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Showing papers by "Woods Hole Oceanographic Institution published in 1980"


Journal ArticleDOI
TL;DR: The results support the view that nitrification is an important source of N(2)O in the environment and that nitrite-oxidizing bacteria (Nitrobacter sp.) and the dinoflagellate Exuviaella sp.
Abstract: Pure cultures of the marine ammonium-oxidizing bacterium Nitrosomonas sp. were grown in the laboratory at oxygen partial pressures between 0.005 and 0.2 atm (0.18 to 7 mg/liter). Low oxygen conditions induced a marked decrease in the rate for production of NO2-, from 3.6 × 10−10 to 0.5 × 10−10 mmol of NO2- per cell per day. In contrast, evolution of N2O increased from 1 × 10−12 to 4.3 × 10−12 mmol of N per cell per day. The yield of N2O relative to NO2- increased from 0.3% to nearly 10% (moles of N in N2O per mole of NO2-) as the oxygen level was reduced, although bacterial growth rates changed by less than 30%. Nitrifying bacteria from the genera Nitrosomonas, Nitrosolobus, Nitrosospira, and Nitrosococcus exhibited similar yields of N2O at atmospheric oxygen levels. Nitrite-oxidizing bacteria (Nitrobacter sp.) and the dinoflagellate Exuviaella sp. did not produce detectable quantities of N2O during growth. The results support the view that nitrification is an important source of N2O in the environment.

759 citations


Journal ArticleDOI
28 Mar 1980-Science
TL;DR: High-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation.
Abstract: Hydrothermal vents jetting out water at 380° ± 30°C have been discovered on the axis of the East Pacific Rise. The hottest waters issue from mineralized chimneys and are blackened by sulfide precipitates. These hydrothermal springs are the sites of actively forming massive sulfide mineral deposits. Cooler springs are clear to milky and support exotic benthic communities of giant tube worms, clams, and crabs similar to those found at the Galapagos spreading center. Four prototype geophysical experiments were successfully conducted in and near the vent area: seismic refraction measurements with both source (thumper) and receivers on the sea floor, on-bottom gravity measurements, in situ magnetic gradiometer measurements from the submersible Alvin over a sea-floor magnetic reversal boundary, and an active electrical sounding experiment. These high-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation.

687 citations


Journal ArticleDOI
24 Jan 1980-Nature
TL;DR: In this paper, the first direct measurements of seasonal change in the total flux of particles <13 cm and in the flux of organic carbon associated with those particles are reported, and the change seems to be related to seasonal changes in the primary productivity of the surface water.
Abstract: Recent evidence1–5 has suggested that diurnal and annual periodicities affect the deep sea which traditionally had been thought to be the least variable environment at the surface of the Earth6,7. We report here what we believe to be the first direct measurements of seasonal change in the total flux of particles <13 cm and in the flux of organic carbon associated with those particles. The change seems to be related to seasonal change in the primary productivity of the surface water.

318 citations


Journal ArticleDOI
26 Sep 1980-Science
TL;DR: Many planktonic foraminiferal species deposit their shells at the chlorophyll maximum zone, and it is the temperature range here that is relevant to oceanographic models which use ratios of oxygen-18 to oxygen-16 in fossil foraminifera and foraminIFeral fossil assemblages to ascertain past climates.
Abstract: Many planktonic foraminiferal species deposit their shells at the chlorophyll maximum zone, and it is the temperature range here that is relevant to oceanographic models which use ratios of oxygen-18 to oxygen-16 in fossil foraminifera and foraminiferal fossil assemblages to ascertain past climates. During periods of stratification of the upper water column, the temperature at the chlorophyll maximum may differ from the sea surface temperature by 10°C in the western North Atlantic.

