The choice of materials used in coastal infrastructure not only influences colonization by marine life, but it can also influence the extent to which colonizing organisms modify the surface topography of the structure. This study examines the role of limpets as ecosystem engineers on the 180 year-old Plymouth Breakwater, a large artificial coastal structure composed of limestone, granite, and concrete. By comparing biodiversity patterns across these substrates, the research highlights how limpet bioerosion and grazing activities influence community structure and ecological succession. The study found that limestone pools, formed through differential erosion, support higher biodiversity and distinct functional groups compared to emergent granite habitats. On concrete blocks of varying ages, a clear successional pattern was observed: early colonization by green algae (< 2 yrs) was followed by the establishment of fucoids (2–3 yrs) and, subsequently, dense limpet populations that reduced algal cover (4–10 yrs). Over time, as the blocks aged and eroded (> 25 yrs), red algae became dominant, and limpet populations declined. This study highlights the importance of substrate type and erosion in shaping ecological communities on artificial coastal structures. The research contributes to a growing understanding of the complex interactions between biotic and abiotic factors in engineered marine environments, offering insights for the design and management of sustainable coastal infrastructure to support biodiversity.