Structure and composition of intertidal communities at exposed and sheltered habitat, Central Namibian coast

Communities of intertidal organisms were investigated along the Namibian coast between Swakopmund and Walvis Bay at two locations that differs in small-scale topography and wave action. A systematic transect design study was performed at both sites to determine the occurrence of intertidal invertebrates and macro-algae within the eulittoral zone. A quadrant (30 cm x 30 cm) was used for sampling and three eulittoral horizons, i.e. at high, mid and low water level, were identified. In each zone, ten (10) quadrants, five on each side of the transect line, were sampled. Results indicated significant differences in species diversity between high, mid and low eulittoral zone at sheltered area, but not at the exposed area. In addition, there were significant differences in species diversity between the two sites. Differences in the diversity of intertidal organisms with zone could be due to a-biotic factors and biological interactions that prevail at higher and lower water mark, respectively. It was concluded that the rocky intertidal at the central Namibian coast is a very diverse habitats that support a multitude of organisms and shows several patterns which are characterized by specific species compositions although an overlap between assemblages was observed.