313 citations


Journal ArticleDOI
04 Jan 1980-Science
TL;DR: Oxygen isotope analyses of seven species reveal that nonspinose species (algal symbiont-barren) apparently calcify in oxygen isotope equilibrium, whereas spinose species usually calcify out of oxygen isotopes equilibrium.
Abstract: Thirteen species of planktonic foraminifera collected with vertically stratified zooplankton tows in the slope water, Gulf Stream cold core ring, and northern Sargasso Sea show significant differences in their vertical distributions in the upper 200 meters of these different hydrographic regimes. Gulf Stream cold core rings may be responsible for a southern displacement of the faunal boundary associated with the Gulf Stream when reconstructed from the deep-sea sediment record. Oxygen isotope analyses of seven species reveal that nonspinose species (algal symbiont-barren) apparently calcify in oxygen isotope equilibrium, whereas spinose species usually calcify out of oxygen isotope equilibrium by approximately –0.3 to –0.4 per mil in δ18O values. The isotope data indicate that foraminifera shells calcify in depth zones that are significantly narrower than the overall vertical distribution of a species would imply.

299 citations


Journal Article
TL;DR: Sediment trap experiments have been carried out at sites in the Sargasso Sea (S/sub 2/) and in the Atlantic off Barbados (E) to determine the mass flux and chemical composition of material sinking to the sea floor as discussed by the authors.
Abstract: Sediment trap experiments have been carried out at sites in the Sargasso Sea (S/sub 2/) and in the Atlantic off Barbados (E) to determine the mass flux and chemical composition of material sinking to the sea floor. At the S/sub 2/ site, the mass flux increases with depth, at the E site the flux is constant. Chemical analyses show that K, Ti, Al, La, V, Co and /sup 232/Th are derived largely from terrigenous materials whereas Ca, Sr, Mg, Si, Ba, /sup 220/Ra, U and I are carried by biogenic particles. The reactive elements Mn, Cu, Fe, Sc, and /sup 230/ /sup 234/Th, show increasing ratios to Al with depth due to scavenging from the water column. A mean particle settling velocity of 21 m day/sup -1/ and scavenging residence times ranging from 22 years for Th to 500 years for Cu have been calculated. The flux of aluminosilicates increases with depth, and this cannot be attributed to changes in trap efficiency. Thus horizontal transport of material must be invoked.

277 citations


Journal ArticleDOI
31 Jan 1980-Nature
TL;DR: Sill intrusions into highly porous sediments in the Guaymas Basin, Gulf of California, lead to low-grade metamorphism, thermal alteration and migration of organic compounds, marked changes in interstitial water chemistry, and large-scale expulsion of heated pore fluids as mentioned in this paper.
Abstract: Sill intrusions into highly porous sediments in the Guaymas Basin, Gulf of California, lead to low-grade metamorphism, thermal alteration and migration of organic compounds, marked changes in interstitial water chemistry, and large-scale expulsion of heated pore fluids. The latter process creates space for the intruding magma and initiates a hydrothermal system, which can explain the observed hydrothermal deposits around fault scarps on the basin floor.

272 citations


Journal ArticleDOI
TL;DR: From GEOSECS stations, largely, the 1974 distributions of Pu and of 137 Cs are described in the Pacific Ocean north of about 20°S latitude by the authors as mentioned in this paper.

254 citations


Journal ArticleDOI
01 Apr 1980
TL;DR: A new high pressure equation of state for water and seawater has been derived from the experimental results of Millero and coworkers in Miami and Bradshaw and Schleicher in Woods Hole as mentioned in this paper.
Abstract: A new high pressure equation of state for water and seawater has been derived from the experimental results of Millero and coworkers in Miami and Bradshaw and Schleicher in Woods Hole The form of the equation of state is a second degree secant bulk modulus K = Pv0(v0−vp=K0+AP+BP2 K = Kw0+aS+bS32 A = Aw+cS+dS32 B = Bw+eS where ν0 and νP are the specific volume at 0 and P applied pressure and S is the salinity (ℵ) The coefficients KWO, AW, and BW for the pure water part of the equation are polynomial functions of temperature The standard error of the pure water equation of state is 43 × 10−6 cm3 g−1 in νWP The temperature dependent parameters a, b, c, d, and e have been determined from the high pressure measurements on seawater The overall standard error of the seawater equation of state is 90 × 10−6 cm3 g−1 in νP Over the oceanic ranges of temperature, pressure, and salinity the standard error is 50 × 10−6 cm3 g−1 in νP This new high pressure equation of state has recently (1979) been recommended by the UNESCO Joint Panel on Oceanographic Tables and Standards for use by the oceanographic community

251 citations


Journal ArticleDOI
TL;DR: In this paper, the authors showed that the heat loss associated with a single vent of this type is three to six times the total theoretical heat loss for a 1-km segment of ridge out to 1 m.y.

