Deep-sea Sites Research Articles

Meiofauna communities of continental slope and deep-sea sites off SE Brazil

There is little meiofauna data from the southwest Atlantic, and especially lacking are studies examining deep-sea communities. In this study, the structure of meiofauna communities, particularly nematodes, was analyzed from data derived from 101 samples (48 samples on the continental-slope and 53 samples at a deep-sea site) collected at Campos Basin, SE Brazil. Differences in the meiofauna densities and in the number of taxa between continental slope and deep-sea sites depended on the taxonomic level examined. While total meiofauna abundance did not differ significantly between sites, nematode densities were significantly higher in the deep sea (mean of 157 inds.10 cm −2) than on the slope (mean of 129 inds.10 cm −2). The number of meiofauna taxa was significantly higher at the continental slope site. Yet for the most abundant meiofaunal group, the nematodes, whilst the number of families did not differ between continental slope and deep sites, the number of genera was significantly higher in the deep sea. The remarkable resemblance between the dominant nematodes ( Halalaimus, Acantholaimus, Daptonema, Theristus and Sabatieria) from SE Brazil and other deep sea studies confirmed earlier suggestions of a typical deep-sea nematode community with a broad geographical distribution. Multivariate analysis derived from meiofauna and nematode data showed that the structure of the fauna differed significantly between sites. Correlations detected between meiofauna and some sediment properties, such as grain size and sediment heterogeneity, although significant, were very low.

Viruses, prokaryotes and DNA in the sediments of a deep‐hypersaline anoxic basin (DHAB) of the Mediterranean Sea

Viral and prokaryote abundance were investigated in a deep-hypersaline anoxic basin of the Eastern Mediterranean Sea (DHAB Atalante basin at c. 3000 m depth). This system was compared with two nearby deep-sea sites characterized by oxic conditions. Viral abundance and virus to prokaryote abundance ratio in hypersaline anoxic sediments displayed values close to those reported in oxic sites. The analysis of vertical profiles of viral abundance in the Atalante basin revealed the lack of significant changes with depth in the sediment, suggesting that benthic viruses in these anoxic and hypersaline conditions are preserved or resistant to decay. The anoxic basin displayed also very high concentrations of labile organic components (proteins and lipids) and extracellular DNA. These findings suggest that the DHAB sediments represent a reservoir for long-term preservation of benthic viruses and nucleic acids.

Rates of organic carbon oxidation in deep sea sediments in the eastern North Atlantic from pore water profiles of O 2 and the δ13C of dissolved inorganic carbon

The remineralization rate of sedimentary organic carbon ( R org) and the depth-integrated, diffusion-supplied O 2 consumption rate (IOC) during microbial metabolism in sediments was investigated in three deep-sea sites at 1100, 2000 and 3500 m water depth in the eastern north Atlantic during the spring and summer 1998. In-situ pore water O 2 profiles yielded an IOC of 0.45±0.07 mmol O 2 m −2 day −1 at the deepest site ( n=3) and ca. 1–1.5 mmol O 2 m −2 day −1 at the shallowest site ( n=2). The R org was independently estimated at all three sites from ex-situ pore water profiles of the isotopic composition of total dissolved inorganic carbon ( δ 13C T), assuming that the concentration and isotopic composition of pore water C T with depth in the sediment was controlled only by microbial oxidation of isotopically depleted sedimentary organic carbon. The R org was thus estimated to be ca. 0.5–0.6 mmol C m −2 day −1 at the shallowest site and ca. 0.3–0.4 mmol C m −2 day −1 at the two deeper sites. Stoichiometric and isotopic constraints indicated that oxic remineralization of sedimentary organic matter was the dominant metabolic pathway in the sediments at 3500 m water depth. Similarly, stoichiometric and isotopic constraints suggested that the R org estimates from the ex-situ pore water δ 13C T profiles from 1100 and 2000 m water depth were likely to be minimum values and provided evidence for the occurrence of post-oxic remineralization processes. Post-oxic metabolism in the sediments of these sites could be linked to, or even augmented by, the non-diffusive mode of supply of organic matter mediated by infaunal organisms below the oxic sediment layer.

