A distortion of coastal communities has been reported along the European Atlantic in recent years. In NW Spain, the lack of studies focusing on long-term changes was resolved when several common perennial seaweeds were shown to have diminished in occurrence between 1998/99 and 2014. To ascertain whether their decline reflected a genuine long-term trend, the same network of monitoring locations and the same set of perennial seaweeds was re-surveyed in 2018. Contrary to our expectations, the average number of species per site increased in semi-exposed and semi-sheltered locations to become statistically indistinguishable from 1998/99 estimates. Nevertheless, site occupancy rates continued to be below 1998/99 estimates for several seaweeds, and warming, both from rising average temperatures and from more frequent and intense marine heatwaves in autumn, seems a plausible explanation for their decline. The benefits of routinely monitoring a network of fixed stations, especially when they are subject to different levels of wave exposure, are discussed.

近年来，欧洲大西洋沿岸沿海社区发生了扭曲。在西班牙西北部，当几个常见的多年生海藻在1998/99至2014年间的发病率有所降低时，解决了缺乏针对长期变化的研究的问题。为了确定其下降是否反映了真正的长期趋势，相同监测地点和同一套多年生海藻的监测网络在2018年进行了重新调查。与我们的预期相反，半暴露和半庇护的地点中每个地点的平均物种数量有所增加，与1998/99年的估算值在统计上没有区别。尽管如此，一些海藻和变暖的场地占用率仍低于1998/99的估计值，无论是由于平均温度升高，还是由于秋季更频繁，更强烈的海洋热浪，似乎都是其下降的合理解释。讨论了定期监视固定站网络的好处，尤其是当它们受到不同程度的波辐射时。