渤海中部和渤海海峡及其邻近海域浮游植物粒级生物量的初步研究 I.浮游植物粒级生物量的分布特征

The preliminary study on size-fractionated biomass of phytoplankton in the central Bohai Sea, the Bohai Straits and its adjacent area

对1998年9月和1999年4月在渤海(37°～41°N,117 5°～122 5°E)进行的两次生态系统综合外业调查,对蓬莱、长岛两地进行15个月的连续资料监测,对渤海调查区浮游植物粒级生物量的平面分布、垂直分布、昼夜变化和周年变化特征进行了研究.结果表明,秋季主要以小型浮游植物为主,然后依次为微型和微微型浮游植物;春季主要以微型浮游植物所占比重最高,其次为小型浮游植物,微微型浮游植物占比例最低.1998年秋季对断面1,2浮游植物粒级组分的垂直分布研究表明,在不同海区(调查区西部、南部、渤海中部和渤海海峡)的不同水层,浮游植物粒级生物量的分布有明显差异.潮汐对浮游植物粒级生物量的周日变化影响较大.蓬莱、长岛两地的连续调查资料表明,浮游植物各粒级组分除微微型浮游植物外1a有两个峰.网采浮游植物在4和7月有高峰,4月是主峰;小型网采浮游植物在6和11月有高峰,6月是主峰;微型浮游植物在4和11月有高峰,两峰值接近;微微型浮游植物在9月有高峰.调查区与其他海区浮游植物叶绿素a浓度粒级组分比较,表明小型浮游植物所占比重较大.

Based on the two cruises of Sino-Germany cooperative ecosystem surveys which were carried out in the Bohai Sea (37°～ 41°N, 117.5°～122.5°E) in September 1998 and April 1999, and a monthly monitoring investigation at the Penglai and Changdao Island, the distribution and variations of phytoplankton size-fractionated biomass were studied. The size-fractionated chlorophyll a was measured. Phytoplankton was classified with four size fractions as follows: netphytoplankton, >76 μm (the standard mesh size of phytoplankton net used in China); small netphytoplankton, 20～76 μm; nanophytoplankton, 2～20 μm; picophytoplankton, 0.2～2.0 μm. The percentage of chlorophyll a concentrations of the four size fraction in the survey area are (31.11 ± 11.46)%, ((18.95) ± 9.76)%, (33.06 ± 10.71)% and (16.88 ± 8.52)% (n=239) respectively in the autumn of 1998, and (13.34 ± 7.48)%, (16.87 ± 5.57)%, (52.95 ± 13.51)% and (16.84 ± 13.26)% (n=259) respectively in the spring of 1999. The netphytoplankton and small netphytoplankton can be combined into microphytoplankton. This result shows that the nanophytoplankton is the most important primary producer in spring and microphytoplankton is the most important one in autumn in the Bohai Sea. The smallest picophytoplankton cannot be neglected and took a percentage of 17% compared with the other phytoplankton size components. The vertical profile patterns of size-fractionated chlorophyll a concentration of Transects 1 and 2 in the survey area show that microphytoplankton usually occupies in the upper water layer. The annual variation of size-fractionated chlorophyll a concentrations in the Bohai Straits show that: high values of chlorophyll a concentrations of netphytoplankton appear in April and July, the maximum is in April; high values of chlorophyll a concentrations of small netphytoplankton appear in June and November, the maximum is in June; similar high values of chlorophyll a concentrations of nanophytoplankton appear in April and November; and high values of chlorophyll a concentrations of picophytoplankton appear in September. The chlorophyll a contribution to total of the various size of phytoplankton in the survey area shows that microphytoplankton is relatively important primary producer compared with the other regions.