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971.
Hydrodynamic and sediment transport measurements from instrumentation deployed during a 54-day winter period at two sites on the Louisiana inner shelf are presented. Strong extratropical storms, with wind speeds of 7.8 to 15.1 m s-1, were the dominant forcing mechanism during the study. These typically caused mean oscillatory flows and shear velocities about 33% higher than fair weather (averaging 12.3 and 3.2 cm s-1 at the landward site, and 11.4 and 2.7 cm s-1 at the seaward site, respectively). These responses were coupled with mean near-bottom currents more than twice as strong as during fair weather (10.3 and 7.5 cm s-1 at the landward and seaward sites, respectively). These flowed in approximately the same direction as the veering wind, causing a net offshore transport of fine sand. Weak storms were responsible for little sediment transport whereas during fair weather, onshore sand transport of approximately 25-75% of the storm values appears to have occurred. This contradicts previous predictions of negligible fair-weather sediment movement on this inner shelf. 相似文献
972.
Akihiko Morimoto Tetsutaro Takikawa Goh Onitsuka Atsushi Watanabe Masatoshi Moku Tetsuo Yanagi 《Journal of Oceanography》2009,65(1):61-71
We conducted hydrographic observations ten times in the Tsushima Strait to reveal seasonal variations of horizontal material
transports such as of heat, freshwater, chlorophyll a, and dissolved inorganic nitrogen (DIN) and phosphorus (DIP) through the eastern channel of the Tsushima Strait (ECTS). The
volume, freshwater, and heat transport results are of nearly the same order as results reported in previous studies. The annual
mean DIN and DIP transports of 3.59 kmol/s and 0.29 kmol/s are large relative to those of the Changjiang and the Taiwan Strait
and are horizontally transported through the ECTS. Nutrient transports are high in July–August and October and low in April
and November. Increased nutrient transports in July–August and October are due to the appearance of a cold saline water mass
in the bottom layer of the ECTS. Changes in DIN transports in summer and autumn, which account for two-thirds of the total
annual DIN transport, would have a large effect on the nitrogen budget and biological productivity in the Tsushima Warm Current
region. 相似文献
973.
Kensuke Iwamoto Akihiro Takemura Tetsuo Yoshino Hideyuki Imai 《Journal of Oceanography》2009,65(1):103-112
The mitochondrial DNA (mtDNA) control region was sequenced to examine the genetic variability and gene flow of juvenile Siganus spinus and S. guttatus. In total, 461 nucleotide sequences were obtained from 69 specimens of juvenile S. spinus from Okinawa Island and Ishigaki Island, in which 17 variable sites and 22 haplotypes were identified. Haplotype diversity
(h) was high (0.9244 in Okinawa and 0.8984 in Ishigaki), whereas nucleotide diversity (π) was low (0.0063 in Okinawa and 0.0059 in Ishigaki). The two populations were not genetically distinct. Siganus guttatus, which do not form large schools at recruitment, in contrast S. spinus, were also analyzed by studying 152 individuals collected off Okinawa Island, Miyako Island, and Ishigaki Island. Of 476
nucleotide sequences, 50 were variable, and 42 haplotypes were identified. Genetic variability values were high (h = 0.8766 and π = 0.0151 in Okinawa; h = 0.9640 and π = 0.0192 in Miyako; h = 0.9161 and π = 0.0199 in Ishigaki). The Okinawa population was genetically isolated from the Miyako and Ishigaki populations. As a result,
genetic diversity was high for each of these siganid populations despite their being target species for fisheries; however,
the degree of inter-population gene flow was higher for S. spinus than S. guttatus, suggesting that these species exhibit different dispersal strategies. 相似文献
974.
