The distribution and biomass of Zostera capensis (Setchell) in the Kromme Estuary is discussed in relation to substratum, nutrients, season and other abiotic parameters. It was found that substratum alone does not limit the distribution of Zostera beds and that this species can tolerate large variations in such abiotic factors as salinity and temperature. Declines in biomass are due mainly to episodic floods and the deposition of large quantities of fluvial silt. Annual net production rates of Zostera capensis were estimated from results of other studies. Few animals apparently feed directly on Zostera capensis, and the major proportion of this species' production is probably channelled through the estuarine detrital food chain.