Litter production and accumulation in stressed mangrove communities in the Embley River Estuary, north-eastern Gulf of Carpentaria, Australia

From March 1993 to March 1994, the three main mangrove communities in the Embley River Estuary (12 degrees 37'S,141 degrees 52'E) were studied: Rhizophora forest in the main river channel and in a small creek, and Ceriops forest and Avicennia forest in a small creek. In November 1993, all A. marina trees in the main river channel lost their leaves, and some understorey species in Avicennia forests in tributaries died; this is attributed to environmental stress. This defoliation and death continued for at least a year. The Rhizophora forests were moderately to highly productive of litter, were the tallest, and had the greatest canopy cover and the greatest surface area of ground structures or potential refugia for juvenile finfish and crustaceans; all the litter was quickly transported by the tides to other parts of the estuary. The Ceriops and Avicennia forests produced less litter and were probably under water stress and salinity stress during the dry season; litter accumulated on the forest floor for much of the year, but from November to March was carried away by the higher tides and rainfall. Hence, in the wet season, pulses of litter are exported to the estuary, potentially forming temporary habitats in the estuary for juvenile finfish and crustaceans.