Shifts between clear and turbid states in a shallow lake: multi-causal stress from climate, nutrients and biotic interactions
Shifts between clear and turbid states in a shallow lake: multi-causal stress from climate, nutrients and biotic interactions
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DOI：
10.1127/0003-9136/2004/0161-0433
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发表时间：
2004-12-01
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影响因子：
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通讯作者：
Hansson, LA
中科院分区：
文献类型：
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作者：
Hargeby, A;Blindow, I;Hansson, LA
我们使用长期监测数据来评估瑞典Takern湖最近从清澈到浑浊的水状态转变背后的原因。该湖有以前的记录之间的转变清水和浑浊的状态。但这些变化背后的原因并不为人所知。在1995-1997年发生的最近一次转变中，淹没植被在经过30年的清水和丰富植被之后随后下降。在可能的解释中，我们确定了几个不太可能导致最近从清澈到浑浊的条件转变的过程。包括磷的外部输入的长期变化。水位波动。和浮游动物摄食压力的变化。相反，可能导致大型植物减少的情况，从而导致这种转变：（1）一系列温和的冬季，冰层覆盖时间短，没有冬季鱼类死亡，导致极移前底食性和反食性鱼类的生物量高，从而增加了生物扰动和内部营养循环，（2）极移前和极移期间的春季异常凉爽和多风，导致沉水植物在生长阶段的不利条件。冬季和春季的短时间冰盖和高风速都与气候有关。北大西洋涛动（NAO）我们认为，这些过程中没有一个可以单独迫使湖前的清澈到浑浊的状态，但几个应力因素在演唱会是必要的，以启动一个转变。因此，我们的结论是，气候变异性很可能有助于多原因的压力。减少了清水状态的恢复力，并最终通过跨年度的变化触发了转变;在沉水植物和鱼类的生物量中，已知在浅水湖泊动态中发挥关键作用的生物群。
We used long-term monitoring data to assess causes behind a recent shift front a clear to a turbid water state in Lake Takern, Sweden. The lake has a previous record of shifts between clear-water and turbid states. but the causes behind these shifts are not well known. During the recent shift, which occurred in 1995-1997, Submerged vegetation Subsequently declined after a 30-year period of clear-water and abundant vegetation. Among the possible explanations we identify several processes unlikely to have contributed to the recent shift from clear to turbid conditions. including long-term changes in external input of phosphorus. fluctuations in water level. and changes in zooplankton grazing pressure. Instead, likely scenarios to have contributed to the macrophyte decline, and thereby to the shift were: (1) a series of mild winters with short ice cover and absence of winter-kills of fish, leading to high biomasses of benthivorous and planktivorous fish before the shift, and thereby increased bioturbation and internal nutrient recycling, (2) unusually cool and windy springs the years before and during, the shift, leading to unfavourable conditions during the establishing phase of submerged macrophytes. Both shorter periods of ice cover and high wind velocity in winter and spring were associated with climate. approximated by the North Atlantic Oscillation (NAO). We argue that none of these processes alone can force the lake front the clear to the turbid state, but that several stress factors in concert are necessary to initiate a shift. Hence, we conclude that climate variability is likely to have contributed to a multi-causal stress. reducing the resilience of the clear-water state and finally triggering the Shift through inter-year dependent changes; in biomass of submerged macrophytes and fish, organism groups known to have key roles in the dynamics of shallow lakes.