Showing papers by "Woods Hole Oceanographic Institution published in 1992"
TL;DR: Evidence for the widespread occurrence of unusual archaea in oxygenated coastal surface waters of North America is provided and it is suggested that these microorganisms represent undescribed physiological types of archaea, which reside and compete with aerobic, mesophilic eubacteria in marine coastal environments.
Abstract: Archaea (archaebacteria) are a phenotypically diverse group of microorganisms that share a common evolutionary history. There are four general phenotypic groups of archaea: the methanogens, the extreme halophiles, the sulfate-reducing archaea, and the extreme thermophiles. In the marine environment, archaeal habitats are generally limited to shallow or deep-sea anaerobic sediments (free-living and endosymbiotic methanogens), hot springs or deep-sea hydrothermal vents (methanogens, sulfate reducers, and extreme thermophiles), and highly saline land-locked seas (halophiles). This report provides evidence for the widespread occurrence of unusual archaea in oxygenated coastal surface waters of North America. Quantitative estimates indicated that up to 2% of the total ribosomal RNA extracted from coastal bacterioplankton assemblages was archaeal. Archaeal small-subunit ribosomal RNA-encoding DNAs (rDNAs) were cloned from mixed bacterioplankton populations collected at geographically distant sampling sites. Phylogenetic and nucleotide signature analyses of these cloned rDNAs revealed the presence of two lineages of archaea, each sharing the diagnostic signatures and structural features previously established for the domain Archaea. Both of these lineages were found in bacterioplankton populations collected off the east and west coasts of North America. The abundance and distribution of these archaea in oxic coastal surface waters suggests that these microorganisms represent undescribed physiological types of archaea, which reside and compete with aerobic, mesophilic eubacteria in marine coastal environments.
2,687 citations
TL;DR: The cloning and sequencing of both cDNA and genomic clones of GFP from the cnidarian, Aequorea victoria, show three different restriction enzyme patterns which suggests that at least three different genes are present in the A. victoria population.
2,365 citations
TL;DR: A sequential extraction method (SEDEX) was developed to separate five sedimentary P reservoirs: loosely sorbed P; ferric iron-bound P; authigenic carbonate fluorapatite + biogenic apatite+ CaCO3-associated P; detrital apatitic P; and organic P.
Abstract: A sequential extraction method (SEDEX) has been developed to separately quantify five sedimentary P reservoirs: loosely sorbed P; ferric iron-bound P; authigenic carbonate fluorapatite + biogenic apatite + CaCO3-associated P; detrital apatite P; and organic P. The SEDEX method successfully separates two of the main categories of authigenic phosphate phases called upon most often as sedimentary sinks for diagenetically mobilized P: ferric oxyhydroxide-associated P and authigenic carbonate fluorapatite (CFAP). It offers a means for separating authigenic CFAP from detrital apatite of igneous or metamorphic origin. The importance of this distinction is that CFAP represents an oceanic sink for reactive P, whereas detrital apatite does not. In addition, a means for reversing secondary adsorption of P onto residual solid surfaces during extraction has been developed.
Extensive standardization of the SEDEX method for application to marine sediments has been performed with analogs for naturally occurring phosphatic phases.
1,016 citations
TL;DR: Many oceanic island basalts show sublinear subparallel arrays in Sr-Nd-Pb isotopic space, but the depleted upper mantle is rarely a mixing end-member of these arrays, as would be expected if mantle plumes originated at a 670-kilometer boundary layer and entrained upper mantle during ascent.
Abstract: Many oceanic island basalts show sublinear subparallel arrays in Sr-Nd-Pb isotopic space. The depleted upper mantle is rarely a mixing end-member of these arrays, as would be expected if mantle plumes originated at a 670-kilometer boundary layer and entrained upper mantle during ascent. Instead, the arrays are fan-shaped and appear to converge on a volume in isotopic space characterized by low (87)Sr/(86)Sr and high (143)Nd/(144)Nd, (206)Pb/(204)Pb, and (3)He/(4)He ratios. This new isotopic component may be the lower mantle, entrained into plumes originating from the core-mantle boundary layer.