238 citations


Journal ArticleDOI
TL;DR: In this paper, 15 sections from an anoxic sediment core were analyzed for polycyclic aromatic hydrocarbons (PAH) and two types of PAH were observed: those from combustion sources such as pyrene and chrysene and those from natural sources, such as retene and perylene.

Book ChapterDOI
01 Jan 1980
TL;DR: In this article, the authors used the 14C labeling technique to measure the growth rate of a phytoplankton in the marine environment and found that the results from 14C-labelled incubations can be used to extrapolate results from in situ bottle tests involving standard rate measuring incubation methods.
Abstract: After more than thirty years of intensive research in phytoplankton ecology, our knowledge of how to measure accurately growth rates of photosynthetic organisms in nature is still very limited (1–3). Difficulties in extrapolating results from in situ bottle tests involving standard rate-measuring incubation methods (such as the 14C-labelling technique) are becoming increasingly evident (3–6); hence, we now are faced with conflicting opinions regarding the magnitude of phytoplankton growth rates in the marine environment (5,7–10).

Journal ArticleDOI
01 Jul 1980-Nature
TL;DR: In the Southern Hemisphere, magnetotactic bacteria with unidirectional motility have been observed in marine and freshwater sediments of the Northern Hemisphere as mentioned in this paper, showing that their magnetic dipole is systematically orientated with the North-seeking pole forward.
Abstract: Several species of aquatic bacteria which orient in the Earth's magnetic field and swim along magnetic field lines in a preferred direction (magnetotaxis) have been observed in marine and freshwater sediments of the Northern Hemisphere1,2. Their orientation is due to one or more intracytoplasmic chains of single-domain magnetite particles3. These linearly arranged particles impart a net magnetic dipole moment to the bacterium, parallel to the axis of motility. Northern Hemisphere magnetotactic bacteria with unidirectional motility swim consistently in the direction of the magnetic field, that is, to the geomagnetic North1,2,4. This implies that their magnetic dipole is systematically orientated with the North-seeking pole forward. The magnetic polarity can be reversed by single, magnetic pulses of high field strength (1–2 µs, 300–600 G), and these bacteria then swim along magnetic field lines to the South5. Due to the inclination of the Earth's magnetic field, magnetotactic bacteria which swim to the North in the Northern Hemisphere are directed downward at an angle increasing with latitude. It has been suggested that this downward-directed motion confers a biological advantage by guiding the bacteria, when dislodged, back to the sediments1. On the basis of this hypothesis, magnetotactic bacteria of the Southern Hemisphere would be expected to swim to the South to reach the bottom. We report here several morphological types of magnetotactic bacteria present in sediments of the Southern Hemisphere. These bacteria indeed swim consistently to the South, hence downward along the Earth's inclined magnetic field lines, as hypothesized. As revealed by electron microscopy, they contain internal chains of electron-opaque particles similar to those observed in magnetotactic bacteria from the Northern Hemisphere. Like their Northern Hemisphere counterparts, their magnetic polarity can be permanently reversed and they cannot be demagnetized. We also report on Northern Hemisphere magnetotactic bacteria incubated in Southern Hemisphere magnetic conditions, confirming the biological relevance of downward directed motility.


Journal ArticleDOI
TL;DR: Cysts formed during the late spring in temperate waters are capable of excystment several months later as fall temperatures decrease; those formed in the fall take longer to mature, but are viable after six months of overwintering.
Abstract: Plankton samples from a dense bloom of the toxic red tide dinoflagellate Gonyaulax tamarensis Lebour were incubated in the laboratory to study the formation and development of thick-walled, overwintering cysts. Samples, contained very few cysts, and fusing cells were seen only twice. However, thousands of elongate cysts were formed from large posteriorly biflagellated cells (presumed to be planozygotes) that comprised approximately 50% of the initial motile population. Development of these new cysts (hypnozygotes) was studied under different storage conditions. Each hypnozygote lost pigmentation and formed a thick cell wall during the first several days of storage, producing a starch-filled cell with a yellow accumulation body. Starch reserves decreased rapidly during storage at warm (22 C) temperatures and more slowly at 5 C (with no apparent effect from light, dark, or added nutrients). Excretion of mucilaginous material was also observed. Periodic germination experiments showed that 22 C temperatures led to rapid development of the hypnozygote, with germination possible 1 mo after formation, whereas 5 C storage retarded development, with the first revivals after nearly 4 mo. Excystment was initiated only after an applied stimulus—either a temperature increase or decrease depending on the previous storage temperature. Cysts formed during the late spring in temperate waters are thus capable of excystment several months later as fall temperatures decrease; those formed in the fall take longer to mature, but are viable after six months of overwintering. Alternating spring and fall blooms seeded by germinating populations of dormant cysts are thus possible, a finding consistent with recent field observations.

