鸭绿江河口最大浑浊带水动力特征对叶绿素分布的影响

The influence of hydrodynamic characteristics on the distribution of chlorophy ll concentration in the maximum turbidity of the Yalu Estuary

在河口最大浑浊带有独特的生态动力过程。利用鸭绿江河口最大浑浊带上下游两个定点站和大面站的流速、叶绿素和浊度数据,在分析最大浑浊带形成的基础上探讨了悬沙浓度与叶绿素浓度分布的对应关系及最大浑浊带水动力特征对叶绿素分布的影响。分析结果表明,定点站大小潮涨落潮时均出现悬沙浓度与叶绿素a浓度的高值分布中心,该中心主要出现在底部,且高叶绿素a浓度与高悬沙浓度中心相对应。通过对最大浑浊带形成机制的分析发现,强烈的底部泥沙再悬浮是鸭绿江河口最大浑浊带形成的主要原因。最大浑浊带内悬沙浓度与叶绿素a浓度的相关关系均为底层大于表层,大潮高于小潮;高叶绿素a浓度与高悬沙浓度时刻有很好的对应关系,在一定程度上表明水动力特征对叶绿素a浓度在时间和空间上的分布有重要影响。初步分析认为鸭绿江河口最大浑浊带内的高叶绿素a浓度主要是由再悬浮作用使底部沉积物中的底栖藻类和沉积物一起聚集在水体的底部造成的,但是该结论还有待结合其他相关研究进一步检验。

There exists unique ecological dynamic process in the estuarine maximum turbidity zone.Based on the data of velocity,chlorophyll concentration and turbidity at two mooring stations at upstream and downstream areas of the maximum turbidity zone of the Yalu River,the variations of suspended sediment and chlorophyll concentration is analyzed during neap and spring tidal cycles,and the relationship between the chlorophyll concentration and the hydrodynamic characteristion is discussed through transport flux decomposition of suspended sediment and chlorophyll.The results indicate that the distributions of higher suspended sediment concentration are consistent with thoses of chlorophyll concentration,especially in the bottom both in spring and neap tide.Sea bed sediment resuspension in the bottom caused by strong tides plays a major role in the formation of the estuarine maximum turbidity zone in the Yalu River.The relationship between the suspended sediment and chlorophyll concentrations in the bottom is higher than that in the surface,and more correlated in spring tides than that in neap tides,which,in a way,indicates that hydrodynamic characteristics have a significant impact on the distribution of chlorophyll a concentration distribution in time and space.High chlorophylla concentration distribution is mainly due to resuspension which makes the sediment and benthic algae in the bottom accumulate in bottom water.However,this conclusion remains to be tested with further research.