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Abstract：
Extreme environmental events can strongly affect coastal marine ecosystems but are typically unpredictable. Reliable data on benthic community conditions before such events are rarely available, making it difficult to measure their effects. At the end of October 2018, a severe storm hit the Ligurian coast (NW Mediterranean) producing damages to coastal infrastructures. Thanks to recent data collected just before the event on two Posidonia oceanica seagrass meadows hit by the storm, it has been possible to assess the impact of the event on one of the most valuable habitats of the Mediterranean Sea. By means of seagrass cover and depth data gathered along four depth transects positioned within the two meadows in areas differently exposed to the storm waves, and by using models (WW3® + SWAN + XBeach 1D) to evaluate wave height and bed shear stress, we showed that meadows experienced erosion and burial phenomena according to exposure. Paradoxically, meadows in good conditions suffered more damage as compared to those already suffering from previous local anthropogenic impacts. Besides the direct effect of waves in terms of plant uprooting, a major loss of P. oceanica was due to sediment burial in the deepest parts of the meadows. Overall, the loss of living P. oceanica cover amounted to about 50%. Considering that previous research showed that the loss of the original surface of P. oceanica meadows in 160 years due to anthropogenic pressures was similarly around 50%, the present study documented that an extreme environmental event can generate in a single day a loss of natural capital equal to that produced gradually by more than a century of human impact.
摘要：
极端环境事件可以强烈影响沿海海洋生态系统，但通常是不可预测的。在此类事件发生之前，有关底栖群落状况的可靠数据很少可用，很难衡量它们的影响。2018年10月底，一场严重的风暴袭击了利古里亚海岸（地中海西北部），对沿海基础设施造成了破坏。多亏了最近在风暴袭击的两个海洋波西多尼亚海草草甸事件之前收集的数据，有可能评估该事件对地中海最有价值的栖息地之一的影响。通过沿两个草地内暴露于暴风波不同区域的四个深度剖面收集的海草覆盖和深度数据，并使用模型(WW3®+SWAN+XBeach1D)评估波高和河床剪应力，我们表明，根据暴露，草地经历了侵蚀和埋葬现象。矛盾的是,与以前已经遭受当地人为影响的草地相比，条件良好的草地遭受的破坏更大。除了波浪对植物连根拔起的直接影响之外，海洋原虫的主要损失是由于草地最深处的沉积物掩埋。总的来说,活的海洋保护区的损失约为50%。考虑到先前的研究表明，由于人为压力，160年中海洋海洋草甸原始表面的损失类似约为50％，本研究表明，一个极端的环境事件可以在一天内产生的自然资本损失相当于一个世纪以上人类影响逐渐产生的自然资本损失。
