Understanding Mn-nodule distribution and evaluation of related deep-sea mining impacts using AUV-based hydroacoustic and optical data

In this study ship- and AUV-based multibeam data from the German Mn-nodule license area in the Clarion-Clipperton Zone (CCZ; eastern Pacific) are linked to ground truth data from optical imaging. Photographs obtained by an AUV enable semi-quantitative assessments of nodule coverage at a spatial resolution in the range of meters. Together with high resolution AUV bathymetry this revealed a correlation of small-scale terrain variations ( 1.8° and concave terrain. On a more regional scale, factors such as the geological setting (existence of horst and graben structures, sediment thickness, outcropping basement) and influence of bottom currents seem to play an essential role for the spatial variation of nodule abundance and the related hard substrate habitat. AUV imagery was also successfully employed to map the distribution of re-settled sediment following a disturbance and sediment cloud generation during a sampling deployment of an Epibenthic Sledge. Data from before and after the "disturbance" allows a direct assessment of the impact. Automated image processing analyzed the nodule coverage at the seafloor, revealing nodule blanketing by resettling of suspended sediment within 16 hours after the disturbance. The visually detectable impact was spatially limited to a maximum of 100m distance from the disturbance track, downstream of the bottom water current. A correlation with high resolution AUV bathymetry reveals that the blanketing pattern varies in extent by tens of meters, strictly following the bathymetry, even in areas of only slightly undulating seafloor (< 1 m vertical change). These results highlight the importance of detailed terrain knowledge when engaging in resource assessment studies for nodule abundance estimates and defining minable areas. At the same time, it shows the importance of high resolution mapping for detailed benthic habitat studies that show a heterogeneity at scales of 10 m to 100 m. Terrain knowledge is also needed to determine the scale of the impact by seafloor sediment blanketing during mining-operations

Temporal variability of gas seeps offshore New Zealand: Multi-frequency geoacoustic imaging of the Wairarapa area, Hikurangi margin

Cold seeps of the Wairarapa area situated around 1000 metres water depth on the Hikurangi margin offshore New Zealand’s North Island have been investigated using multibeam bathymetry, 75 and 410 kHz sidescan sonar imagery as well as 2-8 kHz Chirp sediment echosounder data. Towed video camera observations allowed groundtruthing the various geoacoustic data. At least eight different seep locations displaying various degrees of seep activity have been identified in the study area which consists of an elongated, northward-widening ridge that is part of the Hikurangi margin accretionary complex and well separated from direct terrigenous input by margin channels surrounding the ridge. The geoacoustic signature of individual cold-seep sites range from smooth areas with slightly elevated backscatter intesity resulting from high gas content or the presence of near-surface gas hydrates to rough areas with widespread patches of carbonates at the seafloor. Two cold seeps also show indications for active gas emissions in form of acoustic plumes in the water column. Repeated sidescan sonar imagery of the plumes indicates they are highly variable in intensity and directivity in the water column reflecting a likely control of gas emission by tides and currents. Although gas emission appears strongly focused in the Wairarapa area the actual extent of the cold seep structures are slightly wider in the subsurface as shown by sediment echosounder profiles. On a larger scale, however, fluid seepage at the Wairarapa area is still highly focused

Bottom-simulating reflector dynamics at Arctic thermogenic gas provinces: An example from Vestnesa Ridge, offshore west Svalbard

The Vestnesa Ridge comprises a >100 km long sediment drift located between the western continental slope of Svalbard and the Arctic mid-ocean ridges. It hosts a deep water (>1000 m) gas hydrate and associated seafloor seepage system. Near-seafloor headspace gas compositions and its methane carbon isotopic signature along the ridge indicate a predominance of thermogenic gas sources feeding the system. Prediction of the base of the gas hydrate stability zone for theoretical pressure and temperature conditions and measured gas compositions results in an unusual underestimation of the observed bottom-simulating reflector (BSR) depth. The BSR is up to 60 m deeper than predicted for pure methane and measured gas compositions with >99% methane. Models for measured gas compositions with >4% higher-order hydrocarbons result in a better BSR approximation. However, the BSR remains >20 m deeper than predicted in a region without active seepage. A BSR deeper than predicted is primarily explained by unaccounted spatial variations in the geothermal gradient and by larger amounts of thermogenic gas at the base of the gas hydrate stability zone. Hydrates containing higher-order hydrocarbons form at greater depths and higher temperatures and contribute with larger amounts of carbons than pure methane hydrates. In thermogenic provinces, this may imply a significant upward revision (up to 50% in the case of Vestnesa Ridge) of the amount of carbon in gas hydrates