Circulation and variability in the Chile Basin

Current observations at several depths between 250 and 3750m are reported from a 30°S, deep sea site 150km off the Chile coast for the period July 1993–June 2001. These results are used with current observations from a nearby slope site, satellite altimeter data, and hydrographic and Acoustic Doppler Current Profiler data from the WOCE P6E section along 32.5°S to address mean and variable flow in the Chile Basin. Strong current variability in the upper ocean for periods more than 100 days is explained in terms of remotely forced Rossby waves, local baroclinic instabilities of coastal currents and variable wind forcing. Intraseasonal to seasonal current variability at the deep ocean site was greatest during La Niña events while intraseasonal variability at the slope site was greatest during the 1997–1998 El Niño event. Mean westward and poleward flow was observed at all depths at the deep sea site but upper ocean means were not significantly different from zero. There was a well-defined, mean poleward flow of 0.6±0.3cms−1 at 2450m depth there. Geostrophic current calculations are presented for the P6E section with levels of no motion based on our current observations and other constraints. These reference choices yield reasonable and consistent results for the steady-state heat balance of the deep Chile and Peru Basins. Results show a deep equatorward flow of 3–4Sv on the eastern flank of the East Pacific Rise and a deep poleward boundary flow of about 10Sv within 1500km of the Chile coast. Up to half of the total mid-depth outflow of the South Pacific may take place east of the Rise. Thus the deep poleward boundary current off Chile is a major component of the deep circulation of the global ocean but the dynamics of this current remain a puzzle.

The macro- and micro-scale patchiness of meiobenthos associated with the Darwin Mounds (north-east Atlantic)

Meiobenthic community structure was investigated at different spatial scales (from 100 metres to centimetres) on and adjacent to a group of coral-topped sandy mounds in the bathyal north-east Atlantic (Darwin Mounds, Rockall Trough) and related to the environmental conditions in the area, mainly differences in sediment organic carbon content and presence of biogenic structures. Meiobenthos abundances were similar to those observed in other deep-sea sites, with nematodes representing at least 94% of the total community. The dominant nematode genera were Microlaimus, followed by Sabatieria, Richtersia, Rhynchonema and Trefusia, together with typical deep-sea genera (e.g. Halalaimus and Acantholaimus). Multivariate analysis of nematode generic relative abundances at the different stations indicated that there was no significant influence on distribution resulting from large scale topographic and biogeochemical conditions around the mounds. The same genera were associated with dead tests of the xenophyophore Syringammina fragilissima and in the surrounding sediments. The vertical distribution of nematodes on and adjacent to the mound showed some unusual features, as the deeper layers of the sediments were inhabited by stilbonematids. These genera harbour ectosymbiotic, chemoautotrophic bacteria and have not previously been recorded from the deep sea. The occurrence of stilbonematids in notable numbers in the subsurface layers of the sediments in the vicinity of the Darwin Mounds provides evidence for the occurrence of anoxic microenvironments.

Temporal patterns in diversity and species composition of deep-sea benthic copepods in bathyal Sagami Bay, central Japan

Little is known about temporal changes in the diversity and species composition of deep-sea metazoan meiofauna and their relationships with changes in the food supply. Those changes were studied for benthic copepod assemblages based on 2-year time-series data at a bathyal site in Sagami Bay (1430 m depth), central Japan, where annual fluctuation in the abundance of benthic foraminiferans was previously observed. Species diversity of benthic copepods at the site was as high as, or slightly higher than, that observed at other deep-sea sites, but did not fluctuate temporally through the study period. Multivariate analyses did not reveal any clear seasonal or directional change occurring over the longer term in their species composition, although there was some consistent pattern. These results indicate a lack of, or only weak, seasonality in the diversity and species structure of the deep-sea benthic copepod assemblages, even though the fresh organic food supply fluctuates seasonally. They also suggest that there are differences between copepods and foraminiferans in the response to changes in environmental factors, and that spatial differences in the composition of copepod communities are greater than temporal ones at this deep-sea site.

