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本文根据收集到的1960s到2000s年间东海长江口附近海域(30.5～32°N,122～123°E)的营养盐数据,分析了长江口海域营养盐的季节变化及历史变化趋势。其中根据1959～1960年,1985～1986年和2002～2003年长江口海域营养盐的季节变化数据,发现50 a来,营养盐的季节变化差异不大,均呈现出春夏低,秋冬高的季节变化趋势,其中2002～2003年四个季节之间营养盐含量的变化幅度较其它两年略小。从1960s～2000s年的历史变化可以看出,调查海域的DIN含量呈现出显著上升的趋势,但是在2000年以后,DIN的年平均含量略有降低但变化不大,基本保持在18μmol/L。DIP年平均浓度变化不明显,浓度范围维持在0.39～0.60μmol/L之间。SiO3-Si的年平均含量呈现出明显的降低趋势。就营养盐组成变化来说,DIN/P比例和Si/DIN比值的变化趋势相反,DIN/P比例呈现出升高的趋势而Si/DIN呈现出降低的趋势。生物数据表明从1980s以后该海域赤潮优势种有从硅藻演变为甲藻的趋势,结合营养盐的变化分析认为过量的DIN和持续升高的DIN/P是造成这一藻种长期演变现象的主要原因。
Based on the collected data of nutrients in the waters near the Changjiang Estuary (30.5 ~ 32 ° N, 122 ~ 123 ° E) from 1960s to 2000s, the seasonal variations and historical changes of nutrients in the Yangtze Estuary were analyzed. According to the seasonal variation of nutrients in the Changjiang estuary waters from 1959 to 1960, from 1985 to 1986 and from 2002 to 2003, it was found that there was no significant difference in the seasonal changes of nutrients in the past 50 years, both showing low spring and summer and high in autumn and winter Seasonal change trend, of which the change of nutrient content between the four seasons from 2002 to 2003 was slightly smaller than the other two years. According to the historical changes from 1960s to 2000s, the DIN content of the surveyed sea area showed a significant upward trend. However, after 2000, the average annual DIN content decreased slightly but remained unchanged at 18μmol / L. The average concentration of DIP did not change significantly, the concentration range maintained at 0.39 ~ 0.60μmol / L between. The average annual content of SiO3-Si shows a clear downward trend. In terms of nutrient composition changes, the trend of DIN / P ratio and Si / DIN ratio is opposite. The DIN / P ratio shows an increasing trend and the Si / DIN ratio shows a decreasing trend. Biological data show that the dominant species of red tide developed from diatoms to dinoflagellates since 1980s. Combined with the analysis of nutrients, excessive DIN and continuously increasing DIN / P are the long-term evolutionary phenomena of this species main reason.