Distribution of hornblende on the Atlantic continental shelf off Georgia, United States

Hornblende is the least stable, and most diagnostic, mineral of the sediment blanketing the continental shelf off Georgia, U.S.A. Recent work by others has shown that the probable sources of hornblende-rich sands on the shelf are the Savannah and Altamaha Rivers, both of which originate in the southern Appalachian piedmont. Rivers with drainage basins confined to the coastal plain carry stable, low-hornblende heavy-mineral assemblages and contribute sediment to the shelf only during episodes of regression or transgression. Distribution of hornblende on the continental shelf reveals the importance of the Altamaha and Savannah Rivers, especially the Savannah, as sources of sediment. It is postulated that original point concentrations of hornblende-rich sand associated with Late Pleistocene deltas or estuaries of the Savannah River have been modified by southwest currents, possibly during winter storms. The resulting configuration is a series of northeast-trending, linear high-hornblende anomalies. The origin of the hornblende-distribution anomalies probably is identical to the origin of linear shoals that also trend northeast across the continental shelf.     

Observations of turbulent mixing and vertical diffusive salt flux in the Changjiang Diluted Water

Based on micro structure measurements from a repeated sampling station southwest of the Jeju Island during summer,we studied the hydrography,pycnocline turbulence,and vertical salt flux in the Changjiang Diluted Water(CD W).The water column was well stratified with the CDW occupied the surface～20 m.Most of the large turbulent kinetic energy dissipation rate(ε) were found in the bottom boundary layer.Interestingly,intermittent strong turbulence(ε>10^-6 W/kg) occurred in the pycnoclin...     

Benthic Associations of the Shelfbreak and Upper Slope off Ubatuba-SP, South-eastern Brazil

The composition and distribution of the benthic communities at the shelfbreak and upper slope of the Ubatuba region (south-eastern Brazil) were studied from a limited set of 15 dredge hauls taken between 130 and 600 m depth. Data analysis using multivariate methods showed the presence of three distinct benthic associations, related to depth and substratum. The first, between 130 and 180 m depth, was associated with the presence of large amounts of calcareous algal blocks, serving as a shelter for most of the organisms sampled, as well as an important substratum for sessile and filter-feeding animals. The second association was from the slope (240–350 m) comprising organisms exclusive to that area, and species common on shallower stations. The major faunal changes were observed in the third association at 500 m, which presented a fauna totally distinct from the former regions. It is suggested that this area is probably an upper limit for deep-living organisms in the region.     

Skewed Water Temperature Occurrence Frequency in the Sea off Sanriku, Japan, and Intrusion of the Pure Kuroshio Water

Temperature and salinity data obtained by the Iwate Fisheries Technology Center were analyzed for the period 1971–1995. It was found that occurrence frequency distributions of temperature and salinity are very skewed at depths deeper than 200 m and that temperature sometimes exceeds m + 5σ (m: mean and σ: standard deviation. If such abnormally high temperatures are real the 3σ criterion cannot be adopted. Oceanic conditions were surveyed in 1972 and 1979, when temperatures exceeding m + 5σ were observed. It was found that the abnormally high temperature (and high salinity) water was the pure Kuroshio Water introduced into the region due to some special conditions such as abnormal approach of large warm-core ring to the Sanriku Coast or abnormal northward extension of the Kuroshio along the coast. These events are very rare, occurring only twice in the 25-year period analyzed, but the abnormally high temperature observed is real. This revised version was published online in July 2006 with corrections to the Cover Date.     

The downward flux of biogenic material in the NE subarctic Pacific: importance of algal sinking and mesozooplankton herbivory

