VERTICAL ZONATION OF EPIPHYTIC ALGAE ASSOCIATED WITH AVICENNIA-MARINA(FORSSK) VIERH PNEUMATOPHORES AT BEACHWOOD MANGROVES NATURE-RESERVE, DURBAN, SOUTH-AFRICA

A new sampling technique designed to study the vertical distribution o f macroalgae associated with Avicennia marina (Forssk.) Vierh. pneumat ophores is described. Correspondence Analysis was the primary techniqu e computed to identify relationships between species, pneumatophore he ight intervals and density associations. The relationships between spe cies frequency and pneumatophore height intervals were summarized in k ite diagrams. Vertical zonation along the aerial roots was detected, b eing most obvious in samples where the tall, dense pneumatophores occu rred along the water's edge. Three zones were identified: an upper Rhi zoclonium-, a mid Bostrychia- and a lower Caloglossa-zone. The photoph ilic Cyanophyceae were not limited to any particular zone as their occ urrence was along the entire length of the pneumatophores. Vertical di stribution was generally limited to heights attained at tidal ebb and flow on the aerial mangrove roots. Environmental factors predicted to govern vertical zonation include tidal phenomena such as tidal inundat ion and wetting frequency, desiccation, salinity, as well as light int ensity and temperature.