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Military sonar has the potential to negatively impact marine mammals. To investigate factors affecting behavioral disruption in California sea lions (Zalophus californianus), fifteen sea lions participated in a controlled exposure study using a simulated tactical sonar signal (1 s duration, 3250–3450 Hz) as a stimulus. Subjects were placed into groups of three and each group received a stimulus exposure of 125, 140, 155, 170, or 185 dB re: 1 μPa (rms). Each subject was trained to swim across an enclosure, touch a paddle, and return to the start location. Sound exposures occurred at the mid-point of the enclosure. Control and exposure sessions were run consecutively and each consisted of ten, 30-s trials. The occurrence and severity of behavioral responses were used to create acoustic dose–response and dose–severity functions. Age of the subject significantly affected the dose–response relationship, but not the dose–severity relationship. Repetitive exposures did not affect the dose–response relationship. 相似文献
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Macrofaunal polychaete communities (>500 µm) in the South Eastern Arabian Sea (SEAS) continental margin (200–1000 m) are described, based on three systematic surveys carried out in 9 transects (at ~200 m, 500 m and 1000 m) between 7°00′and 14°30′N latitudes. A total of 7938 polychaetes belonging to 195 species were obtained in 136 grab samples collected at 27 sites. Three distinct assemblages were identified in the northern part of the SEAS margin (10–14°30′N), occupying the three sampled depth strata (shelf edge, upper and mid-slope) and two assemblages (shelf edge and slope) in the south (7–10°N). Highest density of polychaetes and dominance of a few species were observed in the shelf edge, where the Arabian Sea oxygen minimum zone (OMZ) impinged on the seafloor, particularly in the northern transects. The resident fauna in this region (Cossura coasta, Paraonis gracilis, Prionospio spp. and Tharyx spp.) were characteristically of smaller size, and well suited to thrive in the sandy sediments in OMZ settings. Densities were lowest along the most northerly transect (T9), where dissolved oxygen (DO) concentrations were extremely low (<0.15 ml l−1, i.e.<6.7 μmol l−1). Beyond the realm of influence of the OMZ (i.e. mid-slope, ~1000 m), the faunal density decreased while species diversity increased. The relative proportion of silt increased with depth, and the dominance of the aforementioned species decreased, giving way to forms such as Paraprionospio pinnata, Notomastus sp., Eunoe sp. and lumbrinerids. Relatively high species richness and diversity were observed in the sandy sediments of the southern sector (7–9°N), where influence of the OMZ was less intense. The area was also characterized by certain species (e.g. Aionidella cirrobranchiata, Isolda pulchella) that were nearly absent in the northern region. The gradients in DO concentration across the core and lower boundary of the OMZ, along with bathymetric and latitudinal variation in sediment texture, were responsible for differences in polychaete size and community structure on the SEAS margin. Spatial and temporal variations were observed in organic matter (OM) content of the sediment, but these were not reflected in the density, diversity or distribution pattern of the polychaetes. 相似文献
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《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(7):1627-1649
Distribution of larger protozoans (armoured dinoflagellates, tintinnids, heliozoans, radiolarians and foraminiferans >64 μm) is presented for three major water masses of the Southern Ocean: the Polar Front region (PFr), the southern Antarctic Circumpolar Current (southern ACC) and the northern Weddell Gyre. Sampling took place during the SO-JGOFS cruise ANT X/6 of R/V Polarstern (October–November 1992) along a meridional transect at 6°W between 48°00′S and 59°30′S. Multinet samples (64 μm mesh size) were taken at six stations from the surface down to 500 m depth at five different depth intervals. In the upper 100 m of the water column abundances of larger protozoans varied between 94 and 10,930 ind. m–3, with highest abundances in the PFr, where phytoplankton blooms occurred, and lowest values in the Antarctic Circumpolar Current–Weddell Gyre Boundary (AWB). Foraminiferans and polycystine and smaller (<300 μm) phaeodarian radiolarians dominated larger protozoan assemblages in the PFr. In open water of the southern ACC, tintinnids, armoured dinoflagellates, foraminiferans and smaller (<300 μm) phaeodarian radiolarians were equally important. The heliozoans Sticholonche spp. and nassellarian radiolarians dominated assemblages in the Weddell Gyre and AWB. Larger protozoan biomasses ranged between 2 and 674 μg C m−3 and were always dominated by larger (>300 μm) phaeodarians. Highest biomasses were found in the AWB between 200 and 500 m depth. Standing stocks of larger protozoans constituted a negligible fraction of zooplankton biomass in the upper 200 m of the water column. In deeper layers of the ice-covered Weddell Gyre and AWB their biomasses, dominated by larger (>300 μm) phaeodarians, was significant contributing up to 45% to total larger protozoan and metazoan biomass. Analysis of correlation between distribution patterns and environmental conditions at the stations sampled indicate that spring distribution patterns of heterotrophic armoured dinoflagellates, polycystine radiolarians and foraminiferans follow productivity in the water column. Of the protozoan groups studied the smaller (<300 μm) phaeodarian radiolarians also showed a significant correlation with productivity during spring, however, results from previous studies do not suggest a consistent pattern. Spring distribution patterns of other larger protozoans were not related to differences in productivity in the water column, and effects such as ice-cover, grazing or silica limitation might be determining. Dead radiolarian skeletons constituted on average 27, 8 and 11% of the population of nassellarians, spumellarians and smaller (<300 μm) phaeodarians, respectively. The contribution of dead radiolarian skeletons to total radiolarian stocks varied with depth and water mass. Differences between live and skeleton assemblages composition were observed. These differences should be taken into consideration when interpreting the geological record. 相似文献
