Benthic communities on recent and historical volcanic lava flows of an oceanic island

Understanding how benthic communities develop on newly formed marine substrates is essential for explaining ecological succession after large natural disturbances. However, different benthic components may respond at different temporal scales. Here, we examined successional patterns in selected components of shallow benthic communities across three submarine lava flows of contrasting ages on La Palma Island (Canary Islands, Spain): less than 1 year, 73 years, and 473 years old. Specifically, we focused on macroalgal assemblages, early post-settlement microinvertebrates collected using artificial collectors, and established rock-associated microinvertebrate communities. To do so, we combined underwater photoquadrats, settlement collectors, and direct sampling of rock-associated microinvertebrates to compare successional patterns among these three benthic components. Species richness and community composition differed among substrate ages, but the strength and shape of the response varied among biological components. Macroalgal richness was lowest on the youngest flow and showed similar values between the intermediate and oldest substrates, suggesting relatively early compositional stabilization. In contrast, established rock-associated microinvertebrates showed maximum richness and taxonomic distinctiveness on the 73-year-old lava flow, followed by greater dominance of specialized and predatory taxa on the oldest flow. Early post-settlement assemblages showed intermediate patterns, linking initial colonization to the development of mature benthic communities. The ratio between newly settled and successfully established taxa declined with substrate age, suggesting an increasing role of post-settlement filtering as communities matured. Overall, our results show that successional patterns differed among benthic components, with macroalgal assemblages showing early compositional stabilization, whereas established rock-associated microinvertebrates exhibited a clearer richness peak at the intermediate successional stage. These patterns highlight the combined role of substrate age, habitat structure, and post-settlement processes in shaping selected components of shallow benthic assemblages on volcanic coasts.