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Anthropogenic influences on shoreline and nearshore evolution in the San Francisco Bay coastal system 总被引:1,自引:0,他引:1
Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km2 area, which equates to a total volume loss of 100 ± 52 million m3 of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m3 of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ∼54 million m3 of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches. 相似文献
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Mapping benthic macroalgal communities in the coastal zone using CHRIS-PROBA mode 2 images 总被引:2,自引:0,他引:2
G. Casal T. KutserJ.A. Domínguez-Gómez N. Sánchez-CarneroJ. Freire 《Estuarine, Coastal and Shelf Science》2011,94(3):281-290
The ecological importance of benthic macroalgal communities in coastal ecosystems has been recognised worldwide and the application of remote sensing to study these communities presents certain advantages respect to in situ methods. The present study used three CHRIS-PROBA images to analyse macroalgal communities distribution in the Seno de Corcubión (NW Spain). The use of this sensor represent a challenge given that its design, build and deployment programme is intended to follow the principles of the “faster, better, cheaper”. To assess the application of this sensor to macroalgal mapping, two types of classifications were carried out: Maximum Likelihood and Spectral Angle Mapper (SAM). Maximum Likelihood classifier showed positive results, reaching overall accuracy percentages higher than 90% and kappa coefficients higher than 0.80 for the bottom classes shallow submerged sand, deep submerged sand, macroalgae less than 5 m and macroalgae between 5 and 10 m depth. The differentiation among macroalgal groups using SAM classifications showed positive results for green seaweeds although the differentiation between brown and red algae was not clear in the study area. 相似文献
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Lide Jiang Xiao-Hai Yan Yu-Heng Tseng Laurence C. Breaker 《Estuarine, Coastal and Shelf Science》2011
The responses of coastal upwelling to different magnitudes of wind stress over a narrow and a wide shelf are studied using a 3-D primitive equation numerical model. The results show that the position of the upwelling front depends on both the strength and the duration of the wind forcing. The comparison between different shelf widths shows that wide shelf will limit the cold water intrusion, so that the corresponding decrease in sea surface temperature is less compared to narrow shelves. Besides, the difference between hydrostatic and nonhydrostatic model results shows that nonhydrostatic effects will enhance the growth of surface meandering, and can be more pronounced near steep fronts. Although difference does exist, our results show that the nonhydrostatic effects are very small at least in this idealized study case. 相似文献
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福建沿岸海域浒苔藻类的营养成分含量与食用安全 总被引:4,自引:0,他引:4
对福建沿岸海域浒苔(Enteromorpha)样品的主要组成成分、氨基酸、脂肪酸、矿物质含量的研究表明,浒苔属高膳食纤维(49.0%~59.1%)、高蛋白质(19.60%~38.24%)、低脂肪(0.20%~0.55%)的藻类.浒苔中17种氨基酸总量(Ctaa)与蛋白质含量的比值为74.1%~91.0%;其必需氨基酸含量(Ctaa)占C11从的35.4%~40.0%,CⅢ与非必需氨基酸含量(C。Ⅲ)之比为0.55~0.67,且呈味氨基酸的含量丰富(47.1%),氨基酸组成均衡.浒苔油脂中脂肪酸组成丰富,n一3PUFA含量达油脂总量的20.0%~26.4%,其中含有EPA、DHA.浒苔中矿物质含量较高,尤其富含镁、钙、铁、锌、硒、钾等人体必需矿物元素.有害元素测定结果表明,中、低潮区浒苔的铅、汞、镉、砷含量均能够符合《无公害食品海藻》安全指标的限量要求,养殖区、高潮区部分浒苔的Pb含量超标.研究结果认为,在低污染海区生长的浒苔是一种高蛋白质、高膳食纤维、低脂肪、矿物元素丰富且安全的海洋食品. 相似文献
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苏北废黄河三角洲经历了150多a的侵蚀演变过程,目前仍处在侵蚀演变中.据2007-08和2008-07废黄河口附近断面调查结果显示,沉积类型出现粗化趋势,10 m以浅的浅水区,砂粒含量达60%以上,平均粒径达0.06 mm,物质粗化显著,岸滩呈现了强烈的波蚀作用;10 m以深至15 m的深水区,泥粒含量增多,平均粒径为... 相似文献
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