Arsenic and high affinity phosphate uptake gene distribution in shallow submarine hydrothermal sediments

The toxicity of arsenic (As) towards life on Earth is apparent in the dense distribution of genes associated with As detoxification across the tree of life. The ability to defend against As is particularly vital for survival in As-rich shallow submarine hydrothermal ecosystems along the Hellenic Volcanic Arc (HVA), where life is exposed to hydrothermal fluids containing up to 3000 times more As than present in seawater. We propose that the removal of dissolved As and phosphorus (P) by sulfide and Fe(III)(oxyhydr)oxide minerals during sediment-seawater interaction, produces nutrient-deficient porewaters containing < 2.0 ppb P. The porewater arsenite-As(III) to arsenate-As(V) ratios, combined with sulfide concentration in the sediment and/or porewater, suggest a hydrothermally-induced seafloor redox gradient. This gradient overlaps with changing high affinity phosphate uptake gene abundance. High affinity phosphate uptake and As cycling genes are depleted in the sulfide-rich settings, relative to the more oxidizing habitats where mainly Fe(III)(oxyhydr)oxides are precipitated. In addition, a habitat-wide low As-respiring and As-oxidizing gene content relative to As resistance gene richness, suggests that As detoxification is prioritized over metabolic As cycling in the sediments. Collectively, the data point to redox control on Fe and S mineralization as a decisive factor in the regulation of high affinity phosphate uptake and As cycling gene content in shallow submarine hydrothermal ecosystems along the HVA

Arsenic stress after the Proterozoic glaciations

Protection against arsenic damage in organisms positioned deep in the tree of life points to early evolutionary sensitization. Here, marine sedimentary records reveal a Proterozoic arsenic concentration patterned to glacial-interglacial ages. The low glacial and high interglacial sedimentary arsenic concentrations, suggest deteriorating habitable marine conditions may have coincided with atmospheric oxygen decline after ~2.1 billion years ago. A similar intensification of near continental margin sedimentary arsenic levels after the Cryogenian glaciations is also associated with amplified continental weathering. However, interpreted atmospheric oxygen increase at this time, suggests that the marine biosphere had widely adapted to the reorganization of global marine elemental cycles by glaciations. Such a glacially induced biogeochemical bridge would have produced physiologically robust communities that enabled increased oxygenation of the ocean-atmosphere system and the radiation of the complex Ediacaran-Cambrian life

Modes of carbon fixation in an arsenic and CO₂-rich shallow hydrothermal ecosystem

Abstract The seafloor sediments of Spathi Bay, Milos Island, Greece, are part of the largest arsenic-CO2-rich shallow submarine hydrothermal ecosystem on Earth. Here, white and brown deposits cap chemically distinct sediments with varying hydrothermal influence. All sediments contain abundant genes for autotrophic carbon fixation used in the Calvin-Benson-Bassham (CBB) and reverse tricaboxylic acid (rTCA) cycles. Both forms of RuBisCO, together with ATP citrate lyase genes in the rTCA cycle, increase with distance from the active hydrothermal centres and decrease with sediment depth. Clustering of RuBisCO Form II with a highly prevalent Zetaproteobacteria 16S rRNA gene density infers that iron-oxidizing bacteria contribute significantly to the sediment CBB cycle gene content. Three clusters form from different microbial guilds, each one encompassing one gene involved in CO2 fixation, aside from sulfate reduction. Our study suggests that the microbially mediated CBB cycle drives carbon fixation in the Spathi Bay sediments that are characterized by diffuse hydrothermal activity, high CO2, As emissions and chemically reduced fluids. This study highlights the breadth of conditions influencing the biogeochemistry in shallow CO2-rich hydrothermal systems and the importance of coupling highly specific process indicators to elucidate the complexity of carbon cycling in these ecosystems

New insights into hydrothermal vent processes in the unique shallow-submarine arc-volcano, Kolumbo (Santorini), Greece

We report on integrated geomorphological, mineralogical, geochemical and biological investigations of the hydrothermal vent field located on the floor of the density-stratified acidic (pH , 5) crater of the Kolumbo shallow-submarine arc-volcano, near Santorini. Kolumbo features rare geodynamic setting at convergent boundaries, where arc-volcanism and seafloor hydrothermal activity are occurring in thinned continental crust. Special focus is given to unique enrichments of polymetallic spires in Sb and Tl (6Hg, As, Au, Ag, Zn) indicating a new hybrid seafloor analogue of epithermal-to-volcanic-hosted-massive-sulphide deposits. Iron microbial-mat analyses reveal dominating ferrihydrite-type phases, and high-proportion of microbial sequences akin to &quot;Nitrosopumilus maritimus&quot;, a mesophilic Thaumarchaeota strain capable of chemoautotrophic growth on hydrothermal ammonia and CO2. Our findings highlight that acidic shallow-submarine hydrothermal vents nourish marine ecosystems in which nitrifying Archaea are important and suggest ferrihydrite-type Fe31-(hydrated)-oxyhydroxides in associated low-temperature iron mats are formed by anaerobic Fe21-oxidation, dependent on microbially produced nitrate

The Society for Environmental Geochemistry and Health (SEGH): building for the future.

