Thomas Burel1, Ignacio Bárbara2, Anaëlle Bizien1, Jacques Grall1, Michel Le Duff1, Céline Rebours3, Thomas Rossiter4, Gauthier Schaal1, Dagmar Stengel4, Erwan Ar Gall1
1Université de Brest, France - 2Universidade da Coruña, Spain - 3Møreforsking, Norway - 4University of Galway, Ireland
Coastal marine biodiversity is shaped by intricate interactions between biological, physical, and anthropogenic processes, each operating at distinct spatial scales. European temperate rocky shores host vertically structured macroalgal communities dominated by canopy-forming Fucales, supporting high biodiversity, yet most studies focus on a single species and examine either local drivers or broad geographic patterns. The relative importance of large-scale biogeographic processes versus local environmental conditions in shaping beta diversity across hypsometric gradients remains poorly understood. In this study, we hypothesize that local scale environmental conditions strongly influence upper shore communities, while large scale biogeographic patterns play a significant role in structuring lower shore communities. To test this, we conducted quantitative surveys along the northeastern Atlantic coast, spanning Galician, Breton, Irish, and Norwegian rocky shores. Sampling was carried out using random quadrats, focusing on three vertically structured Fucales-dominated communities: (1) Fucus spiralis, (2) Ascophyllum nodosum – Fucus vesiculosus, and (3) Fucus serratus. Both macrofloral and macrofaunal assemblages were assessed together with in situ wave exposure estimated by sensors. A total of 119 macroalgal species and 28 faunal taxa were identified. The results confirm that upper shore communities exhibit minimal variation along the latitudinal gradient, with physical factors playing a dominant role in their structuring. Although mid- and lower shore communities show a significant biogeographic influence, they are unexpectedly more strongly shaped by physical factors than by latitude. This study underscores the critical role of small-scale variations in physical conditions in shaping intertidal communities. Understanding these localized influences is essential, particularly in the context of accelerating environmental changes, as they provide valuable insights into how these ecosystems may respond to shifting climatic and anthropogenic pressures.
Biography
Thomas Burel is a marine biologist specializing in coastal ecology teaching at the University of Brest. His research focuses on rocky shores in the framework of European directives. He also study the structure of macroalgal communities associated to coastal habitats such as maerl beds and seagrass meadows. He is an expert in macroalgal taxonomy and contributes to non-indigenous species monitoring across European coasts.