COASTAL FEATURES ASSOCIATED WITH DIATOM DISCOLORATION OF SURF-ZONES

A survey of the southern African coastline from the Kunene River in th e north-west to Kosi Bay in the northeast showed that five coastal fea tures are associated with diatom accumulations that turn surf-zone wat er brown. Accumulations are only found on sandy beaches with wide surf -zones; medium to high energy surf conditions; well-developed rip curr ents and adjacent to coastal dunes with nutrient-rich aquifers. These physical features are common to beaches where surf diatom accumulation s have been reported. The absence of one of these features was concomi tant with the absence of concentrations of surf diatoms turning the wa ter brown. An exhaustive list of South African beaches where surf diat om accumulations have been recorded is provided.