ALBERT

Description: Highlights • Regional investigation of precious and base metal-rich deposits in the Cyclades • Pb-isotope and trace element analyses in galena by laser ablation ICP-MS • Galena inherits the Pb-isotopic signature of the underlying basement. • Distinct Pb-isotope signatures in the west and north-central Cyclades, Greece. • 206Pb/204Pb line follows the trace of known tectonostratigraphic units. Polymetallic ore deposits of the Aegean Sea, Greece, are temporally and spatially associated with the emplacement of Miocene granitoids and Pliocene to Quaternary volcanic units along the active volcanic arc and occur adjacent to the crustal-scale detachment systems. A variety of mineral deposits (e.g., carbonate-replacement, skarn, porphyry, vein-type, and low- to high-sulfidation epithermal deposits) formed during different stages of back-arc evolution and can be found in the footwall and hanging wall of the major detachment systems and all tectono-stratigraphic units. New galena Pb-isotope data collected by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis exhibit a range of isotopic ratios: 206Pb/204Pb: 18.68–18.91, 207Pb/204Pb: 15.67–15.75 and 208Pb/204Pb: 38.83–39.18, with a resolvable geographic pattern. Together with compiled Pb-isotope data of Cycladic galena, large-scale regional similarities in the Pb-isotope signatures are recognized, suggesting distinct sources of lead in the underlying basement. Base metal-rich deposits in the west Cyclades have a common lead source with a more radiogenic signature, whereas lead in the deposits in the north-central Cyclades was derived from a less radiogenic source. Similarities between the Pb-isotopic signature of galena and regional host rocks suggest, that the pre-Alpine Cycladic Basement was the main source of lead for the deposits in the north and central, and the metamorphosed volcano-sedimentary Lower Cycladic Blueschist Nappe was the source of lead for the deposits in the west. Moreover, there is a close spatial relationship of the 206Pb/204Pb 18.84 line and trace of the proposed Trans-Cycladic Thrust. Regional trends were also observed in the new LA-ICP-MS trace element analysis in galena. Galena in carbonate-replacement and skarn deposits in the west is enriched in base metals and silver, whereas galena in vein-type deposits in the north and low- to high-sulfidation epithermal deposits along the active volcanic arc is enriched in gold, tellurides and selenium. Combined trace element and isotopic data of galena indicate distinct metal sources in the Cyclades. Heterogenous rock assemblages of mixed provenance and age account for the differences in lead isotopes. Whereas the base metals and silver are ultimately sourced from the basement, the precious metals might be derived from the metasomatized lithospheric mantle.

Description: Sediment porewater dialysis passive samplers, also known as “peepers,” are inert containers with a small volume of water (usually 1–100 mL) capped with a semi-permeable membrane. When exposed to sediment over a period of days to weeks, chemicals (typically inorganics) in sediment porewater diffuse through the membrane into the water. Subsequent analysis of chemicals in the peeper water sample can provide a value that represents the concentrations of freely-dissolved chemicals in sediment, a useful measurement for understanding fate and risk. Despite more than 45 years of peeper uses in peer-reviewed research, there are no standardized methods available, which limits the application of peepers for more routine regulatory-driven decision making at sediment sites. In hopes of taking a step towards standardizing peeper methods for measuring inorganics in sediment porewater, over 85 research documents on peepers were reviewed to identify example applications, key methodological aspects, and potential uncertainties. The review found that peepers could be improved by optimizing volume and membrane geometry to decrease the necessary deployment time, decrease detection limits, and provide sufficient sample volumes needed for commercial analytical laboratories using standardized analytical methods. Several methodological uncertainties related to the potential impact of oxygen presence in peeper water prior to deployment and oxygen accumulation in peepers after retrieval from sediment were noted, especially for redox-sensitive metals. Additional areas that need further development include establishing the impact of deionized water in peeper cells when used in marine sediment and use of pre-equilibration sampling methods with reverse tracers allowing shorter deployment periods. Overall, it is expected that highlighting these technical aspects and research needs will encourage work to address critical methodological challenges, aiding in the standardization of peeper methods for measuring porewater concentrations at contaminated regulatory-driven sediment sites.

Description: PUBLIC SUMMARY: Endothermy has evolved multiple times not only in mammals and birds but also in fishes (teleosts and chondrichthyans) A chromosome-level genome sequence of the whole-body endothermic opah was generated, explaining genetic changes in heat production, sensory, and adaptive immune system Convergent evolution in endothermic vertebrate lineages was investigated, and genes essential for heart function and metabolic heat production were screened Analyses of the unique pectoral muscle of opah revealed that numerous proteins were co-opted from dorsal swimming muscles for thermogenesis and oxidative phosphorylation ABSTRACT: Few fishes have evolved elevated body temperatures compared to ambient temperatures and only in opah (Lampris spp) is the entire body affected. To understand the molecular basis of endothermy, we analyzed the opah genome and identified 23 genes with convergent amino acid substitutions across fish, birds, and mammals, including slc8b1, which encodes the mitochondrial Na+/Ca2+ exchanger and is essential for heart function and metabolic heat production. Among endothermic fishes, 44 convergent genes with suggestive metabolic functions were identified, such as glrx3, encoding a crucial protein for hemoglobin maturation. Numerous genes involved in the production and retention of metabolic heat were also found to be under positive selection. Analyses of opah’s unique inner heat-producing pectoral muscle layer, an evolutionary key-innovation, revealed that many proteins were co-opted from dorsal swimming muscles for thermogenesis and oxidative phosphorylation. Thus, the opah genome provides valuable resources and opportunities to uncover the genetic basis of thermal adaptations in fish.

