Hydrothermal activity and metallogenesis in the Lau back-arc basin

The lost vent gastropod species of Lothar A. Beck

Deep-sea hydrothermal vents host many endemic species adapted to these chemosynthesis-based ecosystems. The exploration of vent fields including those in the tropical Pacific is currently accelerating, due to the development of deep-sea mining for valuable minerals. Molecular evidence has shown that many vent endemic gastropod lineages include sibling species pairs in adjacent oceanic basins. While the fauna of the Manus Basin is relatively well described, many lineages in adjacent regions in North Fiji or Lau Basins are recognised as separate species, but unnamed. Valuable material from this fauna was studied by Lothar A. Beck in the 1990s, who fully drafted descriptions for these species, but did not publish them. Beck's manuscript names, prior to the present study, represented real species but nomina nuda without taxonomic validity. Here we present the descriptions of seven new species and one new genus, extracted from Beck's unpublished manuscript that was rediscovered after his death in 2020. The publication of these descriptions makes them taxonomically available and respects the scientific contributions of Beck. Providing valid descriptions of these species is critically important now to enable the recognition of species that may require conservation in the face of future environmental destruction. Symmetriapelta Beck, gen. nov. is described as new genus. Bathyacmaea nadinae Beck, sp. nov., Pyropelta ovalis Beck, sp. nov., Pseudorimula leisei Beck, sp. nov., Lepetodrilus fijiensis Beck, sp. nov., Shinkailepas conspira Beck, sp. nov., Symmetromphalus mcleani Beck, sp. nov. and Symmetriapelta wareni Beck, sp. nov. are introduced as new species.

Strontium, Hydrogen and Oxygen Behavior in Vent Fluids and Plumes from the Kueishantao Hydrothermal Field Offshore Northeast Taiwan: Constrained by Fluid Processes

Strontium (Sr), hydrogen (H) and oxygen (O) in vent fluids are important for understanding the water–rock interaction and hydrothermal flux in hydrothermal systems. We have analyzed the Sr, H and O isotopic compositions of seawater, vent fluid and hydrothermal plume samples in the Kueishantao hydrothermal field, as well as their calcium (Ca), total sulfur (S), Sr, arsenic (As), stibium (Sb), chlorine (Cl) and manganese (Mn) concentrations for understanding the origin and processes of fluids. The results suggest that most As, Sb and Mn are leached from andesitic rocks into the fluids, and most Ca and Cl remained in the deep reaction zone during the fluid–andesitic rock interaction. The ranges of 87Sr/86Sr, δDV-SMOW and δ18OV-SMOW values in the yellow spring, white spring and plumes are small. The 87Sr/86Sr, δDV-SMOW and δ18OV-SMOW values of fluids and plumes are like those of ambient seawater, indicating that the Sr, H and O of vent fluids and hydrothermal plumes are derived primarily from seawater. This suggests that the interaction of andesite and subseafloor fluid is of short duration and results in the majority of As, Sb and Mn being released into fluids, while most Ca and Cl remained in the deep reaction zone. In addition, there was no significant variation of Sr, H and O isotopic compositions in the upwelling fluid, keeping the similar isotopic compositions of seawater. There are obvious correlations among the pH values, As and Sb concentrations, and H isotopic compositions of the vent fluids and hydrothermal plumes, implying that the As and Sb concentrations and H isotopic compositions can trace the dispersion of plumes in the ambient seawater. According to the Sr concentrations and 87Sr/86Sr values, the water/rock ratios are 3076~8124, which is consistent with the idea that the interaction between fluid and andesite at the subseafloor is of short duration. The hydrothermal flux of Sr discharged from the yellow spring into the seawater is between 2.06 × 104 and 2.26 × 104 mol/yr, and the white spring discharges 1.18 × 104~1.26 × 104 mol/yr Sr if just andesites appear in the reaction zone.

A Novel Device for the In Situ Enrichment of Gold from Submarine Venting Fluids

Gold and other metals (Cu, Zn, Ag, etc.) are enriched in vent fluids, approximately 3–5 orders of magnitude higher than those in seawater, and this leads to the formation of sulfide enrichment in Cu, Zn, Au, and Ag deposited on the mid-ocean ridge and island arcs, as well as in back-arc basins. We developed a device that can extract the elements such as Cu, Zn, Au, and Ag from the vent fluids before the formation of the hydrothermal plume, sulfide deposit, and metalliferous sediment at the seafloor over a long period, which is beneficial to collecting hydrothermal resources effectively and avoiding the damage of ecological environments caused by mining the polymetallic sulfide resources. The application of this device will have significance for the development and utilization of seafloor hydrothermal resources, the sustainable development and implementation of the blue economy, and the construction of the marine ecological civilization in the future.