Fine-fraction carbonate stable isotopes as indicators of seasonal shallow mixed-layer paleohydrography

We have measured stable isotopic compositions of Miocene pelagic fine-fraction (<63 μm) carbonates from oligotrophic deep-sea sites in the Pacific and Atlantic oceans and compared them with those of coexisting foraminifers to test their utility as near sea-surface indicators. Fine-fraction carbonates (primarily polyspecific nannofossils) and surface-dwelling planktic foraminiferal ( Globigerinoides) stable isotopes both have been considered to reflect surface-water hydrographic conditions. However, our results indicate that fine-fraction stable isotopes are offset from and do not correlate well with those of Globigerinoides. In contrast, stable isotopic records of the deep-dwelling planktic foraminifer Globoquadrina are in good correspondence with the fine-fraction records in terms of long-term (ca. >1 m.y.) trends and temporal variability. On the basis of a time-series hydrography and flux study site in the oligotrophic subtropical North Atlantic, we interpret the isotopic discrepancies between fine-fraction and Globigerinoides as resulting primarily from season of calcification, as well as possible vital effects. We suggest that fine-fraction stable isotope values from oligotrophic waters reflect late winter–early spring relatively cool, nutrient-rich shallow mixed-layer conditions during the time of deep mixing (i.e., spring bloom), whereas Globigerinoides stable isotope values record conditions that prevailed in the stratified surface waters in the warmer late spring–fall. This implies that paired analyses of fine-fraction and surface-dwelling planktic foraminiferal δ 18O could be applied to reconstruct paleoseasonality of the open oceans. However, because the fine-fraction δ 13C values are not representative of the annual mean surface-water δ 13C, we recommend use of near surface-dwelling planktic foraminiferal δ 13C as a proxy for δ 13C of stratified surface waters that are more or less in equilibrium with the atmosphere with respect to pCO 2.

Paleocene oceanography of the eastern subtropical Indian Ocean: An integrated magnetobiostratigraphic and stable isotope study of ODP Hole 761B (Wombat Plateau)

Surface and deep water circulation patterns in the eastern Indian Ocean during the Paleocene Epoch are inferred based on an integrated magnetobiostratigraphic and stable isotope investigation of Ocean Drilling Program Hole 761B, drilled on the Wombat Plateau. A combination of magnetostratigraphy, biostratigraphy and isotope stratigraphy demonstrates that numerous deep sea sites that have been considered to show continuous, or nearly continuous sedimentation through the Paleocene are punctuated by a series of hiatuses, some of which exceeding a duration of 1 Myr. Therefore, our study is based on a detailed temporal interpretation of the stratigraphic successions we used for paleoceanographic reconstructions. We compare detailed planktonic and benthic foraminiferal carbon and oxygen isotope records from Hole 761B with several temporally correlative records published from different oceanic provinces in order to distinguish between local and global patterns within the eastern Indian Ocean. Although Site 761 was situated at low latitudes during the Paleocene, its surface waters were predominantly influenced by circulation originating from the Southern Ocean as indicated by inferred cool sea surface temperatures and reduced surface to deep water temperature gradients. We suggest that deep waters in the eastern Indian Ocean were not directly fed by the Southern or Tethys Oceans. Rather, the more negative δ 13C composition of the bottom waters recorded by benthic foraminifera implies the presence and/or active contribution of aged deep waters from the Pacific during this time, at least prior to ∼60.2 Ma and subsequent to ∼59.0 Ma. The Indian continent, Ninetyeast Ridge, Kerguelen Plateau and Broken Ridge may have played a significant role as submarine barriers to deep water circulation during the Paleocene.

