泰晤士河口水温和水化学特性对鱼类的影响研究

根据1915~2005年的长系列数据,对泰晤士河口水温和水化学特性对鱼类的影响进行了评价。结果表明,20世纪60年代之前河口上中游水温持续上升,此后下游水温开始上升而上中游水温下降,河口地区的温度变化模式受电厂热排水影响。水温与鱼类平均数量和水体溶解氧呈负相关,其Spearman相关系数分别为-0.468和-0.607(p<0.05)。BOD、氨氮和溶解氧与鱼类消失和重现存在对应关系,说明污染是影响鱼类长期变化的一个主要因素。气候变化也可能通过径流和潮汐的改变对鱼类产生影响。由于河口环境复杂以及各因子间的协同作用,泰晤士河口生态改善的影响因子还有待进一步深入研究。

Relative Effects of Water Temperature and Water Chemistry on the Fish of the Thames Tideway

Based on the long-term datasets for the period of 1915～2005 from various sources, effects of water temperature and water chemistry on the fish in the Thames Tideway were assessed. There was a steady rise in temperature in the upper and middle reaches before 1960s. After that the temperature dropped in the upper and middle reaches while it increased in the lower reach. These patterns were influenced by the thermal discharge from power stations. Temperature was negatively correlated with average individual fish numbers and dissolved oxygen (DO) with Spearman's rho of -0.468 and -0.607 (p＜0.05) respectively. The fact that high BOD and ammonia and low dissolved oxygen coincided with no presence of fish prior to 1960s while return of fish corresponded to the marked rise in dissolved oxygen and decrease in BOD as well as ammonia indicated that pollution was the main factor influencing fish over the long period. Climate change may have affected the fish community; however it was assumed that it influenced fish more likely through changing the freshwater flow and tide regime in the tideway. It may be difficult to assess the effects of every single factor on fish in the tideway because they were more synergistic than that in other water bodies; thus, further studies on the factors influencing the improvement in ecological status will be necessary.