春季东海赤潮发生前后营养盐及溶解氧的平面分布特征

Distribution of Dissolved Inorganic Nutrients and Dissolved Oxygen in the High Frequency Area of Harmful Algal Blooms in the East China Sea in Spring

依据2010年4月8～26日和5月7～14日对东海赤潮高发区调查所得的数据,分析了该海域赤潮发生前后各生源要素的含量及分布特征,并对其影响因素进行了初步探讨.结果表明,调查海域4月处于赤潮暴发前期,以硅藻为优势藻种;5月赤潮大规模暴发,以甲藻为优势藻种.5月DIN和PO34--P浓度与4月相比大幅降低,DIN平均值由18.04μmol·L-1降至10.80μmol·L-1,下降幅度为40%;PO34--P平均值由0.47μmol·L-1降至0.27μmol·L-1,下降幅度为43%.这表明在赤潮发生过程中赤潮生物对营养盐具有强烈的消耗作用.5月东海赤潮主要藻种为甲藻,甲藻在繁殖过程中不消耗SiO23--Si,加之长江冲淡水的补充,所以SiO23--Si平均值由16.15μmol·L-1略升至16.96μmol·L-1,变化幅度不大.DO平均值由4月的8.76mg·L-1下降至5月的6.09 mg·L-1,这主要是由于5月水温对DO的影响大于浮游植物光合作用的影响,5月水温较4月高,氧气在水中的溶解度随温度的升高而降低,所以5月DO浓度低于赤潮发生前期.

According to two cruises in the high frequency area of Harmful Algal Blooms（HABs） in ECS from Apr.8th to 26th and May 7th to 14th 2010,concentrations and distributions of biogenic elements before and after HABs were analyzed,and their influenced factors were also discussed.The results showed that April was the earlier stage of HAB breaking out,and diatom was the dominant species;while Dinoflagellate became the dominant species when large-scale HAB broke out in May.The concentrations of DIN and PO34--P decreased significantly from April to May.The Mean value of DIN decreased from 18.04 to 10.80 μmol.L-1,its decline rate was 40%.As for PO34--P,its Mean value decreased from 0.47 to 0.27 μmol.L-1,and its decline rate was 43%.This phenomenon indicated the significant depletion of nutrients by harmful algae in the process.However,the primary species of HABs in ECS was dinoflagellates in May.Since dinoflagellates did not consume SiO23--Si during the breed,as well as the supplement from Changjiang Diluted Water,the mean value of SiO23--Si increased slightly from 16.15 to 16.96 μmol.L-11 in the researched area.The Mean value of DO decreased from 8.76 to 6.09 mg·L-1 from April to May,because the effect of temperature to DO was more obvious than that of phytoplankton photosynthesis.The temperature was higher in May,and the solubility of oxygen decreased with increasing temperature,therefore,the concentration of DO was lower after the Harmful algal blooms.