77 research outputs found
Chemosynthetic communities in the deep sea : ecological studies
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1989Deep-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.Portions of this dissertation were supported by grants from NSF, ONR, Sea Grant, and the WHOI Ocean Ventures Fund, by the WHOI Education Office, the WHOI Biology Department, and an NSF graduate fellowship
an atlas of protected hydrothermal vents
Abstract Active hydrothermal vents are valued worldwide because of the importance of their biodiversity and their influence on scientific discovery and insight about life on Earth and elsewhere in the Universe. There exist at least 20 areas and area networks with conservation measures for deep-sea hydrothermal vents, established by 12 countries and three Regional Fisheries Management Organisations, in six oceanic regions. Area-based management tools (ABMT) implemented by these countries illustrate multiple categories and means of protection and management of these rare and vulnerable habitats. Some ABMTs only regulate bottom and deep-trawling fisheries activities, others manage additional activities such as mining, scientific research, and bioprospecting, while still others protect active hydrothermal vents through broad conservation interventions. This atlas summarizes the "who", "what", "when", "where" of protected hydrothermal vents worldwide and underscores recognition of the importance of hydrothermal-vent ecosystems by coastal States
The influence of vent fluid chemistry on trophic structure at two deep-sea hydrothermal vent fields on the Mid-Cayman Rise
The two known deep-sea hydrothermal vent fields along the Mid-Cayman Rise are separated by a distance of only
21 km, yet their chemistry and faunal diversity are distinct. The deeper of the two vent fields, Piccard (with active
venting from Beebe Vents, Beebe Woods and Beebe Sea), at 4980 m is basalt hosted. The shallower vent field,
Von Damm, at 2300 m appears to have an ultramafic influence. The Von Damm vent field can be separated into
two sites: The Spire and The Tubeworm Field. The dominant vent fluids at the Tubeworm Field are distinct from
those at the Spire, as a result of fluid modification in the sub-surface. Von Damm and Piccard vent fields support
abundant invertebrates, sharing the same biomass-dominant shrimp species, Rimicaris hybisae. Although there
are some other shared species (squat lobsters (Munidopsis sp.) and gastropods (Provanna sp. and Iheyaspira sp.))
between the vent fields, they are much more abundant at one site than the other
SyPRID sampler: A large-volume, high-resolution, autonomous, deep-ocean precision plankton sampling system
AbstractThe current standard for large-volume (thousands of cubic meters) zooplankton sampling in the deep sea is the MOCNESS, a system of multiple openingâclosing nets, typically lowered to within 50m of the seabed and towed obliquely to the surface to obtain low-spatial-resolution samples that integrate across 10s of meters of water depth. The SyPRID (Sentry Precision Robotic Impeller Driven) sampler is an innovative, deep-rated (6000m) plankton sampler that partners with the Sentry Autonomous Underwater Vehicle (AUV) to obtain paired, large-volume plankton samples at specified depths and survey lines to within 1.5m of the seabed and with simultaneous collection of sensor data. SyPRID uses a perforated Ultra-High-Molecular-Weight (UHMW) plastic tube to support a fine mesh net within an outer carbon composite tube (tube-within-a-tube design), with an axial flow pump located aft of the capture filter. The pump facilitates flow through the system and reduces or possibly eliminates the bow wave at the mouth opening. The cod end, a hollow truncated cone, is also made of UHMW plastic and includes a collection volume designed to provide an area where zooplankton can collect, out of the high flow region. SyPRID attaches as a saddle-pack to the Sentry vehicle. Sentry itself is configured with a flight control system that enables autonomous survey paths to low altitudes. In its verification deployment at the Blake Ridge Seep (2160m) on the US Atlantic Margin, SyPRID was operated for 6h at an altitude of 5m. It recovered plankton samples, including delicate living larvae, from the near-bottom stratum that is seldom sampled by a typical MOCNESS tow. The prototype SyPRID and its next generations will enable studies of plankton or other particulate distributions associated with localized physico-chemical strata in the water column or above patchy habitats on the seafloor
The spatial scale of genetic subdivision in populations of Ifremeria nautilei, a hydrothermal-vent gastropod from the southwest Pacific