930 citations
TL;DR: In this article, trace element studies of melt/rock reaction zones in the Trinity peridotite provide evidence for reaction of the mantle lithosphere with ascending melts, which dissolved calcium-pyroxene and precipitated orthopyroxene as magma mass decreased.
Abstract: Many mantle peridotite samples are too rich in Si02 (in the form of orthopyroxene) and have ratios of light to heavy rare earth elements that are too high to be consistent with an origin as the residuum of partial melting of the primitive mantle. Trace element studies of melt/rock reaction zones in the Trinity peridotite provide evidence for reaction of the mantle lithosphere with ascending melts, which dissolved calcium-pyroxene and precipitated orthopyroxene as magma mass decreased. This process can account for the observed major and trace element compositions of lithospheric mantle samples, and may accordingly be prevalent in the upper mantle.
618 citations
TL;DR: Sudden changes in the flow of warm Atlantic surface waters into the Norwegian Sea occurred frequently during the last deglaciation, typically involving shifts in sea surface temperature of ⩾5 °C in fewer than 40 years as discussed by the authors.
Abstract: Sudden changes in the flow of warm Atlantic surface waters into the Norwegian Sea occurred frequently during the last deglaciation, typically involving shifts in sea surface temperature of ⩾5 °C in fewer than 40 years. These led to equally large and rapid changes in atmospheric temperatures, and to shifts in Atlantic deep thermo-haline circulation and ice-sheet melting rates.
580 citations
TL;DR: The 28 June Landers earthquake brought the San Andreas fault significantly closer to failure near San Bernardino, a site that has not sustained a large shock since 1812, and stress on theSan Andreas north of Los Angeles dropped, potentially delaying the next great earthquake there by 2 to 10 years.
Abstract: The 28 June Landers earthquake brought the San Andreas fault significantly closer to failure near San Bernardino, a site that has not sustained a large shock since 1812. Stress also increased on the San Jacinto fault near San Bernardino and on the San Andreas fault southeast of Palm Springs. Unless creep or moderate earthquakes relieve these stress changes, the next great earthquake on the southern San Andreas fault is likely to be advanced by one to two decades. In contrast, stress on the San Andreas north of Los Angeles dropped, potentially delaying the next great earthquake there by 2 to 10 years.
576 citations
TL;DR: Patterns of association among bottlenose dolphins resident in Shark Bay, Western Australia were analyzed using party membership data and found male-female associations were generally inconsistent and depended in part on female reproductive state.
Abstract: Patterns of association among bottlenose dolphins resident in Shark Bay, Western Australia were analyzed using party membership data. Parties contained an average of 4.8 individuals, but party size and composition were unstable. While these temporary parties often contained both males and females, long term consistent associations generally were between members of the same sex. The highest association coefficients, resulting from very frequent co-occurrence within parties were between males and between mothers and offspring. Males formed subgroups of two or three individuals who consistently associated with each other, and these were stable over periods of at least seven years in some cases. Male subgroups preferentially associated with particular other male subgroups. Females associated most consistently with other females, although not to the same extent as some males. Female associations were better described as a network rather than discrete subgroups. Male-female associations were generally inconsistent and depended in part on female reproductive state. Mothers and their offspring associated very consistently for at least 4 years.
536 citations
TL;DR: In this paper, a study aimed at distinguishing among autotrophic nitrification, denitrification, and abiological processes as sources of NO and N2O production following wetting of dry soil was presented.
Abstract: A study is presented which is aimed at distinguishing among autotrophic nitrification, denitrification, and abiological processes as sources of NO and N2O production following wetting of dry soil. To distinguish among these processes, combinations of treatments in laboratory incubations of soil were used which included varying soil water content, autoclaving, C2H2 inhibition, and NO2(-) addition. Biological sources of NO and N2O commenced within minutes of wetting dry soil. Acetylene inhibition revealed that emissions of NO were dependent on nitrification, although a combination of NO2(-) production by nitrifiers and abiological reduction of NO2(-) to NO is also possible. NO emissions exceeded N2O emissions, and nitrification was the dominant source of both gases when soil water was below field capacity. It is concluded that NO emissions appear to be more important when good soil aeration favors nitrification, whereas N2O emissions appear more important when elevated soil water favors denitrification.
