Cho, J.-S.; Lee, J.-S., and Kim, J.-W., 0000. Distribution of Phragmites australis communities with different habitat salinity. To analyze vegetation distribution and environmental factors, 22 regions containing Phragmites australis communities were selected from the west to south coastline of South Korea. In the studied soil environments, the average moisture content was 28.07%, soil salinity was 5.86 ppt, and total nitrogen was 1.02 mg/g. In water environments, the average dissolved oxygen was 9.04 mg/L, water salinity was 13.66 ppt, nitrate nitrogen (NOx–N) was 1.0712 mg/L, and ammonia nitrogen (NH4+–N) was 0.3790 mg/L. The correlation analysis of P. australis communities revealed that there was a relatively strong negative correlation between soil salinity and annual production (r = −0.584, N = 22). The ordination using canonical correspondence analysis (CCA) of edaphic factors and water quality factors showed that soil salinity, water salinity, and water nitrate–nitrogen play important roles...

This study investigated the flow patterns and affecting factors in the North Port of Incheon, South Korea, to understand the inner-port circulation characteristics by applying an unstructured grid finite volume community ocean model (FVCOM) together with a field survey. The FVCOM considered the tide, river discharge, surface winds, and atmospheric pressure with the highest resolution of 50 m around the port. The model results were validated with current velocity and salinity observations. In the main channel, the difference in salinity between the sea surface and bottom increased during the neap tide due to weakened tidal currents, thus strengthening the stratification. However, at the inner port, strong stratification was observed during spring tide as the near-surface freshwater from upstream of the estuary moved relatively farther south of the port than that during the neap tide. Freshwater flowed into the port during the flood current and was trapped in the semi-closed geometry of the inner port. The horizontal salinity gradient between the trapped fresher water in the port and saltier water in the main channel increased during the flood current. As a result, density-driven circulations associated with near-bed currents towards the port were maintained for more than 3 h after high tide. This result implies that the baroclinic effect, mainly due to the salinity gradient in the North Port, could significantly affect residual circulation at the inner harbor in a macro-tidal environment and the mass transport mechanism, such as sediment transport. In general, such enhanced baroclinic effects due to salinity and tides are not limited to the North Port and can have greater effects on inner-port circulation in other macro-tidal harbors that suffer from severe sedimentation problems.

Many estuaries have been damaged by such material movements as marine debris, suspended sediment, and pollutants. Understanding the estuarine circulation system is necessary to solve such problems. Salt transport analysis provides an insight into hydrodynamic processes about material circulation in the estuary. In this study, to understand the mechanisms of salt transport, a three-dimensional hydrodynamic model was applied in the hypertidal estuary system—Yeomha Channel in Gyeonggi Bay. The simulation period of the model was a total of 245 days (20 January to 20 September 2020), including the dry and wet seasons. The model results for the temporal variation in tide, current velocity, and salinity were validated by comparing them with the observed in-situ data. The total salt transport (F_S) was calculated in three cross sections of the Yeomha Channel and was decomposed into three components (Q_fS₀: advective salt transport; F_E: steady shear dispersion; F_T: tidal oscillatory salt transport). During the dry season with strong tidal forces, the total salt transport patterns were mainly dominated by Q_fS₀. During the wet season with high river discharge, the total salt transport patterns were determined by the balance between Q_fS₀, F_E, and F_T. The long-term tidal constituents (MS_f and M_m) were the main mechanisms causing Q_fS₀ with the spring–neap variation during the dry season. The tidal trapping effect, caused by a phase difference of less than 90° between tidal current and salinity, generated landward F_T in the dry and wet seasons. In addition, the high river discharge during the wet season decreased the phase difference between tidal current and salinity to less than 70°, resulting in a much stronger landward F_T. This study suggests that the long-term tidal constituents and tidal trapping effect are unique characteristics that contribute to material circulation in the hypertidal estuary.