摘要
尽管北方的淡水水体一般有着孤立的地理位置,但是它们仍然受到一系列的环境压力。高纬区域对最近气候变暖的影响尤为敏感,气候变暖已经导致了许多北极湖泊和池塘生物群落显著的情况变化。这些湖沼学变化的重要驱动力包括冰雪覆盖的量和持续时间的变化,以及对河流和湖泊的三角洲来说,春季洪水的频率和范围的变化。其它重要的与气候有关的变化包括蒸降比的变更,由于冰川和永久冻土带的加速融化而流入湖泊和河流中水的质和量的显著变化,以及降雪占降水量百分率的减少。北方上空等温层臭氧的损耗,加之许多北极湖泊的清澈见底,使得湖中的生物特别易受紫外线辐射伤害。另外,大气污染物的远程传输,加上带菌生物体带入一些当地生态系统(例如鲑鱼养殖湖、海鸟聚居的池塘)的污染物传输的聚焦效应和长食物链中的生物放大作用,导致许多长效有机污染物(例如杀虫剂,它们从来没在北极区域被使用过)和其它污染物(例如汞)浓度的增加。油气管道的飞速发展、钻石和金属的开采、人口的增长,以及全年运营的公路、海港和水电大坝的发展都给北方的水生生态系统施加了压力。这些压力的累积效应将远比因气候变化单独引起的那些效应严重得多。
Despite their generally isolated geographic locations,the freshwaters of the north are subjected to a wide spectrum of environmental stressors.High-latitude regions are especially sensitive to the effects of recent climatic warming,which have already resulted in marked regime shifts in the biological communities of many Arctic lakes and ponds.Important dnvers of these limnological changes have included changes in the amount and duration of snow and ice cover,and,for rivers and lakes in their deltas,the frequency and extent of spring floods.Other important climate-related shifts include alterations in evaporation and precipitation ratios,marked changes in the quality and quantity of lake and river water inflows due to accelerated glacier and permafrost melting,and declining percentages of precipitation that falls as snow.The depletion of stratospheric ozone over the north,together with the clarity of many Arctic lakes,renders them especially susceptible to damage from ultraviolet radiation.In addition,the long-range atmospheric transport of pollutants,coupled with the focusing effects of contaminant transport from biological vectors to some local ecosystems (e.g.,salmon nursery lakes,ponds draining seabird colonies) and biomagnification in long food chains,have led to elevated concentrations of many persistent organic pollutants (e.g.,insecticides,which have never been used in Arctic regions) and other pollutants (e.g.,mercury).Rapid development of gas and oil pipelines,mining for diamonds and metals,increases in human populations,and the development of all-season roads,seaports,and hydroelectric dams will stress northern aquatic ecosystems.The cumulative effects of these stresses will be far more serious than those caused by changing climate alone.
