Stepping stones towards Antarctica: Switch to southern spawning grounds explains an abrupt range shift in krill
Stepping stones towards Antarctica: Switch to southern spawning grounds explains an abrupt range shift in krill
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DOI：
10.1111/gcb.16009
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发表时间：
2021-12-18
影响因子：
11.6
通讯作者：
Perry, Frances A.
中科院分区：
文献类型：
--
作者：
Atkinson, Angus;Hill, Simeon L.;Perry, Frances A.
向极范围的变化是对变暖的全球范围的反应，但这些变化在类群之间差异很大，并且很难预测单个物种、局部区域或更短（几年到十年）的时间尺度。在北极向极地移动可能比在南大洋更容易，在南大洋，范围变化的证据很少而且相互矛盾。在这里，我们编制了南极磷虾幼体数据库，与成体数据库一起，显示了它们的活动范围变化如何与变暖的速度不同步。在长达 70 年的快速变暖时期（1920 年代至 1990 年代），尽管气温升高了 0.5-1.0 摄氏度并且海冰消失，但西大西洋地区幼虫和成虫的分布中心仍然保持不变。随后，地表变暖和冰层流失出现中断，但在此期间，磷虾生命阶段的分布向西南方向发生了约 1000 公里的巨大变化。了解此类阶跃变化的机制至关重要，因为它们预示着当前建模方法难以预测的系统重组。我们认为，这种突然转变是由作用于局部招募热点的气候控制以及热生态位保守主义推动的。在变暖中断期间，南部环形模式指数继续变得越来越积极，并且可能是由于幼虫摄食成功率的降低，导致了沿着南部斯科舍省弧的主要繁殖热点的招募急剧下降。这减少了北部磷虾资源的补充，密度和群体频率下降就证明了这一点。与此同时，20 世纪 90 年代后出现了一个新的南部繁殖区，尽管地表没有变暖，但仍加强了分布范围的变化。新的产卵热点可能为范围转移到极地地区提供所需的垫脚石，因此适应气候变化的海洋保护区的规划应包括未来栖息地的这些关键区域。
Poleward range shifts are a global-scale response to warming, but these vary greatly among taxa and are hard to predict for individual species, localized regions or over shorter (years to decadal) timescales. Moving poleward might be easier in the Arctic than in the Southern Ocean, where evidence for range shifts is sparse and contradictory. Here, we compiled a database of larval Antarctic krill, Euphausia superba and, together with an adult database, it showed how their range shift is out of step with the pace of warming. During a 70-year period of rapid warming (1920s-1990s), distribution centres of both larvae and adults in the SW Atlantic sector remained fixed, despite warming by 0.5-1.0 degrees C and losing sea ice. This was followed by a hiatus in surface warming and ice loss, yet during this period the distributions of krill life stages shifted greatly, by similar to 1000 km, to the south-west. Understanding the mechanism of such step changes is essential, since they herald system reorganizations that are hard to predict with current modelling approaches. We propose that the abrupt shift was driven by climatic controls acting on localized recruitment hotspots, superimposed on thermal niche conservatism. During the warming hiatus, the Southern Annular Mode index continued to become increasingly positive and, likely through reduced feeding success for larvae, this led to a precipitous decline in recruitment from the main reproduction hotspot along the southern Scotia Arc. This cut replenishment to the northern portion of the krill stock, as evidenced by declining density and swarm frequency. Concomitantly, a new, southern reproduction area developed after the 1990s, reinforcing the range shift despite the lack of surface warming. New spawning hotspots may provide the stepping stones needed for range shifts into polar regions, so planning of climate-ready marine protected areas should include these key areas of future habitat.