In the present study we examine factors that affect the downward flux of biogenic carbon in the NE subarctic Pacific, one of the important high-nutrient-low-chlorophyll (HNLC) regions in the open ocean. We focus on the role of mesozooplankton, since their seasonal peaks in biomass and growth are in phase with the seasonal variations in the downward POC fluxes, whereas phytoplankton biomass is more-or-less uniform year-round. The relative importance of mesozooplankton and algal sinking was examined using the pigment composition of material accumulated in short-term free-drifting sediment traps positioned just below the upper stratified surface layer (ca. 100–200 m). This was compared with the phytoplankton composition in the surface waters, and with the grazing activity (gut pigments and fecal pellet production rates) of the most abundant large copepods. We also examined whether the relationships between the downward flux of carbon and pelagic processes were similar in the coastal, continental margin and offshore HNLC regions of the NE subarctic Pacific, the latter represented by Ocean Station Papa (OSP).Our results show that grazing had a variable impact on the downward flux of biogenic carbon. Carbon-transformed pheopigments (particularly pyropheophorbide a, frequently associated with copepod grazing) represented up to 13% of the total downward POC flux inshore (in May 1996) and 8–9% at OSP in May and February 1996, respectively. This flux of pheopigments was accompanied by a large potential input of fecal pellets from large copepods (as estimated from defecation rates of freshly collected animals) only in May 1996 at OSP, suggesting that pheopigments came from other sources (other herbivores, senescing algae) in February. The larger flux of pheopigments in May was probably related to the abundance of mesozooplankton at that time of the year. During summer (August 1996), both the flux of pheopigments and the potential input of fecal pellets from large copepods were negligible at OSP, consistent with more intense pelagic recycling reported in other studies. Inshore, the flux of carbon-transformed pheopigments was slightly higher than at OSP, and its contribution to the downward POC flux in May 1996 was twice that in August 1996. In contrast, the potential input of feces carbon was higher in August than in May 1996, again suggesting other sources for pheopigments found in the traps. The contribution of sinking phytoplankton to the downward biogenic flux was negligible in summer, when prymnesiophytes (indicated by the presence of 19′-hexanoyloxyfucoxanthin) and pelagophytes (19′-butanoyloxyfucoxanthin-containing) dominated in surface offshore waters. The contribution of sinking algae was maximal (9%) in winter (February 1996) at OSP, when fucoxanthin (mainly a diatom marker) dominated the carotenoid composition in the traps and when the abundance of diatoms in surface waters showed its seasonal maximum for this station. Inshore, the low contribution of diatoms (fucoxanthin) to the sinking fluxes may have resulted from inadequate sampling (i.e. the spring bloom may have been missed).Overall, we conclude that: (a) large copepods significantly influenced the downward POC flux only during spring at OSP; (b) unidentified herbivores (e.g. salps, pteropods) producing pigmented, fast-sinking fecal material likely had an important impact during winter; (c) algal sinking made a small contribution to the downward POC flux (maximum in winter); and (d) neither algal sinking nor mesozooplankton grazing had a significant influence on the downward flux of biogenic material in summer at OSP.     

Surface circulation and vertical structure of current off the Keum River estuary,Korea in later spring 2008

To examine the surface circulation and vertical structure of currents in the region of the Keum River (KR) plume, we analyzed the subinertial surface currents obtained by high frequency radar and the vertical profiles of currents measured at a station (M1) located 10 km distance from the estuary mouth for one month in late spring 2008. Monthly-mean surface circulation is composed of the westward flow from the estuary mouth and the northward flow in the offshore. These surface mean currents are a gradient (geostrophic) current around the monthly-mean plume bulge. Dominant variabilities of the surface currents, winds, and KR-outflow are decomposed by the Empirical Orthogonal Functions (EOF). The first current EOF mode, explaining 39% of total variation, is primarily related to the first wind EOF mode varying along the coast and the second current mode, explaining 33% of total variation, is mainly related to the first KR-outflow EOF mode varying along the mean KR-outflow direction. Meanwhile, vertical profile of the monthly-mean current at M1 shows a two-layer structure of the current flowing offshore (onshore) in the upper (lower) layer because the water column is divided by a pycnocline at 7-9 m depths below the plume water. This two layer structure is a background persisting current structure, at least in spring, maintained by the geostrophic balance induced by the sea level slope and density gradient along the line normal to the westward mean surface current direction due to monthly-mean plume bulge off the KR estuary. EOF analysis of vertical current profiles reveals that the first mode, explaining 43% of total variation, represents the two-layer structure of the current variability. The upper-layer current varies along a line normal to the mainland coastline and the low-layer one varies approximately along a line parallel to the coastline, with direction difference of about 115° between the upper-and low-layer. From the correlation analysis it is found that 60% of the first mode variation is influenced by the first mode of KR-outflow and 36% by the first mode of wind. Any forcing modes of KR-outflow and wind influencing the other current vertical modes could not be found in the present study.     

