浅海筏式海带养殖活动对水动力及沉积环境影响研究

发布时间：2018-07-25 08:10

【摘要】：本论文综合利用黑泥湾海带养殖区附近海域的海流、悬浮体、表层沉积物、柱状样、水深地形等实测数据资料,计算了不同季节养殖区内外的潮流边界层参数、沉积物再悬浮沉降以及输运通量,结合潮流波浪泥沙数值模拟、沉积物粒径趋势分析、水深地形对比等方法,对比了海带养殖季节与无养殖季节养殖区内外的潮流动力、沉积物分布与输运的时空变化规律,以及养殖活动开展前后的海底地形冲淤变化特征,进而分析了海带养殖活动对研究区海域水动力和沉积环境的影响。研究区海带养殖覆盖的水体,由于养殖阻力作用使得潮流流速明显减弱,并使潮流流速的垂向剖面特征发生改变。受养殖活动的影响,潮流流速垂向剖面可以形成三种比较典型的异常模式,分别为标准的双阻流速剖面,上层稳定、中下层形成双阻流速形态的流速剖面,以及上下层两个双阻流速形态的流速剖面。这三种不同的流速剖面形态会因潮流流速和流向的变化而相互转化。海带养殖活动的存在使得底部边界层切应力减弱,从而造成再悬浮作用减弱;相比于自然水域,养殖区内部近底层以及垂向平均悬浮体浓度均显著降低。海带养殖区内部由于速度剪切显著减弱,海带藻体与潮流相互作用在其后部产生湍流等原因,使得受养殖活动影响的区域水体存在很强的垂向混合作用。研究区在自然状态下总体上处于冲刷状态,冲刷区域位于基岩岬角外侧,该区域海底沉积物类型主要为砂砾等粗颗粒沉积物,而海湾内近岸浅水区域存在一定的淤积作用。海带养殖活动开展以后,研究区海域沉积格局发生改变,海带养殖区内部形成范围较大的淤积环境,而养殖区内侧近岸浅水区淤积减弱,近岸沉积物出现粗化的现象,南北两侧基岩岬角以及黑石礁西侧冲刷作用减弱,养殖区东侧海域形成一定范围的细颗粒沉积区。另外,由于海带的生长具有季节性变化,短期的季节性交替变化使得养殖区附近海域水动力条件处在循环变化的过程中,致使海底无法出现持续稳定的冲淤环境,而是出现交替的侵蚀和淤积变化过程,这种剧烈变化对区域海底沉积格局会带来更大的影响。
[Abstract]:Based on the measured data of currents, suspensions, surface sediments, columnar samples and bathymetric topography, the parameters of tidal current boundary layer inside and outside the mariculture area in different seasons are calculated in this paper. Combined with the numerical simulation of tidal current, wave and sediment, the analysis of sediment particle size trend, and the comparison of water depth and topography, the tidal current dynamics inside and outside the kelp culture season were compared with those in the no-culture season. The temporal and spatial variation of sediment distribution and transport, as well as the characteristics of scour and siltation of seafloor before and after aquaculture activities were analyzed, and the effects of mariculture activities on hydrodynamic and sedimentary environment in the study area were analyzed. In the water covered by kelp culture, the tidal current velocity is obviously weakened and the vertical profile characteristics of tidal current velocity are changed due to the effect of culture resistance. Under the influence of aquaculture activities, the vertical profile of tidal current velocity can form three typical abnormal models, which are standard double resistance velocity profile, stable upper layer, and double resistance velocity profile in middle and lower layers. And two double resistance velocity profiles of the upper and lower layers. These three different velocity profiles transform each other due to the variation of tidal current velocity and direction. The shear stress of the bottom boundary layer is weakened because of the existence of the kelp culture activity, which results in the weakening of the resuspension. Compared with the natural waters, the concentration of the near bottom layer and the vertical average suspended body in the culture zone decreases significantly. Because of the obvious weakening of velocity shear and turbulence in the posterior part of the kelp algae body and tidal current, there is a strong vertical mixing effect in the regional water body affected by the culture activities. The study area is generally in the state of scour under the natural state, and the scour area is located outside the headland of bedrock. The type of seabed sediment in this area is mainly coarse grain sediment such as sand and gravel, while there is certain siltation in the shallow water area of the inshore of the bay. After the activities of kelp culture were carried out, the sedimentary pattern of the study area changed, and a large area of siltation environment was formed inside the kelp culture area, while the siltation of the shallow water area inside the inner shore of the culture area weakened, and the coarsening of the inshore sediment appeared. The erosion in the north and south sides of bedrock headland and the west side of Heishi reef is weakened, and a certain range of fine grain deposition area is formed in the eastern sea area of the breeding area. In addition, because of seasonal variation in the growth of kelp, short-term seasonal alternation makes hydrodynamic conditions in the waters near the aquaculture area in the process of cyclic change, resulting in no sustainable and stable environment for scouring and silting on the seafloor. Instead, there are alternate processes of erosion and siltation, which will have a greater impact on the regional seabed sedimentary pattern.
【学位授予单位】：中国科学院研究生院(海洋研究所)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S968.421;S931.3

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