Ecosystem Health Assessment Of The Egong Bay Fisheries Waters In Shenzhen

The bay ecosystem is composed of biological community and semi-closed water in nearshore surrounded by land. The bay ecosystem has some distinctive characteristics, such as: complex environmental factors changes, high productivity, habitat diversity, and susceptible to human activity. In the past 30 years, eutrophication, nutrient imbalance, abnormalities of biological community structure, frequent red tides, erosion and collapse of embankment have been appeared in most of the bay ecosystem in our country, induced by the increasing human activities. Frequent ecosystem health issues including marine pollution and natural disasters caused huge losses of life and property and have become obstacles of economic development. Therefore, the bay ecosystem health issues have become an important problem urgently to be solved during the period of social and economic sustainable development.Egong Bay, a typical offshore fisheries water in the South China Sea, is a part of Dapeng Bay located in Shenzhen. There are two kinds of marine functional zones in the bay: shallow sea aquaculture region and artificial reef area. According to national marine functional zoning and marine functional zoning of Shenzhen, Egong Bay develops mainly in marine conservation, tourism and leisure entertainment. The environment of Egong bay has been well protected, and major affected factors are aquaculture and the sewage from land-based sources.Based on the survey data from 2012 to 2013 and the development of the bay, the model of ecosystem health assessment, the pressure-state-response model(PSR), as well as analytic hierarchy process(AHP) were applied to assess the ecosystem health of the bay. The results are as follows:(1) The ecosystem health of the Egong Bay fisheries waters was in healthier and healthy states during the whole investigation period, and it improved gradually. The index of ecosystem health assessment from highness to lowness were spring, summer, autumn, and winter, sequentially. The most important influencing factor was organic pollution index. Concentrations of COD and PO43-P were over standard, which may be mainly related to sewage discharge from 7 sewage outlet of Dapeng Bay in Shenzhen.(2) The artificial reef area and control area in the Egong Bay fisheries waters were in healthier and healthy states, and the health state of the artificial reef area was better and more stable. Artificial reefs improved the health states of the density of eggs and larvae resources, the density of nekton resources and the benthos resources. This indicated that the artificial reefs partly improved the local ecosystem health.And the index of biological integrity of fish(F-IBI) was applied in the bay. The results are as follows:(1) Based on the survey data from 2012 to 2013, 6 indicators were used in computing the index of biological integrity of fish(F-IBI) of Egong Bay fisheries waters. The total number of species, percentage of Sciaenidae species, percentage of Sparidae species, percentage of planktivorous species, percentage of benthic-feeding species and percentage of benthic-feeding and piscivorous species. Principal component analysis of these indicators showed that percentage of Sciaenidae species, percentage of Sparidae species, percentage of planktivorous species and percentage of benthic-feeding species mainly contribute to F-IBI.(2) F-IBI was significantly correlated with salinity, chemical oxygen demand(COD) and suspended matter. F-IBI has positive correlation with salinity, and has negative correlation with suspended matter. The correlation between F-IBI and COD needs further research.It showed that PSR and F-IBI were feasible in the bay and their results verify each other. We figured out the health state and F-IBI of Egong bay and F-IBI’s influencing factors, providing technical support for the assessment of the ecology effect of artificial reef and fishery resources multiplication and conservation. Our research provided a scientific basis for the sustainable development of Egong bay, and furthermore, positively promoted the application of PSR model and F-IBI in bay ecosystem in China.