The residual circulation profile of the Bons Sinais Estuary in central Mozambique - potential implications for larval dispersal and fisheries

The residual circulation in estuaries determines the net exchange of water, heat, salt, fine sediments and drifting biological organisms between estuarine nearshore marine waters. Bons Sinais Estuary central Mozambique is ~ 30 km long with city Quelimane an industrial port on northern bank its upper reaches. To investigate estuary, seasonal (wet, dry transition season) CTD profiling data were collected at 11 fixed stations estuary mouth, vertical current profiles measured over a full tidal cycle mid-estuary station. Strong longitudinal gradients salinity density indicated that was river-dominated during wet season tide-dominated season, but water column remained partially mixed. Tidally averaged from station revealed: uniform temperatures, warmest season; depth-stratified seasons highest when also highest. somewhat lower even lower, stratified. velocity profile showed classical two-layer model, downstream flow intensifying surface, upstream bottom, transitory seasons, freshwater discharges into estuary. velocities obtained calibrated Hansen Rattray model fitted observed well, confirming simplified modelling approach adequate to describe Estuary. provides insights useful for fisheries research predicting spread water-borne pollutants