Connelly Douglas P.

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Douglas P.

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  • Article
    Composition of hydrothermal fluids and mineralogy of associated chimney material on the East Scotia Ridge back-arc spreading centre
    (Elsevier, 2014-05-06) James, Rachael H. ; Green, Darryl R. H. ; Stock, Michael J. ; Alker, Belinda J. ; Banerjee, Neil R. ; Cole, Catherine ; German, Christopher R. ; Huvenne, Veerle A. I. ; Powell, Alexandra M. ; Connelly, Douglas P.
    The East Scotia Ridge is an active back-arc spreading centre located to the west of the South Sandwich island arc in the Southern Ocean. Initial exploration of the ridge by deep-tow surveys provided the first evidence for hydrothermal activity in a back-arc setting outside of the western Pacific, and we returned in 2010 with a remotely operated vehicle to precisely locate and sample hydrothermal sites along ridge segments E2 and E9. Here we report the chemical and isotopic composition of high- and low-temperature vent fluids, and the mineralogy of associated high-temperature chimney material, for two sites at E2 (Dog’s Head and Sepia), and four sites at E9 (Black & White, Ivory Tower, Pagoda and Launch Pad). The chemistry of the fluids is highly variable between the ridge segments. Fluid temperatures were ∼350 °C at all vent sites except Black & White, which was significantly hotter (383 °C). End-member chloride concentrations in E2 fluids (532–536 mM) were close to background seawater (540 mM), whereas Cl in E9 fluids was much lower (98–220 mM) indicating that these fluids are affected by phase separation. Concentrations of the alkali elements (Na, Li, K and Cs) and the alkaline earth elements (Ca, Sr and Ba) co-vary with Cl, due to charge balance constraints. Similarly, concentrations of Mn and Zn are highest in the high Cl fluids but, by contrast, Fe/Cl ratios are higher in E9 fluids (3.8–8.1 × 10−3) than they are in E2 fluids (1.5–2.4 × 10−3) and fluids with lowest Cl have highest Cu. Although both ridge segments are magmatically inflated, there is no compelling evidence for input of magmatic gases to the vent fluids. Fluid δD values range from 0.2‰ to 1.5‰, pH values (3.02–3.42) are not especially low, and F concentrations (34.6–54.4 μM) are lower than bottom seawater (62.8 μM). The uppermost sections of conjugate chimney material from E2, and from Ivory Tower and Pagoda at E9, typically exhibit inner zones of massive chalcopyrite enclosed within an outer zone of disseminated sulphide, principally sphalerite and pyrite, in an anhydrite matrix. By contrast, the innermost part of the chimneys that currently vent fluids with lowest Cl (Black & White and Launch Pad), is dominated by anhydrite. By defining and assessing the controls on the chemical composition of these vent fluids, and associated mineralisation, this study provides new information for evaluating the significance of hydrothermal processes at back-arc basins for ocean chemistry and the formation of seafloor mineral deposits.
  • Article
    Vailulu'u Seamount, Samoa : life and death on an active submarine volcano
    (National Academy of Sciences, 2006-04-13) Staudigel, Hubert ; Hart, Stanley R. ; Pile, Adele ; Bailey, Bradley E. ; Baker, Edward T. ; Brooke, Sandra ; Connelly, Douglas P. ; Haucke, Lisa ; German, Christopher R. ; Hudson, Ian ; Jones, Daniel O. B. ; Koppers, Anthony A. P. ; Konter, Jasper G. ; Lee, Ray ; Pietsch, Theodore W. ; Tebo, Bradley M. ; Templeton, Alexis S. ; Zierenberg, Robert ; Young, Craig M.
    Submersible exploration of the Samoan hotspot revealed a new, 300-m-tall, volcanic cone, named Nafanua, in the summit crater of Vailulu'u seamount. Nafanua grew from the 1,000-m-deep crater floor in <4 years and could reach the sea surface within decades. Vents fill Vailulu'u crater with a thick suspension of particulates and apparently toxic fluids that mix with seawater entering from the crater breaches. Low-temperature vents form Fe oxide chimneys in many locations and up to 1-m-thick layers of hydrothermal Fe floc on Nafanua. High-temperature (81°C) hydrothermal vents in the northern moat (945-m water depth) produce acidic fluids (pH 2.7) with rising droplets of (probably) liquid CO2. The Nafanua summit vent area is inhabited by a thriving population of eels (Dysommina rugosa) that feed on midwater shrimp probably concentrated by anticyclonic currents at the volcano summit and rim. The moat and crater floor around the new volcano are littered with dead metazoans that apparently died from exposure to hydrothermal emissions. Acid-tolerant polychaetes (Polynoidae) live in this environment, apparently feeding on bacteria from decaying fish carcasses. Vailulu'u is an unpredictable and very active underwater volcano presenting a potential long-term volcanic hazard. Although eels thrive in hydrothermal vents at the summit of Nafanua, venting elsewhere in the crater causes mass mortality. Paradoxically, the same anticyclonic currents that deliver food to the eels may also concentrate a wide variety of nektonic animals in a death trap of toxic hydrothermal fluids.