Journal ArticleDOI
TL;DR: Gyre scale and local vorticity balances for a single numerical experiment designed to elucidate the role of eddies in the oceanic general circulation are examined in this article, where the applicability of Sverdrup dynamics in various parts of the fluid and the manner in which the deep abyssal gyres are driven are examined.
Abstract: Gyre scale and local vorticity balances are examined for a single numerical experiment designed to elucidate the role of eddies in the oceanic general circulation. Due to the complex nature of the flow, a combination of different analyses is needed. In particular the mean potential vorticity fields are calculated and related to local and global vorticity fluxes. The nature of eddy generation and decay is discussed in terms of eddy enstrophy balances in the fluid. Momentum balances in various parts of the gyre are deduced through the application of the circulation theorem. Fields of eddy diffusivity for the mixing of potential vorticity and heat are determined. The applicability of Sverdrup dynamics in various parts of the fluid and the manner in which the deep abyssal gyres are driven are examined. The net picture is a complex but consistent one. In the upper layer, eddy generation occurs in the separation region of the eastward jet and in the region of westward return flow. Eddy decay occurs pri...

Journal ArticleDOI
TL;DR: A 2-month marine geophysical study of the Banda arc region was conducted in late 1976 using the R/V Atlantis II of WHOI and the R /V Thomas Washington of SIO; 19 seismic refraction lines were successfully completed as discussed by the authors.
Abstract: A 2-month marine geophysical study of the Banda arc region was conducted in late 1976 using the R/V Atlantis II of WHOI and the R/V Thomas Washington of SIO; 19 seismic refraction lines were successfully completed. Oceanic crust underlies the Banda Sea and Weber Deep. Continental crust 35 to 40 km thick underlies the Australian Shelf. Thick continental crust is also present beneath the Timor and Aru Troughs. Low-amplitude magnetic anomalies are present over the Australian Shelf and extend to near the western edge of the Banda outer arc and, together with the presence of metamorphic rocks, suggest that continental crust may extend to the eastern lip of the Weber Deep. Continuous seismic reflection profiling shows the Australian Shelf sedimentary sequence dipping beneath th accretionary prisms of the outer Banda arc at the Timor and Seram Troughs: the tectonic front of the subduction zone lies along the axis of these troughs. The bathymetric profile on the outer flank of the Timor and Seram Troughs is unusual in that the profile asymptotically approaches a shallow depth near sea level and no outer rise is present as at oceanic trenches. An elastic-flexure analysis of this topographic profile indicates that an elastic plate is an incorrect model for the lithosphere at this plate-convergence zone. The Aru Trough, although structurally on trend with the Timor Trough, is not presently a site of subduction and compression tectonics. Instead, it is now a place of crustal extension, and is an example of graben formation that is separating a block of Australian co tinental crust (beneath the Kai Islands) from the Australian platform. The present lack of structural continuity between the Seram Trough and the Aru and Timor Troughs is best demonstrated by the pattern of gravity anomalies. The discontinuity between the Seram and Aru Troughs supports the seismic evidence that the Seram subduction zone is separate from the Southern Banda subduction zone that is continuous with that beneath Java on the west. The Bouguer gravity anomaly pattern indicates a division of the Banda arc into four segments: a southern segment, Timor to Babar, with relative plate convergence possibly trending about N20°W between the Banda and Australian plates; a central segment from Tanimbar to about Kasiui beneath which the Java to Timor Benioff zone is bent to a northwar trend; a Seram segment that is converging with the Australian platform along approximately a S70°W trend; and a Buru segment that has rifted away from the Sulu Islands. The southern segment has been undergoing compressional deformation distributed across the width of the arc for the last 3 m.y. with attendant slowing of the differential-slip rate between the leading edge of the accretionary wedge and the underthrust Australian margin crust. Oblique convergence and the bend of the Benioff zone produce in the Tanimbar to Kasiui segment a slower convergence rate normal to the arc at the southern end which diminishes northward and changes to extension normal to the arc at the Aru Trough. Thrust focal mechanisms indicate that subduction is presently active at the Seram Trough. Seafloor- preading magnetic anomalies appear to have been found in the south Banda basin. The trend approximately N60 to 70°E, similar to Cretaceous anomalies in the eastern Wharton basin, suggests the possibility that the Banda Sea may be trapped oceanic crust. Water depths of 5 km and low heat flow (generally 1.5 HFU or less) are compatible with an old age (greater than 25 to 60 m.y.) for the Banda Sea crust. We conclude that the Outer Banda arc from Buru around to Timor, and possibly to Sumba, contained Australian continental crustal blocks and fragments prior to its collision with the Australian margin in the last 3 to 6 m.y. Continuous convergence following the addition of a thick Australian margin sedimentary sequence to the south Banda subduction zone has led to deformation being distributed over the width of the arc and not simply being taken up on a single thrust surface. This scenario helps reconcile the geologic relations on Timor, Seram, and Buru with the structural continuity of the Timor Trough with the Java Trench. End_Page 868------------------------------

