Algae associated with mangroves in southern African estuaries. I. Rhodophyceae

Macroalgae associated with 19 mangrove estuaries from Kosi estuary to the Nahoon River have been studied. Twelve taxa of the Class Rhodophyceae are described with information on the nature of the substrata for settlement and the seasonal occurrence of fertile plants. Bostrychia moritziana (Sonder) J. Ag., B. radicans (Mont.) Mont. and Caloglossa leprieurii (Mont.) J. Ag. form the persistent components of the mangrove bostrychietum. Bostrychia tenella (Vahl) J. Ag., B. tangatensis Post and B. scorpioides (Gmelin) Mont. have restricted distributions. Polysiphonia subtilissima Mont. and Gelidium spp. are more common associates than Murrayella periclados Schm. and Catenella nipae Zanardini. A freshwater alga is also an associate of the bostrychietum. The findings are discussed and compared with mangrove bostrychieta from other countries, particularly Australia