Gerten Dieter, Adrian Rita
Leibniz-Institut für Gewässerökologie und Binnenfischerei, Müggelseedamm 301, D-12587 Berlin, Germany.
ScientificWorldJournal. 2002 Mar 8;2:586-606. doi: 10.1100/tsw.2002.141.
Impacts of climate warming on freshwater ecosystems have been documented recently for a variety of sites around the globe. Here we provide a review of studies that report long-term (multidecadal) effects of warming trends on thermal properties and plankton dynamics in northern hemispheric lakes. We show that higher lake temperatures, shorter periods with ice cover, and shorter stagnation periods were common trends for lakes across the hemisphere in response to the warmer conditions. Only for shallow dimictic lakes was it observed that deep-water temperatures decreased. Moreover, it became evident that phytoplankton dynamics and primary productivity altered in conjunction with changes in lake physics. Algal spring blooms developed early and were more pronounced in several European lakes after mild winters with short ice cover periods, and primary productivity increased in North American lakes. Effects of elevated temperatures on zooplankton communities were seen in an early development of various species and groups, as is documented for cladocerans, copepods, and rotifers in European lakes. Furthermore, thermophile species reached higher abundance in warmer years. Obviously, the nature of responses is species specific, and depends on the detailed seasonal patterning of warming. Complex responses such as effects propagating across trophic levels are likely, indicating that observed climate-ecosystem relationships are not generally applicable. Nonetheless, the picture emerges that climate-driven changes in freshwater ecosystems may be synchronised to a certain extent among lakes even over great distances if climatic influences are not masked by anthropogenic impacts or differences in lake morphology. Macro-scale climatic fluctuations--such as the North Atlantic Oscillation or the El Niño-Southern Oscillation--were identified as the most important candidates responsible for such coherence, with the former predominating in Europe and the latter in North America. We emphasise, however, that the driving mechanisms and the future behaviour of these oscillations are rather uncertain, which complicates extrapolation of observed effects into the future. Thus, it is necessary to quantify the most important climate-ecosystem relationships in models of appropriate complexity. Such models will help elucidate the multiple pathways climate affects freshwater ecosystems, and will indicate possible adverse effects of a warmer future climate.
近期，全球各地的诸多研究都记录了气候变暖对淡水生态系统的影响。在此，我们对一些研究进行综述，这些研究报告了北半球湖泊升温趋势对热性质和浮游生物动态的长期（数十年）影响。我们发现，湖泊温度升高、冰封期缩短以及停滞期缩短是整个半球湖泊对变暖条件的常见响应趋势。仅在浅水双季湖观察到深水温度下降。此外，很明显浮游植物动态和初级生产力会随着湖泊物理状况的变化而改变。在欧洲的几个湖泊中，暖冬且冰封期短之后，藻类春季水华提前出现且更为显著，而北美湖泊的初级生产力有所增加。温度升高对浮游动物群落的影响表现为各类物种和群体发育提前，欧洲湖泊中的枝角类、桡足类和轮虫类的情况便是如此。此外，嗜热物种在较暖年份的丰度更高。显然，响应的性质具有物种特异性，并且取决于变暖的详细季节模式。诸如跨营养级传播的影响等复杂响应很可能存在，这表明所观察到的气候 - 生态系统关系通常并不适用。尽管如此，仍呈现出这样一种情况：如果气候影响未被人为影响或湖泊形态差异所掩盖，那么淡水生态系统中由气候驱动的变化在一定程度上可能在相距甚远的湖泊之间同步。大尺度气候波动——如北大西洋涛动或厄尔尼诺 - 南方涛动——被确定为造成这种一致性的最重要因素，前者在欧洲占主导，后者在北美占主导。然而，我们强调这些波动的驱动机制和未来行为相当不确定，这使得将观察到的影响外推到未来变得复杂。因此，有必要在适当复杂程度的模型中量化最重要的气候 - 生态系统关系。此类模型将有助于阐明气候影响淡水生态系统的多种途径，并指出未来气候变暖可能产生的不利影响。