  • Article
    The discovery of new deep-sea hydrothermal vent communities in the Southern Ocean and implications for biogeography
    (Public Library of Science, 2012-01-03) Rogers, Alex D. ; Tyler, Paul A. ; Connelly, Douglas P. ; Copley, Jonathan T. ; James, Rachael H. ; Larter, Robert D. ; Linse, Katrin ; Mills, Rachel A. ; Naveira Garabato, Alberto C. ; Pancost, Richard D. ; Pearce, David A. ; Polunin, Nicholas V. C. ; German, Christopher R. ; Shank, Timothy M. ; Boersch-Supan, Philipp H. ; Alker, Belinda J. ; Aquilina, Alfred ; Bennett, Sarah A. ; Clarke, Andrew ; Dinley, Robert J. J. ; Graham, Alastair G. C. ; Green, Darryl R. H. ; Hawkes, Jeffrey A. ; Hepburn, Laura ; Hilario, Ana ; Huvenne, Veerle A. I. ; Marsh, Leigh ; Ramirez-Llodra, Eva ; Reid, William D. K. ; Roterman, Christopher N. ; Sweeting, Christopher J. ; Thatje, Sven ; Zwirglmaier, Katrin
    Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR) in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more complex than previously recognised.
  • Article
    Detection and quantification of a release of carbon dioxide gas at the seafloor using pH eddy covariance and measurements of plume advection
    (Elsevier, 2021-10-22) Koopmans, Dirk ; Meyer, Volker ; Schaap, Allison ; Dewar, Marius ; Färber, Paul ; Long, Matthew H. ; Gros, Jonas ; Connelly, Douglas P. ; Holtappels, Moritz
    We detected a controlled release of CO2 (g) with pH eddy covariance. We quantified CO2 emission using measurements of water velocity and pH in the plume of aqueous CO2 generated by the bubble streams, and using model predictions of vertical CO2 dissolution and its dispersion downstream. CO2 (g) was injected 3 m below the floor of the North Sea at rates of 5.7–143 kg d − 1. Instruments were 2.6 m from the center of the bubble streams. In the absence of injected CO2, pH eddy covariance quantified the proton flux due to naturally-occurring benthic organic matter mineralization (equivalent to a dissolved inorganic carbon flux of 7.6 ± 3.3 mmol m − 2 d − 1, s.e., n = 33). At the lowest injection rate, the proton flux due to CO2 dissolution was 20-fold greater than this. To accurately quantify emission, the kinetics of the carbonate system had to be accounted for. At the peak injection rate, 73 ± 13% (s.d.) of the injected CO2 was emitted, but when kinetics were neglected, the calculated CO2 emission was one-fifth of this. Our results demonstrate that geochemical techniques can detect and quantify very small seafloor sources of CO2 and attribute them to natural or abiotic origins.
  • Article
    Hydrothermal activity on the ultra-slow spreading southern Knipovich Ridge
    (American Geophysical Union, 2007-08-28) Connelly, Douglas P. ; German, Christopher R. ; Asada, Miho ; Okino, K. ; Egorov, A. ; Naganuma, T. ; Pimenov, N. ; Cherkashev, G. ; Tamaki, K.
    We report first evidence for hydrothermal activity from the southern Knipovich Ridge, an ultra-slow spreading ridge segment in the Norwegian-Greenland Sea. Evidence comes from optical backscatter anomalies collected during a systematic side-scan sonar survey of the ridge axis, augmented by the identification of biogeochemical tracers in the overlying water column that are diagnostic of hydrothermal plume discharge (Mn, CH4, ATP). Analysis of coregistered geologic and oceanographic data reveals that the signals we have identified are consistent with a single high-temperature hydrothermal source, located distant from any of the axial volcanic centers that define second-order segmentation along this oblique ridge system. Rather, our data indicate a hydrothermal source associated with highly tectonized seafloor that may be indicative of serpentinizing ultramafic outcrops. Consistent with this hypothesis, the hydrothermal plume signals we have detected exhibit a high methane to manganese ratio of 2–3:1. This is higher than that typical of volcanically hosted vent sites and provides further evidence that the source of the plume signals reported here is most probably a high-temperature hydrothermal field that experiences some ultramafic influence (compare to Rainbow and Logachev sites, Mid-Atlantic Ridge). While such sites have previously been invoked to be common on the SW Indian Ridge, this may be the first such site to be located along the Arctic ultra-slow spreading ridge system.
  • Article
    Hydrothermal vent fields and chemosynthetic biota on the world's deepest seafloor spreading centre
    (Nature Publishing Group, 2012-01-10) Connelly, Douglas P. ; Copley, Jonathan T. ; Murton, Bramley J. ; Stansfield, Kate ; Tyler, Paul A. ; German, Christopher R. ; Van Dover, Cindy L. ; Amon, Diva ; Furlong, Maaten ; Grindlay, Nancy ; Hayman, Nicholas W. ; Huhnerbach, Veit ; Judge, Maria ; Le Bas, Tim ; McPhail, Stephen ; Meier, Alexandra ; Nakamura, Ko-ichi ; Nye, Verity ; Pebody, Miles ; Pedersen, Rolf B. ; Plouviez, Sophie ; Sands, Carla M. ; Searle, Roger C. ; Stevenson, Peter ; Taws, Sarah ; Wilcox, Sally
    The Mid-Cayman spreading centre is an ultraslow-spreading ridge in the Caribbean Sea. Its extreme depth and geographic isolation from other mid-ocean ridges offer insights into the effects of pressure on hydrothermal venting, and the biogeography of vent fauna. Here we report the discovery of two hydrothermal vent fields on the Mid-Cayman spreading centre. The Von Damm Vent Field is located on the upper slopes of an oceanic core complex at a depth of 2,300 m. High-temperature venting in this off-axis setting suggests that the global incidence of vent fields may be underestimated. At a depth of 4,960 m on the Mid-Cayman spreading centre axis, the Beebe Vent Field emits copper-enriched fluids and a buoyant plume that rises 1,100 m, consistent with > 400 °C venting from the world’s deepest known hydrothermal system. At both sites, a new morphospecies of alvinocaridid shrimp dominates faunal assemblages, which exhibit similarities to those of Mid-Atlantic vents.