春、夏季长江口海域营养盐的时空分布特征及营养结构分析

2009年春季（5月）和夏季（8月）分别对长江口海水中的营养盐（DIN、SiO32--Si、PO43--P）进行调查,分析其时空分布特征,探讨其影响机理,并对富营养化水平进行了评价。结果表明：春、夏季表、底层DIN、SiO32--Si的平面分布有从近岸向离岸逐渐降低的特点,而PO43--P则表现出一种缓冲现象;各营养盐在表、底层的质量浓度春季均小于夏季,且DIN的主要存在形式均为NO3-_N;DIN、SiO32--Si主要来源于径流输入,PO43--P则有多种来源。春、夏季表、底层SiO32--Si/PO43--P、DIN/PO43--P均远大于Redfield值,具有营养盐比例不平衡的特征,且DIN/PO43--P、SiO32--Si/DIN、SiO32--Si/PO43--P在长江口海域的分布不均匀;从浮游植物吸收DIN/PO43--P的配比分析,PO43--P是春、夏季长江口海域潜在性营养限制因子;春、夏季E值均远大于富营养化阀值,该海域富营养化现象严重。

Distribution features of nutrients and nutrient structure in the Changjiang estuary in spring and summer

Based on the data of surveys during spring（May） and summer（August） from the Changjiang Estuary in 2009,the distribution characteristics of nutrients（DIN,SiO32——Si,PO43——P） and nutrient structure and its influencing mechanism were analyzed,meanwhile,the pollution level was evaluated.The results showed that： the distribution characteristics of DIN,SiO32——Si decreased from inshore areas to the open sea in surface and bottom waters,in spring and summer,the distribution of PO43——P was characterized by the buffer mechanism.The concentrations of nutrients were lower in spring than in summer.NO3-_N was the predominant species of DIN;DIN、SiO32——Si was sourced by runoff,PO43——P was regulated by many kinds of source.SiO32——Si/PO43——P,DIN/PO43——P value was higher than Redfield value with the characteristic of ratio of nutrient imbalance.The distribution of three kinds of nutrients was uneven in the Changjiang Estuary.Analyzed on the ratio of phytoplankton to absorb DIN/PO43——P,PO43——P was the potential limited factor in spring and summer.The eutrophication index of the Changjiang Estuary was higher than eutrophication threshold.