南海南部海域夏季分粒级叶绿素a分布及影响因素

Distributions of Size-fractions of Chlorophyll A and Its Controlling Factors in Summer in the Southern South China Sea

利用2009年6月南海综合调查数据,分析了分粒级叶绿素a(Chl a)的分布特征及其影响因素。Chl a浓度为未检出至0.51μg/L,平均值为(0.10±0.09)μg/L,自表层向底层逐渐升高,至50 m达到最高值,而后迅速降低,在100 m以深的水体中,Chl a含量很少,水深达到200 m时,Chl a的含量接近于零,部分站位Chl a含量低于检出限。分粒级Chl a结果表明,Pico级Chl a(<2μm)浓度0.02～0.40μg/L,平均值(0.10±0.07)μg/L,垂向分布上与Chl a总量一致,浓度最高值位于50 m;Nano级Chl a(2～20μm)浓度0.004～0.12μg/L,平均值(0.02±0.02)μg/L,垂向分布变化不大,在50 m为高值;Micro级Chl a(20～200μm)浓度0.001～0.05μg/L,平均值(0.006±0.009)μg/L,垂向分布变化不大,在表层为高值。分级Chl a对总Chl a的贡献主要以细胞粒径0.7～2μm的Pico级Chl a占优势(81.7%±8.9%),其次是2～20μm的Nano级Chl a(13.2%±6.2%),粒径>20μm的Micro级Chl a的贡献最小(5.1%±3.7%)。调查海域内普遍存在潜在氮限制因素,但不存在硅限制。温度、营养盐浓度、营养盐比值、真光层厚度和水文状况是控制不同粒级Chl a含量及分布的主要因素。

Chlorophyll a（Chl a） of micro（20-200 μm）,nano（2-20 μm） and picoplankton（2 μm） were measured in different layers of the Nansha Islands in the South China Sea（SCS） to explore the marine environment in June,2009.The spatial distribution and contribution of chlorophyll of micro,nano,and picoplankton to phytoplankton were studied.Chl-a contents were varied from below detection limit to 0.51 μg / L with an average of 0.10 ± 0.09 μg / L,and decrease gradually below the depth of 50 m with the depth,reaching the level of zero in the layer of 200 m.Picoplankton contents were ranged from 0.02 to 0.04 μg / L with a mean value of 0.10 ± 0.07 μg / L.The concentrations of chlorophyll of micro and nanoplankton were ranged from 0.001-0.05 μg / L（0.006 ± 0.009 μg/L） and 0.004-0.12 μg/L（0.02 ±0.02 μg/L）,respectively.Picoplankton was the most important contributor to primary production accounting for 81.7% ± 8.9% of total phytoplankton Chl a,whereas micro and nano plankton accounted for only 5.1% ± 3.7% and 13.2% ± 6.2%,respectively.According to the results,temperature,dissolved oxygen concentration,nutrient distribution and limitation,hydrological conditions,euphoric were the main factors restricting the phytoplankton growth and their distributions.