Bengal Fan sediment transport activity and response to climate forcing inferred from sediment physical properties

We obtained sediment physical properties and geochemical data from 47 piston and gravity cores located in the Bay of Bengal, to study the complex history of the Late Pleistocene run-off from the Ganges and Brahmaputra rivers and its imprint on the Bengal Fan. Grain-size parameters were predicted from core logs of density and velocity to infer sediment transport energy and to distinguish different environments along the 3000-km-long transport path from the delta platform to the lower fan. On the shelf, 27 cores indicate rapidly prograding delta foresets today that contain primarily mud, whereas outer shelf sediment has 25% higher silt contents, indicative of stronger and more stable transport regime, which prevent deposition and expose a Late Pleistocene relic surface. Deposition is currently directed towards the shelf canyon ‘Swatch of No Ground’, where turbidites are released to the only channel–levee system that is active on the fan during the Holocene. Active growth of the channel–levee system occurred throughout sea-level rise and highstand with a distinct growth phase at the end of the Younger Dryas. Coarse-grained material bypasses the upper fan and upper parts of the middle fan, where particle flow is enhanced as a result of flow-restriction in well-defined channels. Sandier material is deposited mainly as sheet-flow deposits on turbidite-dominated plains at the lower fan. The currently most active part of the fan with 10–40-cm-thick turbidites is documented for the central channel including inner levees (e.g., site 40). Site 47 from the lower fan far to the east of the active channel–levee system indicates the end of turbidite sedimentation at 300 ka for that location. That time corresponds to the sea-level lowering during late isotopic stage 9 when sediment supply to the fan increased and led to channel avulsion farther upstream, probably indicating a close relation of climate variability and fan activity. Pelagic deep-sea sites 22 and 28 contain a 630-kyear record of climate response to orbital forcing with dominant 21- and 41-kyear cycles for carbonate and magnetic susceptibility, respectively, pointing to teleconnections of low-latitude monsoonal forcing on the precession band to high-latitude obliquity forcing. Upper slope sites 115, 124, and 126 contain a record of the response to high-frequency climate change in the Dansgaard–Oeschger bands during the last glacial cycle with shared frequencies between 0.75 and 2.5 kyear. Correlation of highs in Bengal Fan physical properties to lows in the δ 18O record of the GISP2 ice-core suggests that times of greater sediment transport energy in the Bay of Bengal are associated with cooler air temperatures over Greenland. Teleconnections were probably established through moisture and other greenhouse-gas forcing that could have been initiated by instabilities in the methane hydrate reservoir in the oceans.

Deep-sea paleotemperature record of extreme warmth during the Cretaceous

Research Article| February 01, 2002 Deep-sea paleotemperature record of extreme warmth during the Cretaceous Brian T. Huber; Brian T. Huber 1Department of Paleobiology, NHB-121, Smithsonian Institution, Washington, D.C. 20560, USA Search for other works by this author on: GSW Google Scholar Richard D. Norris; Richard D. Norris 2Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA Search for other works by this author on: GSW Google Scholar Kenneth G. MacLeod Kenneth G. MacLeod 3Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA Search for other works by this author on: GSW Google Scholar Geology (2002) 30 (2): 123–126. https://doi.org/10.1130/0091-7613(2002)030<0123:DSPROE>2.0.CO;2 Article history received: 19 Jun 2001 rev-recd: 01 Oct 2001 accepted: 17 Oct 2001 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Brian T. Huber, Richard D. Norris, Kenneth G. MacLeod; Deep-sea paleotemperature record of extreme warmth during the Cretaceous. Geology 2002;; 30 (2): 123–126. doi: https://doi.org/10.1130/0091-7613(2002)030<0123:DSPROE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Oxygen isotope analyses of well-preserved foraminifera from Blake Nose (30°N paleolatitude, North Atlantic) and globally distributed deep-sea sites provide a long-term paleotemperature record for the late Albian–Maastrichtian interval that is difficult to reconcile with the existence of significant Cretaceous ice sheets. Given reasonable assumptions about the isotopic composition of Cretaceous seawater, our results suggest that middle bathyal water temperatures at Blake Nose increased from ∼12 °C in the late Albian through middle Cenomanian to a maximum of 20 °C during the latest Cenomanian and earliest Turonian. Bottom waters were again ∼12 °C during the middle Campanian and cooled to a minimum of 9 °C during the Maastrichtian. Correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from Blake Nose. Comparison of global bottom-water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late Albian through late Cenomanian to a hot greenhouse phase during the latest Cenomanian through early Campanian, then to cool greenhouse conditions during the mid-Campanian through Maastrichtian. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Diversity of free-living prokaryotes from a deep-sea site at the Antarctic Polar Front

