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151.
A case study was carried out in 2000 in the shallow coastal area of the Northern Adriatic Sea (Gulf of Trieste) where untreated domestic sewage and industrial wastes are discharged at rate of 5500 m3·day?1. The sewage plume above the outfall was followed using faecal coliforms (FC) and overturning length scale (lT). The latter was rejected as a marker as the discharge conditions prohibit following the turbulence of sewage water. Intermittent sewage discharge is reflected in the minimal effect of eutrophication. Increase of phytoplankton biomass is thus only minor compared with the unpolluted area regardless of elevated concentrations of sewage‐derived nutrients (confirmed by correlation coefficients between FC and NH4+, TP, PO43?: 0.78, 0.71 and 0.67, respectively). Deteriorated trophic status, determined by the TRIX index, was observed only in the surface layer (average TRIX: 5.67). High FC content well above the regulation limit (up to 2.6 × 105 FC·100 ml?1) represents, therefore, the major negative impact of the improperly treated waste for the risk to human health. 相似文献
152.
Using seismic and Chirp sonar profiles, this paper tests the hypothesis that hyperpycnal flows are the main factor controlling
the formation and maintenance of the meandering Kaoping submarine canyon off SW Taiwan. Cross-section geometries, and erosional
as well as depositional features vary along the canyon course. In the proximal, sinuous part of the canyon, down-cutting into
the shelf strata has created a relief of 340 m. The cause of this intense erosion of the seafloor is suggested to be the frequent
development of hyperpycnal flows. A seismic section across a meander in the distal part of the canyon shows levees formed
by overspilled sediments at the outer bend, and a terrace characterized by relatively flat stratified facies at the inner
bend. The geological setting and climatic conditions in SW Taiwan (e.g. earthquakes, typhoons, floods), as well as major river–canyon
connections (for example, direct input of highly concentrated suspended sediment) would all promote hyperpycnal flow generation.
This causes axial incision, canyon wall slumping, and the formation of levees by spill-over deposition in the upper reach
of the Kaoping Canyon. 相似文献
153.
Hydrodynamics and sediment resuspension events, induced at the shoreline by a deep-draft vessel passing nearby, are described.
Measurements (pressure, currents and turbidity) were obtained at 4 Hz, on a lower beach ~50 m from a channel where large car
ferries operate in Wootton Creek, Isle of Wight. The study focuses on a representative 8-min 32-s-long record, during which
two large vessels passed the channel section. At the shore, the passage of each vessel induced a long-period water-level drawdown,
followed by a water-level oscillation (seiche) of similar period, and the short-period waves of the wake. Both drawdowns were
the main constituents of the prevailing wave pattern. The second drawdown was the largest in amplitude, in response to a higher
speed of the ferry, and the influence of the seiche which had been activated during the preceding event. Two successive peaks
of turbidity were observed shortly after this drawdown. Analyses of current velocity and direction indicate that the sediments
resuspended originated from the shallower upper beach. Anthropogenically induced erosion of the foreshore is predicted at
Wootton Creek. 相似文献
154.
Hua?YuEmail author Yingqian?Xiong Zhenxia?Liu Serge?Berné Chi-Yue?Huang Guodong?Jia 《Geo-Marine Letters》2008,28(3):131-136
Based on new and existing data on oxygen isotopes, alkenone-surface seawater temperature trends, planktonic foraminifers,
lithology, and clay mineral composition of piston cores, a distinct cooling event has been identified around 8,200 cal a b.p. in the middle Okinawa Trough, northwest Pacific. This corresponds to the 8,200 a b.p. cooling event recorded in many places of the Northern Hemisphere. During this event, the local temperature decreased by
1°C, and the δ18O value increased by 0.6‰. A strengthened Asian winter monsoon is the most probable cause for this event, which thus adds
further credibility to the contention that we are dealing here with a global phenomenon. 相似文献
155.
