Field Measurements for Investigating the Dynamics of the Tidal Prism during a Spring-Neap Tidal Cycle in Jiaozhou Bay, China

The tidal prism is a crucial environmental index for evaluating the water self-purification capacity in semi-enclosed bay systems, but quantitative studies linking spring-neap tidal variations are few. In this paper, field measurements of the tidal level and tidal flux were conducted in Jiaozhou Bay (JZB) to estimate the hydrodynamic and tidal prism variations during a spring-neap tidal cycle. JZB is located on the south coast of Shandong Peninsula, China, with a narrow inlet of 3.1 km width, which was accessible for continuous shipboard Acoustic Doppler Current Profiler measurements over 15 days. Unfortunately, due to the violent sea induced by typhoon "Chan-hom,'' the measurements were suspended for 2 days. However, the fluxes during the temporary suspension were reproduced using the significant linear relationship between the inlet fluxes and the changes in tidal level (r(2) = 0.94, P, 0.001), without considering the storm surge. The relationship between tidal range and tidal prism was also linearly correlative (r(2) = 0.69, P < 0.001), indicating that the tidal prism was primarily controlled by the tidal range in JZB. These linear relationships are well verified by historical data in JZB. Compared with previous studies in JZB, the tidal prism has decreased 26% from 1928 to 2008. The decreased intertidal areas, caused by large-scale land reclamations, were likely responsible for the decrease in the tidal prism, which in turn weakened the self-purification capability and triggered the chronic pollutant enrichment. However, the tidal prism increased 4% from 2008 to 2015 as the restoration of water area through protective policies formulated by government. These findings will contribute to designing maintenance strategies for reducing human activity impacts on the health of JZB in the future.