Journal ArticleDOI
TL;DR: The metazoan parasite fauna of 52 species of deep-living benthic fishes from depths of 53 to 5000m off the New York Bight is studied to find out why fish from within the submarine canyon are more heavily infested than those living without.
Abstract: We have studied the metazoan parasite fauna of 52 species of deep-living benthic fishes from depths of 53 to 5000m off the New York Bight (39–49°N; 70–72°W). 17144 parasites were recovered from 1712 fishes. The infestation rate was 80%, with an average of 12.5 worms per host. Percentage occurrence by group among all fishes was Monogenea 12.9%, Digenea 48%, Cestoda 22.1%, Nematoda 54.5%, Acanthocephala 3.8%, and Copepoda 4.5%. Differing composition of the parasite fauna in different fish species reflects differences in diet. Specialized feeders are rather distinct; generalized feeders, which predominate, show overlaps in parasite fauna. In individual species, changes in diet with growth are reflected in changes in the parasite fauna. Infestation rate is directly related to abundance of the free-living fauna; hence, fish from within the submarine canyon are more heavily infested than those living without. Although it contains fewer families and genera than shallow faunas, the deep-sea parasite fauna is not extremely unusual in terms of its abundance, diversity, or host specificity. At the greatest depths, parasite abundance and diversity dramatically decline.

Journal ArticleDOI
01 Aug 1980-Nature
TL;DR: In this article, direct flux measurements and composition of lipids obtained by organic geochemical studies of particulate material collected in a deep-sea moored sediment trap experiment in the equatorial Atlantic Ocean are reported.
Abstract: The vertical flux of particulate organic matter to the ocean floor is controlled by complex remineralization and transport processes. Rapidly sinking, large (>32 µm) particles may account for most of the vertical mass flux1–3. Experiments involving collection of sedimenting particles in traps deployed at varying depths in the water column provide a way of assessing these processes directly2–12. Measurement of organic carbon content of trap material may lead to a general understanding of the flux of particulate organic matter to the sea floor3,8–10. However, details of the transport and transformation phenomena involving sinking particulate organic material can be elucidated only by determining distributions of specific organic compounds associated with the particles11,12. We report here direct flux measurements and composition of lipids obtained by organic geochemical studies of particulate material collected in a deep-sea moored sediment trap experiment in the equatorial Atlantic Ocean.