Acoustic and visual characterisation of methane-rich seabed seeps at Omakere Ridge on the Hikurangi Margin, New Zealand

Six active methane seeps and one cold-water reef that may represent a relict seep were mapped at Omakere Ridge on New Zealand's Hikurangi Margin during cruises SO191 and TAN0616. Hydroacoustic flares, interpreted to be bubbles of methane rising through the water column were identified in the area. The seep sites and the cold-water reef were characterised by regions of high backscatter intensity on sidescan sonar records, or moderate backscatter intensity where the seep was located directly below the path of the sidescan towfish. The majority of sites appear as elevated features (2–4 m) in multibeam swath data. Gas blanking and acoustic turbidity were observed in sub-bottom profiles through the sites. A seismic section across two of the sites (Bear's Paw and LM-9) shows a BSR suggesting the presence of gas hydrate as well as spots of high amplitudes underneath and above the BSR indicating free gas. All sites were ground truthed with underwater video observations, which showed the acoustic features to represent authigenic carbonate rock structures. Live chemosynthetic biotic assemblages, including siboglinid tube worms, vesicomyid clams, bathymodiolin mussels, and bacterial mats, were observed at the seeps. Cold-water corals were the most conspicuous biota of the cold-water reef but widespread vesicomyid clam shells indicated past seep activity at all sites. The correlation between strong backscatter features in sidescan sonar images and seep-related seabed features is a powerful tool for seep exploration, but differentiating the acoustic features as either modern or relict seeps requires judicial analysis and is most effective when supported by visual observations

Silicate weathering in anoxic marine sediments

Two sediment cores retrieved at the northern slope of Sakhalin Island, Sea of Okhotsk, were analyzed for biogenic opal, organic carbon, carbonate, sulfur, major element concentrations, mineral contents, and dissolved substances including nutrients, sulfate, methane, major cations, humic substances, and total alkalinity. Down-core trends in mineral abundance suggest that plagioclase feldspars and other reactive silicate phases (olivine, pyroxene, volcanic ash) are transformed into smectite in the methanogenic sediment sections. The element ratios Na/Al, Mg/Al, and Ca/Al in the solid phase decrease with sediment depth indicating a loss of mobile cations with depth and producing a significant down-core increase in the chemical index of alteration. Pore waters separated from the sediment cores are highly enriched in dissolved magnesium, total alkalinity, humic substances, and boron. The high contents of dissolved organic carbon in the deeper methanogenic sediment sections (50–150 mg dm−3) may promote the dissolution of silicate phases through complexation of Al3+ and other structure-building cations. A non-steady state transport-reaction model was developed and applied to evaluate the down-core trends observed in the solid and dissolved phases. Dissolved Mg and total alkalinity were used to track the in-situ rates of marine silicate weathering since thermodynamic equilibrium calculations showed that these tracers are not affected by ion exchange processes with sediment surfaces. The modeling showed that silicate weathering is limited to the deeper methanogenic sediment section whereas reverse weathering was the dominant process in the overlying surface sediments. Depth-integrated rates of marine silicate weathering in methanogenic sediments derived from the model (81.4–99.2 mmol CO2 m−2 year−1) are lower than the marine weathering rates calculated from the solid phase data (198–245 mmol CO2 m−2 year−1) suggesting a decrease in marine weathering over time. The production of CO2 through reverse weathering in surface sediments (4.22–15.0 mmol CO2 m−2 year−1) is about one order of magnitude smaller than the weathering-induced CO2 consumption in the underlying sediments. The evaluation of pore water data from other continental margin sites shows that silicate weathering is a common process in methanogenic sediments. The global rate of CO2 consumption through marine silicate weathering estimated here as 5–20 Tmol CO2 year−1 is as high as the global rate of continental silicate weathering

