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101.
The Bay of La Paz, a coastal and shallow basin of the Gulf of California (depth<420 m), exchanges mixed-layer waters with the Gulf of California predominantly through Boca Grande (Big Mouth), in the northeastern part of the bay. Equatorial Surface Water (ESW) flows from the gulf to the bay; once there, due to evaporation processes, this water increases its salinity above 35.00, therefore becoming Gulf of California Water (GCW) Mass. During June 1998, the baroclinic circulation in the bay was dominated by a cyclonic gyre. The hydrographic dome, related to this gyre, is depicted until approximately 150-m depth. However, the vertical mixing of water between the mixed-layer and the ones below practically does not occur because of the development of a sharp pycnocline. This fact and the isolation of the bottom of the bay by a bathymetric sill (approximately 250-m depth) at Boca Grande induce low oxygen content, particularly in the bottom-waters (O2<0.1 ml/l). Chlorophyll values are higher and with larger vertical fluctuations within the Bay of La Paz than outside. 相似文献
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根据2004~2007年的调查数据,结合以往资料,分析了近20 a来天津港海域浮游植物种类、丰度、生物量及多样性的变化规律及其影响因素。结果表明,天津港海域共有浮游植物7门126种,以硅藻和甲藻为主。2000年后,夏季甲藻比例升高,绿藻开始出现。与20世纪90年代相比,2000年后浮游植物的丰度和生物量均维持在较高水平,表现为春季达到重度富营养水平,夏季为中营养水平。浮游植物多样性在2005年呈现下降趋势。研究表明,港口航道工程可能是影响天津港海域浮游植物种群变化的重要原因。 相似文献
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通过对湄洲湾海域生态环境和人文环境的描述,结合中国海洋环境污染的典型案例,阐述保护湄洲湾海域环境的法律措施,并展望保护湄洲湾海域环境的设想。 相似文献
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针对胶州湾海底隧道青岛端接线工程匝道开挖对主隧道的振动影响,在主隧道内进行爆破振动监测。以实测振速数据为依据,分析主隧道内对应匝道工作面前后震动波的传播规律,得到垂直振速、水平径向振速以及水平切向振速随测点距工作面距离不同的变化规律。分析发现,主隧道内已开挖区爆破振速大于未开挖区振速,未开挖区振速在一定范围内相对稳定。 相似文献
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Caitlin M. Jensen Ellen Hines Barbara A. Holzman Thomas J. Moore Jaime Jahncke Jessica V. Redfern 《Coastal management》2015,43(6):575-588
Shipping traffic poses a worldwide threat to many large whale species. Spatially explicit risk assessments are increasingly being used as a tool to minimize ship-strike risk. These assessments often use static representations of shipping patterns. We used Automatic Identification System data to quantify variability in cargo shipping traffic entering and exiting San Francisco Bay, which contains some of the busiest ports in the United States, at three temporal resolutions: (1) before and after implementation of the California Air Resources Board's Ocean-Going Vessels Fuel Rule, (2) among seasons, and (3) day versus night. We used the nonparametric Mood's Median test to compare median daily distance traveled because the data were not normally distributed and the variance was not homogeneous. Our analyses show that shipping traffic off San Francisco is dynamic at both interannual and daily temporal resolutions, but that traffic was fairly consistent among the seasons considered. Our analyses emphasize the importance of economic and regulatory drivers on interannual shipping traffic patterns. Shipping traffic is expected to continue to change off the U.S. West Coast and to increase globally. These changes in shipping traffic could have implications for the risk of ships striking whales and should be included in risk assessments. 相似文献
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Matthieu Waeles Ricardo D. Riso Jean-Franois Maguer Jean-Franois Guillaud Pierre Le Corre 《Journal of Marine Systems》2008,72(1-4):358
The dissolved lead was studied in the whole salinity gradient of the system composed of the Loire estuary and the North Biscay continental shelf. About 130 samples were collected in winter 2001 and spring 2002 during Nutrigas and Gasprod campaigns (Programme PNEC-Golfe de Gascogne, RV Thalassa) and metal measurements were conducted on board by Potentiometric Stripping Analysis. In the Loire estuary, levels of dissolved lead ranged from 0.15 to 0.24 nM and from 0.04 to 0.26 nM in winter and spring, respectively. Compared to the concentrations reported in 1987 and 1990 (0.4–1.7 nM; Boutier, B., Chiffoleau, J.F., Auger, D., Truquet, I., 1993. Influence of the Loire river on dissolved lead and cadmium concentrations in coastal waters of Brittany. Estuar. Coast. Shelf S., 36:133–143, Estuarine, Coastal and Shelf Science 36, 133–143) our study indicated much lower values. The fall in concentration in the estuary could be attributed to the stopping of activity of Octel, a big manufacturer of tetra alkyl lead. Discharge in dissolved metal to the continental shelf by the Loire river was assessed as 7.5 and 1.9 kg day− 1 for winter and spring, respectively. On the continental shelf, levels of dissolved lead varied within 0.06 and 0.27 nM in winter (0.15 ± 0.06 nM, sd = 1.96, n = 49), whereas concentrations measured in spring were in the range 0.06–0.17 nM (0.09 ± 0.03 nM, sd = 1.96, n = 60). This difference in metal concentration was related to the amounts of rainfall that have fallen over the continental shelf: estimations of inputs by this way (74 and 32 kg day− 1 in winter and spring, respectively) appeared to be significantly higher than inputs from the Loire river (7.5 and 1.9 kg day− 1 in winter and spring, respectively). The distributions of dissolved metal in the surface waters highlighted the role of suspended particular matter (SPM) for a rapid “trapping” of lead near the mouth of the estuary. The vertical distributions showed, in the stratified area, a biological transfer of lead between winter and spring from surface waters to the halocline. 相似文献
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杭州湾跨海大桥VTS软科学研究 总被引:2,自引:0,他引:2
邱民 《交通部上海船舶运输科学研究所学报》2003,26(1):21-26
船舶交通管理系统(VTS)是一项牵涉面非常广、极复杂的系统工程,开展软科学研究,是合理规划和科学管理的前提和依据。杭州湾跨海大桥桥区水域建立船舶交通管理系统,条件、情况比较特殊复杂,应该更加重视和加强实现系统功能所必须依赖的软科学研究。 相似文献