Phosphorus dynamics in waters of the Pacific Ocean@en

Tagged phosphorus was used to measure principal indices of mineral phosphorus variations in the euphotic zone of the East Pacific, i.e. total rate of uptake of phosphate phosphorus by microplankton (A_t), fraction consumed by phytoplankton (A_p/A_t), and turnover time (T). A_t reached its greatest values (150-280 ng/l/hour) in the upwelling zone of the Peru traverse, where development of phytoplankton was induced by upwelling. In other areas of this traverse values were 40-80 ng/l/hour in surface layers. In less productive waters on two other profiles (off Central America and California), values were lower, between 20 and 40 ng/l. On the vertical profile maxima of A_t were found at the upper boundary of the thermocline. Turnover time of PO4 phosphorus (T) in zones of phytoplankton abundance was very short, between 1.5 and 4 days. At most other stations it was 10-40 days, increasing to 100-200 days or longer at the lower boundary of the euphotic zone. In areas of phytoplankton abundance it accounted for 60-80% of total uptake of PO4 phosphorus. But in zones of elevated bacterial abundance, A_p/A_t fell to 20-40%. Data indicating lack of correlation between PO4 phosphorus and productivity are presented. It is emphasized that the above measures of PO4 phosphorus dynamics can be used for obtaining measures of functional condition and successional phase of marine plankton communities.本研究采用标记磷测定了东太平洋真光层内矿物态磷变化的核心指标，具体包括微型浮游生物对磷酸盐磷的总摄取速率（A_t）、浮游植物摄食占总摄取量的比例（A_p/A_t）以及周转时间（T）。在秘鲁断面的上升流区，上升流诱导浮游植物大量繁殖，该处A_t达到峰值（150~280 ng/升/小时）；该断面其余区域的表层水体中，A_t取值为40~80 ng/升/小时。在另外两条调查断面（中美洲外海与加利福尼亚外海）的低生产力海域，A_t数值更低，介于20~40 ng/升之间。在垂直剖面上，A_t的最大值出现在温跃层上界处。浮游植物繁盛海域的正磷酸盐磷（PO₄-P）周转时间（T）极短，仅为1.5~4天；在多数其他站位，周转时间为10~40天，至真光层下界时可增至100~200天甚至更长。在浮游植物繁盛海域，浮游植物摄食占总正磷酸盐磷摄取量的60%~80%；但在细菌丰度升高的区域，A_p/A_t降至20%~40%。本文还提供了正磷酸盐磷浓度与生产力无相关性的相关数据。需要强调的是，上述正磷酸盐磷动力学指标可用于表征海洋浮游生物群落的功能状态与演替阶段。