中文摘要：

本文通过南海北部冬、夏季航次的现场观测,研究了海表浮游植物光合作用速率对光强的响应特征（P-E曲线）。结果表明南海北部浮游植物P-E曲线存在明显的季节变化。在冬季,P-E曲线呈现高P^Bm、高α、高β的特征,这表明冬季浮游植物在低光照环境中光合作用速率增加迅速,其最大光合作用速率较高但容易受到光抑制。与冬季相反,夏季P-E曲线呈现低P^Bm、低α、低β的特征,浮游植物受光抑制影响小,但最大光合作用速率低于冬季。水温和粒级结构等指标与P-E参数存在显著相关,这意味着环境和群落的季节变化可能对光合作用特性有一定影响。通过P-E参数模拟得到真光层内光合作用速率,模拟值与现场结果之间呈明显的线性相关但存在高估。此研究有助于认识南海浮游植物光合作用特征,并为初级生产力模型研究提供依据。

英文摘要：

The phytoplankton photosynthesis rate is important to understand the variations of oceanic primary production（PP）.In this study,we measured sea surface photosynthesis-irradiance（P-E）parameters fromin situexperiments during summer and winter cruises,which was carried out in the northern South China Sea（nSCS）in2004.The results showed that the P-E parameters had obvious seasonal variations in the nSCS.In winter,the P-E parameters were characterized by highα,highβ,and high P^Bm.It indicated that phytoplankton could achieve relatively higher maximum photosynthesis rate,but the light-inhabitation would be significant when the light was supersaturate.In contrast to winter,the P-E parameters,α,β,and P^Bm,were relatively lower in summer,which indicated that phytoplankton favorites high photosynthetically active radiation environment,and its maximum photosynthesis rate was lower than that in winter but the light-inhabitation was very slight.We found some factors,such as temperature and size structure of phytoplankton,have significant correlation with P-E parameters.This implied that the photosynthesis rate was affected by both the seasonal changes of environment and the phytoplankton groups.The photosynthesis rate（P^Bmodel）,calculated by P-E parameters,had significant linear correlation with the in situ photosynthesis rate（P^Bin situ）which was derived by PP experiments.However,the P^Bmodelresults also showed overestimation,which was mainly due to the fact that the respiration rate could not be neglected in the P-E experiment.The results are helpful in the understanding of the characters of phytoplankton photosynthesis in the nSCS.