The marine ‘great wall’ of China: local‐ and broad‐scale ecological impacts of coastal infrastructure on intertidal macrobenthic communities

Abstract Aim Increasing areas of artificial infrastructure are being built along coastlines for purposes of land reclamation and coastal defences. Impacts of these structures on intertidal communities could be severe. Here, we tested the hypothesis that artificial structures can alter intertidal community composition by providing hard substrata for rocky intertidal species, and can serve as ‘stepping stones’ that facilitate broad‐scale migration of rocky intertidal species and may weaken a phylogeographic transition. Location Chinese intertidal ecosystem. Methods Three‐year field ecological survey of macrobenthic species and phylogeographic analyses of three common species found on artificial structures and nearby natural rocky shores. Results (1) Artificial substrata were rapidly colonized by rocky intertidal species, and in the mid‐ and high‐intertidal zone, habitats were occupied by some widely distributed rocky intertidal species. (2) Distance to the nearest rocky shore and age of the artificial structures were important for species richness and community composition on the artificial structures. (3) Both ecological and genetic data showed that most populations on the artificial structures north of the Yangtze River estuary were derived by migration from natural rocky shores south of the Yangtze River estuary. This estuary formed a phylogeographic and biogeographic transition for intertidal species along China's coastline. Main conclusions (1) Artificial structures associated with large‐scale land reclamation along China's coastline provide appropriate habitats for rocky shore species; (2) because artificial structures are ubiquitous world‐wide, the biogeography of rocky shore species and other ecological impacts of this infrastructure along global coastlines should be reconsidered under the coupled impacts of climate change and human activities.