Chemical characteristics and estimation on the vertical flux of N, P, Si in upwelling area of Taiwan Strait

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Plankton dynamics and carbon flux in an area of upwelling off the coast of Morocco

A carbon flux study was carried out off the coast of Morocco, at 31°N, in a region characterized by the presence of a persistent cyclonic eddy. Two short-term (4 and 3 day) deployments of free-floating sediment traps were combined with water column sampling and rate process measurements as the ship followed the traps. For a period of 36 h between trap deployments, a hydrographic section was run along 31°30'N as part of a larger scale survey being carried out simultaneously on the R.V. A. von Humboldt. The first trap deployment was near the eastern margin of the eddy and the traps moved to the north and west in a frontal jet associated with its northern boundary. After the second deployment, which was at the recovery point of the first, the traps moved to the west and then to the southwest. Throughout the study, chlorophyll concentrations varied between 27 and 125 mg m⁻² (0–100 m), with highest concentrations in the upwelled water nearest the coast and in upwelled water generated within the cyclonic eddy. Particulate organic carbon (POC) and particulate organic nitrogen (PON) concentrations were relatively uniform (13.6±1.8 and 1.63±28 g m⁻² with phytoplankton carbon accounting for 16–85% of total POC. Bacterial carbon was 5% of total POC and mesozooplankton carbon concentrations were equivalent to 9% of total POC. Microzooplankton biomass was not assessed but POC:PON ratios in the water column were often high, suggesting there was sometimes a large detrital component in the POC. Primary production rates varied between 1.0 and 2.5 g C m⁻² day⁻¹. Bacterial consumption accounted for 50% of primary production. Metabolic rates suggested that copepods were ingesting more than 0.4 g C m⁻² day⁻¹. while filtration rates suggested that ingestion of phytoplankton carbon was only 0.2 g C m⁻²day⁻¹, even when phytoplankton constituted 85% of the POC. f-ratios (based on uptake rates for ¹⁵N-nitrate and ammonia) were between 0.1 and 0.4, and excretion by mesozooplankton could account for 40% of the daily ammonium uptake by phytoplankton. HPLC pigment analysis showed that when chlorophyll biomass was high, diatoms were dominant, whereas when it was low, small prymnesiophytes, chlorophytes and diatoms were all important. The composition of the fluoresecent pigments in material in the sediment traps indicated that intact phytoplankton and copepod faecal pellets were the main sources but the relative rates of sedimentation of pigment, POC and PON for the two trapping periods did not reflect differences that were observed in the overlying water column. This was likely to be the result of spatial heterogeneity and strong horizontal currents heterogeneity and strong horizontal currents within the euphotic zone. Thus, material collected at 100 m probably did not originate in the water column immediately overlying the traps and trapping efficiencies might also have been variable.     

Marine ecosystem approaches to management: challenges and lessons in the United States

This study examined how the United States’ largest marine resource management agency, the National Oceanic and Atmospheric Administration (NOAA), has begun to change its management strategy away from traditional marine resource management approaches towards an Ecosystem Approach to Management (EAM). Surveys were conducted with 57 NOAA scientists and resource managers in nine NOAA programs in 8 different geographic regions across the United States in 2005. A qualitative analysis examined the attitudes and experiences of participants with respect to implementing EAM and identified four major challenges to enhancing cooperation and understanding of EAM. We conclude with recommendations for concrete initiatives that future efforts in EAM that any management agency can undertake to facilitate further ecosystem management opportunities.     

Thorium-234 as a tracer of spatial,temporal and vertical variability in particle flux in the North Pacific