Description: Highlights • Fermentation, methanogenesis and methanotrophy prevail at the As-contaminated site. • Reducing aquifer consists of gray sediment and is dominated by Fe(III) (oxyhydr)oxides and As(III). • Less reducing aquifer consists of yellow-brown sediment and is dominated by goethite and As(V). • Anaerobic CH4 oxidation likely supports carbonate mineral formation. • Methanotrophic Fe(III)-reducer Ca. Methanoperedens coincides with As and Fe peaks in sediments. High arsenic (As) concentrations in groundwater are a worldwide problem threatening the health of millions of people. Microbial processes are central in the (trans)formation of the As-bearing ferric and ferrous minerals, and thus regulate dissolved As levels in many aquifers. Mineralogy, microbiology and dissolved As levels can vary sharply within aquifers, making high-resolution measurements particularly valuable in understanding the linkages between them. We conducted a high spatial resolution geomicrobiological study in combination with analysis of sediment chemistry and mineralogy in an alluvial aquifer system affected by geogenic As in the Red River delta in Vietnam. Microbial community analysis revealed a dominance of fermenters, methanogens and methanotrophs whereas sediment mineralogy along a 46 m deep core showed a diversity of Fe minerals including poorly crystalline Fe (II/III) and Fe(III) (oxyhydr)oxides such as goethite, hematite, and magnetite, but also the presence of Fe(II)-bearing carbonates and sulfides which likely formed as a result of microbially driven organic carbon (OC) degradation. A potential important role of methane (CH4) as electron donor for reductive Fe mineral (trans)formation was supported by the high abundance of Candidatus Methanoperedens, a known Fe(III)-reducing methanotroph. Overall, these results imply that OC turnover including fermentation, methanogenesis and CH4 oxidation are important mechanisms leading to Fe mineral (trans)formation, dissolution and precipitation, and thus indirectly affecting As mobility by changing the Fe-mineral inventory.

Description: Ultratrace concentrations of Ti were determined by catalytic differential pulse adsorptive stripping voltammetry (cDPAdSV) in samples collected in the Pará and Amazon estuaries and plume into the Atlantic Ocean. Different end members including rivers Tocantins, Amazon and Pará and Atlantic seawater were sampled as well as the salinity gradients in the mixing zone between the river outflows and waters from the North Brazil Current during several transects. The Mangrove Belt southeast of the Pará river mouth with its extensive groundwater discharge was also sampled. Most samples were taking during cruise M147 (GEOTRACES process study GApr11) during the high discharge period in April and May 2018. In addition to high resolution determination of dissolved Ti distributions in this region, size fractionation was investigated by using several filtration steps with pore sizes (0.2 μm, and 0.015 μm) and ultrafiltration (10 kDa and 1 kDa) at four selected stations. Dissolved Ti varied significantly between different river end members and showed a non-conservative behavior along the mixing gradients with strong removal at low salinities and some enrichments at higher salinity ranges. The results suggest that there was both adsorption and desorption of Ti from suspended particles from both riverine and marine sources or flocculation and aggregation of colloids and particulate matter from end member rivers as well as resuspension at particular salinity ranges. The 0.015 μm filtered and 10 kDa and 1 kDa ultrafiltered aliquots showed variable distributions of Ti in the different size fractions, depending on the sampling zone. This very complex behavior of Ti along the mixing gradient and the dynamic system of the Amazon estuary, which comprises a fifth of the global freshwater flux into the ocean, is the key to controlling the fluxes of Ti into the Atlantic.

Description: The Amazon and the Pará are two major rivers that carry dissolved and suspended particulate trace metals to the Atlantic Ocean. In the dynamic mixing zone of the estuary, competing processes of trace metal sorption and release play a role, which might affect transport to the open ocean. Here we investigate the behavior of dissolved (〈0.2 μm), soluble (〈0.015 μm) and truly dissolved (〈10 kDa and 〈 1 kDa) molybdenum (Mo), uranium (U), and vanadium (V) during estuarine mixing between river water (S 〈 1) and seawater (S 〉 35) end members during the high discharge period, as well as during aging of the plume in its northward flow along the coast. Molybdenum behaved conservatively during estuarine mixing and showed no colloidal fraction, suggesting Mo is solely present in the soluble or even truly dissolved fraction. Uranium behaved mostly conservatively but showed removal in the low salinity range (ca. S 〈 9). This is potentially due to colloidal flocculation at low salinities, as indicated by colloidal (0.015–0.2 μm) fractions of up to 30% for U but decreasing with increasing salinity until no significant difference could be discerned at S 〉 10. Vanadium shows a general conservative mixing, but with more scatter in the data than for Mo and U and potential removal at low to mid-salinities. Removal of V to the sediments is also indicated by surface sediment data from the mid-salinity region of the estuary but no size fractionation in the dissolved phase could be observed. Hence, V seems to be predominantly present in the soluble or even truly dissolved phase and export to the sediments might take place through particles 〉0.2 μm. No considerable removal or release of Mo, U and V was observed in their water column depth profiles, indicating a conservative behavior in the water column of the estuaries studied here. Additionally, we present a comparison of differential pulse adsorptive stripping voltammetry and inductively coupled plasma – mass spectrometry analyses for Mo and V, which showed excellent agreement within analytical uncertainty in this challenging sample material covering the full salinity range from freshwater to seawater.