广东大亚湾西南部海域营养盐结构的长期变化

The long term variation of the nutrient structure in southwest Daya Bay

分析了大亚湾西南部海域1982～2002年营养盐结构的长期变化。水域中溶解无机氮(DIN)的含量呈上升趋势,磷酸盐(PO4)含量从80年代初到90年代末逐年下降,2000年后有所恢复,硅酸盐(SiO3)的含量波动较大,3-2-但平均维持在20μmol·L-1的较高水平上。各营养盐浓度比值的长期变化表现为氮磷比上升,硅氮比下降,硅磷比稳中有升。结合营养盐浓度及其比值的变化,可以认为大亚湾西南部海域中浮游植物生长的营养盐限制因子已经由过去的氮限制转变为磷限制;各营养盐的浓度及其比值在各季度的分布表明,浮游植物的生长春季和冬季受到氮限制的可能性较大,而夏季和秋季受磷限制的可能性较大;在营养盐的平面分布上,大鹏澳内DIN高于澳外水域,而PO4自3-1997年后低于澳外水域。

The long term variation of nutrient structure in the southwest part of Daya Bay from 1982 to 2002 is analyzed in this study. The dissolved inorganic nitrogen (DIN) has increased steadily, phosphate has a trend of decrease from the 1980s to the end of 1990s and slightly increased after 2000, while silicate fluctuated at high level ~ 20μmol·L-1 in different years. The nutrient atomic ratios also changed in this period: N/P ratio had a trend of increase, Si/N ratio decreased, and Si/P ratio increased slightly. These long term variations of the nutrient concentrations and their atomic ratios suggested that the nutrient limiting factor for phytoplankton growth could turn to phosphate limitation from nitrogen limitation in the last decade. The growth of phytoplankton is likely limited by nitrogen in spring and winter while by phosphate in summer and autumn. The spatial distribution in the southwest Daya bay shows the higher DIN concentration inside the Dapeng’Ao cove than that outside the cove, and phosphate concentration inside the cove is lower than that outside since 1997.