An extensive ²³⁴Th data set was collected at two sites in the North Pacific: ALOHA, an oligotrophic site near Hawaii, and K2, a mesotrophic HNLC site in the NW Pacific as part of the VERTIGO (VERtical Transport In the Global Ocean) study. Total ²³⁴Th:²³⁸U activity ratios near 1.0 indicated low particle fluxes at ALOHA, while ²³⁴Th:²³⁸U ～0.6 in the euphotic zone at K2 indicated higher particle export. However, spatial variability was large at both sites—even greater than seasonal variability as reported in prior studies. This variability in space and time confounds the use of single profiles of ²³⁴Th for sediment trap calibration purposes. At K2, there was a decrease in export flux and increase in ²³⁴Th activities over time associated with the declining phase of a summer diatom bloom, which required the use of non-steady state models for flux predictions. This variability in space and time confounds the use of single profiles of ²³⁴Th for sediment trap calibration purposes. High vertical resolution profiles show narrow layers (20–30 m) of excess ²³⁴Th below the deep chlorophyll maximum at K2 associated with particle remineralization resulting in a decrease in flux at depth that may be missed with standard sampling for ²³⁴Th and/or with sediment traps. Also, the application of ²³⁴Th as POC flux tracer relies on accurate sampling of particulate POC/²³⁴Th ratios and here the ratio is similar on sinking particles and mid-sized particles collected by in-situ filtration (>10–50 μm at ALOHA and >5–350 μm at K2). To further address variability in particle fluxes at K2, a simple model of the drawdown of ²³⁴Th and nutrients is used to demonstrate that while coupled during export, their ratios in the water column will vary with time and depth after export. Overall these ²³⁴Th data provide a detailed view into particle flux and remineralization in the North Pacific over time and space scales that are varying over days to weeks, and 10's–100's km at a resolution that is difficult to obtain with other methods.     

海南东方近岸海底活动沙波的地球物理特征及其迁移机制

海南东方近岸海底发育有大量沙波,利用多波束测深、侧扫声呐、浅地层剖面、单道地震资料综合分析了活动沙波的地球物理特征,探讨了沙波的分布特征、迁移机制、活动性及形态演变特征。结果表明,研究区海底沙波分布和规模具有显著空间差异性,大中型沙波主要发育于沙脊上,小型沙波主要发育于沙脊两侧,坑槽区发育近对称沙波,研究区西南部沙波不发育。受潮流和科氏力约束,在海底沙脊西侧沙波迁移方向主要为向北（略偏东）,在沙脊东侧主要为向南（略偏西）;受地形制约,坑槽区近对称沙波迁移可能停止或方向发生改变。沙波活动性强的标志主要包括：① 形态呈不对称的“脊尖槽缓”,② 叠置小沙波与沙纹发育,③ 浅部有透明层,④ 陡坡面反射模糊,⑤ 内部斜交前积结构。分析认为,沙波活动性与其形态密切相关,包括弱运动、强运动、不运动3个演变阶段。     

Hydrocarbon migration and accumulation of the Suqiao buried-hill zone in Wen'an Slope,Jizhong Subbasin,Bohai Bay Basin,China

The hydrocarbon migration and accumulation of the Suqiao deep buried-hill zone, in the Jizhong Subbasin, the Bohai Bay Basin, eastern China, was investigated from the perspective of paleo-fluid evidence by using fluid inclusions, quantitative fluorescence techniques (QGF), total scanning fluorescence method (TSF) and organic geochemical analysis. Results show that the current condensate oil-gas reservoirs in the study area once were paleo-oil reservoirs. In addition, the reservoirs have experienced at least two stages of hydrocarbon charge from different sources and/or maturities. During the deposition of the Oligocene Dongying Formation (Ed), the deep Ordovician reservoirs were first charged by mature oils sourced from the lacustrine shale source rocks in the fourth member of Shahejie and Kongdian Formations (Es₄+Ek), and then adjusted at the end of Ed period subsequently by virtue of the tectonic movement. Since the deposition of the Neogene Minghuazhen Formation (Nm), the reservoirs were mainly charged by the gas that consisted of moderate to high-maturity condensate and wet gas sourced from the Es₄+Ek lacustrine shale source rocks and mature coal-derived gas sourced from the Carboniferous-Permian (C-P) coal-bearing source rocks. Meanwhile, the early charged oil was subjected to gas flushing and deasphalting by the late intrusion of gas. The widely distributed hydrocarbon inclusions, the higher QGF Index, and FOI (the frequency of oil inclusions) values in both gas-oil and water zone, are indicative of early oil charge. In addition, combined with the homogenization temperatures of the fluid inclusions (<160 °C) and the existence of solid-bitumen bearing inclusions, significant loss of the n-alkanes with low carbon numbers, enrichments of heavier components in crude oils, and the precipitation of asphaltene in the residual pores suggest that gas flushing may have played an important role in the reservoir formation.     

