Status and long-term changes of coral reefs around Zanzibar

Coral reefs around Zanzibar, including those near Stone Town, exhibit significant long-term declines in hard coral coverage, particularly following El Niño events. Branching Porites and Acropora dominate sheltered reefs, while soft corals and algae thrive in areas with strong hydrodynamic conditions. Seasonal variations, especially in soft coral Corallimorpharia, further shape reef communities, with northern exposed reefs showing distinct differences from more sheltered ones like Chumbe. The study analyzed benthic composition across ten reefs from 1992 to 2016, revealing average dissimilarities of 60–75% between sites and highlighting the impact of human activity and physical exposure on coral health. Hard corals, which covered 40–70% in most years, declined sharply post-1998 but showed recovery signs at remote reefs. Continued monitoring is crucial to assess the effectiveness of management strategies for sustaining these vital ecosystems.

Ussi, A. M., Mohammed, M. S., Rashid, R. J., Sheikh, M. A., Staehr, P. A., Muhando, C. A., Yahya, S., & Dahl, K. (2024). Status and long-term changes of coral reefs around Zanzibar. Frontiers in Marine Science, 11. https://doi.org/10.3389/fmars.2024.1334235