Beschreibung: Floating mangrove leaves with associated organisms were sampled in 62 hauls during 6 expeditions from January to August 1992 in the Rio Mucuri estuary, northeast Brazil. Leaves were collected by hand-dipping a 100 μm plankton net with a mouth opening of 22 cm. In January, February and June 500 μm plankton nets were hauled in 18 oblique, superficial and neuston trawls. In August settling experiments with drifting substrata were performed. In each settling experiment 10 marked pasteboard stripes and mangrove leaves, respectively, were set out approximately 500 m southeast of the inlet and collected in the estuary. Crabs were the predominant animals collected. Thirtyeight groups of organisms were found associated to floating leaves. Among those groups were 16 decapods. Some decapods, including megalopae and postlarval Penaeus schmitti, dinged to the leaves collected. Megalopae occured in 70,9 % of the leave samples, followed by the first zoeal stages of palaemonids (52,7%), isopods (61,8 %) and zoeae of crabs (38 %). Among decapod larvae zoeae (910 ind./m2) and megalopae (686 ind./m2) of crabs were found with the highest densities under leaves. Four groups were found to occur at higher densities during flood than during ebb tides in leave samples. These groups were: crab megalopae, postlarvae of Penaeus schmitti, postlarvae of Potimirim potimirim and non-identified caridean zoeal stages. These groups were imported into the estuary. Thirtyseven groups were identified in the plankton samples, including 22 decapod groups. Three groups were reliably quantified in the neuston samples. These groups occurred in significantly higher densities in neuston samples than in leave samples. This difference is presumably due to the higher degree of avoidance against the small hand net used for sampling the leaves. The drifting substrata were settled by 22 groups of organisms, including 8 decapod groups. A difference between the densities under pasteboard stripes and mangrove leaves was not found for any of the registered groups. These organisms did not show a chemotactic preference for drifting mangrove leaves. Consequently they probably do not feed upon them. In this study a transport model for decapod larvae in the Rio Mucuri estuary is presented. This model considers diverse transport and retention phenomena, such as landward advection in bottom currents, transport by winddriven surface currents, landward transport by tidally rhythmic vertical migration, accumulation in internal waves and the settling on floating substrata.