Impacts of heavy metal pollution on benthic communities on the coast of Zanzibar, Tanzania

The world today has a population of over 7 billion people, with more than half of that number living in coastal areas, which accounts for only 5% of the inhabited land. This aspect is clearly reflected when one realises that of the 33 biggest megacities in the world, 22 are on the coast (UNEP, 2011). Especially in developing states such as Zanzibar, sewage still flows untreated into the sea, causing pollution of coastal habitats. The Zanzibar Archipelago, consists of two main islands – Unguja and Pemba with a combined population of nearly one million, while the urban population which is concentrated in Stone Town is around 200,000 (National Bureau of Statistics, 2002). The study focuses on the impact of trace metal pollution derived from dumping of household and industrial sewage, on the benthic communities found in the intertidal zone along the coast of Zanzibar. This study also serves as an extension to the paper by Rumisha et al. (2012) which assessed the influence of trace metal pollution on the community structure of soft bottom molluscs at the Dar es Salaam coast, across the Zanzibar Channel.