The challenges of sustainable development are ever more pressing, and the skills, interests and capabilities of the SEGH member are well-placed to continue to make more meaningful contributions to the environment, society and well-being. We reflect on the historical development of the society, its response to the dynamic international research landscape and the great opportunities ahead. In 2018, SEGH implemented a new board structure after 2–3 years of consultation, with approval of a new constitution and a new strategy across the large number of international board members. While regions were represented by sections in Europe, Asia/Pacific and the USA, the structure required renewal in order to be more representative of the distribution of members and website traffic that had evolved in preceding years. In addition, the society wanted to improve its position for future growth opportunities across rapidly developing regions

Mercury in the Urban Topsoil of Athens, Greece

The present study documents the Hg content in 45 urban topsoil samples from the highly urbanized city of Athens, Greece. The Hg concentrations were quantified by applying aqua regia digestion on the &lt;100 μm soil fraction followed by inductively coupled plasma-mass spectrometry (ICP-MS) with a detection limit of 5 μg·kg−1. The median concentration of Hg in Athens soil is 96 μg·kg−1; ten out of 45 soil samples were found to contain Hg concentrations higher than 200 μg·kg−1, which is the maximum concentration value expected to be present in normal uncontaminated soils. Results obtained by multivariate principal component and hierarchical cluster analysis incorporating a large suite of chemical elements were notably effective for elucidating the anthropogenic origin of Hg in the studied soil. The elevated concentrations are most likely related to site-specific point source contamination rather than to the widely documented influences from the vehicular traffic emissions in urban settings. Given the proximity of urban population to the contaminated urban soils, we suggest the implementation of different soil extraction tests with the aim to evaluate the fraction of soil Hg available for absorption by the human body

Lead Determination and Heterogeneity Analysis in Soil from a Former Firing Range

Public places can have an unknown past of pollutants deposition. The exposition to such contaminants can create environmental and health issues. The characterization of a former firing range in Athens, Greece will allow its monitoring and encourage its remediation. This study is focused on Pb contamination in the site due to its presence in ammunition. A dense sampling design with 91 location (10 m apart) was used to determine the spatial distribution of the element in the surface soil of the study area. Duplicates samples were also collected one meter apart from 8 random locations to estimate the heterogeneity of the site. Elemental concentrations were measured using a portable XRF device after simple sample homogenization in the field. Robust Analysis of Variance showed that the contributions to the total variance were 11% from sampling, 1% analytical, and 88% geochemical; reflecting the suitability of the technique. Moreover, the extended random uncertainty relative to the mean concentration was 91.5%; confirming the high heterogeneity of the site. Statistical analysis defined a very high contamination in the area yielding to suggest the need for more in-depth analysis of other contaminants and possible health risks

Geology and Origin of Supergene Ore at the Lavrion Pb-Ag-Zn Deposit, Attica, Greece

Abstract The Lavrion carbonate-hosted Pb-Ag-Zn deposit in southeast Attica, Greece, consisted of signifi cant nonsulfi de ore bodies. The polymetallic sulfi de mineralization was subjected to supergene oxidation, giving rise to gossan. The principal non-sulfi de minerals of past economic importance were smithsonite, goethite and hematite. The supergene mineral assemblages occupy secondary open spaces and occur as replacement pods within marble. Calamine and iron ore mainly fi lled open fractures. X-ray diffraction and scanning electron microscopy of samples of oxidized ore indicate complex gossan mineralogy depending on the hypogene mineralogy, the degree of oxidation and leaching of elements, and the local hydrologic conditions. Bulk chemical analysis of the samples indicated high ore-grade variability of the supergene mineralization. On multivariate cluster analysis of geochemical data the elements were classifi ed into groups providing evidence for their differential mobilization during dissolution, transport and re-precipitation. The mode of occurrence, textures, mineralogy and geochemistry of the non-sulfi de mineralization confi rm that it is undoubtedly of supergene origin: the product of infl ux into open fractures in the country rock of highly acidic, metal-rich water resulting from the oxidation of pyrite-rich sulfi de protore. Dissolution of carbonates led to opening of the fractures. Mineral deposition in the supergene ore took place under near-neutral to mildly acidic conditions. The supergene dissolution and re-precipitation of Fe and Zn in the host marble increased metal grades and separated iron and zinc from lead, thereby producing economically attractive deposits; it further contributed to minimization of pollution impact on both soil and ground water