秦皇岛外海低氧区颗粒物吸收光谱特征

ABSORPTION SPECTRUM OF PARTICULATE MATTER IN LOW-OXYGEN AREA OFF THE QINHUANGDAO

近年来,渤海夏季低氧现象频发,引起了人们的广泛关注。然而对该海域低氧形成的机制还未得到充分认识。研究基于在秦皇岛外海的现场观测,分析了海水中颗粒物吸收光谱特征及其与不同粒径浮游植物叶绿素a(chl a)组成、环境因子的关系,评估了夏季底层水体脱氧过程中有机物来源与特征。结果显示,夏季秦皇岛外海微型浮游植物chl a占总量的80%。表层水体中,总颗粒物吸收光谱[ap(λ)]特征由浮游植物色素吸收光谱[aph(λ)]主导,在中、底层水体中则由碎屑颗粒物吸收光谱[ad(λ)]主导。垂向上,ap(440)和ad(440)均表现为表层<中层<底层。结果还表明,浮游植物粒径主导秦皇岛外海chl a的光吸收效率,即a*ph(440)。基于三粒级chl a含量,可利用多元回归预测aph(440)。碎屑颗粒物的吸收光谱同样受浮游植物群落、有机质相对含量等的影响。研究结果表明初级生产产生的微型颗粒有机物是底层水体脱氧的主要底物。

More and more attention has been paid on the oxygen depletion in the Bohai Sea in recent years.However,the mechanism of deoxygenation has not been well known.We investigated the characterization of the absorption spectra of suspended particles in seawater off Qinhuangdao,Hebei,China.Furthermore,and evaluated the sources and features of organic matter responsible for deoxygenation in bottom water in summer based on the relationships of particulate absorption spectra with the size-based components of chlorophyll a(chl a)and with environment factors.Results show that nano-phytoplankton contributed approximately 80%of total chl a.The absorption spectra of pigment[aph(λ)]reflected the major feature of total particulate absorption spectra[ap(λ)]in surface water,while that of detritus[ad(l)]was dominant in middle and bottom layers.ap(440)and ad(440)increased from surfac to bottom waters.The size of phytoplankton controlled the absorption efficiency of pigment,i.e.,a*ph(440).Therefore,aph(440)could be calculated using multiple regression based on Chl a concentrations of three phytoplankton size classes.The characters of ad(λ)were also influenced by the phytoplankton community and the relative abundance of organic detritus.This study revealed that nano-sized organic particles produced during primary production were the main substrates of deoxygenation in summer in Bohai Sea.