Potential Causes of Salinity Trend in Seawater Overlaying a Mudflat inside a Semi-Enclosed Bay

Abstract

To achieve better management and conservation, it is important to monitor the salinity of seawater that overlies mudflats and attribute any salinity trend to its potential causes. This study analyzes the salinity trend observed in a semi-enclosed bay and identifies the main causes using numerical modeling. The intertidal mudflat within a Ramsar site in Deep Bay, China is used as a case study. The salinity at the bay’s mouth and toward its interior displayed opposite trends from 1994 to 2007, and previous research has attributed the decreasing salinity over the mudflat in the inner bay to an increase in river flow discharge. However, the simulation results in this study show that the effect of land reclamation during this period was 1.5 times that of the freshwater discharge increase. The effect has propagated from the outer and middle bay to the inner bay, and also to the side where the mudflat is situated. Water mixing due to tides has been weakened, and wind has become more influential in the mixing. Overall, this study is beneficial to other regions considering land reclamation, highlighting its potential effect compared with other factors that could influence the salinity, and thus the overall health of mudflats.