Rapid coupling between solid earth and ice volume during the Quaternary

The solid earth plays a major role in controlling Earth's surface climate. Volcanic degassing of carbon dioxide (CO2) and silicate chemical weathering are known to regulate the evolution of climate on a geologic timescale (> 106 yr), but the relationship between the solid earth and the shorter (< 105 yr) fluctuations of Quaternary glacial-interglacial cycles is still under debate. Here we show that the seawater osmium isotope composition (187Os/188Os), a proxy for the solid earth's response to climate change, has varied during the past 300,000 years in association with glacial-interglacial cycles. Our marine Os isotope mass-balance simulation reveals that the observed 187Os/188Os fluctuation cannot be explained solely by global chemical weathering rate changes corresponding to glacial-interglacial climate changes, but the fluctuation can be reproduced by taking account of short-term inputs of (1) radiogenic Os derived from intense weathering of glacial till during deglacial periods and (2) unradiogenic Os derived from enhanced seafloor hydrothermalism triggered by sea-level falls associated with increases of ice sheet volume. Our results constitute the first evidence that ice sheet recession and expansion during the Quaternary systematically and repetitively caused short-term (< 105 yr) solid earth responses via chemical weathering of glacial till and seafloor magmatism. This finding implies that climatic changes on < 105 yr timescales can provoke rapid feedbacks from the solid earth, a causal relationship that is the reverse of the longer-term (> 106 yr) causality that has been conventionally considered.

Response of gram-positive bacteria to copper stress

The Gram-positive bacteria Enterococcus hirae, Lactococcus lactis, and Bacillus subtilis have received wide attention in the study of copper homeostasis. Consequently, copper extrusion by ATPases, gene regulation by copper, and intracellular copper chaperoning are understood in some detail. This has provided profound insight into basic principles of how organisms handle copper. It also emerged that many bacterial species may not require copper for life, making copper homeostatic systems pure defense mechanisms. Structural work on copper homeostatic proteins has given insight into copper coordination and bonding and has started to give molecular insight into copper handling in biological systems. Finally, recent biochemical work has shed new light on the mechanism of copper toxicity, which may not primarily be mediated by reactive oxygen radicals.

Formation of Zn- and Fe-sulfides near hydrothermal vents at the Eastern Lau Spreading Center: implications for sulfide bioavailability to chemoautotrophs

BACKGROUND

The speciation of dissolved sulfide in the water immediately surrounding deep-ocean hydrothermal vents is critical to chemoautotrophic organisms that are the primary producers of these ecosystems. The objective of this research was to identify the role of Zn and Fe for controlling the speciation of sulfide in the hydrothermal vent fields at the Eastern Lau Spreading Center (ELSC) in the southern Pacific Ocean. Compared to other well-studied hydrothermal systems in the Pacific, the ELSC is notable for unique ridge characteristics and gradients over short distances along the north-south ridge axis.

RESULTS

In June 2005, diffuse-flow (< 50 degrees C) and high-temperature (> 250 degrees C) vent fluids were collected from four field sites along the ELSC ridge axis. Total and filtered Zn and Fe concentrations were quantified in the vent fluid samples using voltammetric and spectrometric analyses. The results indicated north-to-south variability in vent fluid composition. In the high temperature vent fluids, the ratio of total Fe to total Zn varied from 39 at Kilo Moana, the most northern site, to less than 7 at the other three sites. The concentrations of total Zn, Fe, and acid-volatile sulfide indicated that oversaturation and precipitation of sphalerite (ZnS(s)) and pyrite (FeS2(s)) were possible during cooling of the vent fluids as they mixed with the surrounding seawater. In contrast, most samples were undersaturated with respect to mackinawite (FeS(s)). The reactivity of Zn(II) in the filtered samples was tested by adding Cu(II) to the samples to induce metal-exchange reactions. In a portion of the samples, the concentration of labile Zn2+ increased after the addition of Cu(II), indicating the presence of strongly-bound Zn(II) species such as ZnS clusters and nanoparticles.

CONCLUSION

Results of this study suggest that Zn is important to sulfide speciation at ELSC vent habitats, particularly at the southern sites where Zn concentrations increase relative to Fe. As the hydrothermal fluids mix with the ambient seawater, Zn-sulfide clusters and nanoparticles are likely preventing sulfide oxidation by O2 and reducing bioavailability of S(-II) to organisms.

