有机氮对大亚湾亚历山大藻种群生长的促进作用

2008年1~12月对大亚湾澳头养殖海域溶解有机氮(DON)组成、含量与亚历山大藻种群动态进行了周年调查,同步监测了无机营养盐、水温、盐度等主要环境因子.结果显示,大亚湾澳头海域DON水平4~6月较高,最大值达21.27μmolN/L,其余月份较低,全年平均浓度为7.44μmolN/L.尿素是DON的重要组分,全年平均浓度为1.98μmolN/L,约占DON的20%~30%.可溶性游离氨基酸(DFAA)波动较大,介于1~5μmolN/L.4~6月亚历山大藻种群维持较高密度.4月21日澳头海域发生亚历山大藻水华,最高细胞密度达到3319cells/mL.DON和尿素浓度高峰与亚历山大藻密度高峰同步出现,水华消散后DON和尿素浓度分别大幅下降至高峰期的23.84%和62.86%.统计结果显示,表征有机污染程度的DON、尿素和CODMn与亚历山大藻种群密度具有显著正相关关系(p<0.05).DON含量的增加能够促进亚历山大藻的生长,并在温度、盐度等环境条件适宜的情况下可能成为赤潮暴发的重要诱因.

Facilitation of DON on population growth ofAlexandrium sp.in Daya Bay

Population dynamics of Alexandrium sp.and DON were investigated in aquaculture areas of Daya Bay from January to December in 2008 while environmental factors including nutrients,water temperature and salinity were investigated simultaneously.The concentration of DON was higher from April to June than that in other months.The maximum value for DON was 21.27μmolN/L while the annual average value was 7.44μmol N/L.Urea was one of the most important components of DON.The annual average concentration of urea was 1.98μmol N/L which represented about 20%~30% of DON.DFAA fluctuated significantly ranging from 1 to 5μmol N/L.Cell densities of Alexandrium sp.were found higher from April to June than those in other months.Alexandrium sp.bloom was observed in Aotou aquaculture area with the highest cell density of 3319 cells/mL on April 21.The concentrations of DON and urea and the cell density of Alexandrium sp.peaked synchronously,and DON and urea fell sharply to 23.84% and 62.86% of the maximum when the bloom attenuated.Significant correlations were revealed between cell density of Alexandrium sp.and environmental factors representing the extent of organic pollution such as DON,urea and CODMn.The increase of DON favored the growth of some harmful algal species and may play key roles in the formation of blooms provided suitable water temperature and salinity.