Abstract
The South African coast has roughly 250 estuaries, and approximately 70% of these have been classified as temporarily open/closed systems. These environments are highly dynamic and their ecology is strongly influenced by seasonal rain cycles. For example, estuarine phytoplankton decrease in individual size as well as in total productivity during dry periods, while microphytobenthic biomass increases. Because estuaries exchange organisms and nutrients with the ocean when their mouths are open, changes in estuarine food-web structure are likely to impact adjacent coastal systems, including sandy beaches. Here we report on a study that monitored a series of eight intertidal transects arranged along a symmetrical gradient to the north and south of the mouth of the temporary open/closed Umlalazi River, KwaZulu-Natal, South Africa. The study period covered the end of the dry (closed) phase, the early summer rains (spring) and the end of the wet phase (late summer). Coupled with samples from within the estuary, biological and environmental samples were analysed using standard multivariate approaches to trace the influence of the estuary on the benthic communities inhabiting the beach. Results provide evidence of coupling between the estuary, the surf zone and beach benthos and highlight the importance of integrated management of coastal features.