Small-scale marine fisheries policy in Vietnam 总被引:1,自引:0,他引:1
Vietnam's marine fisheries are considered to be small scale and are concentrated in coastal near-shore waters. This has resulted in heavy pressure on near-shore fisheries resources. Near-shore fisheries are considered by fishers and the government to be over-exploited, causing hardship for many coastal communities. This paper reviews and analyzes changes in policy towards small-scale fisheries in Vietnam over the last two decades. The primary issues facing the small-scale fisheries in Vietnam are to restructure the near-shore fisheries and to address over-capacity. Recommended actions include improved fisheries statistics, resources for provincial fisheries staff, and a coordinated and integrated approach involving a mixed strategy of resource management; resource restoration; economic and community development; and new governance arrangements. 相似文献
156.
Altimeter data and output from the HYbrid Coordinate Ocean Model global assimilation run are used to study the seasonal variation
of eddy shedding from the Kuroshio intrusion in the Luzon Strait. The results suggest that most eddy shedding events occur
from December through March, and no eddy shedding event occurs in June, September, or October. About a month before eddy shedding,
the Kuroshio intrusion extends into the South China Sea and a closed anticyclonic eddy appears inside the Kuroshio loop which
then detaches from the Kuroshio intrusion. Anticyclonic eddies detached from December through February move westward at a
speed of about 0.1 m s−1 after shedding, whereas eddies detached in other months either stay at the place of origin or move westward at a very slow
speed (less than 0.06 m s−1). The HYCOM outputs and QuikSCAT wind data clearly show that the seasonal variation of eddy shedding is influenced by the
monsoon winds. A comparison between eddy volume and integrated Ekman transport indicates that, once the integrated Ekman transport
exceeds 2 × 1012 m3 (which roughly corresponds to the volume of an eddy), the Kuroshio intrusion expands and an eddy shedding event occurs within
1 month. We infer that the Ekman drift of the northeasterly monsoon pushes the Kuroshio intrusion into the SCS, creates a
net westward transport into the Strait, and leads to an eddy detachment from the Kuroshio. 相似文献
157.
Roles of Biogeochemical Processes in the Oceanic Carbon Cycle Described with a Simple Coupled Physical-Biogeochemical Model 总被引:1,自引:0,他引:1
Masahiko?FujiiEmail author Motoyoshi?Ikeda Yasuhiro?Yamanaka 《Journal of Oceanography》2005,61(5):803-815
To evaluate the contribution of biogeochemical processes to the oceanic carbon cycle and to calculate the ratio of calcium
carbonate to organic carbon downward export, we have incorporated biological and alkalinity pumps in the yoked high-latitude
exchange/interior diffusion-advection (YOLDA) model. The biogeochemical processes are represented by four parameters. The
values of the parameters are tuned so that the model can reproduce the observed phosphate and alkalinity distributions in
each oceanic region. The sensitivity of the model to the biogeochemical parameters shows that biological production rates
in the euphotic zone and decomposition depths of particulate matters significantly influence horizontal and vertical distributions
of biogeochemical substances. The modeled vertical fluxes of particulate organic phosphorus and calcium carbonate are converted
to vertical carbon fluxes by the biological pump and the alkalinity pump, respectively. The downward carbon flux from the
surface layer to the deep layer in the entire region is estimated to be 3.36 PgC/yr, which consists of 2.93 PgC/yr from the
biological pump and 0.43 PgC/yr from the alkalinity pump, which is consistent with previous studies. The modeled rain ratio
is higher with depth and higher in the Pacific and Indian Oceans than in the Atlantic Ocean. The global rain ratio at the
surface layer is calculated to be 0.14 to 0.15. This value lies between the lower and higher ends of the previous estimates,
which range widely from 0.05 to 0.25. This study indicates that the rain ratio is unlikely to be higher than 0.15, at least
in the surface waters. 相似文献
158.