Geomicrobiological exploration and characterization of a novel deep-sea hydrothermal system at the TOTO caldera in the Mariana Volcanic Arc

Novel hydrothermal activities accompanying effluent white smokers and elemental sulfur chimney structures at the north-east lava dome of the TOTO caldera depression in the Mariana Volcanic Arc have been explored and characterized by geochemical and microbiological surveys. White smoker hydrothermal fluids were observed in the potential hydrothermal activity centre of the field and represented the maximal temperature of 170 degrees C and the lowest pH of 1.6. The chimney structures, all consisting of elemental sulfur (sulfur chimney), were also unique to the TOTO caldera hydrothermal field. Microbial community structures in a sulfur chimney and its formation hydrothermal fluid with a high concentration of hydrogen sulfide (15 mM) have been investigated by culture-dependent and -independent analyses. 16S rRNA gene clone analysis and fluorescence in situ hybridization (FISH) analysis revealed that epsilon-Proteobacteria dominated the microbial communities in the sulfur chimney structure and formed a dense microbial mat covering the sulfur chimney surface. Archaeal phylotypes were consistently minor components in the communities and related to the genera Thermococcus, Pyrodictium, Aeropyrum, and the uncultivated archaeal group of 'deep-sea hydrothermal vent euryarchaeotal group'. Cultivation analysis suggested that the chemolithoautotrophs might play a significant ecological role as primary producers utilizing gas and sulfur compounds provided from hydrothermal fluids.

4,4‘-Dimethyldinaphtho[a,d]cycloheptane, a Naturally Occurring Polyaromatic Derivative Related to Triterpenoids of the Serratane Series

[reaction: see text] The polyaromatic hydrocarbon 4,4'-dimethyldinaphtho[a,d]cycloheptane (1a) has been identified by NMR studies after isolation from an Oligocene sediment. The original symmetrical structure of 1a, which bears a central seven-membered ring, is closely related to higher plant triterpenoid precursor(s) of the serratane series and is believed to have been formed in the subsurface by a microbially mediated aromatization process.

Terrane processes at the margins of Gondwana: introduction

The process of terrane accretion is vital to the understanding of the formation of continental crust. Accretionary orogens affect over half of the globe and have a distinctively different evolution to Wilson-type orogens. It is increasingly evident that accretionary orogenesis has played a significant role in the formation of the continents. The Pacific-margin of Gondwana preserves a major orogenic belt, termed here the ‘Australides’, which was an active site of terrane accretion from Neoproterozoic to Late Mesozoic times, and comparable in scale to the Rockies from Mexico to Alaska, or the Variscan-Appalachian orogeny. The New Zealand sector of this orogenic belt was one of the birthplaces of terrane theory and the Australide orogeny overall continues to be an important testing ground for terrane studies. This volume summarizes the history and principles of terrane theory and presents 16 new works that review and synthesize the current state of knowledge for the Gondwana margin, from Australia through New Zealand and Antarctica to South America, examining the evolution of the whole Gondwana margin through time.

Addition of hydrogen sulfide to juglone

Evidence of the addition of hydrogen sulfide to 5-hydroxy-1,4-naphthoquinone (juglone) in aqueous solution was obtained by nuclear magnetic resonance spectrometry (NMR), electron paramagnetic resonance spectrometry (EPR), UV-visible absorbance spectroscopy, and kinetic measurements. Although numerous addition reactions of thiolated alkane and aromatic compounds to quinones have been previously reported, this study indicates that inorganic forms of S(-II) act as nucleophiles and electrophiles in addition reactions to the alpha,beta-conjugated system of the quinone. The results obtained are consistent with competing Michael and radical addition reactions, with radical addition favored with increasing pH. The simplest structure that simulated the NMR spectrum was a sulfur molecule containing sulfur bonded between two juglone molecules at C-2 or C-3, while EPR measurements of aqueous reaction solutions indicated the presence of a stable semiquinone that contained a sulfur substituent at C-2 or C-3. Quinones are present in trace amounts in natural organic matter, and the addition of S(-II) has important implications with respect to transport and transformation of a variety of compounds that react with natural organic matter.

Mantle wedge control on back-arc crustal accretion

At mid-ocean ridges, plate separation leads to upward advection and pressure-release partial melting of fertile mantle material; the melt is then extracted to the spreading centre and the residual depleted mantle flows horizontally away. In back-arc basins, the subducting slab is an important control on the pattern of mantle advection and melt extraction, as well as on compositional and fluid gradients. Modelling studies predict significant mantle wedge effects on back-arc spreading processes. Here we show that various spreading centres in the Lau back-arc basin exhibit enhanced, diminished or normal magma supply, which correlates with distance from the arc volcanic front but not with spreading rate. To explain this correlation we propose that depleted upper-mantle material, generated by melt extraction in the mantle wedge, is overturned and re-introduced beneath the back-arc basin by subduction-induced corner flow. The spreading centres experience enhanced melt delivery near the volcanic front, diminished melting within the overturned depleted mantle farther from the corner and normal melting conditions in undepleted mantle farther away. Our model explains fundamental differences in crustal accretion variables between back-arc and mid-ocean settings.

