Van Dover Cindy L.

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Van Dover
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Cindy L.
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  • Preprint
    Diverse styles of submarine venting on the ultraslow spreading Mid-Cayman Rise
    ( 2010-06-24) German, Christopher R. ; Bowen, Andrew D. ; Coleman, Max ; Honig, D. L. ; Huber, Julie A. ; Jakuba, Michael V. ; Kinsey, James C. ; Kurz, Mark D. ; Leroy, S. ; McDermott, Jill M. ; Mercier de Lepinay, B. ; Nakamura, Ko-ichi ; Seewald, Jeffrey S. ; Smith, J. L. ; Sylva, Sean P. ; Van Dover, Cindy L. ; Whitcomb, Louis L. ; Yoerger, Dana R.
    Thirty years after the first discovery of high-temperature submarine venting, the vast majority of the global Mid Ocean Ridge remains unexplored for hydrothermal activity. Of particular interest are the world’s ultra-slow spreading ridges which were the last to be demonstrated to host high-temperature venting, but may host systems particularly relevant to pre-biotic chemistry and the origins of life. Here we report first evidence for diverse and very deep hydrothermal vents along the ~110 km long, ultra-slow spreading Mid-Cayman Rise. Our data indicate that the Mid- Cayman Rise hosts at least three discrete hydrothermal sites, each representing a different type of water-rock interaction, including both mafic and ultra-mafic systems and, at ~5000 m, the deepest known hydrothermal vent. Although submarine hydrothermal circulation, in which seawater percolates through and reacts with host lithologies, occurs on all mid-ocean ridges, the diversity of vent-types identified here and their relative geographic isolation make the Mid-Cayman Rise unique in the oceans. These new sites offer prospects for: an expanded range of vent-fluid compositions; varieties of abiotic organic chemical synthesis and extremophile microorganisms; and unparalleled faunal biodiversity - all in close proximity.
  • Thesis
    Chemosynthetic communities in the deep sea : ecological studies
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1989-05) Van Dover, Cindy L.
    Deep-sea benthic communities dependent on chemosynthetic primary production are associated with areas of active venting of chemically-modified seawater. Patterns in the distribution of species that occur at hydrothermal vents can be used to predict locations of the vent sites. Patterns in the distributions of species among vents along ridge segments are used to identify the spatial scales over which biological and physical processes operate to control community composition. Within a vent, a zonation in species distributions correlates with gradients of temperature and water chemistry. Along a given ridge segment, vent communities share the same species pool, but the relative abundance of each species varies from one site to another. On a basin-wide scale, the fauna of vent communities represent biological continua, where gradual morphological and genetic differentiation in species is correlated with increasing distance between vent sites. Differentiation of distinctive faunals assemblages at vents occursat a global scale. Populations of species at vents are established and maintained through recruitment of larval stages. To study recruitment processes at vent sites, slate panels were placed at and near vent sites on the seafloor for varying lengths of time. Size distributions of animals on retrieved panels suggest that recruitment is an intermittent or continuous process rather than a single episodic event. Recruitment of vent-associated species was greater on panels placed within vent communities compared to panels placed adjacent to these communities, a pattern consistent with the observed maintenance of communities in discrete regions of hydrothermal flux. The trophic structure of chemosynthetic communities can be complex. Primary production by chemoautotrophic bacteria can take place within host tissues of some invertebrates as well as on surfaces and in the water column and subsurface conduits. Carbon and nitrogen isotopic compositions of host tissues can be used to demonstrate the dependence of symbiont species on chemosynthetically-derived organic material. From the patterns in the isotopic compositions of vent and seep symbionts, potential sources of inorganic carbon are identified. Deep-water dissolved inorganic carbon serves as a large, isotopically buffered pool of inorganic carbon used by tubeworms and bivalves at hydrothermal communities of Juan de Fuca, Gorda, Guaymas Basin, East Pacific Rise, Galapagos, and Marianas vents. Variability in tubeworm carbon isotopic compositions at seeps may be attributed to significant contributions of isotopically variable DIC in seep effluents. Isotopic techniques are also used to explore trophic relationships among a variety of heterotrophic and symbiont-containing fauna at Hanging Gardens on the East Pacific Rise and at Marianas vents. Carbon isotopic measurements suggest that free-living bacteria are important sources of food at both sites. Nitrogen isotopic analyses show that the Marianas community may be simpler in trophic structure than the Hanging Gardens community. The biomass of most known vent sites is conspicuously dominated by large invertebrates with symbiotic bacteria. At vent sites on the Mid-Atlantic Ridge, large swarms of shrimp dominate the biomass. There is no evidence for endosymbionts in these shrimp, based on analyses of morphology, stable isotopes, lipopolysaccharides and ribulose- l, 5-bisphosphate carboxylase activity. Instead, the shrimp appear to be normal heterotrophs, grazing on free-living microorganisms associated with black smoker chimneys. High bacterial productivity within the sulfide matrix of the chimneys must be required to sustain the shrimp populations. Hydrothermal vent environments exhibit some of the most extreme gradients of temperature and chemistry found in the biosphere. Many of the animals that colonize vent sites exhibit adaptations that allow them to exist in such an unusual environment. A novel eye in shrimp from Mid-Atlantic Ridge vents is described. The eye, comprised of a pair of large organs within the cephalothorax, contains a visual pigment but lacks image-forming optics. The eye appears to be adapted for detection of low-level illumination and is suggested to have evolved in response to a source of radiation associated with the environment of hydrothermal vents. An electronic camera was used to detect light emitted from high-temperature (350°C) plumes that rise from the orifice of black smoker chimneys on the Endeavour Segment of the Juan de Fuca Ridge. Calculations suggest that thermal radiation from hot water may account for most of the light detected and that this light may be sufficient for geothermally-drive photosynthesis by bacteria.
