Abstract:
Water circulation patterns in a tropical mangrove-fringed bay with seagrass and coral reef are driven by
tides that generate strong reversing tidal currents. The wind, which has an onshore component, generates a
net clockwise-rotating eddy. The dominant tidally driven water circulation pattern, coupled with the effects
of onshore wind and alongshore current generated by wave breaking, promotes the coastal trapping of turbid
brackish water and its inherent nutrient content. This brackish water inundates the mangrove swamp and
seagrass beds but not the coral reef ecosystem. Weak stratification prevails during the wet season in the upper
parts of Kidogoweni Creek as a result of freshwater influx from rivers. In the dry season, well-mixed
homogeneous water is found in most regions of the bay. A small zone of hypersaline water (salinity reaching
38 PSU) is found in the upper region of the mangrove-dominated creeks during the dry season. The connection
between the mangrove swamp, with its wide salinity variations, and seagrass beds is apparently through river
plumes and tidal effects. The link between seagrass beds and coral reefs is mainly through tidal influences.