Hiroshi Ishida Yutaka W. Watanabe Joji Ishizaka Toshiya Nakano Naoki Nagai Yuji Watanabe Akifumi Shimamoto Nobuhiro Maeda Michimasa Magi 《Journal of Oceanography》2009,65(2):179-186
Our analysis of the last three decades of retrospective data of vertical distributions and size composition of chlorophyll-a
(Chl-a) over the western North Pacific has revealed significant changes of three indices related to Chl-a during summer season,
as follows: (1) decreasing linear trend of the proportion of Chl-a in surface layer to that of the whole water column by 0.4
and 2.3% year−1 in the subtropical area along 137°E (STA137) during 1972 to 1997 and in the Kuroshio Extension area along 175°E (KEA175) during 1990 to 2001; (2) increasing linear trend of the depth of subsurface Chl-a maximum (DCM) by 0.4 and 2.6 m year−1 in STA137 and KEA175; and (3) decreasing linear trend of larger-size Chl-a (>3 μm) by 0.1 and 2.5% year−1 in STA137 and KEA175, respectively. Water density (σ
θ
) at 75 m depth had also decreased by 0.006 and 0.05 year−1 in STA137 and KEA175, respectively. The ratio of biogenic opal to biogenic CaCO3 in the sinking flux decreased by 0.015 year−1 in the subtropical region from 1997 to 2005. These findings may indicate that the subsurface chlorophyll maximum is deepening
and larger phytoplankton such as diatoms has been decreasing during the past decade, associated with the decreasing density
of surface water caused by warming in the western North Pacific, especially in the summer. 相似文献
975.
Dissolved proteins in seawater samples collected from a coastal area of Tokyo Bay, Sagami Bay and a location off the Kuroshio
Current were investigated by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and high
resolution two-dimensional electrophoresis (2-DE). Four to nine protein bands were detected in SDS-PAGE in the apparent molecular
weight (MW) range from 12 kilo Dalton (kDa) to 49 kDa. The 2-DE technique distinguished 10 to 46 protein spots exhibiting
isoelectric point (pI)/MW ranging 4.3–9.2/12–63 kDa. The elecrophoretic patterns were similar between the coastal and pelagic samples, as well
as previously reported patterns from various pelagic areas. The close similarity of electrophoretic mobility on both SDS-PAGE
and 2-DE gels indicates the compositional homogeneity of dissolved proteins in seawater throughout a broad range of marine
environments. Proteinaceous dissolved organic matter (DOM) that was unresolved and smeared staining characteristics on both
SDS-PAGE and 2-DE gels was first observed in Tokyo Bay waters in the present study and its possible sources are discussed.
Although the two protein species, 48 kDa and 39 kDa proteins, have been identified as homologues of Porin P and low molecular
weight-alkaline phosphatase of Pseudomonas aeruginosa PAO1, respectively, four strains of P. aeruginosa and two species of Pseudomonas spp. have been newly identified as the source organisms of these proteins using the N-terminal amino acid sequence data determined in previous studies. 相似文献
976.
977.
Organized bacterial assemblies in manganese nodules: evidence for a role of S-layers in metal deposition 总被引:1,自引:0,他引:1
Xiaohong Wang Heinz C. Schröder Ute Schloßmacher Werner E. G. Müller 《Geo-Marine Letters》2009,29(2):85-91
Polymetallic/ferro-manganese nodules (Mn-nodules) reach sizes of up to 10 cm in diameter and are abundantly found on the seabed.
To date, the origin of Mn-nodules remains unclear, and both abiogenic and biogenic origins have been proposed. In search of
evidence for a contribution of microbial processes to the formation of Mn-nodules, we analyzed those spherical nodules which
contain a concentrically banded texture in their interior. The Mn-nodules were collected at a depth of 5,152 m from the Clarion-Clipperton
Zone. Our high-resolution scanning electron microscopy analyses reveal first published evidence that endolithic microorganisms
exist and are arranged in a highly organized manner on plane mineral surfaces within the nodules. These microorganisms are
adorned on their surfaces with S-layers, which are indicative for bacteria. Moreover, the data suggest that these S-layers
are the crystallization seeds for the mineralization process. We conclude that the mineral material of the Mn-nodule has a
biogenic origin, and hope that these data will contribute to the development of biotechnological approaches to concentrate
metals from seawater using bacteria in bioreactors. 相似文献
978.
