Rufiji-Mafia Channel - Ecology

The Rufiji–Mafia inshore marine ecosystem serves many important functions. Most notably, it has extremely high primary and secondary productivity and supports a great abundance and diversity of fish, birds, invertebrates and macro fauna. The latter provide biogenic structure in the inshore, creating refuge for young fish and invertebrates, thereby nurseries. The coastal area enclosed between Rufiji Delta-Mafia Channel forms one of the finest complexes of estuaries, mangrove, coral reefs and marine channel ecosystem (Darwall and Guard, 2000; Mgaya 2004). Mangroves frequently occur in conjuction with coral reefs and sea grass beds; they often interact with one another and with the terrestrial and open ocean areas. Mangroves and sea grass beds filter freshwater discharges from land promoting the growth of coral reefs offshore. Without this function, high sediment loads derived from upland activities and then transported by Rufiji River would be detrimental to corals. Corals in turn, are physical buffers for oceanic currents and waves, creating, over geologic time, a suitable protected environment for sea grass beds and mangroves. The detritus from mangroves provides food for many commercially important species, mostly demersal fish and benthic invertebrates, thereby supporting a wide variety of sea life. Most of the energy throughput is within trophic levels II and III, as expected from an estuarine coastal ecosystem where there is high input of organic matter from the rivers. However, the unique Mafia island ecosystem provides a vast array of larvae which are swept into the Indian Ocean, and carried northwards by the prevailing North East African Current ultimately adding to the rich diversity of marine life found as far north as the Red Sea.