摘要
海水中的铁是海洋浮游植物的微量营养元素之一,有些实验证实,海水中的铁往往是浮游植物生长的限制因素。在近海,其主要来源是陆地排水。为了解长江口附近海域中的铁的分布规律及对该海域的生产力有无影响,我们在六十年代某年5、8、11月和次年2月对长江口附近海域中的铁作了4个航次的调查,结果如下。
Iron is one of the micro-nutrient elements for phytoplankton.Observations were carried out for total iron,particulate iron and reactive iron in the sea water of the region off Changjiang River(Yangtze River)Estuary in four cruises from May to Feb.next year.The results are described as follows:Iron content in this region is particularly high and the particulate iron is in large fraction.The average concentration of total iron was 1.02×10^(3),362,3.63×10^(3)and 3.72×10^(3)μg/l in May,Aug.,Nov.and Feb.respectively.The fraction of particulate iron was 91.2,71.3,93.2 and 68%respectively.Concentration of reactive iron varies from a fewμg/1 to tens ofμg/l.In Aug.the average concentration was 15μg/l,the lowest value in the four cruises.In Feb.it was 52μg/1,the highest value.Total and particulate irons showed similar trend of horizontal distribution in this region.The concentrations of them were higher near coast than far off coast.There was no obvious gradient in distribution of reactive iron.The concentration of total and particulate irons increases gradually with depth of water.No regularity was found in vertical distribution of reactive iron.Reviewing above results,we can summarize as follows:1.The Changjiang River is the main source of iron in the East China Sea.In rough estimate,the Changjiang River effuses total iron as high as more than 20 million tons per year and the fraction of particulate iron is over 98%.2.Flocculation occurs in the process of mixing of the fresh water of Changjiang River with sea water.It is interesting to note that the average concentration of each station’s total and particulate irons and the concentration of total and particulate irons of each station’s bottom layer sample are negatively correlated to the salinity of corresponding surface water.3.The average concentration of total and particulate irons in the region off Changjiang Estuary is not only related to the iron flux from Changjiang River but also to the pattern of current.In summer the direction of coastal current in this region is the same as Taiwan Warm Current,from SW to NE,and the diluted water of Changjiang River is consequently forced to pour into the region over 32°,out of our observed region.Although flux of the Changjiang Eiver in Aug.is the largest in whole year,the concentration of iron in Aug.was the lowest in our four cruises because of the reason described above.In winter,the direction of coastal current in this region is different from Taiwan Warm Current,from NE to SW,and the diluted water of Changjiang River pours into our observed region,so the value of Feb.was the highest in the four cruises.4.Comparing the vertical distribution of reactive iron with the vertical distribution of phosphate,it can be seen that in this region,vertical distribution of reactive iron is not similar to that of the phosphate,which is usually the minimum in euphotic zone,but increases obviously in water below the euphotic zone.This phenomenon indicates that,the reactive iron is not a limiting element for the growth of phytoplankton in this region because of the amount of the iron utilized by phytoplankton is too small as compared with that present in the sea water.
作者
马锡年
李全生
黄华瑞
华文贞
沈万仁
李国基
姜传贤
Ma Xinian;Li Quansheng;Huang Huarui;Hua Wenzhen;Shen Wanren;Li Guoji;Jiang Chuanxian(Institute of Oceanology,Academia Sinica)
出处
《海洋与湖沼》
1982年第3期241-253,共13页
Oceanologia Et Limnologia Sinica
