钦州湾营养盐的分布特征及影响因素

Study of the nutrient distribution and its influence factors in the Qinzhou Bay

利用2008-2009年4个航次的调查资料,研究了钦州湾海域营养盐的分布变化特征。结果表明,钦州湾营养盐分布呈显著的季节变化。NO3-N和NO2-N夏季含量最高,NH4-N和PO4-P含量冬季最高,夏季最低,秋季DIN的形态以NH4-N为主,而夏季则以NO3-N为主。C N/CP夏季>春季>秋季>冬季,该海域春季和夏季浮游植物生长受P限制。NO3-N和NO2-N的平面分布基本呈现钦州湾内向湾外逐渐降低的分布规律,径流输入是影响其分布的主要因素,在外湾余流作用对其分布规律影响显著,NH4-N和PO4-P平面分布规律则受到外海环境因素的影响。经与历史资料对比,DIN和C N/CP呈逐年代大幅上升的变化趋势,钦州湾营养盐结构已从N缺乏到P缺乏转变。

Based on data from four cruises obtained by field survey and experiments in the Qinzhou Bay during 2008 to 2009,the distribution characteristics of nutrients were studied. The result showed that the distribution of nutrients in the Qinzhou Bay remarkably changed seasonally. The concentrations of nitrate and nitrite were highest in summer. But those of ammonia and phosphorus were lowest in summer and highest in winter. It indicated that ammonia was the main form of inorganic nitrogen during autumn,and nitrate was the main form during summer in the Qinzhou Bay. N/P ratio decreased in the sequence of summer, spring, autumn and winter gradually, and the active phosphorus was the nutrient limiting the growth of phytoplankton during spring and summer in the Qinzhou Bay. It was discovered that the contents of nitrate and nitrite constantly reduced from the inner bay to the outer bay. Their special distributions were dominated by the runoff input and influenced remarkably by the residual tidal current in the Qinzhou Bay simultaneously. The environmental factors of open sea played an important role in the ammonia and phosphorus distributions. Based on the historical data, the changes of nutrients in three decades were investigated. It was suggested that the concentrations of dissolved inorganic and N/P ratio increased distinctly. The nutrient structure had changed from N shortage to P shortage.