【作者】 卞红霞；

【导师】 孙秀云；

【作者基本信息】 南京理工大学 ， 环境工程， 2012， 硕士

【摘要】 水华是浮游植物在一定条件下快速繁殖的结果,研究浮游植物生长的影响因素,对揭示水华发生的生态机制具有重要意义。论文建立了COHERENS水动力及水质模型,研究渤海浮游植物生长季节性变化与水动力的关系,重点分析温度、盐度和湍流作用等物理环境因子对渤海浮游植物生长的影响,探讨浮游植物水华发生的物理环境。论文从三维水动力及水质方程组出发,考虑气象条件和径流条件,首先建立了符合实际的水动力模型,从调和常数、潮位和温盐三个方面对其进行验证,模拟了温盐的季节性变化和层化特征。模拟结果表明：温跃层从春季开始出现,夏季温跃层结构最为明显,底层南北两侧出现非对称冷核结构,秋季温跃层消失；盐跃层结构在夏季也最明显,表、底层盐度分布差别较大,但相比于温跃层,盐跃层出现时期较为滞后,层化结构较弱。论文建立的水动力数值模型可以较好地反映温盐场长期变化规律。其次,通过调节浮游动物捕食压,底层沉积物中所含硝酸盐和氨氮通量等重要参数,建立符合实际的水质生态模型,验证水质生态要素,模拟并分析叶绿素、硝酸盐和氨氮的时空特征。模拟结果表明：时间序列上,叶绿素年循环呈双峰结构,硝酸盐和氨氮大体经历了冬季积累、夏季消耗的历程；水平分布上,由于水深和河口径流等影响,近岸和河口附近叶绿素浓度、硝酸盐和氨氮始终保持较高浓度。论文建立的水质生态模型能够较准确地模拟表层叶绿素、硝酸盐和氨氮年循环特征。最后,研究了温度、盐度与叶绿素浓度的相关性关系,模拟渤海湍流粘性系数的表层分布,分析温盐和湍流作用对渤海浮游植物生长的影响。研究表明：四季(冬、春、夏和秋)海洋表层温度与叶绿素浓度的相关系数分别为：-0.32、0.83、0.82和-0.21；四季(冬、春、夏和秋)海洋表层盐度与叶绿素浓度的相关系数分别为：-0.54、-0.92、-0.86和-0.53。水平分布上,冬秋季,虽然垂直湍流混合较好,表层营养盐充足,但由于受到温度和光照限制,使得渤海叶绿素含量较低；春夏季,光照和温度适宜,渤海表层叶绿素含量较高,但深水区的湍流混合变小,出现层化结构,营养盐含量降低,使深水区域叶绿素含量较低。浮游植物生长是温度、盐度、湍流作用等多种因素综合作用的结果。更多还原

【Abstract】 The algal bloom is the process that phytoplankton biomass accumulates rapidly. Studying the phytoplankton growth factors is of great significance to reveal the ecological mechanism of the algal bloom. In the paper, the hydrodynamic and water quality model COHERENS is adopted to simulate the phytoplankton growth seasonal changes and research the relationship between the phytoplankton and hydrodynamic environment in the Bohai Sea. The physical environment of the phytoplankton bloom is explored, focusing on temperature, salinity and turbulence effect.The 3-D hydrodynamic and water quality equations are applied to establish the actual model in which the weather conditions and runoff conditions are considered. The model is verified from the harmonic constants, tide level, temperature and salinity. The seasonal changes and stratification characteristics of temperature and salinity are simulated firstly. The results show that the thermocline gradually emerged from the spring, the strength of thermocline reaches its maximum in the summer. The temperature of the bottom existed asymmetric nuclear structure. After that, the thermocline decreases and finally disappeared in the autumn. The halocline only occurred in the summer, compared to the thermocline, the halocline relatively delayed. It can be found that the long term variation of temperature and salinity can be reasonably simulated with the hydrodynamic model.By adjusting zooplankton prey pressure, nitrate and ammonia nitrogen fluxes in the sediments, and other important parameters, the water quality model is established to simulate the chlorophyll, nitrate and ammonia nitrogen characteristics. The results show that the annual cycle of chlorophyll presents bimodal structure, the nitrate and ammonia shows the process of winter accumulation and summer consumption at time series. In the horizontal distribution, chlorophyll concentration, nitrate and ammonia always maintained a high concentration near coastal and estuarine due to the impact of water depth and runoff. It can be found that the year cycle characteristics of surface chlorophyll, nitrate and ammonia can be accurately simulated with the water quality model.Finally, the paper researches the relationship between the phytoplankton growth and the physical environment, such as temperature, salinity and turbulence effect. The surface distribution of turbulent viscosity in the Bohai Sea is simulated. The results show that the correlation coefficients of sea surface temperature and chlorophyll concentration in winter, spring, summer and autumn are -0.32,0.83,0.82 and -0.21. The correlation coefficients of sea surface salinity and chlorophyll concentration in winter, spring, summer and autumn are-0.54,-0.92,-0.86 and -0.53. In the horizontal distribution, in autumn and winter, the strong vertical turbulent mixing causes the surface nutrients adequate. However, the temperature and light limitation leads to lower chlorophyll content in the Bohai Sea. In spring and summer, the suitable light and temperature makes higher surface chlorophyll content. Nevertheless, the weaker turbulent mixing results in the stratification structure and reduced nutrient concentrations in the abyssal zone. Eventually, the chlorophyll content is low in the abyssal zone. The phytoplankton growth is the result of multiplex factors including temperature, salinity and turbulent effect.更多还原