2016年夏季长江口邻近海域溶解氧的周日变化特征及其影响因素

Diurnal variation characteristics and influencing factors of dissolved oxygen in the Yangtze River Estuary adjacent sea area in summer of 2016

2016年7月对长江口邻近海域(30°36.22′~31°12.05′N,122°37.72′~122°47.87′E)进行现场综合调查,采样测定了溶解氧等化学要素,初步分析了该航次溶解氧的周日变化特征及其主要影响因素.结果显示:调查海域溶解氧含量范围为1.25~8.55 mL/L,整体上由表层到底层随之降低.表层溶解氧饱和度除C3站(31°12.03′N,122°47.86′E)较高外,其他观测站表层溶解氧饱和度平均约为78%;在D3站(30°59.40′N,122°46.26′E)10 m以深出现了非持续但明显的低氧现象.潮汐是影响溶解氧周日变化的主要物理因素,夏季出现的水体层化和深水中有机物的分解对低氧区的形成至关重要,浮游植物生物量激增等对个别站溶解氧的影响显著.对比2014年、2015年和2016年夏季溶解氧的调查结果,发现2016年夏季低氧现象有所加剧.

A summer cruise was carried out in July of 2016 in the Yangtze River Estuary adjacent sea area(30°36.22′-31°12.05′N,122°37.72′-122°47.87′E).Seawater samples were collected to determine content of dissolved oxygen(DO)and other chemical parameters,and then diurnal variation characteristics and main influencing factors of DO in this cruise were analyzed preliminarily.The results showed that the content of DO ranged from 1.25 mL/L to 8.55 mL/L and decreased from the surface water to the bottom water.The DO in surface water was unsaturated with an average saturation degree of about 78%except for C3 station(31°12.03′N,122°47.86′E)that had higher values.Nonpersistent but significant hypoxia was observed at D3 station(30°59.40′N,122°46.26′E)at the depth≥10 m.Tide was the main physical factor that affected the diurnal variation of DO.Stratification in summer and decomposition of organic matter were important to the occurrence of hypoxia.The effects on DO via increased biomass of marine phytoplankton were significant only at a few stations.Comparison of DO in summers of 2014,2015 and 2016 showed that hypoxia became worse in 2016.