Aggregative feeding behavior in sea urchins leads to destructive grazing in a Nova Scotian kelp bed
Aggregative feeding behavior in sea urchins leads to destructive grazing in a Nova Scotian kelp bed
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DOI：
10.3354/meps09441
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发表时间：
2012-01-01
影响因子：
2.5
通讯作者：
Lauzon-Guay, J. S.
中科院分区：
文献类型：
--
作者：
Feehan, C.;Scheibling, R. E.;Lauzon-Guay, J. S.
海胆的放牧聚集推动了新斯科舍省不同生态系统状态之间的转变，从高产的海藻床到生产力较低的贫瘠地带。这种转变可以通过在海带床内形成缝隙来启动，海带床内含有密集的海胆聚集物。我们研究了海胆的局部密度和海带冠层中预先存在的间隙在调节海胆在海带床上形成破坏性的放牧聚集物方面的重要性。我们将14000只成年海胆从新斯科舍省大西洋海岸的一片荒地移植到附近海带床内类似4.5米(2)的地块，密度高于和低于预测的破坏性放牧阈值，并通过移除一半地块的海带树冠来模拟对海带床的干扰。每周监测海胆的丰度和林隙的形成和扩大(如海带树冠盖度的丧失)，为期9周。在引入海胆后3wk，Grazer介导的缺口形成开始，并在实验的其余部分增加。我们的结果表明，在未受干扰的处理中，海胆的丰度与林隙面积的增加之间存在直接的线性关系。当海胆密度低于破坏性放牧的假定阈值时，海藻床上的缺口扩大，这表明海带床对放牧的适应能力低于预期。我们的发现为控制新斯科舍省海带床生态系统状态的稳定性和调节从海带床到荒地的转变的机制提供了洞察。
Grazing aggregations of the sea urchin Strongylocentrotus droebachiensis drive the transition between alternative ecosystem states in Nova Scotia, from productive kelp beds to less productive barrens. This transition can be initiated by the formation of gaps within a kelp bed, containing dense aggregations of sea urchins. We examined the importance of local density of sea urchins and pre-existing gaps in a kelp canopy in mediating the formation of destructive grazing aggregations of sea urchins in a kelp bed. We transplanted 14 000 adult sea urchins from a barrens on the Atlantic coast of Nova Scotia into similar to 4.5 m(2) plots within a nearby kelp bed, at densities above and below a predicted threshold value for destructive grazing, and simulated disturbance to the kelp bed by removing the kelp canopy in half of the plots. Sea-urchin abundance and gap formation and expansion (as loss of kelp canopy cover) were monitored in and around plots weekly for 9 wk. Grazer-mediated gap formation began 3 wk after sea urchins were introduced, and increased for the remainder of the experiment. Our results indicate a direct linear relationship between sea-urchin abundance and increase in gap area within undisturbed treatments. Gaps expanded in the kelp bed at sea-urchin densities below the putative threshold for destructive grazing, indicating that the kelp bed was less resilient to grazing than predicted. Our findings provide insights into mechanisms controlling the stability of the kelp-bed ecosystem state and mediating shifts from kelp beds to barrens in Nova Scotia.