Journal ArticleDOI
TL;DR: The major assemblages (identified by the dominant taxa) are the Dictyococcites minutus, Cyclicargolithus floridanus, Coccolithus pelagicus, Reticulofenestra pseudoumbilica-R. haqii, and Discoaster-Sphenolithus as mentioned in this paper.
Abstract: Biogeographic patterns of Miocene calcareous nannoplankton in the North and South Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico are apparent from a Q-mode factor analysis of census data from 49 DSDP sites. In a total of 444 relatively well-preserved Miocene samples, 5 major and 1 minor (but relatively important) assemblages were recognized, most of which show distinct spatial and temporal distribution patterns. The major assemblages (identified by the dominant taxa) are the Dictyococcites minutus, Cyclicargolithus floridanus, Coccolithus pelagicus, Reticulofenestra pseudoumbilica-R. haqii, and Discoaster-Sphenolithus assemblages. Four of the major assemblages show distinct shifts through latitudes that are interpreted as a response to changing climate. Four warming and cooling cycles of 4 to 4.5 m.y. duration are identified in the Miocene. Both the paleobiogeographic and available isotopic data show the warming episode between 17 and 15.5 Ma and the cooling trend that followed, as well as the warming episode between 9 and 7 Ma, to have been particularly extreme in both Hemispheres, and probably of global extent. The sharp cooling centered at 1 5 Ma and the biogeographic changes at this time suggest this event to have been associated with the development of an extensive ice-cap on Antarctica. Biogeographic history of Miocene calcareous nannoplankton and paleoceanography of the Atlantic Ocean

Journal ArticleDOI
TL;DR: In this article, a simplified pore-fluid age equation for 4He and 222Rn is presented, which is virtually independent of the porosity, the water/rock ratio, the rock density and the uranium concentration.


Journal ArticleDOI
22 Feb 1980-Science
TL;DR: In this article, the heat transported by currents across 25°N in the Atlantic Ocean is estimated from oceanographic measurements to be 1.1 x 1015watts northward.
Abstract: The heat transported by currents across 25°N in the Atlantic Ocean is estimated from oceanographic measurements to be 1.1 x 1015watts northward. This figure agrees, within estimated error, with the value obtained from charts of energy exchange between ocean and atmosphere but is smaller by a factor of 2 than the recent value derived from satellite radiation measurements.

Journal ArticleDOI
01 Apr 1980-Geology
TL;DR: In this article, the authors show that seafloor-spreading magnetic lineations can be used to identify minor and variable offset fracture zones formed by the decoupling of adjacent spreading centers over a period of at least 15 m.y.
Abstract: Normal oceanic crust in the North Atlantic is typically formed in strips 50 to 80 km wide separated by fracture zones. Anomalous seismic crustal structure (less than 10 km wide) is found beneath fracture zones regardless of the amount of offset. Although many of these fracture zones exhibit minor and variable offsets in the seafloor-spreading magnetic lineations, they separate crust with distinctively different basement morphology and magnetic signatures even when there is no offset apparent in the magnetic lineations. The pattern of both the basement relief and the magnetic anomalies provides the evidence for the persistence of minor and variable offset fracture zones formed by the decoupling of adjacent spreading centers over a period of at least 15 m.y. of seafloor spreading.

Journal ArticleDOI
TL;DR: In this article, a survey of the region between the Grand Banks and the Mid-Atlantic Ridge, including a grid of hydrographic stations, and two long lines of near-bottom current-meter moorings across the Gulf Stream and North Atlantic Current, respectively, is described.
Abstract: During April–June 1972 three ships conducted a survey of the region between the Grand Banks and the Mid-Atlantic Ridge, including a grid of hydrographic stations, and two long lines of near-bottom current-meter moorings across the Gulf Stream and North Atlantic Current, respectively. The purpose was to map the property distributions and current field where the Gulf Stream branches, in greater detail and with less ambiguity than hitherto; that material is described here. Worthington's hypothesis that the primary current system there is not a branching Gulf Stream but portions of two separate (and nongeostrophic) gyres is criticized at length in terms of the observed property distributions; it is shown that, given a moderate degree of lateral mixing, they are consistent with the branching, geostrophic flow field, and that there is no need to abandon established physics in order to rationalize them. The deep motions recorded by the current meters on the North Atlantic Current line were roughly sugge...

