夏季长江口东北部上升流海域的生态环境特征

CHARACTERISTICS OF THE ECOLOGICAL ENVIRONMENT IN THE UPWELLING AREA NORTHEAST OF THE CHANGJIANG RIVER ESTUARY

基于2006年7月18—23日对长江口东北部海域的大面调查,重点分析和探讨了长江口东北部海域的上升流现象及生态环境特征。结果显示:(1)大约在122°—123°E,32.3—33.7°N的海域范围内存在着较为明显的下层高盐冷水抬升的现象。(2)伴随着冷水的上升运动,对DO、营养盐以及Chl.a的平面和断面分布均存在一定的影响:表层和10m层出现了与冷水区相吻合的DO低值区,表明抬升后的低氧冷水已明显影响到表层和10m层的DO分布,且各断面低氧水体的涌升也和上升流相对应;10m层,调查海域中部等值线半封闭区的高营养盐不是直接来自上层的长江冲淡水,而是源于下、底层的高盐冷水;表层和10m层,调查海域中部的Chl.a高值区与高盐冷水的位置虽然存在一定的偏离,但总体上也还是保持了一致,这同上升流对营养盐的持续供给以及其对光照条件的改善密切相关。(3)DO、营养盐和Chl.a的分布特征较好地佐证了长江口东北部海域存在上升流现象。

Based on the cruise carried out in the northeast of the Changjiang estuary from July 18--23, 2006, the upwelling and its impacts on the ecological environment were analyzed. An upwelling of cold and saline water was present in the area of 122°--123°E, 32°--33°N. This upwelling has significantly affected the distribution of dissolved oxygen （DO）, nutrients as well as c.hlorophyll.a, for example, the low dissolved oxygen appeared in the surface water and the 10 m layer, due to the the uplift of the hypoxic cold water. The high nutrient water in the 10 m layer did not come directly from the Changjiang River Diluted Water, rather it came from the high salinity cold water in the deep and bottom layer. The high Chl.a area and the location of the high-salinity cold water were closely associated, and the upwelling provided continuous supply of nutrients and improved light conditions in the upwelling area. The distribution of DO, nutrients and Chl.a also showed that the upwelling phenomenon indeed existed in the northeast area of the Changjiang River estuary.