黄海、东海上层海水磷循环的同位素示踪研究

Phosphorus cycling in the upper ocean of the East China Sea using natural ^(32)P and ^(33)P

采用超低本底液闪β计数的方法,测定了春季黄海、东海海水中溶解态、悬浮物、筛绢颗粒物和雨水中天然32P和33P的比活度.结果显示,上层海水各相33P,32P的比活度相当低,其中TDP的32P,33P比活度的浓度最高,悬浮物次之,筛绢颗粒物最低.海水各相中33P与32P活度比值从TDP到悬浮物、筛绢颗粒物逐渐增大,反映出食物链传递过程中磷的年龄逐渐增加.根据稳态模式的估算结果,海水各相中磷的停留时间具有明显的区域变化特征,其中近岸和内陆架溶解磷的停留时间比外陆架短,仅为3~4 d,意味着近岸和内陆架海区低浓度的磷也可能维持高生物生产力的运转.利用稳态模式还估算出浮游植物的碳同化通量为189~814 mg/(m2.d),浮游动物的碳摄食通量为10~161 mg/(m2.d).此外,通过比较雨水32P,33P的输入通量和海水32P,33P积存量,利用质量平衡方法估算出上层海水POC输出通量为102~972 mg/(m2.d).

Natural activities of ^32p （t1/2 = 14.3 d） and 33p （t1/2 =25.3 d） in total dissolved P （TDP）, suspended particulate matter, net-plankton and rainwater during the spring of 2001 were measured by an ultra-low level liquid scintillation counter. A continuous steady-state model was used to estimate residence times of various phosphorus pools, uptake rates of the biological food chain within the upper ocean of the East China Sea. ^32P/^33P ratios increased from the dissolved pools to the suspended matter and to net-plank- ton, reflecting that the age of P increased as one moved up through the food chain. The residence time of P in the dissolved pools of coastal water and mid-shelf area were very short （3-4 d）, which suggests that low phosphorus concentrations could support relatively high levels of primary production. A phytoplank- ton assimilating flux of 189-814 mg/（m^2· d） and a zooplankton grazing flux of 10-161 mg/（^2· d） were also estimated and show that grazing rates of carbon corresponded to 3%-20% of primary production. In addition, the particulate organic carbon fluxes from the upper ocean were calculated by directly comparing the measured seawater inventory of ^32P and ssp with that measured in rain, and were found to range between 102 and 972 mg/（m · d）.