Physical and biogenic complexity mediates ecosystem functions in urban sessile marine communities

Abstract The influence of habitat complexity on biodiversity is a central theme in ecology, with many studies reporting positive relationships. Reconciliation approaches urbanised areas, such as eco‐engineering, have increasingly focused ‘re‐building’ the degraded and/or homogenised habitats to support biodiversity. Yet, effects increasing and ecological functions are rarely measured. We assessed how physical biogenic affects net primary productivity (NPP) gross (GPP), community respiration nutrient cycling (specifically dissolved inorganic phosphorus nitrogen) intertidal sessile marine communities at three sites. manipulated using two types settlement tiles: ‘complex’, crevices ridges, ‘flat’. increased half replicates each tile type by seeding oysters. Increased resulted greater species richness all Although variables varied sites time measurements, overall, GPP NPP were flat tiles than complex ones. These patterns not explained differences total surface area tiles. Daily flux rates had significant relationship complexity. There no or fluxes nitrogen. Effects largely unrelated diversity measures, abundance key taxa functional groups. Synthesis applications . Eco‐engineering practices that manipulate might benefit from explicit targets also consider associated ecosystem services, we found under some conditions there trade‐off between targets. Our results suggest has effect richness, but necessarily (GPP NPP). pool available well light availability likely mediate assemblages, so local environment needs be consideration when designing interventions.