Seok-Gwan?Choi Eun-A?Yoon Doo-Hae?An Sangdeuk?Chung Jaebong?Lee Kyounghoon?LeeEmail author 《Ocean Science Journal》2018,53(4):667-677
In this study, the dB difference and characteristics of krill swarms inhabiting Subarea 48.1, which includes the west and south of the South Shetland Island and the Elephant Island peripheries, were estimated to distinguish Antarctic krill, using acoustics. From April 13 to 24, 2016, acoustic data were collected along 24 survey lines using the frequencies 38 and 120 kHz, and middle trawling was performed at 7 stations. Using the difference between the dB values of two volume backscattering strength (Sv) frequencies (38 and 120 kHz), a clear acoustic distinction could be made between Antarctic krill (4.9 to 12.0 dB) and fish (?4.0 to ?0.2 dB). The distributions and mean Sv of krill swarms in the Elephant Island peripheries and south of South Shetland Island were higher than those in the west of South Shetland Island. The mean length/ height ratio of krill swarms in the west of the South Shetland Island (64.5) was higher than that in the south (35.9) and the Elephant Island peripheries (33.8), with the length of the aggregations exceeding their height. Most krill swarms were distributed between the surface layer (less than 10 m below sea level) and within 200 m of water depth. These results are expected to serve as baseline data for evaluating krill density and biomass by distinguishing them from fish, using acoustics. 相似文献
159.
Sakineh?Mashjoor Fatemeh?Heidary?Jamebozorgi Ehsan?KamraniEmail author 《Ocean Science Journal》2018,53(4):655-665
Ecosystem-based management is one of the most important approaches that may lead to reducing the impacts of fishing on ecosystems. In this context, we have assessed the impact of Iranian coastal fishing (using landing data of 49 exploited species) on the ecosystem of the North Sea of Oman (Sistan and Baluchestan Province), during the last decade (2002–2011), with emphasis on testing the occurrence of the “fishing down? phenomenon. The Mean Trophic Level (MTL) and Fishing-in-Balance (FiB) index are two indicators that we used for analysis. The data indicated that the increased total landings in this region might be related to the exploitation of marine fishery resources especially with regard to large pelagic fish. Over the past decade, moderate decreasing trends in MTL and an increasing trend in the FiB-index were observed. In this regard, an upward trend in the spatial expansion factor and also a downward trend in the piscivory index and in Primary Production Required (PPR) in the time period could all indicate a spatial expansion toward deep waters, the catching of the large pelagic piscivorous species, such as tuna, and a sign of fishing pressures on the ecosystem. The results suggest a range of fishery exploitation patterns throughout the food web but it seems that these patterns are not a consequence of ?fishing down?. We suggest that the monitoring research be continued in this region and these indicators should be used to make fisheries management decisions and to prevent the continuance of this trend in future. 相似文献
160.
S. Jejčič P. Heinzel N. Labrosse A. N. Zhukov A. Bemporad S. Fineschi S. Gunár 《Solar physics》2018,293(2):33
We determine the optimal width and shape of the narrow-band filter centered on the He?i D3 line for prominence and coronal mass ejection (CME) observations with the ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) coronagraph onboard the PROBA-3 (Project for On-board Autonomy) satellite, to be launched in 2020. We analyze He?i D3 line intensities for three representative non-local thermal equilibrium prominence models at temperatures 8, 30, and 100 kK computed with a radiative transfer code and the prominence visible-light (VL) emission due to Thomson scattering on the prominence electrons. We compute various useful relations at prominence line-of-sight velocities of 0, 100, and 300 km?s?1 for 20 Å wide flat filter and three Gaussian filters with a full-width at half-maximum (FWHM) equal to 5, 10, and 20 Å to show the relative brightness contribution of the He?i D3 line and the prominence VL to the visibility in a given narrow-band filter. We also discuss possible signal contamination by Na?i D1 and D2 lines, which otherwise may be useful to detect comets. Our results mainly show that i) an optimal narrow-band filter should be flat or somewhere between flat and Gaussian with an FWHM of 20 Å in order to detect fast-moving prominence structures, ii) the maximum emission in the He?i D3 line is at 30 kK and the minimal at 100 kK, and iii) the ratio of emission in the He?i D3 line to the VL emission can provide a useful diagnostic for the temperature of prominence structures. This ratio is up to 10 for hot prominence structures, up to 100 for cool structures, and up to 1000 for warm structures. 相似文献