桑沟湾养殖海域营养盐和沉积物-水界面扩散通量研究

利用2006年4,7,11月和2007年1月4个航次对桑沟湾养殖海域的观测资料,分析了该海域营养盐分布、结构特征、主要控制过程以及沉积物-水界面扩散通量,结果表明,该海域的营养盐分布具有明显的季节变化,海水中NO3-,NO2-,PO43-,DOP,TDP和SiO32-浓度皆是秋季最高,而NH4+,DON,TDN浓度则为夏季最高;各种营养盐的最低值除DON外都出现在春季。春季湾内外海水交换不畅,再加上大型藻类海带等生长旺盛期的消耗,使营养盐浓度处于较低水平,在夏秋两季丰水期沿岸河流注入对该海域营养盐的影响较大,冬季无机营养盐浓度分布主要受沿岸流的影响。磷的结构变化较大,其中DOP百分含量在夏季最高,达到81%。从春季到秋季海水中TDN的结构变化从以DON为主转变成以DIN为主。硅和氮的原子比值全年变化不大,硅和氮和氮和磷原子比值春夏两季的高于秋冬季的。分析营养盐化学计量限制标准和浮游植物生长的最低阈值结果表明,磷是春夏两季桑沟湾浮游植物生长的限制性因素;春季硅浓度低于浮游植物生长的最低阀值,也是一个潜在的限制因素。计算结果显示桑沟湾沉积物释放的NH4+,SiO32-和PO43-对初级生产力的贡献较小,与其他浅海环境相比,桑沟湾沉积物-水界面的营养盐通量处于较低或中等水平。

Distribution features of nutrients and flux across the sediment-water interface in the Sanggou Bay

Four cruises are conducted in the Sanggou Bay in April, July, November 2006 and January 2007, nutrient distributions, structure features, primary control processes and exchange fluxes across the sediment-water interface are dscussed.The results indicate that nutrient concentrations show obvious seasonal changes. The concentrations of NO^-₃, NO^-₂, PO^3-₄, DOP, TDP and SiO^2-₃are the highest in autumn, while the concentrations of NH⁺₄-N, DON and TDN show the highest in summer. The concentrations of nutrients are the lowest in spring except DON. In spring, the water exchange between the Sanggou Bay and the Huanghai Sea and the uptake by large phytoplankton result in the concentrations of nutrients at lower level in the bay. In summer and autumn, the riverine input affects the nutrient levels. In winter, the nutrient levels are affected by coastal waters . The structure of P shows a more obvious change and DOP is the major component in summer which can be 81%. The structure of N transforms from DON to DIN domination. The atom ratio of Si to N changes slightly in the whole year, while the atom ratios of Si to N and N to P in spring and summer are higher those that in autumn and winter. Based on the analysis of nutrient limiting criterion and the lowest threshold values of the phytoplankton growth, P is the limiting factor for the phytoplankton growth in spring and summer in the Sanggou Bay. Si is also a potential limiting factor in spring with the concentration lower than the threshold value of the phytoplankton growth, which shows that the contributions of NH⁺₄, PO^3-₄ and SiO^2-₃fluxes released from the sediment to primary production is quite limited. Comparing to other shallow sea environments, the benthic nutrient fluxes in the Sanggou Bay are ranked at the lower level.