Ecological health of coral reefs in Zanzibar

Coral reef health around Stone Town, Zanzibar, deteriorates significantly with proximity to urban and industrial pressures. While traditional benthic surveys revealed declining hard coral cover near Stone Town—likely due to fishing, tourism, and pollution—trace metal analysis uncovered widespread arsenic and cadmium contamination across all sites, along with concerning levels of chromium, copper, and zinc. These pollutants, not correlated with distance from the city, suggest remote reefs are affected by industrial and urban sewage downstream. The study highlights the necessity of combining multiple assessment methods to fully grasp reef degradation, as sediment and bioindicator data diverged from community structure surveys.

Bravo, H., Cannicci, S., Huyghe, F., Leermakers, M., Sheikh, M. A., & Kochzius, M. (2021). Ecological health of coral reefs in Zanzibar. Regional Studies in Marine Science, 48, 102014. https://doi.org/10.1016/j.rsma.2021.102014