The effects of bioturbation and herbivory by the polychaete Nereis diversicolor on loss of saltmarsh in south‐east England
The effects of bioturbation and herbivory by the polychaete Nereis diversicolor on loss of saltmarsh in south‐east England
复制标题
多毛类沙蚕的生物扰动和食草行为对英格兰东南部盐沼消失的影响
DOI：
10.1111/j.0021-8901.2004.00916.x
复制
发表时间：
2004
影响因子：
5.7
通讯作者：
R. G. Hughes
中科院分区：
文献类型：
--
作者：
O. Paramor;R. G. Hughes
总结
1
英格兰东南部的盐沼正在迅速侵蚀。现场和实验室实验用于检验以下假设：（i）在泥滩-盐沼边界存在两种替代状态，一种以排除穴居动物的先锋带植被为主，另一种以排除植被的内动物无脊椎动物为主； (ii) 英格兰东南部盐沼消失的主要原因是内部溪流侵蚀，而生物扰动和动物性多毛类沙蚕的食草行为加剧了这种侵蚀。
2
在实验室实验中，沙蚕吃海蓬子属的种子和幼苗，海蓬子阻止沙蚕挖洞。在英国埃塞克斯托尔斯伯里的田间实验中，将沙蚕排除在沉积物表面之外会增加海蓬子的密度，但前提是种子来源很近。在托尔斯伯里盐沼中，植物和沙蚕在垂直重叠区域内具有相互排斥的分布。托尔斯伯里管理的重新调整地点最近的植被区域没有沙蚕，但沙蚕在海蓬子被移除的区域定居。这些观察和数据支持第一个假设。
3
托尔斯伯里盐沼的大部分损失是由于内部溪流的侧向侵蚀造成的。仅物理因素不能造成这种侵蚀，因为实验排除沙蚕会导致沉积物堆积。这些结果支持第二个假设。溪流侵蚀可能会产生正反馈，其中溪流扩大导致更快的潮流和进一步的侵蚀，直到溪流扩大到新的平衡形态。
4
合成与应用。我们的结论是，内生动物是盐沼植被面积减少的主要原因，这对盐沼恢复管理具有影响。这些结果对英格兰东南部盐沼侵蚀是由于海平面上升和海岸挤压造成的假设提出了质疑，并要求重新审视管理调整在盐沼再生中的作用。通过排除内生动物和/或降低盐沼溪流的当前速度来降低盐沼溪流的侵蚀率，将减少通过有管理的重新调整来更换侵蚀沼泽的需要，并将减少未来因波浪作用而对现有海堤的侵蚀。
Summary
1
The saltmarshes of south-east England are eroding rapidly. Field and laboratory experiments were used to test the hypotheses that: (i) at the mudflat–saltmarsh boundary there are two alternative states, one dominated by pioneer zone vegetation that excludes burrowing infauna, and the other dominated by infaunal invertebrates that exclude vegetation; and (ii) the major cause of the loss of saltmarshes in south-east England is internal creek erosion, which is exacerbated by bioturbation and herbivory by the infaunal polychaete Nereis diversicolor.
2
In laboratory experiments Nereis ate the seeds and seedlings of Salicornia spp., and Salicornia deterred burrowing by Nereis. In field experiments, at Tollesbury in Essex, UK, exclusion of Nereis from the sediment surface increased the density of Salicornia, but only when a source of seeds was close by. In the Tollesbury saltmarsh the plants and Nereis had mutually exclusive distributions within a vertical zone of overlap. The recently vegetated area of the managed realignment site at Tollesbury contained no Nereis, but Nereis colonized areas where Salicornia had been removed. These observations and data support the first hypothesis.
3
Much of the loss of the Tollesbury saltmarsh is by lateral erosion of the internal creeks. Physical factors alone cannot be responsible for this erosion because experimental exclusion of Nereis led to sediment accretion. These results support the second hypothesis. Creek erosion may create a positive feedback where creek enlargement leads to faster tidal currents and further erosion until creeks have widened to their new equilibrium morphology.
4
Synthesis and applications. We conclude that the infauna are a major cause of reduction in area of saltmarsh vegetation and this has implications for the management of saltmarsh restoration. These results call into question the assumption that saltmarsh erosion in south-east England is due to sea level rise and coastal squeeze, and demands re-examination of the role of management realignment in the regeneration of saltmarshes. Reducing the rates of saltmarsh creek erosion, by exclusion of the infauna, and/or by reducing current velocities in the saltmarsh creeks, would reduce the need to replace eroded marshes by managed realignment, and would reduce future erosion of existing sea walls by wave action.