Ecosystem Health Assessment Of Jiaozhou Bay

The marine ecosystem, as one of the most important ecosystems and the key link of the biogeochemical cycle, plays an important role in the global material cycle and energy flow. Meanwhile, marine ecosystems provide various ecosystem services including food supply, climate regulation, water purification, tourist recreation and disaster buffering. Severe stress imposed by anthropogenic activities resulted in the destruction of marine ecosystem, especially the coastal marine ecosystem. As a comprehensively developed bay, the Jiaozhou Bay is distinctive and representative among the coastal areas of our country. The ecosystem health of Jiaozhou Bay is very important to the development of the coastal areas. The marine ecosystem health assessment of Jiaozhou Bay is significant in the background of the increasing development intensity and types.Field survey is conducted to get the information of environmental factors in Jiaozhou Bay, and then the current environmental quality of Jiaozhou Bay is assessed. Based on the perspective of ecosystem health assessment, diagnosis of ecosystem health of Jiaozhou Bay is discussed in the present study. The state of health of Jiaozhou Bay is available according to the research results, which provides the basic data for the protection and development of Jiaozhou Bay. Moreover, the research enriched the practice of marine ecosystem health assessment, the result of which is convenient for the comparative research to the related marine areas.1. The ecological survey of the Jiaozhou BayThe survey is carried out on seven stations in August of 2006, December of 2006, April of 2007 and October of 2007, respectively. The survey investigated the temporal and spatial distribution of dissolved oxygen, salinity, pH, active phosphate, inorganic nitrogen, phytoplankton, zooplankton and the zoobenthos. Results showed that:(1) The temporal and spatial distribution of the major physical and chemical factors in Jiaozhou BayThe distribution of the physical and chemical factors varied with the season clearly. In spring, the DO concentration in the bay mouth is clearly higher than that in the'inner bay. In summer and winter, the DO concentration of the inner bay is clearly higher than that in the bay mouth. In autumn, no obvious variation of the DO concentration is detected in the space scale. The salinity in the bay mouth is higher than that in the inner bay in spring, summer and autumn, while in autumn the difference is not obvious. pH of the bay mouth is higher than that in the inner bay all over the year, while the active phosphate and inorganic nitrogen of the inner bay are higher than those in the bay mouth all the time.The seasonal variation of the physical and chemical factors of Jiaozhou Bay is obvious. The seasonal trend of DO is spring (9.51 mg/L)> winter(9.40 mg/L)> autumn(7.67 mg/L)> summer(6.62 mg/L). The seasonal trend of salinity is winter(31.33)> spring(31.25)> summer(30.74)> autumn(30.21). pH of spring and autumn are higher(8.11), and pH of summer and winter are lower (8.05). The seasonal trend of active phosphate is winter(0.0181 mg/L)> autumn(0.0168 mg/L)> summer(0.0067 mg/L)> spring(0.0045 mg/L). The seasonal trend of inorganic nitrogen is autumn (0.4404 mg/L)> winter(0.2185 mg/L)> spring(0.1756 mg/L)> summer(0.0798 mg/L). The seasonal trend of oil is spring(0.078 mg/L) >summer(0.059 mg/L)>winter(0.045 mg/L)>autumn(0.031 mg/L).(2) The temporal and spatial distribution of the major biological factors in Jiaozhou BayThe distribution of the biological factors varied with the season significantly. In spring and summer, the density of phytoplankton is higher in the inner bay, while in autumn and winter the variation is not clear. The variation trend of the density of zooplankton is not obvious all over the year. The variation of the zooplankton biomass is not clear between the bay mouth and the inner bay, while in summer the biomass is higher in the bay mouth. The zoobenthos density in the inner bay is higher than that in the bay mouth. The biomass of the zoobenthos in the bay mouth is higher in spring, summer and autumn, while the variation is not clear in winter.The seasonal trends of the density and biomass of phytoplankton, zooplankton and the zoobenthos is clear. The seasonal trend of the average phytoplankton density is summer>spring>winter>autumn. The seasonal trend of the average zooplankton density is spring>autumn>summer>winter. The seasonal trend of zooplankton biomass is spring> summer> winter> autumn. The seasonal trend of zoobenthos density is winter>summer>spring>autumn, while the variation trend of biomass is autumn>spring>winter>summer.2. Environmental assessment of the Jiaozhou BayThe water quality assessment shows that the content of various nutrient salts is not high, the oil pollution is lower, and the heavy mental pollution is lighter. The monitoring values of most of the stations meet the requirement of the national water quality standard, which is level one in nutrient salts and heavy mental. Most of the oil monitoring values are better than level two of national water quality.The sediment assessment of Jiaozhou Bay in autumn shows that no over-level phenomenon happens except for total nitrogen. The content of various pollutants is lower and reaches level one of national sediment test. So there is no risk for the marine sediment environment.The biology quality assessment of Jiaozhou Bay in autumn shows that the oil pollution has higher pollution index and over-level rates in the residues of harmful and toxic substances in vivo. The residual content in vivo reaches level two and attention should be given to this.3. The ecosystem health assessment of Jiaozhou BayGuidelines (HY/T087-2005) for coastal marine ecosystem health assessment, made by SOA of China, are applied to the case study of Jiaozhou Bay. The assessment results are as followed.Water environment:The average health index of water environment over the year is 14.01, which shows Jiaozhou Bay is in health status. In this survey, only active phosphate, inorganic nitrogen and oil cause pollution to the water environment. As the main land-source pollutants, active phosphate and inorganic nitrogen are indispensable for the growth of algae. While oil pollution is mainly caused by shipping incidents and transportation by sea.Sediment environment:The sediment environment is in sub-health status with the health index of 5.5, which is affected by the content of organic carbon.Biological residual toxicity:Oil data are available from only two stations and no heavy metal data for this area can be acquired. From the oil content in the organisms, the health index of biological residual toxicity in Jiaozhou Bay is lower and organisms are in sub-health status.Habitat environment:The assessment of habitat environment is based only on the decreasing area of coastal wetland as lack of data of size fraction composition change. The result shows that the habitat environment is sub-healthy.Biology:The biological health index throughout the year changes from 12.62 to 19.05 as the season flows, which is unhealthy. The best status is in summer and the worst is in spring. Biology in Jiaozhou Bay is unhealthy with annual average health index of 17.14. From the indicators, the density of fish eggs and larvae is the least healthy, followed by phytoplankton density.The comprehensive assessment shows that ecosystem health index of Jiaozhou Bay is 51.65, in sub-health status, which is resulted from sediment environment, habitat environment and biology, especially the biology.Based on the survey and assessment results, the main factors that affect the Jiaozhou Bay ecosystem health are sediment environment, habitat environment and biology. Biology is the worst which caused by the lower density offish eggs and larva and the higher density of phytoplankton. The sub-health state of habitat environment is caused by the higher content of organic carbon. Because the land reclamation is too fast in the recent years, the habitat environment is sub-healthy.Based on the analysis above, three suggestions are given from three aspects.1) To reinforce the environment governance, control the sewage disposal strictly, pursue the cleaner production; 2) To strengthen the exploitation governance of Jiaozhou Bay and pursue fishery enhancement and releasing; 3) To strengthen the monitoring and assessment of the Jiaozhou Bay ecosystem and pursue ecological restoration.