Ecosystem functioning of canopy and turf-forming algae: potential supply of invertebrate prey to pelagic consumers

• Autor(a) principal: Figueiredo, Carla Kühl de
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/59/59139/tde-23032020-115421/
• topic: Competição; Competition; Ecological succession; Ecosystem engineering; Engenharia de ecossistema; Mudanças de fase; Peixe de recife; Phase-shifts; Reef fish; Sucessão ecológica

Canopy-forming algae may provide trophic resources and structural complexity for a wide array of mobile invertebrates, which in turn may sustain pelagic consumers of higher trophic levels. However, algal canopies are declining worldwide and replaced by less-complex macroalgal turfs which may dominate reefscapes. Here, we first compare the assemblages of mobile invertebrates associated to main canopy-forming (Sargassum spp. and Galaxaura marginata) and turf-forming algae (filamentous and articulated coralline turf), and then assess if, and how, canopy-dwelling invertebrate assemblages drift away from the turf baseline during the blooming season of the main canopy habitat (Sargassum). Abundance, biomass and diversity almost always differed between canopies and turfs at sampling sites, while differences within main functional algal types were nearly absent. But, surprisingly, none of those overall metrics varied in any consistent way across sampling sites. Differently, the assemblage structure consistently differed between canopies and turfs, with hard-bodied (as gastropods and brachyuran crabs), and soft-bodied (mainly polychaetes and flatworms) invertebrates characterizing canopy and turf assemblages, respectively. The divergence between invertebrate assemblages at canopies and turfs increased as the canopy-blooming season advanced. Notably, while the invertebrate assemblage structure remained unaltered at turfs, early-successional brittle stars and amphipods were followed by hard-shelled gastropods, bivalves and ostracods in Sargassum, where they become dominant and decreased diversity later on within the season. As hard-shelled prey are preferred items for the main invertivore fish species in the area, results indicate that canopies play a particularly important role in the provisioning of trophic resources to pelagic consumers.