| Wenchang is an important Marine fishery base in Hainan Province.The northern sea area of Wenchang connects to Qiongzhou Strait.It is a precious aquaculture water source area,a significant sea transport channel,and a habitat for various aquatic organisms.In recent years,with the rapid development of aquaculture in Wenchang City and the prosperity of the Qiongzhou Strait waterway,the Marine ecosystem in this area may suffer from potential pollution risks.Hence,there is a need to investigate water ecology in this area.Therefore,seawater’s physical and chemical status was analyzed to determine the status quo of the water environment in this area,and the water ecological health evaluation system based on the plankton integrity index was established.The results of this study will contribute to the sustainable management of the water environment and the protection of the Marine ecological environment in the northern sea area of Wenchang.The survey was conducted in October 2021(autumn)and April 2022(spring).A total of 15 sampling sites were set up to collect water and phytoplankton samples,measure physical and chemical indicators of seawater,and identify and quantify species of phytoplankton and zooplankton.The main results are as follows:1.Physico-chemical analysis revealed a distinct variation in the two seasons,with autumn recording significantly high levels of water temperature(27.30℃),water pressure(760.37 Pa),pH(8.3),(p<0.05),while spring had significantly high levels of nutrients(NH3-N(0.03 mg/L),NO2(0.004 mg/L),and TP(0.002 mg/L)(p<0.05).Further,Cluster analysis separated the seasons into two clusters indicating distinct character variations.Finally,water quality analysis showed that all sampling sites had excellent water quality during the two seasons except WS5,which had good quality during autumn.2.Analysis of phytoplankton identified 7675 phytoplankton species belonging to Cyanophyta,Ochrophyta,Bacillariophyta,Dinophyta,and Chlorophyta.Notably,4958 and 2717 species were identified during autumn and spring,respectively.The results revealed a distinct seasonal variation in the number and density of phytoplankton species,with the highest number of phytoplankton species recorded in autumn,about 1.8 times that in spring.In addition,the PhytoIBI results revealed that the health status of the Wenchang sea ranged from healthy to extremely poor in autumn.In spring,the health status ranged from fair to extremely poor.3.The analysis of zooplankton identified 116 zooplankton species.The highest number of zooplankton species was recorded at WS8,while WS1 and WS2 had the lowest number of species.In addition,the highest zooplankton density was recorded at WS11.The Zooplankton-IBI also indicated that health status ranged from healthy to extremely poor in spring.4.Generally,this study provided valuable data on the water quality status and plankton communities in Wenchang.The results suggested that this aquatic ecosystem in the sea area was degraded to different degrees due to the receiving of pollutants from anthropogenic sources.Therefore,there is a need to develop a management strategy to reduce the pollution loads to protect this ecosystem. |
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