Study on the formation of mudflat and habitat of benthos due to mud transport in shallow water area

本研究利用自动升降仪对潮滩水质进行测量，该仪器长期收集潮滩不同深度的水力数据和水质数据。通过对实测资料的分析，揭示了悬浮物在不同潮期的变化和分布规律。潮滩的各种物理特性的波动信息，成功地提取从所获得的测量。阐明了水位变化下滩涂泥沙输移的一些特征。本研究还试图考虑SS和营养盐的迁移，从而研究它们的特性以及侵蚀对水质的影响。因此，可以说，TN和T-P在很大程度上取决于泥浆的侵蚀行为。在本次有限的调查中，泥质侵蚀对DIN和DIP的影响并不明显。此外，部分营养盐从侵蚀物质中淋溶到水中，并被吸附到悬浮物中。沉积物和营养盐的分析结果揭示了滩涂沉积物的特征。在沉积物-防水布中观察到的沉降通量几乎与从理论计算获得的净沉降通量一致。沉积量的泥滩也估计基于在这项研究中测量的沉降通量。通过对三塔观测资料的检验，证实了该地区细颗粒粘性泥沙的输移，并通过试验提取了<$蛄的偏好因子。结果表明，利用综合适宜度指数对缢蛏的生境进行了评价。

In this study, water quality in a tidal flat is measured using an automatic ascending-descending instrument that collects hydraulic data and water quality data at various depths over a long period. Analysis of the data, focusing on suspended solids, reveals the variations and distribution of suspended solids in different tidal periods. Information regarding the fluctuation in various physical characteristics of tidal flats was successfully extracted from the obtained measurements. Some of the characteristics of sediment transport over mud flats under the variations of water level were also clarified. This research also attempts to consider that the movement of SS and nutrients, and thus their characteristics and the influence of erosion to water quality are investigated. As a result, it can be said that T-N and T-P are much dependent on the behaviors of mud erosion. They contribute a great effect to the water quality, while DIN and DIP may not be affected clearly by the mud erosion in this limited survey. In addition, parts of nutrients leached in the water from eroded matters were adsorbed to suspended matters again.Behaviors of suspended matters on the mud flat were investigated by using the sediment-traps and observation towers. Results obtained from the analysis of the amounts of sedimentation and nutrients reveal the characteristics of settling matters in the mud flat. The settling flux observed in the sediment-tarps almost coincided with the net settling flux obtained from a theoretical calculation. The amount of sedimentation to the mud flat was also estimated based upon the settling flux measured in this study. It is shown that the fine cohesive sediment transport in the area was demonstrated through examining the observed data in three towers.The preference factors of Sinonovacula constrica were extracted by some experiments. As the results, habitat of Sinonovacula constrica was estimated on the base of composite suitability index.