Bennett Sarah A.

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Bennett
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Sarah A.
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  • 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
    Trophic regions of a hydrothermal plume dispersing away from an ultramafic-hosted vent-system : Von Damm vent-site, Mid-Cayman Rise
    (John Wiley & Sons, 2013-02-22) Bennett, Sarah A. ; Coleman, Max ; Huber, Julie A. ; Reddington, Emily ; Kinsey, James C. ; McIntyre, Cameron P. ; Seewald, Jeffrey S. ; German, Christopher R.
    Deep-sea ultramafic-hosted vent systems have the potential to provide large amounts of metabolic energy to both autotrophic and heterotrophic microorganisms in their dispersing hydrothermal plumes. Such vent-systems release large quantities of hydrogen and methane to the water column, both of which can be exploited by autotrophic microorganisms. Carbon cycling in these hydrothermal plumes may, therefore, have an important influence on open-ocean biogeochemistry. In this study, we investigated an ultramafic-hosted system on the Mid-Cayman Rise, emitting metal-poor and hydrogen sulfide-, methane-, and hydrogen-rich hydrothermal fluids. Total organic carbon concentrations in the plume ranged between 42.1 and 51.1 μM (background = 43.2 ± 0.7 μM (n = 5)) and near-field plume samples with elevated methane concentrations imply the presence of chemoautotrophic primary production and in particular methanotrophy. In parts of the plume characterized by persistent potential temperature anomalies but lacking elevated methane concentrations, we found elevated organic carbon concentrations of up to 51.1 μM, most likely resulting from the presence of heterotrophic communities, their extracellular products and vent larvae. Elevated carbon concentrations up to 47.4 μM were detected even in far-field plume samples. Within the Von Damm hydrothermal plume, we have used our data to hypothesize a microbial food web in which chemoautotrophy supports a heterotrophic community of microorganisms. Such an active microbial food web would provide a source of labile organic carbon to the deep ocean that should be considered in any future studies evaluating sources and sinks of carbon from hydrothermal venting to the deep ocean.