Light-driven tipping points in polar ecosystems
Light-driven tipping points in polar ecosystems
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DOI：
10.1111/gcb.12337
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发表时间：
2013-12-01
影响因子：
11.6
通讯作者：
Riddle, Martin J.
中科院分区：
文献类型：
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作者：
Clark, Graeme F.;Stark, Jonathan S.;Riddle, Martin J.
一些生态系统可能会因相对较小的环境变化而发生突然转变。确定迫在眉睫的临界点对于生物多样性保护至关重要，特别是在面临气候变化的情况下。在这里，我们描述了一种可能引发极地生态系统广泛的政权转变的临界点机制。季节性的冰雪覆盖会定期阻挡阳光到达极地生态系统，但这对年度光照的影响主要取决于年度太阳周期内的覆盖时间。在高纬度地区，阳光具有很强的季节性，夏至前后的无冰日接收到的光照比冬季多几个数量级。提前融化使冰损失的日期接近仲夏，这将导致每年到达某些生态系统的阳光量呈指数增加。这可能会推动生态临界点，使初级生产者（植物和藻类）蓬勃发展并在竞争中击败适应黑暗的群落。我们在南极浅海海底生态系统中证明了这一原理，我们的数据表明，该生态系统对海冰消失时间的微小变化很敏感。藻类对光阈值有反应，海冰持续时间的轻微减少很容易超过该阈值。早期海冰消失可能会导致广泛的制度转变，其中特有的浅水无脊椎动物群落被藻类取代，从而减少沿海生物多样性并从根本上改变生态系统功能。模型显示，最近冰雪覆盖的变化已经改变了北极和南极大片地区的年度光预算，水生和陆地生态系统可能会经历进一步的显着光变化。冰损失和太阳辐照度之间的相互作用使极地生态系统极易受到生态系统突然变化的影响，因为光驱动的临界点很容易被雪和冰损失时间相对轻微的变化所突破。
Some ecosystems can undergo abrupt transformation in response to relatively small environmental change. Identifying imminent tipping points' is crucial for biodiversity conservation, particularly in the face of climate change. Here, we describe a tipping point mechanism likely to induce widespread regime shifts in polar ecosystems. Seasonal snow and ice-cover periodically block sunlight reaching polar ecosystems, but the effect of this on annual light depends critically on the timing of cover within the annual solar cycle. At high latitudes, sunlight is strongly seasonal, and ice-free days around the summer solstice receive orders of magnitude more light than those in winter. Early melt that brings the date of ice-loss closer to midsummer will cause an exponential increase in the amount of sunlight reaching some ecosystems per year. This is likely to drive ecological tipping points in which primary producers (plants and algae) flourish and out-compete dark-adapted communities. We demonstrate this principle on Antarctic shallow seabed ecosystems, which our data suggest are sensitive to small changes in the timing of sea-ice loss. Algae respond to light thresholds that are easily exceeded by a slight reduction in sea-ice duration. Earlier sea-ice loss is likely to cause extensive regime shifts in which endemic shallow-water invertebrate communities are replaced by algae, reducing coastal biodiversity and fundamentally changing ecosystem functioning. Modeling shows that recent changes in ice and snow cover have already transformed annual light budgets in large areas of the Arctic and Antarctic, and both aquatic and terrestrial ecosystems are likely to experience further significant change in light. The interaction between ice-loss and solar irradiance renders polar ecosystems acutely vulnerable to abrupt ecosystem change, as light-driven tipping points are readily breached by relatively slight shifts in the timing of snow and ice-loss.