<p>Abstract</p> <p>Background</p> <p>Deep-sea hydrothermal vents provide patchy, ephemeral habitats for specialized communities of animals that depend on chemoautotrophic primary production. Unlike eastern Pacific hydrothermal vents, where population structure has been studied at large (thousands of kilometres) and small (hundreds of meters) spatial scales, population structure of western Pacific vents has received limited attention. This study addresses the scale at which genetic differentiation occurs among populations of a western Pacific vent-restricted gastropod, <it>Ifremeria nautilei</it>.</p> <p>Results</p> <p>We used mitochondrial and DNA microsatellite markers to infer patterns of gene flow and population subdivision. A nested sampling strategy was employed to compare genetic diversity in discrete patches of <it>Ifremeria nautilei </it>separated by a few meters within a single vent field to distances as great as several thousand kilometres between back-arc basins that encompass the known range of the species. No genetic subdivisions were detected among patches, mounds, or sites within Manus Basin. Although <it>I. nautilei </it>from Lau and North Fiji Basins (~1000 km apart) also exhibited no evidence for genetic subdivision, these populations were genetically distinct from the Manus Basin population.</p> <p>Conclusions</p> <p>An unknown process that restricts contemporary gene flow isolates the Manus Basin population of <it>Ifremeria nautilei </it>from widespread populations that occupy the North Fiji and Lau Basins. A robust understanding of the genetic structure of hydrothermal vent populations at multiple spatial scales defines natural conservation units and can help minimize loss of genetic diversity in situations where human activities are proposed and managed.</p
Ecological risk assessment for deep-sea mining
Ecological risk assessment for deep-sea mining is challenging, given the data-poor state of knowledge of deep-sea ecosystem structure, process, and vulnerability. Polling and a scale-intensity-consequence approach (SICA) were used in an expert elicitation survey to rank risk sources and perceived vulnerabilities of habitats associated with seabed nodule, sulfide, and crust mineral resources. Experts identified benthic habitats associated with seabed minerals as most vulnerable to habitat removal with a high degree of certainty. Resource-associated benthic and pelagic habitats were also perceived to be at risk from plumes generated during mining activities, although there was not always consensus regarding vulnerabilities to specific risk sources from different types of plumes. Even for risk sources where habitat vulnerability measures were low, high uncertainties suggest that these risks may not yet be dismissed. Survey outcomes also underscore the need for risk assessment to progress from expert opinion with low certainty to data-rich and ecosystem-relevant scientific research assessments to yield much higher certainty. This would allow for design and deployment of effective precautionary and mitigation efforts in advance of commercial exploitation, and adaptive management strategies would allow for regulatory and guideline modifications in response to new knowledge and greater certainty
Amplicon sequencing of 42 nuclear loci supports directional gene flow between South Pacific populations of a hydrothermal vent limpet
In the past few decades, population genetics and phylogeographic studies have improved our knowledge of connectivity and population demography in marine environments. Studies of deepâsea hydrothermal vent populations have identified barriers to gene flow, hybrid zones, and demographic events, such as historical population expansions and contractions. These deepâsea studies, however, used few loci, which limit the amount of information they provided for coalescent analysis and thus our ability to confidently test complex population dynamics scenarios. In this study, we investigated population structure, demographic history, and gene flow directionality among four Western Pacific hydrothermal vent populations of the vent limpet Lepetodrilus aff. schrolli. These vent sites are located in the Manus and Lau backâarc basins, currently of great interest for deepâsea mineral extraction. A total of 42 loci were sequenced from each individual using highâthroughput amplicon sequencing. Amplicon sequences were analyzed using both genetic variant clustering methods and evolutionary coalescent approaches. Like most previously investigated vent species in the South Pacific, L. aff. schrolli showed no genetic structure within basins but significant differentiation between basins. We inferred significant directional gene flow from Manus Basin to Lau Basin, with low to no gene flow in the opposite direction. This study is one of the very few marine population studies using >10 loci for coalescent analysis and serves as a guide for future marine population studies
