Numerical modeling of hydrodynamic changes due to coastal reclamation projects in Xiamen Bay,China

Xiamen Bay in South China has experienced extensive coastal exploitation since the 1950s,resulting in some severe environmental problems.Local authorities now have completed or are implementing many environmental restoration projects.Evaluating the cumulative impact of exploitation and restoration activities on the environment is a complicated multi-disciplinary problem.However,hydrodynamic changes in the bay caused by such coastal projects can be characterized directly and definitively through numerical modeling.This paper assesses the cumulative effect of coastal projects on the hydrodynamic setting using a high-resolution numerical modeling method that makes use of tidal current speeds and the tidal prism as two hydrodynamic indices.Changes in tidal velocity and the characteristics of the tidal prism show that hydrodynamic conditions have declined from 1938 to 2007 in the full-tide area.The tidal current speed and tidal prism have decreased by 40% in the western part of the bay and 20% in the eastern part of the bay.Because of the linear relationship between tidal prism and area,the degraded hydrodynamic conditions are anticipated to be restored to 1972 levels following the completion of current and proposed restoration projects,i.e.33% and 15% decrease in the hydrodynamic conditions of 1938 for the western and eastern parts of the bay,respectively.The results indicate that hydrodynamic conditions can be restored to some extent with the implementation of a sustainable coastal development plan,although a full reversal of conditions is not possible.To fully assess the environmental changes in a region,more indices,e.g.,water quality and ecosystem parameters,should be considered in future evaluations.

An assessment of “fishing down marine food webs” in coastal states during 1950–2010

Mean trophic level of fishery landings（MTL） is one of the most widely used biodiversity indicators to assess the impacts of fishing. Based on the landing data compiled by Food and Agriculture Organization combined with trophic information of relevant species in Fish Base, we evaluated the status of marine fisheries from 1950 to 2010 for different coastal states in Pacific, Atlantic and Indian Oceans. We found that the phenomenon of ＂fishing down marine food webs＂ occurred in 43 states. Specifically, 27 states belonged to ＂fishing-through＂ pattern, and 16 states resulted from ＂fishing-down＂ scenario. The sign of recovery in MTL was common in the Pacific, Atlantic and Indian Oceans（occurred in 20 states）, but was generally accompanied by significantly decreased catches of traditional low trophic level species. In particular, 11 states showed significant declining catches of lower trophic levels. The MTL-based assessment of ＂fishing down marine food webs＂ needs to be interpreted cautiously.