Ecosystem Health Assessment For Estuary And Bay: Methedologies And Application

Ecosystems of estuaries and bays have been strongly affected by multiple anthropogenic drivers and mostly with degraded health. The increasing recovery actions however have not made up for the health degradation, which is controlled by complex and dynamic biogeochemical processes. How to restore ecosystem health, and obtain ecosystem services from a healthy ecosystem have rosed many concerns. Ecosystem health assessment (EHA) therefore becomes hot issues of marine ecology and ecosystem management. However, current methods in the EHA are mostly based on the individual components of ecosystem and therefore not integrated. In this paper, based on framework of the Millennium Ecosystem Assessment (MA), we develop an ecological conceptual model and a set of indexes for the EHA and using the Pearl River Estuary and Daya Bay as case study.The major contents and results are now summarized:1. Definitions of ecosystem health are discussed. A healthy ecosystem is defined as being stable, which structure and functionings are coordinating, and it can present essential ecosystem services for human-well being.An ecological conceptual model for EHA is constructed based on the fundamentals of integrity, in which key ecological processes influencing ecosystem health is considered and couplings among internal and external elements of ecosystem are illustrated.2. Definitions of ecosystem coordination are discussed and used to quantify interactions of ecosystem element. A set of indexes for the EHA is developed, which focused on ecosystem structure and serives at the estuaries and bays. It is an analytical tools—the index base can serve in evaluating ecosystem health at a generic estuary/bay, while the NPP-related indices, such as cooling water, residual chlorine and artificial radioactive nuclide, allow differentiated assessment in a typical NPP-influenced bay.3. Long-term monitoring data are analyzed to assess the health states of ecosystem at the PRE and Daya bay.①During the period of 1980—2009, EHI ranged from 0.86 to 0.42, refers"ill-healthy". EVI ranged from 0.91 to 0.57 suggesting an unstable ecosystem. ECI ranging form 0.94 to 0.73 shows that ecosystem elements are mismatching and internal health of ecosystem are degraded.②During the period of 1985—2008, EHI at the Daya Bay ranged from 0.99 to 0.47, EVI raged 0.99 to 0.72, and ECI ranged from 0.99 to 0.66. These findings suggest a"ill-healthy"ecosystem.4. Scenarios of ecosystem management are designed, and how EHI reponse to the management variety and strength are tested.①The results suggest that the priority of the restoration inputs is (i) habitat reconstruction, (ii) fisheries, (iii) coastal plants, and (iv) wastewater management.②ECI/EHI can not rise sustainedly under scenarios of single target. Efficiency of integrated management increased from 0～3 % to 25 %. ECI/EHI approaches the desired endpoint under scenarios of ecosystem-based managment. In sum, this study can provide information on state and trends of ecosystem health, priorities in ecosystem management, and management efficiency under various scenarios.