白令海浮游植物添加营养盐培养实验

A SIMPLE NUTRIENT ENRICHMENT INCUBATION IN THE BERING SEA

本文报道 1 999年 7月～ 9月中国首次北极考察期间 ,在白令海进行的一组浮游植物添加营养盐培养实验。实验从 7月 2 3日开始 ,8月 5日结束。培养瓶为两个对照 ,硝酸盐添加为海水浓度的2、4和 8倍 ,磷酸盐添加为海水浓度的 2、4和 8倍。培养瓶在“雪龙”号甲板上的流水控温槽中培养。在培养的第 5天 ,对照、硝酸盐组和磷酸盐组浮游植物增长的趋势一致 ,叶绿素 a增长为初始浓度( 0 .55mg/m3 )的 3.5～ 4.5倍。在培养的第 1 0天 ,硝酸盐组叶绿素 a浓度达到 1 7.6～ 2 4 .0 mg/m3 ,大大高于对照 ( 7.6～ 9mg/m3 )。磷酸盐组叶绿素 a浓度为 9.3～ 1 1 .4mg/m3 ,比对照有所增加 ,但不如硝酸盐组明显。实验结束时各瓶的叶绿素 a浓度都降低。添加较大浓度营养盐的培养瓶中浮游植物的增长要大一些 ,但是并不明显。本实验说明 ,虽然从营养盐的绝对浓度和比例上看 ,都没有明显的 N或 P限制 ,但是白令海潜在着硝酸盐的限制。虽然营养盐的浓度对浮游植物的吸收有一定的影响 。

WT5BZ] During the first Chinese scientific expedition to the Arctic in July-September, 1999, a simple nutrient enrichment incubation experiment was carried out in the Bering Sea. The incubated water was taken from 10 m at station B2 1. The experiment began on 23th July and ended on 5th August. The nutrient concentration was enriched to 2, 4 and 8 times of the initial concentration of phosphate and nitrate respectively. Two controls were set up. The incubation bottles were incubated in a water flow temperature controlled incubator on board the R.V. “Xuelong”. After 5 days of incubation, chlorophyll a concentration increased to the 3.5-4.5 fold of the initial concentration (0.55 μg·l -1 ) in the control and nutrient enriched bottles. No obvious difference showed up at this time. At the tenth day of the incubation, the chlorophyll a concentration in the nitrate enriched bottles, phosphate enriched bottles and the controls were 17.6-24.0, 9.3-11.4 and 7.6-9 μg·l -1 respectively. The chlorophyll a concentrations in all the bottles decreased at the end of the incubation. The result of the incubation showed that nitrate was the potential limitation nutrient. The concentration of the nutrient did not affect the phytoplankton growth obviously. It was the absolute amount of nutrient absorbed by the phytoplankton that limited their growth. [WT5HZ]