Succession of marine fouling community influences the associated mobile fauna via physical complexity increment

Abstract

Sessile communities provide habitat for feeding, reproduction and protection to a diverse mobile fauna. Along succession, the growth and overgrowth of three-dimensional sessile organisms generate structural complexity and microhabitats for mobile organisms. Most studies focus on one species or group of the sessile fauna as a habitat provider, but here we investigated the whole community, using fouling communities as a model. We tested the hypothesis that they would gain structural complexity along succession, resulting in an increase in abundance and biomass, and compositional changes of the associated mobile groups. The organisms were obtained from communities growing on PVC plates left in the water for 6, 9 and 12 months. Early succession fouling communities (6 months) were mostly flatter, dominated by encrusting bryozoans and more empty space and cover of delicate hydrozoans and filamentous algae. Advanced-succession fouling communities (9 and 12 months) showed a biomass increment and compositional changes by the increased cover of structurally complex sessile organisms, such as arborescent bryozoans and sponges. Mobile groups showed higher abundance and biomass, and a different composition at later stages. Thus, our results emphasise how the structural complexity provided by fouling organisms and the changes over succession may mediate the changes in the associated mobile fauna.