444 citations
TL;DR: In this paper, the disequilibrium between the particle-reactive tracer 234 Th (t 1 2 = 24.1 days) and its soluble parent, 238 U, was used to examine Th scavenging and export fluxes during the U.S. JGOFS North Atlantic Bloom Experiment (24 April-30 May 1989) at ∼47°N, 20°W.
425 citations
TL;DR: This paper measured the Li isotope composition of young, pristine basalts from active ocean ridge crests, of progressively older basalts along a dredging transect, and a limited number of hydrothermally altered basalts.
TL;DR: Several strains of this organism have recently been brought into culture and given the name Prochlorococcus marinus, and it is indicated that these cells are more closely related to a cluster of marine cyanobacteria than to their prochlorophyte ‘relatives’ Prochlorothrix and Prochloron.
Abstract: Several years ago, prochlorophyte picoplankton were discovered in the N. Atlantic. They have since been found to be abundant within the euphotic zone of the world's tropical and temperate oceans. The cells are extremely small, lack phycobiliproteins, and contain divinyl chlorophyll a and b as their primary photosynthetic pigments. Phylogenies constructed from DNA sequence data indicate that these cells are more closely related to a cluster of marine cyanobacteria than to their prochlorophyte ‘relatives’ Prochlorothrix and Prochloron. Several strains of this organism have recently been brought into culture, and herewith are given the name Prochlorococcus marinus.
TL;DR: In this paper, the authors report observations of turbulence in Lake Ontario, taken under conditions of strong wave breaking, which reveal a greatly enhanced dissipation rate of kinetic energy close to the air-water interface, relative to the predictions of wall-layer theory.
Abstract: TRANSFER of momentum from wind to the surface layer of lakes and oceans plays a central part in driving horizontal and vertical circulation of water masses. Much work has been devoted to understanding the role of waves in momentum transfer across the air–sea interface, but less is known about the energetics of the near-surface turbulence responsible for the mixing of momentum and mass into the underlying water column. In particular, it has remained unclear whether the structure of the turbulence in the surface layer can be described by analogy to wall-bounded shear flows or whether waves, either through breaking or wave–current interaction, introduce new length- and timescales which must be modelled explicitly. Here we report observations of turbulence in Lake Ontario, taken under conditions of strong wave breaking, which reveal a greatly enhanced dissipation rate of kinetic energy close to the air–water interface, relative to the predictions of wall-layer theory. Because wave breaking is intermittent, short-term measurements of the kinetic energy dissipation in the near-surface layer may therefore result in considerable underestimates, and any general treatment of upper mixed layer dynamics will have to take wave breaking explicitly into account.
TL;DR: In this article, a comparison of Δ14C (the deviation in parts per thousand from the 14C activity of nineteenth-century wood) was made between the DOChtc, DOCuv and humic substances in profiles from the oligotrophic north-central Pacific and Sargasso Sea.
Abstract: RADIOCARBON measurements of dissolved organic carbon (DOC) oxidizable by ultraviolet irradiation (DOCuv) yielded apparent ages of ∼6,000 yr in the deep waters of the oligotrophic north-central Pacific gyre1. Recent reports of a potentially larger pool of DOC as measured by high-temperature catalytic combustion (DOChtc) using discrete injections of sea water2,3 have led to speculation that 'younger', more recently produced DOC could contribute significantly to overall oceanic organic carbon fluxes, owing to its suspected greater biological lability4–6. Here we present a comparison ofΔ14C (the deviation in parts per thousand from the 14C activity of nineteenth-century wood)7 of the DOChtc, DOCuv and humic substances in profiles from the oligotrophic north-central Pacific and Sargasso Sea. For each ocean, the Δ14C values of all three fractions are remarkably similar, yielding no evidence for a component of DOC that is cycled through the system on timescales shorter than several thousands of years. We observe an age difference between the two oceans of ∼ 2,000 yr for the deepest DOC, which can largely be accounted for by differences in the Δ14C of the DOC sources to the deep basins, and by the different deep-water circulation patterns and transit times in the two oceans.
