南极普里兹湾铁加富培养浮游植物的实验

在中国第 1 8次南极科学考察期间 ( 2 0 0 2年 1月至 3月 )于南极普里兹湾进行了 3次铁加富培养浮游植物实验。共在三个站位 (St.Ⅰ 1 ,Ⅶ 1和Ⅶ 5 )的 2 0m水深处采水进行培养实验(分别标记为实验 1 ,2和 3)。三个站位水样的营养盐浓度都很高 (NO3 N 2 2- 2 9μM ,PO4 P1 1- 1 7μM ,SiO3 Si35- 60 μM ) ,而叶绿素a (Chla)浓度却变化很大 ,三个站位的浓度分别为 0 1 3- 0 1 7,0 2 0- 0 2 6和 2 35- 2 65 μg·L- 1 。St.Ⅰ 1和Ⅶ 1是典型的HNLC(high nu trient,low chlorophyllaconcentration ,高营养盐 ,低叶绿素a浓度 )海区特征。结果表明 ,在实验1和 2 ,添加铁大大促进了浮游植物的生长和营养盐的消耗。在实验 1中 ,添加 2 0 ,40和 80nM铁的培养瓶中的Chla浓度指数生长 ,在第 1 7d达到最高 ( 4 0- 43μg·L- 1 ) ,生长率为 0 .36- 0 .38d- 1 。添加 1 0nM铁的培养瓶中Chla浓度增长缓慢 ,在第 2 3d达到最高 ( 1 9.35 μg·L- 1 ) ,生长率为 0 .2 7d- 1 。在对照瓶和添加 5nM铁的培养瓶中 ,Chla浓度的生长率分别为 0 .1 3和0 .1 6d- 1 。在实验 2中 ,对照瓶和添加 1 0和 40nM铁的培养瓶中的Chla浓度的生长率分别为0 .1 3,0 .32和 0 .40d- 1 。在实验 3,对照瓶和添加铁的培养瓶中

IRON ENRICHMENT INCUBATION EXPERIMENTS IN PRYDZ BAY, ANTARCTICA

Three shipboard iron enrichment phytoplankton incubations were carried out in the Prydz Bay, Antarctica, from January to March of 2002. Waters for the incubations (Exp. 1, 2 and 3) were collected from 20 m depth in 3 stations (St. Ⅰ 1, Ⅶ 1 and Ⅶ 5), respectively. Although the nutrient concentrations in the surface waters of the three stations were consistently high, the chlorophyll a concentrations varied much. Chlorophyll a concentrations in the 20 m depth of St. Ⅰ 1 and Ⅶ 1 were 0.13-0.17 μg·L -1 and 0.20-0.26 μg·L -1 , respectively, while this figure was 2.35-2.65 for St. Ⅶ 5. There were six levels of enriched iron concentrations (control, 5, 10, 20, 40 and 80 nM) in Exp. 1 while three enriched iron levels (control, 10 and 40 nM) were arranged in Exp. 2 and 3. The iron enrichments stimulated the phytoplankton growth and nutrient drawdown in Exp. 1 (6-26th, January) and Exp. 2 (20th February-4th March). In Exp. 3, phytoplankton growth and nutrient drawdown were at nearly the same rate in the control and iron enriched bottles. In Exp. 1, the chlorophyll a concentrations in the bottles with 20, 40 and 80 nM iron enrichments grew exponentially to 40-43 μg·L -1 on the 17 th day, with a growth rate of 0.36-0.38 d -1 . Chlorophyll a concentration in the bottle enriched with 10 nM iron reached its peak (19.35 μg L -1 ) on the 23 rd day (growth rate 0.27 d -1 ). Phytoplankton in the control bottle and the bottle enriched with 5 nM iron grew at the rates of 0.13 and 0.16 d -1 , respectively. In Exp. 2, the chlorophyll a growth rates were 0.13, 0.32 and 0.40 d -1 in the control bottle and bottles with 10 and 40 nM iron enrichments, respectively. It seems that 10 nM iron enrichment was not enough to stimulate the phytoplankton to reach their maximum growth rate.