European Code against Cancer 4th edition: Ultraviolet radiation and cancer

Ultraviolet radiation (UVR) is part of the electromagnetic spectrum emitted naturally from the sun or from artificial sources such as tanning devices. Acute skin reactions induced by UVR exposure are erythema (skin reddening), or sunburn, and the acquisition of a suntan triggered by UVR-induced DNA damage. UVR exposure is the main cause of skin cancer, including cutaneous malignant melanoma, basal-cell carcinoma, and squamous-cell carcinoma. Skin cancer is the most common cancer in fair-skinned populations, and its incidence has increased steeply over recent decades. According to estimates for 2012, about 100,000 new cases of cutaneous melanoma and about 22,000 deaths from it occurred in Europe. The main mechanisms by which UVR causes cancer are well understood. Exposure during childhood appears to be particularly harmful. Exposure to UVR is a risk factor modifiable by individuals' behaviour. Excessive exposure from natural sources can be avoided by seeking shade when the sun is strongest, by wearing appropriate clothing, and by appropriately applying sunscreens if direct sunlight is unavoidable. Exposure from artificial sources can be completely avoided by not using sunbeds. Beneficial effects of sun or UVR exposure, such as for vitamin D production, can be fully achieved while still avoiding too much sun exposure and the use of sunbeds. Taking all the scientific evidence together, the recommendation of the 4th edition of the European Code Against Cancer for ultraviolet radiation is: "Avoid too much sun, especially for children. Use sun protection. Do not use sunbeds."

How volcanically active is an abyssal plain? Evidence for recent volcanism on 20 Ma Nazca Plate seafloor

The abyssal plains are generally assumed to be geologically inactive parts of the ocean plate interiors where processes (such as pelagic sedimentation or manganese crust and nodule formation) occur at very slow rates. In terms of intraplate volcanic activity, almost all is assumed to occur at hotspots, leading to little exploration in other intraplate regions. The Peru Basin is an abyssal plain known to host Mn-nodule fields. We present remotely-operated underwater vehicle (ROV) investigations of a small seamount adjacent to such a Mn-nodule field on 20Ma Nazca Plate crust, showing that it appears to have been recently volcanically and hydrothermally active. The seamount lies 1600km east of the nearest spreading axis (East Pacific Rise) and 600km from both the Galapagos Plateau (to the north) and the subduction zone off Peru (to the east), making off-axis, hotspot or petit-spot processes unlikely as a cause of the volcanism. The shallow mantle below the Nazca (and conjugate Pacific) Plate shows globally anomalous low seismic shear-wave velocities, perhaps reflecting higher-than-normal amounts of melt in the mantle below this region which may provide a source for the magmas. Our own regional mapping work and literature sources highlight several similar sites of probable young volcanism elsewhere in the Peru Basin which may also be related to this anomaly. The Nazca abyssal plain may be much more geologically active than previously thought. If so, this could have wider implications for, among other things, chemosynthetic ecosystem connectivity

Estimating the spatial position of marine mammals based on digital camera recordings

Estimating the spatial position of organisms is essential to quantify interactions between the organism and the characteristics of its surroundings, for example, predator–prey interactions, habitat selection, and social associations. Because marine mammals spend most of their time under water and may appear at the surface only briefly, determining their exact geographic location can be challenging. Here, we developed a photogrammetric method to accurately estimate the spatial position of marine mammals or birds at the sea surface. Digital recordings containing landscape features with known geographic coordinates can be used to estimate the distance and bearing of each sighting relative to the observation point. The method can correct for frame rotation, estimates pixel size based on the reference points, and can be applied to scenarios with and without a visible horizon. A set of R functions was written to process the images and obtain accurate geographic coordinates for each sighting. The method is applied to estimate the spatiotemporal fine-scale distribution of harbour porpoises in a tidal inlet. Video recordings of harbour porpoises were made from land, using a standard digital single-lens reflex (DSLR) camera, positioned at a height of 9.59 m above mean sea level. Porpoises were detected up to a distance of ~3136 m (mean 596 m), with a mean location error of 12 m. The method presented here allows for multiple detections of different individuals within a single video frame and for tracking movements of individuals based on repeated sightings. In comparison with traditional methods, this method only requires a digital camera to provide accurate location estimates. It especially has great potential in regions with ample data on local (a)biotic conditions, to help resolve functional mechanisms underlying habitat selection and other behaviors in marine mammals in coastal areas

