中文摘要：

根据在福建罗源湾互花米草盐沼内的沉积动力要素（水深、流速、悬沙浓度和沉降速率）的观测及表层沉积物的粒度分析结果，罗源湾互花米草盐沼表层沉积物组份以粉砂和粘土为主，为粘性沉积物；互花米草盐沼内的潮流流速很小，最大值不超过7cm／s，相应地，底部切应力也相对较小，悬沙在潮周期内多处于沉降状态，表层沉积物在涨潮初期和落潮后期多发生侵蚀。在台风显著影响下，潮流流速平均值变化很小，但水流紊动能量和底部切应力显著增大，导致表层沉积物多处于侵蚀状态，在台风登陆期间潮周期内净侵蚀通量可达到40．099kg／m^2；台风影响过后，底部切应力逐渐减小，沉积物逐渐不发生侵蚀，悬沙多发生沉降，整个潮周期内以悬沙沉降为主。

英文摘要：

The four processes of cohesive sediment of primary interest to the engineer and scientist are erosion, transport, deposition and consolidation, where the erosion and deposition are two more important processes for cohesive sediment behaviors. Understanding erosion and deposition processes of cohesive sediment is very important for better management of coastal and estuarine environments. The Luoyuan Bay, located in the north of Fujian coast, is sheltered from the East China Sea by peninsulas, is dominated by semidiurnal tide with a mean tide range of 4.98re,the intertidal flat covered by muddy sediment presents extensively in the bay, and Spartina alterniflora marsh occurs at the upper intertidal area. In order to understand the behavior processes of cohesive sediment in marsh environment under the different hydrodynamic conditions, an instrument system including OBS sensor, pressure sensor and Acoustic Doppler Velocimeter （ADV） was deployed in the S. alterniflora marsh to measure related sediment dynamic parameters （e. g. water inundation height, current speed, suspended sediment concentration,settling velocity,etc. ）. During observation, three surfacial sediment and some bottom water samples were collected in different time. Surficial sediment analysis indicate that the sediment in S. alterniflora marsh of Luoyuan Bay is mainly composed by silt and clay,and the variations of sediment composition and grain size reveal the sediment dynamic characteristics of spring-neap tidal cycle. In situ observation show that, at the fair weather conditions, the near-bed （5cm above bed）current speed in S. alterniflora marsh is very low with the maximum value no more than 7cm/s, consequently, the bottom shear stress is also low, which induces that the suspended sediment is in the depositional status at the most time within the tidal cycles from later spring tide to neap tide,and the erosion is only occurred at the spring tide. At the time scale of spring-neap tidal cycle, the net deposition flux is only 0. 191kg/m2