To contribute to the understanding of deep-sea planktonic communities, we explored the prokaryotic diversity of a 3000 m deep site at the Antarctic Polar Front using molecular methods. Bacterial 16S rDNA-amplified sequences corresponded to the as yet uncultivated groups SAR11, within the α-Proteobacteria, and SAR324, within the δ-Proteobacteria, as well as to the γ-Proteobacteria, Cytophagales, Planctomyces, Gram-positives, and the group of environmental sequences SAR406. Among them, γ-proteobacterial sequences were the most abundant and diverse. Within Archaea, and using six different primer sets for 16S rDNA amplification, only euryarchaeotal sequences were retrieved. Most of them clustered with the Thermoplasma-related marine groups II and III, but some corresponded to a recently described group of marine sequences emerging at the base of haloarchaea. Our data suggest that γ-Proteobacteria and Euryarchaeota may be dominant elements in terms of genetic diversity of the two prokaryotic domains in this deep-sea pelagic area.

Diversity of free-living prokaryotes from a deep-sea site at the Antarctic Polar Front

To contribute to the understanding of deep-sea planktonic communities, we explored the prokaryotic diversity of a 3000 m deep site at the Antarctic Polar Front using molecular methods. Bacterial 16S rDNA-amplified sequences corresponded to the as yet uncultivated groups SAR11, within the α-Proteobacteria, and SAR324, within the δ-Proteobacteria, as well as to the γ-Proteobacteria, Cytophagales, Planctomyces, Gram-positives, and the group of environmental sequences SAR406. Among them, γ-proteobacterial sequences were the most abundant and diverse. Within Archaea, and using six different primer sets for 16S rDNA amplification, only euryarchaeotal sequences were retrieved. Most of them clustered with the Thermoplasma-related marine groups II and III, but some corresponded to a recently described group of marine sequences emerging at the base of haloarchaea. Our data suggest that γ-Proteobacteria and Euryarchaeota may be dominant elements in terms of genetic diversity of the two prokaryotic domains in this deep-sea pelagic area.

A novel haloarchaeal-related lineage is widely distributed in deep oceanic regions.

During our study of the 16S rRNA gene sequence-based archaeal diversity of a deep-sea site located at a 3,000 m depth at the Antarctic Polar Front, we detected several phylotypes ascribed to already known Group II and III Euryarchaeota, and a cluster of distinct sequences that branched off at the base of haloarchaea. The position of this lineage (marine Group IV) was very robust using distance (neighbour-joining) and maximum-likelihood methods. Subsequently, we designed specific primers for the detection of this archaeal group in other marine environments using polymerase chain reaction amplification and sequence comparison. Group IV archaea were found in the Antarctic area (across a gradient from the Southern ocean to the South Atlantic), and also in North Atlantic and Mediterranean waters. In all oceanic locations, Group IV archaea were never detected in surface waters, but were vertically distributed in the deepest part of the water column.

