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.

The coastal environment is often impacted by anthropogenic actions like marine pollution, which has been affecting biogenic substrates and thus its associated fauna. Some brown macroalgae, like Sargassum spp., can accumulate heavy metals on its tissues, which can directly affect the fitness of herbivorous amphipods that feed upon these algae, which therefore are considered efficient indicators of environmental quality. This study presentes the population dynamics and fecundity rates variations of Sunamphitoe pelagica, a Sargassum-associated herbivorous amphipod, collected in an impacted bay on southeastern Brazil. Sargassum sp. samples were taken in winter and summer at four sampling sites in Flamengo Bay, Ubatuba municipality – SP, at different distances from Saco da Ribeira’s marina, considered an important pollution spot in the area.

As comunidades marinhas são constantemente modificadas por distúrbios naturais e antrópicos, que removem organismos e abrem novos espaços que podem ser colonizados, dando origem a um processo de sucessão ecológica. Este trabalho visa analisar ao longo do processo sucessional, as mudanças que ocorrem tanto no substrato biológico como na fauna associada e como a mudança do substrato pode influenciar na fauna. Para isso foram amostradas comunidades incrustantes que se desenvolveram sobre placas de PVC, durante tempos sucessionais diferentes (seis, nove e 12 meses). As amostras de substrato biológico foram identificadas através de fotografias e quantificadas quanto à área de cobertura que ocupam no substrato e sua biomassa. A fauna associada foi separada em grandes grupos e contabilizada. Foram analisadas as mudanças na composição, abundancia e biomassa da comunidade incrustante e na fauna associada ao longo dos períodos sucessionais.

The aim of this study is to investigate if Sargassum-associated herbivorous amphipods Cymadusa filosa Savigny, 1816 and Sunamphitoe pelagica (H. Milne Edwards, 1830) present differences in their population parameters at sites located at different distances from a state marina, which is the main source of pollution (especially heavy metals) in an impacted bay. The study was conducted at four beach sites within Flamengo Bay, Ubatuba municipality, northern coast of São Paulo State, Brazil. The beaches are Lamberto and Ribeira close to the pollution source and Flamengo and Santa Rita, which are more distant. We observed the predominance of juveniles in the populations of C. filosa and S. pelagica, followed by females, with the sex ratio for both species being favored toward females, and the highest densities of individuals were observed during the summer. Sunamphitoe pelagica presented lower density, smaller ovigerous females and egg volumes at Lamberto beach, indicating a possible higher sensitivity to metal pollution

Este trabalho procura esclarecer possíveis relações entre a biomassa de Sargassum sp. e a abundância de anfípodes herbívoros da família Ampithoidae, assim como sua relação com a sazonalidade e temperatura.