厦门近岸海域营养盐时空变化特征分析及其富营养化评价

Temporal and spatial nutrient variations in inshore waters of Xiamen and eutrophication assessment

本研究根据2016—2020年厦门近岸海域15个航次的监测数据,对该区域营养盐的时空分布特征、影响因素及营养盐限制状况进行综合分析,并评估各海区的富营养化状态。结果表明,空间上,营养盐的分布特征表现为从近岸向远岸逐渐下降的趋势,溶解无机氮(Dissolved Inorganic Nitrogen,DIN)平均浓度排序为:九龙江口>西海域>同安湾>南部海域>东部海域>大嶝海域,溶解无机磷(Dissolved Inorganic Phosphorus,DIP)平均浓度排序为:同安湾>西海域>九龙江口>东部海域>南部海域>大嶝海域;时间上,营养盐浓度总体呈逐年下降趋势;枯水期最高,平水期次之,丰水期最低。研究海域平均DIN/DIP摩尔比值为40,总体表现为磷限制。2016—2020年厦门近岸海域富营养化指数(E)基本呈逐年下降的趋势;从空间分布上看,九龙江口和西海域富营养化较为严重。富营养化指数与盐度呈显著负相关关系,说明陆源输入对研究海域富营养化存在重要影响。

The spatial-temporal distribution characteristics,influencing factors and nutrient limitation in Xiamen coastal waters were analyzed,and the eutrophication conditions were evaluated,based on fifteen cruises in 2016-2020.The results showed that the nutrient concentrations were higher in the coastal waters,and decreased gradually offshore.Specifically,the concentrations of dissolved inorganic nitrogen(DIN)distributed in order of Jiulong River Estuary>West Sea>Tongan Bay>the south sea of Xiamen>the east sea of Xiame>Dadeng seawater,but the concentration of dissolved inorganic phosphorus(DIP)followed the order of Tongan Bay>the west sea of Xiamen>Jiulong River Estuary>the east sea of Xiamen>the south sea of Xiamen>Dadeng seaarea.The results also showed that the average concentrations of nutrients decreased annually and they reached the highest in dry season and the lowest in the wet season.The averaged N∶P molar ratio was 40 in Xiamen coastal area,indicating the potential P-limitation.The levels of eutrophication were decreased yearly from 2016 to 2020.The areas of high eutrophication index E)were mainly located in the sea area near Jiulong River Estuary and the west sea of Xiamen.The eutrophication index that negatively correlated with salinity indicates the eutrophication impacts of terrestrial nutrients to the study area.