Response of abyssal Copepoda Harpacticoida (Crustacea) and other meiobenthos to an artificial disturbance and its bearing on future mining for polymetallic nodules

Long-term effects of an anthropogenic physical disturbance on the Harpacticoida taxocene at a deep-sea site were investigated during the course of the disturbance and recolonization (DISCOL) experiment in a manganese nodule area in the southeastern Pacific. Nineteen harpacticoid copepod families were found, contributing 9–12% to the metazoan meiofauna of the experimental area (Nematoda 72–80%). Twelve families occurred in sufficient numbers to be considered representatively sampled. Dominant are the Ameiridae (17%) followed by Ectinosomatidae, Argestidae, Tisbidae, Neobradyidae, Diosaccidae, Paranannopidae, Paramesochridae, Canthocamptidae, Cletodidae, Thalestridae and Huntemanniidae. These families are mainly distributed at random. Basic data on developmental stage composition and sex ratio of total Harpacticoida as well as vertical distribution of harpacticoid families in the sediment column are provided. Within the overall aim of the experiment, which was to assess the ecological risks of future deep-sea manganese nodule mining, we conducted multivariate community analyses based on the familial composition of the Harpacticoida assemblages immediately before and after experimental impact as well as seven years later. We were not able to detect a community response at the family level immediately after impact. An identification of the Tisbidae to species, however, revealed initial disturbance effects. After seven years we found significant differences in the assemblage composition of the directly disturbed portions of the experimental area and the secondarily disturbed areas in between, which to some extent had received blanketing from sediment plumes created during the experimental disturbance. Best discriminating families for long-term effects are the Ameiridae, Argestidae and Thalestridae. Their potential value as indicator taxa for monitoring disturbances in the deep sea is discussed, including some considerations on a cost-effective design of such monitoring programs that would include the meiofaunal Harpacticoida.

Numerical Simulation of Tidal Current Force on Twin-Tower Pier

Twin-Tower Pier was designed as a new type of pier for a bridge which is constructed at deep sea site. The feature of the Twin-Tower Pier is two slender towers that are enable to reduce the volume of the concrete, resulting the reduction of the construction cost. Tidal current forces acting on the Twin-Tower Pier had been measured by the hydraulic model test in previous paper because the shape of the pier is more complicated than the shape of a conventional pier which is usually a column type. This paper describes the numerical simulation which is modeled to predict the tidal current force on the Twin-Tower Pier without using hydraulic model tests. The tidal current forces predicted by the numerical simulation are compared with those measured by the hydraulic model test. The comparison between them shows good agreement with the error level of less than 10%.

Rapid characterisation of deep-sea actinomycetes for biotechnology screening programmes.

A continual need in natural product discovery is dereplication, that is the ability to exclude previously tested microorganisms from screening programmes. Whole-cell fingerprinting techniques offer an ideal solution to this problem because of their rapidity and reproducibility, dependence on small samples, and automation. One such technique, Curie-point pyrolysis mass spectrometry (PyMS), has been deployed for the characterisation of a unique collection of actinomycetes recovered from Pacific Ocean sediments approximately 2000 to 6500 m below sea level. This paper addresses the question: to what extent are pyrogroups, defined on the basis of PyMS fingerprinting, related to classifications derived from more conventional microbial systematics? A collection of 44 randomly chosen deep-sea rhodococci were coded and subjected to a double-blind PyMS and numerical taxonomic (NT) analysis; the latter sorted the strains into clusters (taxospecies) using large sets of equally weighted phenotypic data. At the end of the experiment the codes were disclosed and the NT classification shown to generate 6 homogeneous clusters corresponding to different deep-sea sites. The matching of these clusters with the resulting pyrogroups was very high with an overall congruence of nearly 98%. Thus, PyMS characterisation is directly ascribable to the phenotypic variation being sought for biotechnology screens. Moreover, the exquisite discriminatory power of PyMS readily revealed infraspecific diversity in these industrially important bacteria.

