The Dynamics of Estuarine Macrophytes in Relation to Flood/siltation Cycles

Intense temporal variability in the distribution of intertidal and submerged macrophytes in response to flooding was recorded in the Kwelera and Nahoon estuaries, South Africa over 4.5 years. The data provide a first approximation of the transition between different vegetation types during flood/siltation cycles in South African estuaries. A flood in November 1985 removed major populations from both estuaries. Recovery of Zostera capensis Setchell, the pre-flood dominant seagrass, was sluggish and lagged behind the process of post-flood sedimentation. This seagrass population is expected to be back to pre-flood levels after 4.2 years. In contrast, Halophila ovalis (R. Br.) Hook. f. rapidly colonized the mouth reaches. The macroalga Codiumtenue Kütz. was even more unstable than the seagrasses, disappearing in response to even slight freshwater runoff. Vegetation above mean tide level (MTL) showed little variability.