertical fluid flow features but not the giant depressions themselves. Instead, the depressions are interpreted as the result of scouring by strong bottom currents for which fluid venting may have created the nucleation points.

Beschreibung: Highlights • Seabed rock drills and real-time fluid monitoring for first time in ocean drilling • First time recovery of continuous sequences along oceanic detachment fault zone • Highly heterogeneous rock type and alteration in shallow detachment fault zone • High methane and hydrogen concentrations in Atlantis Massif shallow basement • Oceanic serpentinites potentially provide important niches for microbial life Abstract IODP Expedition 357 used two seabed drills to core 17 shallow holes at 9 sites across Atlantis Massif ocean core complex (Mid-Atlantic Ridge 30°N). The goals of this expedition were to investigate serpentinization processes and microbial activity in the shallow subsurface of highly altered ultramafic and mafic sequences that have been uplifted to the seafloor along a major detachment fault zone. More than 57 m of core were recovered, with borehole penetration ranging from 1.3 to 16.4 meters below seafloor, and core recovery as high as 75% of total penetration in one borehole. The cores show highly heterogeneous rock types and alteration associated with changes in bulk rock chemistry that reflect multiple phases of magmatism, fluid-rock interaction and mass transfer within the detachment fault zone. Recovered ultramafic rocks are dominated by pervasively serpentinized harzburgite with intervals of serpentinized dunite and minor pyroxenite veins; gabbroic rocks occur as melt impregnations and veins. Dolerite intrusions and basaltic rocks represent the latest magmatic activity. The proportion of mafic rocks is volumetrically less than the amount of mafic rocks recovered previously by drilling the central dome of Atlantis Massif at IODP Site U1309. This suggests a different mode of melt accumulation in the mantle peridotites at the ridge-transform intersection and/or a tectonic transposition of rock types within a complex detachment fault zone. The cores revealed a high degree of serpentinization and metasomatic alteration dominated by talc-amphibole-chlorite overprinting. Metasomatism is most prevalent at contacts between ultramafic and mafic domains (gabbroic and/or doleritic intrusions) and points to channeled fluid flow and silica mobility during exhumation along the detachment fault. The presence of the mafic lenses within the serpentinites and their alteration to mechanically weak talc, serpentine and chlorite may also be critical in the development of the detachment fault zone and may aid in continued unroofing of the upper mantle peridotite/gabbro sequences. New technologies were also developed for the seabed drills to enable biogeochemical and microbiological characterization of the environment. An in situ sensor package and water sampling system recorded real-time variations in dissolved methane, oxygen, pH, oxidation reduction potential (Eh), and temperature and during drilling and sampled bottom water after drilling. Systematic excursions in these parameters together with elevated hydrogen and methane concentrations in post-drilling fluids provide evidence for active serpentinization at all sites. In addition, chemical tracers were delivered into the drilling fluids for contamination testing, and a borehole plug system was successfully deployed at some sites for future fluid sampling. A major achievement of IODP Expedition 357 was to obtain microbiological samples along a west–east profile, which will provide a better understanding of how microbial communities evolve as ultramafic and mafic rocks are altered and emplaced on the seafloor. Strict sampling handling protocols allowed for very low limits of microbial cell detection, and our results show that the Atlantis Massif subsurface contains a relatively low density of microbial life.