TL;DR: In this paper, a large scale fractionation of rare earth elements between colloidal and solution phases is found within the dissolved fraction of Connecticut River water, where colloidal particles carry a large part of the dissolved REE pool.
TL;DR: In this paper, a search for high-temperature activity of sulfate-reducing bacteria was done in hot deep-sea sediments at the hydrothermal vents of the Guaymas Basin tectonic spreading center in the Gulf of California.
Abstract: The currently known upper temperature limit for growth of organisms, shared by a number of archaebacteria, is 110°C. However, among the sulfate-reducing bacteria, growth temperatures of greater than 100°C have not been found. A search for high-temperature activity of sulfate-reducing bacteria was done in hot deep-sea sediments at the hydrothermal vents of the Guaymas Basin tectonic spreading center in the Gulf of California. Radiotracer studies revealed that sulfate reduction can occur at temperatures up to 110°C, with an optimum rate at 103° to 106°C. This observation expands the upper temperature limit of this process in deep-ocean sediments by 20°C and indicates the existence of an unknown group of hyperthermophilic bacteria with a potential importance for the biogeochemistry of sulfur above 100°C.
TL;DR: In this paper, the authors investigated the influence of cold water entrainment on the meridional overturning system of the North Atlantic and found that the entrainments can be explained by warm water entraining alone, but also by recirculation of recirculating cold components.
TL;DR: Ecology and palaeoecology of benthic foraminifera that can be your partner is offered, which offers many book collections from fictions to science at all.
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TL;DR: It is shown that under a constant phytoplankton demand for CO2 an inverse, nonlinear SPOM delta 13C response to ambient [CO2(aq)] is expected, unlike the negative linear relationships indicated by data from the NABE Site and or from Southern Hemisphere waters.
TL;DR: In this paper, the authors analyzed over 1300 km of high resolution along-axis gravity profiles at ridges with half-spreading rates ranging from 1.2 to 5.5 cm/yr.
Abstract: We analyze over 1300 km of high resolution along-axis gravity profiles at ridges with half-spreading rates ranging from 1.2 to 5.5 cm/yr. The results show consistently higher along-axis gradients of mantle Bouguer anomaly at the slow-spreading Mid-Atlantic Ridge (MAR) (0.3–1.2 mgal/km) than at the intermediate- to fast-spreading Cocos-Nazca Ridge and East Pacific Rise (EPR) (0.1–0.2 mgal/km). The regional peak-to-trough amplitude of mantle Bouguer anomaly is also greater along the MAR (30–60 mgal) than the Cocos-Nazca Ridge and the EPR (10–20 mgal). With increasing spreading rate, the regional peak-to-trough amplitude of axial seafloor depth decreases from 1000–1700 m to 200–700 m. 3-D numerical experiments suggest that mantle contributions to the gravity can be significant only near large-offset transforms. At the more commonly observed non-transform offsets, gravity anomalies will reflect crustal thickness variations.
The along-axis gravity data thus indicate that the amplitude of along-axis crustal thickness variation decreases with increasing spreading rate. We propose that this spreading rate dependent crustal accretion style may originate in the mantle: finite-amplitude mantle upwelling is intrinsically plume-like (3-D) beneath a slow-spreading ridge but more sheet-like (2-D) beneath a fast-spreading ridge. Such a transition in mantle upwelling may occur if the relative importance of passive upwelling over buoyant upwelling increases with increasing spreading rate. Small amplitude 3-D upwellings may occur at a fast-spreading ridge, but their effects on crustal thickness variations will be significantly reduced by along-axis melt flows along a persistent low-viscosity crustal magma chamber. In contrast, the large crustal thickness variations due to 3-D mantle upwellings will be maintained at a slow-spreading ridge because less along-axis melt flows can occur in the colder and more rigid crust there.