A strategy for the conservation of biodiversity on mid-ocean ridges from deep-sea mining
Mineral exploitation has spread from land to shallow coastal waters and is now planned for the offshore, deep seabed. Large seafloor areas are being approved for exploration for seafloor mineral deposits, creating an urgent need for regional environmental management plans. Networks of areas where mining and mining impacts are prohibited are key elements of these plans. We adapt marine reserve design principles to the distinctive biophysical environment of mid-ocean ridges, offer a framework for design and evaluation of these networks to support conservation of benthic ecosystems on mid-ocean ridges, and introduce projected climate-induced changes in the deep sea to the evaluation of reserve design. We enumerate a suite of metrics to measure network performance against conservation targets and network design criteria promulgated by the Convention on Biological Diversity. We apply these metrics to network scenarios on the northern and equatorial Mid-Atlantic Ridge, where contractors are exploring for seafloor massive sulfide (SMS) deposits. A latitudinally distributed network of areas performs well at (i) capturing ecologically important areas and 30 to 50% of the spreading ridge areas, (ii) replicating representative areas, (iii) maintaining along-ridge population connectivity, and (iv) protecting areas potentially less affected by climate-related changes. Critically, the network design is adaptive, allowing for refinement based on new knowledge and the location of mining sites, provided that design principles and conservation targets are maintained. This framework can be applied along the global mid-ocean ridge system as a precautionary measure to protect biodiversity and ecosystem function from impacts of SMS mining
Deep-Sea Mining With No Net Loss of BiodiversityâAn Impossible Aim
Deep-sea mining is likely to result in biodiversity loss, and the significance of this to ecosystem function is not known. âOut of kindâ biodiversity offsets substituting one ecosystem type (e.g., coral reefs) for another (e.g., abyssal nodule fields) have been proposed to compensate for such loss. Here we consider a goal of no net loss (NNL) of biodiversity and explore the challenges of applying this aim to deep seabed mining, based on the associated mitigation hierarchy (avoid, minimize, remediate). We conclude that the industry cannot at present deliver an outcome of NNL. This results from the vulnerable nature of deep-sea environments to mining impacts, currently limited technological capacity to minimize harm, significant gaps in ecological knowledge, and uncertainties of recovery potential of deep-sea ecosystems. Avoidance and minimization of impacts are therefore the only presently viable means of reducing biodiversity losses from seabed mining. Because of these constraints, when and if deep-sea mining proceeds, it must be approached in a precautionary and step-wise manner to integrate new and developing knowledge. Each step should be subject to explicit environmental management goals, monitoring protocols, and binding standards to avoid serious environmental harm and minimize loss of biodiversity. âOut of kindâ measures, an option for compensation currently proposed, cannot replicate biodiversity and ecosystem services lost through mining of the deep seabed and thus cannot be considered true offsets. The ecosystem functions provided by deep-sea biodiversity contribute to a wide range of provisioning services (e.g., the exploitation of fish, energy, pharmaceuticals, and cosmetics), play an essential role in regulatory services (e.g., carbon sequestration) and are important culturally. The level of âacceptableâ biodiversity loss in the deep sea requires public, transparent, and well-informed consideration, as well as wide agreement. If accepted, further agreement on how to assess residual losses remaining after the robust implementation of the mitigation hierarchy is also imperative. To ameliorate some of the inter-generational inequity caused by mining-associated biodiversity losses, and only after all NNL measures have been used to the fullest extent, potential compensatory actions would need to be focused on measures to improve the knowledge and protection of the deep sea and to demonstrate benefits that will endure for future generations
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