分别于2014年3月(枯水期)和7月(丰水期)对钦州湾海区Chl a浓度分布及其粒级组成进行了分析。结果表明,研究区域两个时期都具有较高氮浓度和氮磷比,枯水期磷酸盐浓度高于丰水期,Chl a浓度及其粒径结构差异显著。枯水期Chl a浓度(1.70±0.74μg/L)显著低于丰水期浓度(7.81±3.63μg/L)(p<0.01)。优势粒级从枯水期Nano级Chl a(51.8±14.0%)向丰水期Pico级(50.4±17.4%)演变。Pico级与Micro级共同构成了丰水期的Chl a浓度高值,两个时期Nano级Chl a浓度无明显差别。Nano级Chl a对总Chl a浓度的贡献存在着自枯水期优势(51.8±14.0%)至丰水期降低(15.5±9.2%)的动态变化。通过与营养盐和盐度等因子的相关分析,可知浮游植物粒级组成的差异与钦州湾陆地径流的输入、营养盐浓度变动及高密度牡蛎养殖密切相关。 The distribution of Chl a concentration and its grain-size composition in Qinzhou Bay in March 2014 (dry season) and July (wet season) were analyzed. The results showed that the two regions of the study had higher nitrogen and nitrogen and phosphorus ratios, and the phosphate concentration in dry season was higher than that in wet season. The concentration of Chla and its size structure were significantly different. Chl a concentration in dry season (1.70 ± 0.74 μg / L) was significantly lower than that in wet season (7.81 ± 3.63 μg / L) (p <0.01). The dominant grain size evolved from Nano grade Chl a (51.8 ± 14.0%) in dry season to Pico grade (50.4 ± 17.4%) in wet season. Pico grade and Micro grade together constitute a high value of Chl a concentration during the wet season, with no significant difference in the Nano grade Chla between the two periods. The contribution of Nano Chl a to the total Chl a concentration has the dynamic change from 51.8 ± 14.0% in dry season to 15.5 ± 9.2% in wet season. The correlation analysis of nutrients and salinity showed that the differences of grain-size composition of phytoplankton were closely related to the input of land runoff in Qinzhou Bay, the changes of nutrient concentration and high-density oyster culture.