Canopy-forming macroalgae are the main component in some of the most diverse and productive coastal habitats around the world. However, canopy-forming macroalgae are very sensitive to anthropogenic disturbances. In coastal urban areas, intertidal organisms are exposed to the interactive effect of several anthropogenic disturbances that can modify the community’s structure and diversity. Along the North-East Atlantic shores, many studies explored the effect of anthropogenic disturbances on canopy-forming macroalgae, but mainly focused on kelps and fucoids. However, along the intertidal rocky shores of the Atlantic coast of the Iberian Peninsula, the most abundant and frequent canopy-forming macroalgae belong to the family Sargassaceae. To explore the effect of urbanization on these intertidal canopy-forming species the diversity and assemblage structure of canopy species were compared between four urban and four non-urban shores in the north of Portugal. Intertidal canopy assemblages on urban shores were dominated by the non-indigenous Sargassum muticum that was the only canopy-forming species on three of the four studied urban shores. Canopy assemblages on all non-urban shores were more diverse. Moreover, stands of canopy-forming species on urban shores were always monospecific, while at non-urban shores multi-specific stands were common. Therefore, results suggest that urbanization reduces canopy´s biodiversity.

中文翻译：

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葡萄牙北部沿海城市地区潮间带冠层大型藻类多样性低

形成冠层的大型藻类是世界上一些最多样化和生产力最高的沿海生境中的主要组成部分。但是，形成冠层的大型藻类对人为干扰非常敏感。在沿海城市地区，潮间带生物受到几种人为干扰的相互作用的影响，这些相互作用可以改变社区的结构和多样性。在东北大西洋沿岸，许多研究探索了人为干扰对形成冠层的大型藻类的影响，但主要集中在海带和岩藻类。然而，在伊比利亚半岛大西洋沿岸的潮间带多岩石的海岸上，最丰富和最频繁形成冠层的大型藻类属于Sargassaceae科。为了探讨城市化对这些潮间带冠层物种的影响，在葡萄牙北部的四个城市海岸和四个非城市海岸之间比较了冠层物种的多样性和集合结构。非本地人占主导地位的潮间带冠层在城市海岸在四个研究过的城市海岸中的三个中，唯一的形成冠层的物种是Sargassum muticum。在所有非城市海岸上的树冠组合都更加多样化。此外，城市沿岸的形成冠层物种的林分总是单种的，而在非城市沿岸的多林分的种很常见。因此，结果表明，城市化进程会减少冠层的生物多样性。