溢油污染物在海底沉积物中的识别与垂向迁移——大连湾海底沉积物研究

沉积物插管短柱样品于2013年4月采自大连湾2010年“7·16”溢油事故污染区,BQ050站与BQ007站分别位于生物分散剂和化学分散剂喷洒区。沉积物的可溶有机质含量(沥青A)、有机碳同位素组成(δ¹³C_org)和²¹⁰Pb比活度分析结果表明:喷洒生物分散剂的重污染区(BQ050站),沉积物中TOC含量为0.58%～1.51%,平均为1.15%;δ¹³C_org值为-22.2‰～-20.5‰PDB,平均为-21.74‰PDB;沥青A含量为0.061 5%～0.566 4%,平均为0.174 9%;沥青A/TOC比值为7.0%～34.8%,平均为14.13%;²¹⁰Pb_ex比活度存在异常峰值分布,垂向分布特征与沥青A相似;2～16 cm段沉积物的可溶有机质具有明显的外来输入特征。喷洒化学分散剂的较轻污染区(BQ007站),沉积物中TOC含量为0.61%～1.14%,平均为0.87%,除8～14 cm层段外,比BQ050站略低;但沥青A含量与沥青A/TOC比值明显低于前者;δ¹³C_org值较BQ050站轻;²¹⁰Pb_ex比活度随柱样深度呈指数衰减,对数相关;外来有机质输入量较低。截至2013年4月,BQ050站溢油污染物在海底下16 cm深度处有特征信号,溢油污染物沥青A 组分垂向迁移距离约为15 cm。     

The geochemistry of lead in rivers,estuaries and the continental shelf of the Southeastern United States

Transport by southeastern rivers has insignificant influence on the lead concentration of southeastern shelf waters. If the rate of mobilization and transport of lead by these rivers is representative of uncontaminated fluvial transport during the Pleistocene, only about 5% of the prehistoric output of lead to the North Atlantic can be accounted for by river input.Lead concentrations in southeastern shelf waters are similar to those of North Atlantic Water from the upper 1000 m, which is probably similar to the intrusion source water for the shelf. Atmospheric inputs to the shelf of the same magnitude as observed for the Western North Atlantic are difficult to reconcile given the residence time of shelf waters and their lead concentration unless the rate of loss of lead to shelf sediments is about the same as the atmospheric flux.     

Hydrographic Structure and Transport of Intermediate Water in the Kuroshio Region off the Boso Peninsula, Japan

Hydrographic structure and transport of intermediate water were observed in the Kuroshio region south of Japan, focusing on the 26.6–27.5σ_θ density in six cruises from May 1998 through September 2001. In the section off the Boso Peninsula where the Kuroshio exfoliates eastward, the intermediate water was clearly clustered into three groups meridionally composed of the coastal water, the Kuroshio water and the offshore water. Compared with the Kuroshio water characterized by warm, salty water transported by the Kuroshio, the coastal and offshore waters significantly degenerated due to mixing with cold, fresh waters originated from the subarctic region: the former was affected by alongshore spread of the coastal Oyashio and the latter by direct intrusion of the new North Pacific Intermediate Water (NPIW) into the southern side of the Kuroshio current axis. Particularly the offshore water showed higher apparent oxygen utilization (AOU) in layers deeper than 26.9σ_θ while it showed lower AOU in layers shallower than 26.9σ_θ, which indicated that colder, fresher and higher AOU water was distributed on the southeastern side of the Kuroshio in deeper layers. In May 1998, the Oyashio-Kuroshio mixing ratio was estimated to be typically 2:8 for the offshore water on the assumption of isopycnal mixing. Moreover, northeastward volume transport of the Kuroshio water was obtained from geostrophic velocity fields adjusted to lowered acoustic Doppler current profiler (LADCP) data to yield 6.1 Sv at 26.6–26.9σ_θ and 11.8 Sv at 26.9–27.5 σ_θ. This revised version was published online in July 2006 with corrections to the Cover Date.     

