初夏渤海湾营养盐结构特征及其限制状况分析

根据2016年初夏渤海湾营养盐、叶绿素a和相关水文参数等数据，利用浮游植物吸收营养盐最低阈值和化学计量关系作为判断依据对渤海湾营养盐限制状况进行分析.结果表明：受陆地径流和渤海中部冷水输入的影响，初夏渤海湾在近岸、中部和湾口呈现三个明显的温盐特征海区.溶解无机氮（DIN）和活性硅酸盐（SiO₃^2--Si）受陆源输入影响，呈现近岸高湾口低的特征；DIN平均浓度为（7.67±6.48）μmol/L，SiO₃^2--Si平均浓度为（5.44±3.01）μmol/L，在湾口表层，DIN含量较低仅为（2.21±2.94）μmol/L，其中50%站点含量低于阈值（1μmol/L），58.3%的站点存在DIN限制.而活性磷酸盐（PO₄^3--P）受陆源输入和浮游植物吸收储存作用等因素影响，呈现西部和曹妃甸外近海高中部较低的分布特征，平均浓度为（0.07±0.07）μmol/L，近岸受陆源氮磷输入总量差异影响，表层存在磷潜在限制比例达100%，而中部表层受浮游植物消耗吸收的影响，PO₄^3--P含量较低，仅为（0.02±0.02）μmol/L （未检出设为0），其中近74.3%的水样含量低于阈值（0.03μmol/L），磷限制状况严重.随着渤海湾氮磷营养盐陆源输入总量差距不断扩大，磷限制状况必将会进一步发展.

Nutrient structure and nutrient limitation for phytoplankton growth in Bohai bay in the early summer

Based on the data of nutrients, chlorophyll a and hydrological environment parameters collected in Bohai Bay during the early summer of 2016, we studied the distributions of nutrients and analyzed their possible limitation on the phytoplankton growth by analyzing both the minimum threshold and N:P:Si atomic ratios of nutrient required by phytoplankton cells. The results showed that concentrations and spatial distributions of nutrients were influenced by terrigenous input, cold water from central of Bohai Sea and phytoplankton uptake. Both dissolved inorganic nitrogen (DIN) and silicate (SiO₃^2--Si) concentrations decreased from nearshore to the offshore bay mouth, and the mean concentration of DIN was (7.67±6.48) μmol/L and SiO₃^2--Si was (5.44±3.01) μmol/L. In the surface of bay mouth, the concentration of DIN was (2.21±2.94) μmol/L in average, and 50% of samples was below the threshold, especially, 58.3% of them showed DIN limitation for phytoplankton growth. Comparatively, concentrations of activated phosphate (PO₄^3--P) were high in the nearshore and the bay mouth due to riverine input, and a zone with low concentration appeared in the middle probably caused by the phytoplankton uptake. The mean concentration of PO₄^3--P was (0.07±0.07) μmol/L in the whole study area. The concentrations of PO₄^3--P in the surface water were below the threshold of 0.03μmol/L at about 74.3% stations in the middle zone of study area, showing an obvious P limitation for phytoplankton cells. With the increasing disparity of riverine input between nitrogen and phosphorus, the P limitation for phytoplankton would be more serious in our study area.