Respiration of arsenate and selenate by hyperthermophilic archaea

A novel, strictly anaerobic, hyperthermophilic, facultative organotrophic archaeon was isolated from a hot spring at Pisciarelli Solfatara, Naples, Italy. The rod-shaped cells grew chemolithoautotrophically with carbon dioxide as carbon source, hydrogen as electron donor and arsenate, thiosulfate or elemental sulfur as electron acceptor. H2S was formed from sulfur or thiosulfate, arsenite from arsenate. Organotrophically, the new isolate grew optimally in the presence of an inorganic electron acceptor like sulfur, selenate or arsenate. Cultures, grown on arsenate and thiosulfate or arsenate and L-cysteine, precipitated realgar (As2S2). During growth on selenate, elemental selenium was produced. The G+C content of the DNA was 58.3 mol%. Due to 16S rRNA gene sequence analysis combined with physiological and morphological criteria, the new isolate belongs to the Thermoproteales order. It represents a new species within the genus Pyrobaculum, the type species of which we name Pyrobaculum arsenaticum (type strain PZ6*, DSM 13514, ATCC 700994). Comparative studies with different Pyrobaculum-species showed, that Pyrobaculum aerophilum was also able to grow organotrophically under anaerobic culture conditions in the presence of arsenate, selenate and selenite. During growth on selenite, elemental selenium was formed as final product. In contrast to P. arsenaticum, P. aerophilum could use selenate or arsenate for lithoautotrophic growth with carbon dioxide and hydrogen.

Effects of micronutrients on growth and starch hydrolysis of Thermococcus guaymasensis and Thermococcus aggregans

The effects of micronutrients on growth of Thermococcus guaymasensis and Thenrmococcus aggregans in a starch-containing medium were investigated. A trace minerals solution, a vitamins solution and calcium chloride were omitted from the medium or added in different amounts. The growth rates of both species were not affected over a significant range of concentrations of these compounds, but appreciable inhibition of growth was observed after the addition of elemental sulfur to the medium. T. guaymasensis exhibited a significant tolerance to high amounts of trace element and vitamin solutions but growth was inhibited by the omission of these compounds from the medium. Moreover, both amylolytic and pullulytic activities increased in the presence of 6-fold higher amounts of trace element and vitamin solutions, compared to the concentrations used in the usual medium. In T. aggregans, both enzymatic activities were enhanced in the presence of either increased (4-fold) amounts of trace element and vitamin solutions, or after the addition of elemental sulfur to the medium. Furthermore, larger activities of starch-hydrolysing enzymes were detected with a 10-fold higher concentration of calcium chloride, compared to the usual medium, in the absence of trace element and vitamin solutions. When both Thermococcus species were tested for the tolerance to specific cations and oxyanions, T. guaymasensis exhibited higher tolerance compared to T. aggregans, the former strain being capable to grow in the presence of 6 mM Ni2+, 4mM Cu2+, 1.5 mM SeO4(2-), and 1.5 mM MoO4(2-). The content of total cell proteins followed the pattern of starch-hydrolysing enzymes and an over-expression of proteins in the range of 35, 50 and 70 kDa was observed.

Hyperthermophilic life at deep-sea hydrothermal vents

The discovery of deep-sea hydrothermal vents in 1977 considerably modified the views on deep-sea biology. For the first time, an ecosystem totally based on primary production achieved by chemosynthetic bacteria was discovered. Besides the warm vents where dense invertebrate communities and their symbiotic bacteria are located, the "black smokers" venting fluids at temperatures up to 350 degrees C were also investigated by microbiologists. Several strains of hyperthermophilic Archaea (methanogens, sulfate-reducers, sulfur-reducers) were isolated from smokers and surrounding materials. Deep-sea isolates that have been totally described, have been assigned to new species, within genera previously found in coastal geothermally heated environments. However, some species appear to exist in both deep and shallow ecosystems. Some deep-sea hyperthermophiles appear to be adapted to hydrostatic pressure and showed a barophilic response. The distribution of hyperthermophiles in the hot ecosystems of the planet, and their adaptation to pressure are presented and discussed.