夏季长江口外赤潮海区叶绿素a分布特征与固碳能力

Distribution of Chlorophyll a and Carbon Fixation at HABs Coast of Yangtze River Estuary in Summer

2018年和2019年分别对夏季长江口外赤潮海区开展了两个断面水体环境要素调查,叶绿素a(Chl a)原位观测和同步水样采集测定的两套数据均表明该区夏季水体Chl a分布特征:最大值不局限分布于表层2m,可深达10~15m。全水柱Chl a观测值与实测值呈线性显著正相关(r>0.8,p<0.05),表明高深度分辨率的Chl a原位观测数据可全面反映水体浮游植物生物量垂直分布。采用真光层内高深度分辨率Chl a观测值积分优化方法的垂直归一化模型(Vertically Generalized Production Model,VGPM)估算整个藻华水柱初级生产力,充分体现该海区藻华水层叶绿素垂直分布特征与其初级生产的固碳能力,有助于深入理解受人类活动干扰严重的海岸带赤潮海区全水柱的固碳贡献及其在海洋碳中和与碳循环中的角色。

The environmental factors in the water column were investigated along the 2 transects at the Harmful Algae Blooms(HABs)coast of the Yangtze River Estuary and Hangzhou Bay during summer in 2018 and 2019.Based on two datasets of Chl a obtained via in situ sensor-monitoring and simultaneously water sample analysis,it showed that the distribution of Chl a in summer was featured with the maximum concentration not only existing at a surface depth of 2m,but down to a depth range of 10~15 m.The in situ observed Chl a concentrations showed the positively linear regression(r>0.8,p<0.05)with those determined from water samples through the water columns,suggesting that the observed Chl a data with high depth-resolution may be reliable to represent the vertical distribution of phytoplankton biomass.Therefore,based on that,the primary productivity of the whole blooming water column was estimated by the vertically generalized production model(VGPM)using the optimized method of the integrated Chl a concentrations with the photic depths.The optimized VGPM pattern may reflect the vertical distribution feature of Chl a and carbon fixation rate of the whole blooming waterbody,to improve our knowledge on the role of HABs coast water under the impacts of severe anthropogenic activities in the carbon neutrality and fixation in the marine carbon cycle.