TL;DR: The global distribution of freshwater transport in the ocean is presented, based on an integration point at Bering Strait, which connects the Pacific and Atlantic oceans via the Artic Ocean as discussed by the authors.
Abstract: The global distribution of freshwater transport in the ocean is presented, based on an integration point at Bering Strait, which connects the Pacific and Atlantic oceans via the Artic Ocean. Through Bering Strait, 0.8 × 106 m3 s−1 of relatively fresh, 32.5 psu, water flows from the Pacific into the Arctic Ocean. Baumgrtner and Reichel's tabulation of the act gain of freshwater by the ocean in 5° latitude intervals is then integrated from the reference location at Bering Strait to yield the meridional freshwater transport in each ocean. Freshwater transport in the Pacific is directed northward at nearly all latitudes. In the Atlantic, the freshwater transport is directed southward at all latitudes, with a small southward freshwater transport out of the Atlantic across 35°S. Salt transport, which must be considered jointly with the freshwater transport, is northward throughout the Pacific and southward throughout the Atlantic (in the same direction as the freshwater flux) and is equal to the sal...
TL;DR: In this article, the authors studied the shoaling of internal solitary waves of depression in a two-layer system on a uniform slope and found that 15 (± 5) % of the energy lost from first-mode wave motion inshore of the break point goes into vertical mixing.
Abstract: Laboratory experiments have been conducted to study the shoaling of internal solitary waves of depression in a two-layer system on a uniform slope. The shoaling of a single solitary wave results in wave breaking and the production of multiple turbulent surges, or boluses, which propagate up the slope. Significant vertical mixing occurs everywhere inshore of the breaking location. The kinematics of the breaking and bolus runup are described and a breaking criterion is found. The energetics of the breaking are investigated. Over the range of parameters examined, 15 (±5) % of the energy lost from first-mode wave motion inshore of the break point goes into vertical mixing.
TL;DR: In this paper, the interannual path variations of the Kuroshio strongly influenced the water-mass movement in the midlatitudes of the western North Pacific, and they found that a significant portion of the North Pacific was affected.
Abstract: Twenty-two years (1967–88) of hydrographic data collected by the Japan Meteorological Agency along the 137°E meridian and surface wind data compiled by Florida State University (FSU) were analyzed to study the interannual variability in the western North Pacific. In the midlatitude region north of 22°N, the dominant signal in the dynamic height field was the interannual path variations of the Kuroshio. Whereas the eastward transport of the Kuroshio itself had no significant changes between the straight-path and meander-path years, the net transport of the Kuroshio system including recirculations showed a 30% increase during the meander-path years. In the straight-path years when the net transport was small, the Kuroshio tended to take a straight path with a strong recirculation developed to the south. The interannual path variations of the Kuroshio strongly influenced the water-mass movement in the midlatitudes. During the Kuroshio meander years, we found that a significant portion of the North P...
TL;DR: In this article, the authors investigated the efficiency of cross-jet exchange induced by fluctuating meander amplitudes in a two-dimensional kinematic model of a meandering jet using Melnikov's method.
Abstract: The motion of fluid parcels in a two-dimensional kinematic model of a meandering jet is investigated using Melnikov's method. The study is motivated by a recent analysis of float trajectories in the Gulf Stream. The results indicate that the efficiency of cross-jet exchange induced by fluctuating meander amplitudes depends strongly on the frequency of the fluctuations. For high frequencies (≳0.04 cpd), exchange between the core of the jet and regions of “trapped” fluid moving with the meander is preferred, while for low frequencies (≲0.04 cpd), exchange between the “trapped” fluid and the slow-moving fluid surrounding the jet is preferred. Propagating waves superimposed on the meandering jet can efficiently cause exchange between regimes when their phase speeds roughly match the basic flow velocities along the regime boundaries. Numerical results suggest that exchange across the center of the jet is less efficient than exchange between adjacent regimes so that the meandering jet will tend to stir...
