South Africa is a Southern Hemisphere region influenced by two currents; the cold Benguela and warmer Agulhas. The coastline is divided into several distinct biogeographic provinces, dictated by climatic and oceanographic conditions. Temporal change was detected in composition, structure and functioning of communities sampled within and between provinces. This was based on comparisons of historical samples collected in the 1930's and 1980's with contemporary samples at the same sites. Changes coincided with evidence of regional climate change spanning comparable time frames. One change detected was a range shift in the indigenous mussel, Perna perna. The southern range limit of this warm-water species had been compressed in an equator-ward direction (north). This was in conjunction with near-shore cooling driven by climate related shifts in local upwelling regimes. Although this trend supports global climate change predictions, the recession is in the same direction as pole-ward range recessions reported for cold-water, Northern hemisphere species where near-shore waters are warming. Climate change has been linked to increased bioinvasion success. One of the largest contributors to temporal change in the rocky intertidal has been the establishment and spread of the open coast introduced mussel, Mytilus galloprovincialis. Based on the ecological and oceanographic evidence, we proposed that near-shore cooling negatively impacted the overall energy budget of P.perna, contributing toward the observed range recession. Conversely, it enhanced the competitive ability of M. galloprovincialis, which now dominates the rocky shore in this region. Physiological evidence supports this hypothesis.