  • 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.
  • Article
    Making use of relicts: brisingid seastars aggregate on hydrothermally inactive sulfide chimneys near black smokers
    (Frontiers Media, 2022-02-17) Woods, Daniel ; Cheadle, Michael J. ; John, Barbara E. ; German, Christopher R. ; Van Dover, Cindy L.
    When hydrothermal activity ceases at black-smoker chimneys on mid-ocean ridges, populations of associated invertebrates hosting chemoautotrophic endosymbionts decline and then disappear, but the chimneys can persist on the seabed as relicts. Suspension-feeding brisingid seastars colonize hydrothermally inactive (relict) chimneys on the East Pacific Rise (EPR), though their distribution relative to available hard substrata and proximity to hydrothermal activity is poorly documented. In this study, brisingid abundance on sulfide and basalt substrata was assessed along an ∼3,700 m ROV Jason II transect at the summit of Pito Seamount (SE Pacific; ∼2,275 m). Brisingids were non-randomly distributed, with highest densities (up to ∼300 m–2) on relict sulfides chimneys near active black smokers. Brisingids were relatively uncommon on basalt substrata, and absent on black smokers. We infer that both relict sulfide structures and proximity to black smokers play key roles in the maintenance of dense brisingid populations on Pito Seamount and in similar environments on the EPR. Our observations suggest that experimental introduction of “artificial” relict chimneys providing microtopographic relief could test whether such an approach might mitigate potential impacts of mineral extraction on populations of suspension-feeding invertebrates.
  • Article
    Seascape ecology in the vicinity of a Blake Ridge cold seep
    (Frontiers Media, 2023-11-05) Johnson, Kellie ; Taylor, Avery ; Socha, Annika ; Barkyoumb, Ellie ; Nakamura, Koichi ; Kaiser, Carl L. ; German, Christopher R. ; Yoerger, Dana R. ; Lee Van Dover, Cindy
    Systematic surveys of the distribution of epibenthic megafaunal species relative to one another and to environmental variables in the deep sea can lead to inferences and testable hypotheses regarding factors that influence their distributions. Here we use a seascape approach to provide insight into the character and spatial extent of the influence of a chemosynthetic seep on the distribution of epibenthic megafauna and the nature of transition zones (ecotones). Faunal distributions were determined from georeferenced images of the seabed collected during a systematic survey (~ 400 m x 400 m) by the Autonomous Underwater Vehicle Sentry in the vicinity of a newly discovered methane bubble plume on the Blake Ridge Diapir. The survey area was found to include both seep and non-seep habitats. The sphere of influence of seep productivity on the surrounding benthic megafaunal assemblage was limited—on the order of 10’s of meters—based on ecotone analysis. Small but detectable redox anomalies in the water column (5 m above bottom) in the study area occurred on a similar horizontal scale. Distributions of background megafaunal taxa were non-random for many morphotypes and included both positive and negative associations between morphotypes and the seep habitat. Subtle variations in depth (<6 m) correlated with distributions of seep-associated vesicomyid clams, which occupy shallow depressions in the seabed. The seep habitat itself, comprising a patchy mosaic of megafaunal sub-communities (e.g., clam bed, mussel bed, background soft-sediment bathyal taxa) and transition zones, was at least as diverse as the surrounding non-seep habitat and contributes seep endemic morphotypes to regional biodiversity. While seep productivity may support prey fields for deep-diving beaked whales, any relationship between the seeps and whale feeding areas remains intriguing speculation. Like many other regions of the deep sea, Blake Ridge South has accumulated marine litter, including litter likely originating from scientific endeavors. The suite of observations and analyses deployed here underscore the importance of seep habitats in enriching regional biodiversity, provide a glimpse of the non-random complexity of species distributions from a seascape perspective, and establish ecological baselines against which future studies may measure natural and anthropogenic changes in the seascape.