Copepoda (Cyclopinidae and Misophriidae) from a deep-sea hydrothermal site in the northeastern Pacific

Two new copepods are described from a depth of 2254m at a hydrothermal site on the Juan de Fuca Ridge, northeastern Pacific. In Barathricola rimensis, gen. nov., sp. nov. (Cyclopoida: Cyclopinidae), the antennule is 13-segmented, the antenna lacks an exopod, the second segment of the endopod of legs 1–4 has 1, 2, 2, 2 setae, and leg 5 is three-segmented in both sexes, the last segment (exopod) having I, I, l, I in the female and I, I, l, I, l in the male. In Misophriopsis longicauda, gen. nov., sp. nov. (Misophrioida: Misophriidae), the antennule is 18-segmented in the female, 13-segmented in the male, the antenna has a six-segmented exopod, legs 1–4 are biramous with three-segmented rami, leg 5 is biramous with a one-segmented endopod and an exopod which is two-segmented in the female, three-segmented in the male.

Biodiversity in deep-sea sites located near the south part of Japan.

We obtained 100 isolates of bacteria from deep-sea mud samples collected at various depths (1050-10897m). Various types of bacteria such as alkaliphiles, thermophiles, psychrophiles, and halophiles were recovered on agar plates at a frequency of 0.8 x 10(2) to 2.3 x 10(4)/ g of dry sea mud. No acidophiles were recovered. These extremophilic bacteria were widely distributed, being detected at each deep-sea site, and the frequency of isolation of such extremophiles from the deep-sea mud was not directly influenced by the depth of the sampling sites. Phylogenetic analysis of deep-sea isolates based on 16S rDNA sequences revealed that a wide range of taxa were represented in the deep-sea environments. Growth patterns under high hydrostatic pressure were determined for the deep-sea isolates obtained in this study. No extremophilic strains isolated in this study showed growth at 60MPa, although a few of the other isolates grew slightly at this hydrostatic pressure.

New Erebonasteridae (Copepoda) from Vilkitzky Strait in the Arctic and from a Pacific Hydrothermal Vent Site (Northern Fiji Basin)

A new genus of the poecilostomatoid family Erebonasteridae is described from Vilkitzky Strait in the Arctic, the channel connecting the Kara Sea and the Laptev Sea. Within the Erebonasteridae, Nansennaster, new genus, belongs to the Centobnaster-group. The new genus is characterized by the presence of only 2 setae on the mandibular palp, the fusion of the second and third antennal segments, the presence of a single copulatory pore, and the relatively short furca lacking seta I. A previously overlooked sexual dimorphism in Centobnaster is described, the males of this genus having a modified outer spine on the third endopodal segment of leg 3. Amphicrossus tuerkayi, new species, is described from a deep-sea hydrothermal vent site in the northern Fiji basin. The new species has retained some remarkable plesiomorphic characters, such as an incompletely fused genital double-somite in the female, and 2 setae representing the endopod of the maxilla. An identification key to all known genera and species of the Erebonasteridae is provided.

The effect of experimentally increased near-bottom flow on metazoan meiofauna at a deep-sea site, with comparison data on macrofauna

It has been argued that strong near-bottom flows affect macrofauna and meiofauna in the deep sea, but the evidence comes largely from studies that compared sites separated geographically by hundreds to thousands of kilometers and in depth by hundreds of meters. In this paper, the results of the first experimental investigation of the effects of strong near-bottom flow on deep-sea metazoan meiofauna are presented. At a site (32° 27.581′ N, 127° 47.839′ W) at 583 m depth on the Fieberling Guyot summit plain, the submersible Alvin emplaced weirs designed to increase the near-bottom flow locally. After 6.5 weeks, sediments in the weirs and unmanipulated locations in the vicinity were sampled. The abundances of nematodes, harpacticoid copepods, ostracods, and kinorhynchs, considered collectively and as individual taxa, were significantly lower in the weir samples than in the background samples. Parallel responses were observed in total macrofaunal and mollusk abundances. Proportional declines in kinorhynchs and mollusks were observed as well. These results suggest that strong near-bottom flow can reduce the abundance of meiofauna and macrofauna in the deep sea and alter assemblage composition.