2017年春、夏季南黄海西部营养盐的分布特征及其与浒苔暴发的关系

DISTRIBUTIONS OF NUTRIENTS IN THE WESTERN SOUTH YELLOW SEA IN SPRING AND SUMMER OF 2017 AND THEIR RELATIONSHIP WITH ULVA PROLIFERA OUTBREAKS

基于2017年4月、5月、6月和8—9月在南黄海西部海域4个航次的现场调查,分析了春至夏季逐月的营养盐分布特征及其影响因素,初步探讨了营养盐与浒苔绿潮暴发的关系。结果表明:春至夏季苏北近岸浅水区总体呈现出高温、低盐、高营养盐的特征,且各理化要素垂向差异不明显;同时该海域表层水体中的营养盐含量自4月至5月有所下降,而后开始上升,至8—9月达到最大浓度。受长江冲淡水的影响,调查海域西南部表层存在向东北方扩展的低盐、高营养盐水体,在夏季与苏北海域向外扩展的营养盐高值区连成一体。在调查海域的中部至东北部深水区,入春后表层海水不断升温,至夏季于底层形成显著的黄海冷水团,并在其周围呈现出锋面特征;受初级生产过程和温跃层的影响,入春后该海域的上层营养盐浓度总体呈现出下降的趋势并在夏季维持了较低的水平,而底层营养盐浓度从春季至夏季有所升高且影响范围不断向西南方向扩展,至8—9月达到最大范围。苏北近岸海域丰富的营养盐为入春后大型藻类的生长和暴发提供了重要的物质基础,而且5月南黄海西部相关海域表层营养盐浓度降低与浒苔、马尾藻等大型漂浮藻类暴发对营养盐的吸收利用有关。

Based on the on-site survey of four voyages in the western South Yellow Sea in April,May,June,and August-September 2017,the distribution characteristics of nutrients and their impact factors from spring to summer were analyzed.The relationship between nutrients and Ulva prolifera outbreak was explored.The results show that in the Subei(North Jiangsu)coastal area in spring-summer,there was a trend of temperature rising,salinity decreasing,and nutrient concentrations increasing in horizontal directions but no significant vertical difference was presented.The nutrient concentrations in the surface of Subei coastal area decreased from April to May and then reached the peak point in August-September.The shallow water area near the north of the Changjiang(Yangtze)River in the spring to summer was characterized by high temperature,low salinity,and high nutrient contents,while the vertical difference of physical and chemical elements was not obvious.At the same time,the nutrient contents in the surface water of the sea area declined from April to May,and then rose to the peak concentrations in August-September.Affected by the Changjiang River Dilute Water,low-salinity and high-nutrient saline waters formed,expanded to the northeastern and southwestern parts of the sea area,and integrated into the nutrient-rich areas that extended outward off the northern Jiangsu.In the deep-water area from the central to the northeast of the surveyed sea area,the surface seawater was heating up after the spring,and a significant Yellow Sea Cold Water Mass was formed in the bottom layer in the summer with a frontal feature around the cold water mass.Affected by the primary production and the thermocline,after the spring,the nutrient concentrations in the upper layers of the sea area showed a downward trend and maintained a low level in the summer,while the bottom nutrient concentrations increased from spring to summer and the influence range continued to expand southwestward.The maximum range was reached in September.The rich nutrients in the coastal waters of the northern Jiangsu provided an important material basis for the growth and outbreak of macroalgae after spring,and the reduction of surface nutrient concentrations in the relevant sea areas in the western South Yellow Sea in May was related to the absorption and utilization of nutrients by the large-scale outbreaks of floating algae such as U.prolifera and Sargassum sp.