Wetlands of South Africa
Abstract
Mangroves are trees or shrubs that grow in the intertidal zone of estuaries from the Kosi system to the Nahoon River. Of the six taxa within South Africa's borders, two, Ceriops tagal (Perr) CB Robinson and Lumnitzera racemosa Wilid, extend no further south than the Kosi system; three, Rhizophora mucronata Lam., Bruguiera gymnorrhiza (L.) Lam. and Acrostichum aureum L., reach their limits in Transkei while one, Avicennia marina (Forssk.) Vierh., extends almost to East London. Temperature is considered to be the main environmental factor limiting mangrove distribution and growth in subtropical and temperate areas. Inundation by waters which can vary greatly
in salinity and soils that are poorly drained, saline and anoxic, contribute towards creating a harsh environment. To cope with such an environment mangroves possess characteristic physiological and morphological adaptations. Associated with mangroves is a wide diversity of plants and animals. The former includes seagrasses, saltmarshes, fringing estuarine vegetation, and algae either epiphytic on mangroves or occurring as mats of blue-green algae
(cyanobacteria) on the mud substrate. The larger animals include sesarmid and fiddler crabs, gastropods, fish and birds. These associated plants and animals play an integral role in the estuarine food chain towards which decomposing mangrove leaf material makes a major contribution. Mangrove estuaries fulfil important functions
as a breeding and feeding ground for marine species and also as a protection for shorelines against erosion. The future need for management of not only estuaries, but the coastal environment as a whole, is stressed.
GI Cowan (ed).1995.
A general review of the mangroves of South Africa
TD Steinke
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