| In recent decades, marine environment has been deteriorated as a result ofincreased organic pollutants and nutrients inputs from rivers and coastal areas due tothe mighty pressure of increasing population and economic, which result in a series ofenvironment problems, e.g. eutrophication around the world. The phenomenon ofmarine eutrophication may generate a series of environment effects, such asdegradation of quality of water, red tide-frequent-occurrence and fishery slashingproduction, which would be disbenefit to marine ecosystem and economydevelopment.Haizhou Bay is at the most western end of the southern Yellow Sea, and awide-mouthed inlet belonging to the Jiangsu Province. With the coastal economicdevelopment in recent years, large amount of aquaculture and industrial wastewaterdischarge had a significant impact to the marine ecological environment of HaizhouBay. In order to understand the ecological status of the southern inshore waters ofHaizhou Bay, identify their constraints, and promote sustainable development in it, weinitiated a long-term comprehensive investigation of the southern inshore waters ofHaizhou Bay In this study, on the basis of the annual survey of the southern inshorewaters of Haizhou Bay from2011to2012, nutrients distribution and limitations isdescribed, which would provide the theoretical basis for the marine environmentalprotection and decision-making for Haizhou Bay.The main results in the dissertation were drawn as follows:(1) The distributions of temperature and salinity, to some extent, were parallel toshoreline, and there were no obvious differences betweem in the surface and bottomlayers. The distribution of seasonal variation of dissolved oxygen (DO) andchlorophyll a were large, amd the concentrations of them were generally higher in thecentral area of the southern inshore waters of Haizhou Bay and lower in the offshorearea. (2) The seasonal distribution of inorganic nitrogen and phosphate varied greatly,and the concentrations of them were generally higher near the shore and lower in theoffshore area. The concentration of dissolved inorginc nitrogen (DIN) ranged from0.026to2.47mg/L in2011and from0.032to0.95mg/L in2012. The concentration ofphosphate ranged from0.004to0.13mg/L in2011and from under detection to1.36mg/L in2012. The seasonal distraction of silicate varied greatly, and the trend ofconcentration was not obvious. The concentration of silicate ranged from0.005to0.95mg/L in2011and from0.016to0.95mg/L in2012. It showed that difference ofvertical distribution of nutrients were not significant in the research area．(3) Nitrate-nitrogen was the dominant forms of DIN, then ammonia-nitrogen andthen nitrite-nitrogen. The proportion of inorganic nitrogen varied greatly in differentseasons. There was a significant negative correlation between salinity and DIN, thesame as phosphate and silicate. The distribution and characteristics of different formsof nitrogen and phosphorus and silicate were strongly linked to terrestrial input,aquiculture and water exchange. Based on historical records, long-term changes ofDIN and phosphate showed increasing trends in the recent years, but the change ofsilicate showed a downward tendency.(4) Clay silt (YT) and sand silt (ST) were the major components of the sediment inthis area. The concentrations of carbon, nitrogen, and sulfur of the sediment weregenerally higher near the shore and lower in the offshore area, but the trends were notobvious.(5) The ratios range of N/P、Si/N and Si/P were from19.2to143, from0.2to1.1and from6.5to230, respectively. According to the analysis of nutrient structures,phosphorus-limitation and silica-limitation were the major limiting factors.(6) The analysis of eutrophication and organic pollution index indicated that DINand phosphate were the main pollution factors. The potential eutrophicationconditions of water quality showed that the southern inshore waters of Haizhou Baywere in the middle level eutrophication and potential phosphorus-limiting. |
PDF Full Text Request