TL;DR: Using stable isotope ratios of carbon, nitrogen and sulphur as tracers of sewage-derived organic material, the authors showed that this material reaches the sea floor and enters the benthic food web, specifically through surface-deposit feeding activities of the urchin, Echinus affinus and the sea cucumber, Benthodytes sanguinolenta.
Abstract: CHRONIC pollution of the open ocean has occurred since 1986 through disposal of municipal sewage sludge at a deep-water (∼2,500 m) dumpsite off the coast of New Jersey. Dispersal and dilution of sewage particulates in surface waters were presumed to be sufficient to prevent or minimize accumulation of detectable amounts of sewage-derived material on the sea floor. Using stable isotope ratios of carbon, nitrogen and sulphur as tracers of sewage-derived organic material, we show here that this material reaches the sea floor and enters the benthic food web, specifically through surface-deposit feeding activities of the urchin, Echinus affinus and the sea cucumber, Benthodytes sanguinolenta.
TL;DR: In this article, it was shown that chondrite-normalized rare-earth elements (REE) patterns in clinopyroxenes show abrupt changes in slope, which vary with stratigraphic position and rock type.
Abstract: THE segregation of melts from the Earth's upper mantle into the crust is an important process in the chemical evolution of the crust–mantle system. The processes of melt formation and migration in the upper mantle are inadequately understood, but some important characteristics of these processes can be inferred from upper-mantle rocks exposed at the Earth's surface. The Horoman peridotite body in northern Japan is a layered upper-mantle rock. The major-element compositions of the layers are consistent with their formation as residues from varying extents of melting; however, abundances of rare-earth elements (REE) require additional processes to have occurred1, such as post-melting enrichment (metasomatism) resulting from reaction with a migrating fluid phase. We report here that chondrite-normalized REE patterns in clinopyroxenes show abrupt changes in slope, which vary with stratigraphic position and rock type. These data can be modelled by chromatographic fractionation as melts migrated through and interacted with peridotite, creating compositional heterogeneities in the upper mantle. In the Horoman peridotite these heterogeneities occur on a scale length of tens of metres.
TL;DR: These video observations provide new insights into basic plankton ecology by allowing quantitative assessment of individual plankton in their natural, undisturbed state.
Abstract: Oceanic plankton have been hypothesized to occur in micropatches (<10 meters) that can have a large impact on marine ecosystem dynamics. Towed video microscopy was used to unobtrusively determine distributions of oceanic plankton over a continuum of scales from microns to hundreds of meters. Distinct, taxa-specific aggregations measuring less than 20 centimeters were found for copepods but not for nonmotile (cyanobacterial colonies) or asexual (doliolid phorozooids) forms, which suggests that these small patches are related to mating. Significant patchiness was also found on larger scales and was correlated among taxa, indicating physical control. These video observations provide new insights into basic plankton ecology by allowing quantitative assessment of individual plankton in their natural, undisturbed state.
TL;DR: In this paper, the authors used CTD and moored observations from the Oregon, northwest Africa, Peru, and northern California shelves to examine the characteristics of the surface boundary layer in coastal regions during the upwelling season.
Abstract: Observations from the Oregon, northwest Africa, Peru, and northern California shelves are used to examine the characteristics of the surface boundary layer in coastal regions during the upwelling season. The observations from these four regions yield a consistent picture of the structure of the surface boundary layer. Both CTD and moored observations reveal the presence of surface mixed layers that are typically 0–20 m thick with variability at diurnal and subtidal (periods longer than 36 hours) frequencies. The subtidal surface mixed-layer depth variability scales as u*/(NIf)½, where u* = (τS/ρ0)½ is the shear velocity, NI is the buoyancy frequency below the surface mixed layer, and f is the Coriolis frequency. Surprisingly, this relationship indicates that the subtidal variability of surface mixed-layer depth does not depend strongly on either the surface heat flux or advection of heat, both of which are large in coastal upwelling regions. Within the surface mixed layer the cross-shelf current ...