A pattern of slick streaks winding into a spiral, known as a spiral eddy, was identified in 5 images taken by the ERS-1/2
synthetic aperture radar (SAR) in Mutsu Bay (Japan); dynamic and kinematic models of these spiral eddies have been proposed.
Common characteristics of the five spiral eddies are: 1) an eddy diameter of about 15 km; 2) their location in the western
part of the bay; and 3) their cyclonic direction of rotation. Moreover, the wind conditions over the bay were common: prior
to acquiring the images, a strong easterly wind continued blowing for more than one day. The wind field on the bay is known
to be orographically steered and has strong windstress vorticity, which generates cyclonic circulation. The diameter and location
of the circulation simulated with a numerical ocean model corresponded well to those of the identified spiral eddies. Based
on these facts, we propose a dynamic model for the movement of a slick streak, and a kinematic model for the formation of
a spiral eddy. We have assumed calm air, a microlayer and seawater with a cyclonic circulation in the dynamic model. The balance
of forces is established in the microlayer among the frictional force from the seawater, the frictional force from the calm
air, the gravitational force, and the Coriolis force. As a result, the velocity vector of the microlayer deflects slightly
towards the center of the cyclonic circulation. We have assumed a point source of the microlayer in the kinematic model. The
shapes of a slick streak simulated with the models agree well with the identified patterns in the SAR images. 相似文献
979.
In situ Microphytobenthic community dynamics were combined with laboratory measurement of predominant species by fluorescence methods to estimate the areal primary production. Field investigation of community dynamics of microphytobenthos (MPB) was conducted from August 2006 to August 2007 in intertidal flats of the Nakdong River estuary, Korea. MPB Biomass varied between 0.47 and 16.58 μg cm?3 in the surface 1 cm sediment, with two dominant diatom species, Amphora coffeaeformis and Navicula sp., occupying average 77.2 ± 14.9% of total number of MPB cells. The biomass was higher in the slightly muddy sand sites than that in the sand site, and showed different pattern of seasonal variation. The profile of vertical distribution of biomass was an exponential decrease trend with depth in sediments. The biomass proportions in the uppermost 3 mm were 57.6% and 37.8% with and without the presence of biofilm, respectively. The two dominant species were cultured in laboratory, and their photosynthetic parameters, rETRmax (relative maximum electron transport rate), α (light utilization coefficient) and E k (light saturation parameter) were derived from rETR (relative ETR)-irradiance curves by Imaging- PAM (pulse amplitude modulated) fluorometry. The rETR-irradiance curves showed no significant difference of photosynthetic activities between the two species. The areal potential production ranged from 0.74 to 2.22 g C m?2 d?1. 相似文献
980.
Faults with a well-defined strike direction that precisely coincides with the southern rift fault system occur in the study
area in southern Tenerife. This fault system was generated contemporaneously with a chain of cinder cones ~948 ka. Open fractures
in ignimbrites (~668 ka) and fossil beach deposits (~42 ka) of the El Médano area suggest that the rift-associated fault system
was seismically active in the aftermath of the initial volcanic activity (~948 ka) and is probably still active. A second
fault system striking perpendicular to the rift-related faults probably originates from a Holocene paleoearthquake of moderate
intensity. Earthquake-induced ground effects in fossil beach deposits within the study area are consistent with seismically
induced ground effects of several recent and well-documented earthquakes, as well as gravitational sliding triggered by an
intense earthquake in the Nicoya Peninsula of Costa Rica in 1990. Both, the rift-associated and the earthquake-induced fault
system, initially produced open fractures that were occupied by plants and subsequently stabilized by cementation, forming
conspicuous sediment structures in fossil beach deposits of the El Médano site in southern Tenerife. 相似文献