Diel vertical migration of the copepod Calanus sinicus before and during formation of the Yellow Sea Cold Bottom Water in the Yellow Sea

To understand the effects of the Yellow Sea Cold Bottom Water(YSCBW)on the diel vertical migration(DVM)of the copepod Calanus sinicus,we surveyed vertical distribution of C.sinicus at a fixed station in the Yellow Sea before(spring)and during(summer)formation of the YSCBW.Cold water(<10 C)was observed in the bottom layer when the water column was thermally stratified in summer,but the water column was thermally well-mixed in spring 2010.Samples were collected from five different layers at 3-h intervals using an opening-closing net.Adult females(1–155 ind./m3)showed a clear normal DVM pattern throughout the entire water column in spring,whereas adult males did not migrate.DVM of copepodite V(CV)individuals was not clear,but the maximum abundance of CI–CIV occurred consistently in the upper 10–20 m layer,where there was a high concentration of chlorophyll-a(Chl-a)(0.49–1.19μg/L).In summer,weak DVM was limited to cold waters beneath the thermocline for adult females(<30 ind./m3),but not for adult males.The maximum abundance of CI–CIV also occurred consistently in the subsurface layer(20–40 m)together with high concentrations of Chl-a(0.81–2.36μg/L).CV individuals(1–272 ind./m3)moved slightly upward nocturnally to the near-surface layer(10–20 m),where the average temperature was 25.74 C,but they were not found in the surface layer(0–10 m;28.31 C).These results indicate that the existence of the YSBCW affected food availability at depth and the vertical temperature distribution,leading to variation in the amplitude and shape of stage-specific vertical distributions(CI to adults)in C.sinicus before and during the formation of cold waters in the Yellow Sea during the study period.     

Quantifying cross-shelf and vertical nutrient flux in the Coastal Gulf of Alaska with a spatially nested,coupled biophysical model

The Coastal Gulf of Alaska (CGOA) is productive, with large populations of fish, seabirds, and marine mammals; yet it is subject to downwelling-favorable coastal winds. Downwelling regions in other parts of the world are typically much less productive than their upwelling counterparts. Alternate sources of nutrients to feed primary production in the topographically complex CGOA are poorly known and difficult to quantify. Here we diagnose the output from a spatially nested, coupled hydrodynamic and lower trophic level model of the CGOA, to quantify both horizontal and vertical nutrient fluxes into the euphotic zone. Our nested model includes both nitrogen and iron limitation of phytoplankton production, and is driven by a fine-scale atmospheric model that resolves the effects of local orography on the coastal winds. Results indicate significant “rivers” of cross-shelf nitrogen flux due to horizontal advection, as well as “fountains” of vertical transport over shallow banks due to tidal mixing. Using these results, we constructed a provisional budget of nutrient transport among subregions of the CGOA. Contrary to expectations, this budget reveals substantial upwelling of nutrients over major portions of the shelf, driven by local wind-stress curl. These effects are large enough to overwhelm the smaller downwelling flux at the coast throughout the growing season. Vertical mixing by winds and tides, and horizontal flux from the deep basin, are other substantial contributors to nutrients above the 15-m horizon. These findings help to explain the productivity of this coastal ecosystem.     

Water masses in the Humboldt Current System: Properties,distribution, and the nitrate deficit as a chemical water mass tracer for Equatorial Subsurface Water off Chile

Three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern South Pacific and their distributions. Oceanographic data were taken from the SCORPIO (May–June 1967), PIQUERO (May–June 1969), and KRILL (June 1974) cruises. Vertical sections of temperature, salinity, σ_θ, dissolved oxygen, nitrate, nitrite, phosphate, and silicate were used to analyze the water column structure. Five water masses were identified in the zone through T–S diagrams: Subantarctic Water, Subtropical Water, Equatorial Subsurface Water, Antarctic Intermediate Water, and Pacific Deep Water. Their proportions in the sea water mixture are calculated using the mixing triangle method. Vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m. Several characteristic oceanographic features in the study area were analyzed: the shallow salinity minimum displacement towards the equator, the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south, and the equatorward intermediate Antarctic salinity minimum associated with a dissolved oxygen maximum. The nitrate deficit generated in the denitrification area off Peru and northern Chile is proposed as a conservative chemical tracer for the Equatorial Subsurface Waters off the coast of Chile, south of 25°S.