摘要
溶解氧(DO)是海洋生物生存不可缺少的要素。随着人类活动的增加,全球近岸海域低氧情况愈发严重,已经成为威胁海洋生态系统健康的重要因素。通过对2017年5−9月秦皇岛外海区域的观测调查,探讨了该海域低氧与酸化的形成机制并计算了月平均耗氧速率。结果表明,5月秦皇岛外海水体混合较为均匀,表、底层DO浓度一致,均大于8 mg/L;6月开始形成密度跃层,与此同时底层DO浓度和pH开始下降;8月底层呈现明显的低氧和酸化状态,DO浓度下降至2~3 mg/L,pH下降至7.8以下;9月随着层化消失,底层水体DO浓度和pH逐渐升高。相关性分析显示,DO和叶绿素a(Chl a)以及pH具有良好的耦合性,说明秦皇岛外海区域的低氧发生过程主要为局地变化。同时表明DO浓度和pH主要受水体中浮游植物的光合作用和有机物有氧分解的影响。通过箱式模型计算得到2017年6−8月密度跃层以下水体及沉积物耗氧速率为951~1193 mg/(m^2·d)[平均为975 mg/(m^2·d)]。综合来看,水体分层是秦皇岛外海低氧和酸化发生的先决条件,跃层以下的有机物分解耗氧则是底层水体发生低氧和酸化的重要原因。
Dissolved oxygen is an indispensable element for the survival of marine organisms.With the increase of human activities,the situation of hypoxia in the global coastal waters has become exacerbated,which is considered as an important factor threatening the health of the marine ecosystem.The vertical distributions of water temperature,salinity and density were investigated in the offshore area of Qinhuangdao from May to September in 2017.Additionally,the average monthly oxygen consumption rate was evaluated,and hence the mechanism of hypoxia and acidification was discussed.The results showed that the water column in the studied area was vertically homogenous in May,and no obvious difference for dissolved oxygen(DO)between the surface and bottom layers,with the value larger than 8 mg/L.From June to August,the pycnocline presented in the mid of the water column.In this period,DO and pH in bottom water gradually decreased,and reached 2−3 mg/L for DO and less than 7.8 for pH in the end of August,suggesting significant hypoxia and acidification in this area.However,DO and pH in bottom water sharply increased in September,after the pycnocline disappeared.The result indicated that hypoxia and acidification of Qinhuangdao offshore waters are seasonal.DO was significantly correlated with chlorophyll a and pH,indicating that the hypoxic and acidified processes in the offshore area of Qinhuangdao were local.The evaluated oxygen consumption rate,based on the box model,in bottom water and sediment ranged from 951 mg/(m^2·d)to 1193 mg/(m^2·d)(mean:975 mg/(m^2·d))from June to August in 2017.Comprehensive analysis showed that water stratification was the prerequisite for the occurrence of hypoxia and acidification in Qinhuangdao offshore waters,and DO consumption caused by organic matter decomposition was an important reason of hypoxia and acidification in bottom water.
作者
赵紫涵
宋贵生
赵亮
Zhao Zihan;Song Guisheng;Zhao Liang(College of Marine and Environmental Sciences,Tianjin University of Science and Technology,Tianjin 300457,China;School of Marine Science and Technology,Tianjin University,Tianjin 300072,China)
出处
《海洋学报》
CAS
CSCD
北大核心
2020年第10期144-154,共11页
基金
国家重点研发计划项目(2016YFC1401602)
国家自然科学基金(41876018,41606098)
天津市自然科学基金(19JCZDJC40600)。
关键词
秦皇岛外海
低氧
酸化
耗氧速率
the sea off Qinghuangdao
hypoxia
acidification
oxygen consumption rate
