桑沟湾营养盐时空分布及营养盐限制分析

Seasonal distribution and variation of nutrients and nutrients limitation in Sanggou Bay

根据2006年4、7、11月和2007年1月共4个航次的调查数据,分析了桑沟湾水域的溶解无机氮(DIN)、活性磷酸盐(PO43-)和活性硅酸盐(Si)含量的时空分布特征,采用营养盐浓度阈值法和化学计量法对桑沟湾营养盐潜在的限制性进行了分析。结果显示,桑沟湾DIN、PO43-、Si含量及分布呈现出明显的季节变化:DIN在秋季最高,春季最低;PO43-在秋季最高,夏季最低;Si在夏季最高,秋季最低。春季DIN和PO43-的含量低于理论上浮游植物生长的营养盐阈值的站位分别占44%和39%;夏季PO43-的潜在限制性较强,浓度低于营养盐阈值的站位占68%,受PO43-潜在限制的几率达79%,DIN和Si分别为5%和0;秋、冬季Si可能是浮游植物生长的主要限制因子。讨论了海水养殖、陆源输入及外海交换对营养盐时空分布的影响。目前,桑沟湾营养盐浓度基本属于国家一类、二类水质。但是,长期变化趋势显示DIN有上升的趋势。

The distribution of dissolved nutrients in Sanggou Bay was investigated in April,July and November 2006 and January 2007.The concentration and distribution of dissolved inorganic nitrogen （DIN）,phosphate （PO43-） and silicate in Sanggou Bay showed obvious seasonal variation.DIN reached the lowest level in spring and the highest level in autumn; PO43- concentration was at the lowest level in summer and the highest level in autumn; while Si concentration reached the lowest point in autumn and the highest point in summer.Limiting nutrients for the growth of phytoplankton were assessed by the method of theoretical half-saturation constant （Ks） and stoichiometric ratios among DIN,PO43-and SiO2-3.The results showed that in spring,the percentage of stations with concentration of DIN and PO43-below Ks was 44% and 39%,respectively,suggesting for potential N and P limitation.In summer,the percentage of stations with PO43-concentrations below Ks was 68%,and potential P-limitation was at 79% probability,N and Si limitation were at 5% and 0% probability,respectively.In autumn and winter,Si was the major limiting nutrient,and the potential Si-limitation was at 94% and 78% probability,respectively.The effect of mariculture activities,land-based input,and water exchange with Yellow Sea on the space-time distribution of nutrients were discussed.Based on the long-term data,more attention should be paid to DIN enrichment in Sanggou Bay.