The composition and abundance of the meiofauna and macrofauna were studied in a survey carried out within 6locations in a mangrove at the Island of Santa Catarina, South Brazil. Nine meiofaunal taxa were registered withdensities ranging between 77 and 1589 inds.10 cm−2. The nematodes, composed by 94 putative species (86 genera),largely dominated the meiofauna. The most abundant genera were Haliplectus (Haliplectidae), Anoplostoma(Anoplostomatidae) and Terschillingia (Linhomoidae). Contrary to the meiofauna, the macrofauna showed a lownumber of taxa (only 17 recorded) and abundance (up 7250 inds.m−2). The macrofauna was mainly composedby deposit feeders, and numerically dominated by oligochaetes and capitellid polychaetes. For both components,differences in the composition and abundance along the sampling sites were significant but not primarily relatedto the typical variations along estuaries, such as salinity. The results of the stepwise multiple regression analysesshowed that the detritus biomass (ash-free dry weight) was the most important predictor of faunal densities anddiversity. The clear relationship between detritus and fauna, together with the contrasting community structure ofthe two component of the benthos suggest that the meiofauna showed a high efficiency in exploiting the microhabitatcreated by the presence of the detritus. Yet the macrofauna, potentially the main consumer of the debris, isnegatively affected by their low palatability and poor nutritive value.