A mangrove forest can harbour several macroalgal assemblages growing on pneumatophores, roots, stems and other hard substrates. These algae belong to various genera, most typically Bostrychia, and form a community called the Bostrychietum. This study describes the fauna associated with the Bostrychietum and the effect of emersion time on the community. Seasonal samples were collected from pneumatophores on an island in Araçá Bay in 2012, in two areas, one on the border of the island and one inland. Each pneumatophore was considered a sample. The border samples, with a shorter emersion time, contained a richer algal flora associated with pneumatophores, and fauna with species of varied dietary habits. The inland samples, with a longer emersion time, contained only two algal genera and fauna species comprised mostly of omnivorous amphipods and desiccation-resistant detritivorous species. Macrofauna diversity and richness varied over time and were lower in spring. Therefore, the emersion time of the Bostrychietum and the period of the year affect the community structure, for both the macroalgae and the associated fauna.