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Miranda J.M. Silva P.F. Lourenço N. Henry B. Costa R. Saldanha Team the 《Marine Geophysical Researches》2002,23(4):299-318
We present a study of the magnetic properties of a group of basalt samples from the Saldanha Massif (Mid-Atlantic Ridge – MAR – 36° 33 54 N, 33° 26 W), and we set out to interpret these properties in the tectono-magmatic framework of this sector of the MAR. Most samples have low magnetic anisotropy and magnetic minerals of single domain grain size, typical of rapid cooling. The thermomagnetic study mostly shows two different susceptibility peaks. The high temperature peak is related to mineralogical alteration due to heating. The low temperature peak shows a distinction between three different stages of low temperature oxidation: the presence of titanomagnetite, titanomagnetite and titanomaghemite, and exclusively of titanomaghemite. Based on established empirical relationships between Curie temperature and degree of oxidation, the latter is tentatively deduced for all samples. Finally, swath bathymetry and sidescan sonar data combined with dive observations show that the Saldanha Massif is located over an exposed section of upper mantle rocks interpreted to be the result of detachment tectonics. Basalt samples inside the detachment zone often have higher than expected oxidation rates; this effect can be explained by the higher permeability caused by the detachment fault activity. 相似文献
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《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(1):49-62
Carbon overconsumption, i.e. the consumption of inorganic carbon relative to inorganic nitrogen in excess of the Redfield ratio at the sea surface, was examined in relation to the dynamics of dissolved organic carbon and nitrogen (DOC and DON) in the northeast Atlantic. We observed the presence of N-poor dissolved organic matter (DOM) in surface water during summer, requiring the consumption of inorganic carbon and nitrogen in a ratio exceeding the Redfield ratio. The C : N ratio of bulk DOM is not only different from the Redfield ratio but also variable, i.e. no fixed conversion factor of C and N exists where DOM is important in C and N transformations. The existence of N-poor DOM is recognized as a feature typical of oligotrophic systems. At the same time, the C : N ratios of particles conform to Redfield stoichiometry as does deep-ocean chemistry. The implications of this finding are discussed, the conclusion being that, while DOM buildup contributes to CO2 drawdown seasonally, its impact on long-term carbon and nitrogen balance of the ocean is small. 相似文献
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The thermal evolution of sediments in the shallowest part of sedimentary basins is challenging to investigate as most of the geothermometers are at their application limits. This is typically the case of the Callovian–Oxfordian claystones at the eastern border of the Paris Basin. A recent 2000 m deep well penetrated the entire Jurassic and Triassic sedimentary series and permitted coring of sediments never reached by previous drilling in this part of the basin. Thanks to the use of several independent geothermometers (apatite fission track thermochronology, fluid inclusion microthermometry, clay mineralogy and sedimentary organic matter evolution) the burial history of the Mesozoic series has been reconstructed, modeled and calibrated using kinetic algorithms relevant to the various paleothermometers used. In addition to these conventional methods, an innovative approach was developed using the temperature-dependence of the magnetic mineral assemblage within clay-rich sediments (“MagEval”). Thermal modeling indicates that the Callovian–Oxfordian and the Lower Triassic experienced maximum burial temperatures of 50 ± 5 °C and 90 ± 10 °C respectively, i.e., about 25 °C higher than present-day. This temperature offset implies the erosion of several hundred meters of sediments which, depending on the thermal flux and conductivity considered, most likely constituted Upper Cretaceous chalk deposits. Falling sea level resulted in the exposure and subsequent dismantling of the chalk cover at the beginning of Cenozoic times. The eastern border of the basin was then subjected to slow erosion and discrete tectonic deformation. 相似文献
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测绘学名词审定委员会 《海洋测绘》2019,(1)
<正>工程测量学engineering surveying研究城市与工程建设和资源开发与环境治理的规划,设计、施工、竣工、运营管理等各阶段以及设备安装、检测等的测绘理论与技术的学科。测量学surveying研究地球表面局部地区内测绘工作的基本理论、技术、方法和应用的学科。 相似文献
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目前,我国的海洋法律尽管还不完备,但就保障海上交通安全、保护海洋渔业资源、防止海洋环境污染等方面来说,已有法可依,并且各个海上执法系统都在根据各自的职责日夜在海上执法。但我国除了海上交通安全比较有保障外,海洋渔业资源因违规捕捞日趋衰退、沿岸海域赤潮频繁发生、海洋污染日益严重,不能不说是由于海上执法不力造成的。海上执法不力有多种原因,如上述的海洋法律还不够完备和具体, 相似文献
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Yu. I. Portnyagin T. V. Solov’eva E. G. Merzlyakov A. I. Pogorel’tsev E. N. Savenkova 《Izvestiya Atmospheric and Oceanic Physics》2010,46(1):85-94
Height-latitude distributions of the prevailing vertical wind for the mesosphere and lower thermosphere (70–110 km) are calculated
on the basis of the empirical model of the monthly mean zonal mean prevailing horizontal wind. The presence of cellular structures
is the main feature of the obtained vertical and meridional circulations. The ways such structures form and the problems of
their modeling in global numerical models of the atmosphere are discussed. 相似文献
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《海洋学报》2004,(1)
MarineHydrology期 -页1- 1……PracticalimplementationofHilbert-HuangtransformalgorithmHuangDaji,ZhaoJinpingandSuJilan2 - 15 1……Three dimensionalhydrodynamicmodelofXiamenwatersWenShenghui,CaiSong ,TangJunjianandCaiQifu2 - 171……InfragravitywaveswithinternalwavecharacteristicsinthesouthoftheBohaiSeaofChinaFanZhisong ,GaoGuoping ,YinXunqiang ,FanYuandWuWei2 - 179……SpatialandtemporalvariabilityofheatcontentabovethethermoclineinthetropicalPacificOceanPuShuzhen ,YuFei,HuXiaominan… 相似文献