Geological imprint of methane seepage on the seabed and biota of the convergent Hikurangi Margin, New Zealand: box core and grab carbonate results

Short box cores (to 30 cm bsf) and seafloor carbonate grab samples were acquired at mapped hydrocarbon seep sites (600–1200 m water depths) during the 2007 RV SONNE SO191 cruise on the Hikurangi Margin offshore eastern North Island, New Zealand, to evaluate the influence of methane seepage on sedimentologic, biotic, mineralogic and stable isotopic attributes of seabed sediments. Sedimentary horizons in the box cores consist of siliciclastic silts and sands, shell beds and nodular, microcrystalline aragonite bands up to 15 cm thick. The megafauna is dominated by infaunal to semi-infaunal chemosymbiotic bivalves (Calyptogena, Lucinoma, and Acharax), as well as associated worms and carnivorous and grazing gastropods. Burrows in silts, some occupied by worms or juvenile Acharax, mainly have simple morphologies more typical of high-energy, nearshore settings than deep-sea environments, while a few are large and sparsely branched with wall scratch marks inferred to be of decapod crustacean origin. The box core silts and nodular carbonate samples vary in TOC content from 0.2 to 0.9 wt.%, carbonate content from 4 to 78%, and δ13C and δ18O values from − 50.3 to − 0.6‰ PDB and + 0.77 to + 3.2‰ PDB, respectively. Low carbonate content silt samples have the most enriched δ13C values, implying a seawater source for their pore water bicarbonate. Negative δ13C and positive δ18O values typify the nodular, microcrystalline aragonite bands, indicating formation during microbially mediated, sulphate-dependent anaerobic oxidation of methane (AOM) in a cold, near-seafloor environment, as is also supported by lipid biomarker data. A clear isotopic mixing trend of decreasing δ13C and increasing δ18O and carbonate content in the fine (< 100 µm) carbonate fraction of the host silts also has been reported from other methane seep provinces, and suggests a heterogeneous influx of methane-rich see

Fungal Levels in the Home and Allergic Rhinitis by 5 Years of Age

Studies have repeatedly demonstrated that sensitization to fungi, such as Alternaria, is strongly associated with allergic rhinitis and asthma in children. However, the role of exposure to fungi in the development of childhood allergic rhinitis is poorly understood. In a prospective birth cohort of 405 children of asthmatic/allergic parents from metropolitan Boston, Massachusetts, we examined in-home high fungal concentrations (> 90th percentile) measured once within the first 3 months of life as predictors of doctor-diagnosed allergic rhinitis in the first 5 years of life. In multivariate Cox regression analyses, predictors of allergic rhinitis included high levels of dust-borne Aspergillus [hazard ratio (HR) = 3.27; 95% confidence interval (CI), 1.50–7.14], Aureobasidium (HR = 3.04; 95% CI, 1.33–6.93), and yeasts (HR = 2.67; 95% CI, 1.26–5.66). The factors controlled for in these analyses included water damage or mild or mildew in the building during the first year of the child’s life, any lower respiratory tract infection in the first year, male sex, African-American race, fall date of birth, and maternal IgE to Alternaria > 0.35 U/mL. Dust-borne Alternaria and non-sporulating and total fungi were also predictors of allergic rhinitis in models excluding other fungi but adjusting for all of the potential confounders listed above. High measured fungal concentrations and reports of water damage, mold, or mildew in homes may predispose children with a family history of asthma or allergy to the development of allergic rhinitis