The concentration and size-fractionated chlorophyll a in ponds with Portunus trituberculatus cultured in three models were observed from June to November, 2010. The results showed that the chlorophyll a concentration range was (5. 29 ±0. 13) - (48. 00 ± 15. 03) nig · m～3; the minimum appeared in June, while the maximum in August. During the culture period, the chlorophyll a concentration in ponds was significantly higher than that of the estuaries and offshore. Among three culture models, the chlorophyll a rnconcentration in "high-intensive pond" was the highest, the next was the "submerged aeration" culture model, and the minimum appeared in the "aeration" culture model. However, the variation of the chlorophyll a concentration was basically the same; in the early period the concentration was low, then rose quickly to the peak in August, and finally slowly declined. After analyzing the marine aquaculture ecosystem, the author found that chlorophyll a concentration was affected mainly by environmental factors, especially nutrient distribution. The size-fractionated chlorophyll a in Portunus trituberculatus ponds showed that the Nanoplankton was the main contributor, the next were Picoplankton and Netplankton, and the average contribution rate was 66. 9% , 22. 8% and 10. 3% , respectively. In the Portunus trituberculatus culture pond, the Nanoplankton phyloplankton was the main source of the primary productivity, and the Picoplankton photosynthetic microorganism also played an important role in the primary productivity.%2010年6～11月在三疣梭子蟹(Portunus trituberculatus)3种不同]养殖模式的池塘中观测了叶绿素a浓度的变化及其粒级结构.结果表明:池塘中叶绿素a浓度变化范围为(5.29±0.13)～ (48.00±15.03) mg·m-3,最低值出现在养殖初期6月份,最高值出现在夏季8月份.养殖期间,池塘叶绿素a浓度显著高于港湾和近海.比较3种不同养殖模式的叶绿素a浓度,以“高位池”最高,“底充氧”其次,“增氧机”最低,但叶绿素a浓度的变化规律基本一致,呈现出养殖初期低,然后迅速上升,至8月份达最高值,再缓慢下降.分析认为,在海水养殖生态系统中,叶绿素a浓度主要受环境因子尤其是营养盐浓度分布的影响.三疣梭子蟹养殖池塘中叶绿素a浓度粒级结构表明,Nano-粒级为主要贡献者,平均贡献率达66.9％；Pico-粒级次之,平均贡献率为22.8％；Net-粒级贡献率最小,仅为10.3％.在三疣梭子蟹养殖池塘中,Nano-粒级浮游植物是初级生产力的主要来源,而Pico-粒级光合微生物对初级生产力的作用不容小视.
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