Journal ArticleDOI
TL;DR: Levels of microsomal cytochrome P-450 and aminopyrine demethylase activity in liver and in kidney of gonadally mature rainbow and brook trout were markedly greater in males than in females, suggesting sex-specific forms of cytochromes P- 450 of different catalytic function.

Journal ArticleDOI
01 Dec 1980
TL;DR: In this paper, an analysis of two hydrographic sections and records from moored instruments showed that the flow over a 400m high seamount, centred at 36°N, 55°W in the recirculation region of the Gulf Stream system, resembles a stratified Taylor column.
Abstract: Analyses of two hydrographic sections and records from moored instruments show that the flow over a 400-m high seamount, centred at 36°N, 55°W in the recirculation region of the Gulf Stream system, resembles a stratified Taylor column. Potential density sections indicate a bottom intensified uplifting over the seamount with a vertical scale of approx. 3 km. Time series of relative vorticity deduced from the current meter records show a significant correlation with the bathymetry and a similar vertical scale as seen in the density structure. Estimates of the vorticity balance nominally 1000 m above the bottom demonstrate that the balance is between the advection of relative vorticity and vertical vortex stretching which is consistent with Taylor column behavior. Objective stream function maps at the same depth show closed contours near the seamount for most of the nine-month duration of the moored array. The results suggest that the bathymetry distorts the larger scale mean circulation so as to produce large amplitude, small scale variability which should be taken into account before one extrapolates isolated measurements from moored instruments.

Journal ArticleDOI
TL;DR: Changes in concentrations of free sterols in decomposing Spartinn dternijloru indicate that this marsh grass may be a significant source of sterols, primarily sitosterol, to tidal waters.
Abstract: Changes in concentrations of free sterols in decomposing Spartinn dternijloru indicate that this marsh grass may be a significant source ofsterols, primarily sitosterol, to tidal waters. These tidal waters may then transport the sterols {adsorbed to particulate matter) to nearby coastal sediments. Estimates of bacterial and fkngal biomass in the detritus show that the living cells of these microbes account for only a minor part of the relative increase in nitrogen observed during decomposition. Biomass was cstimatcd by direct counts for bacteria and by measuring the concentration of ergosterol-a sterol specific to fungi.

Journal ArticleDOI
TL;DR: In this paper, first-appearance datums (FADs), twenty-three last appearance datums, and three other micropaleontological datums are related to the magnetic-reversal, oxygen-isotope, and calcite-dissolution/coarse-fraction time scales to provide a preliminary basis for subdivision of the Quaternary in deep-sea sediments.

Journal ArticleDOI
01 Sep 1980-Geology
TL;DR: In this article, stable-isotopic signals and biostratigraphic events in Deep Sea Drilling Project (DSDP) cores were used to improve chronologic resolution with an aim to reconstruct the paleoenvironment of the preglacial and postglacial Miocene oceans.
Abstract: A search for stable-isotopic signals and biostratigraphic events in Deep Sea Drilling Project (DSDP) cores to improve chronologic resolution with an aim to reconstruct the paleoenvironment of the preglacial and postglacial Miocene oceans has led to the recognition of an apparently global decrease in the benthic foraminiferal δ 13 C in the latest Miocene. This carbon-isotopic shift is consistently bracketed by the first evolutionary appearances of several taxa of phytoplankton the ages of which have been accurately estimated from paleomagnetically dated piston cores. The first appearance of nannofossils Amaurolithus primus and A. delicatus at 6.25 m.y. B.P. and the diatoms Thalassiosira praeconvexa and Nitzschia miocenica elongata at 6.10 and 6.00 m.y. B.P., respectively, and the carbon-isotopic shift itself (dated between 6.10 and 5.90 m.y. B.P.) provide convenient synchronous events to aid in the reconstruction of the late Miocene world ocean. Magnetostratigraphically estimated ages of other useful late Miocene nannofossil events include first appearances of Discoaster quinqueramus at 8.00 m.y. B.P., D. surculus at 6.40 m.y. B.P., Amaurolithus tricorniculatus s.s. at 5.70 m.y. B.P., A. amplificus at 5.65 m.y. B.P., and Ceratolithus acutus at 5.20 m.y. B.P., and the last appearances of D. quinqueramus at 5.45 m.y. B.P. and A. amplificus at 5.30 m.y. B.P.