Density, diversity, and survival of juvenile corals on reefs of Zanzibar, Tanzania

Robert van Woesik, Department of Ocean Engineering and Marine Sciences, Florida Institute of Technology, 150 West University Blvd, Melbourne, Florida 32901, USA

Abstract
The sustainability of coral populations depends on the steady supply of sexually produced offspring, especially as coral populations attempt to adjust to climate change. Therefore, information on the density, diversity, and survival of juvenile corals is vital for predicting recruitment success and determining the trajectories of coral populations. This study investigated the dynamics of juvenile corals in Zanzibar in three habitats (reef flat, reef crest, and reef slope) and at three sites (Chumbe, Chunguu, and Mnemba) from November 2010 to May 2012. In total, 10,932 juvenile corals were recorded, which belonged to 13 coral families and 38 coral genera. The mean density of juvenile colonies ranged from 10.3 ± 0.8 to 16.4 ± 1.3 colonies per m2. Among the coral genera recorded, Acropora and Porites were the most prolific. Survival of juvenile corals was high at all three sites, between 60−78%, with the highest survival on the reef slopes of Chumbe. There were significant seasonal differences in juvenile coral survival rates, with the highest survival occurring during the northeastern monsoon. On the western coast, at Chumbe, the co-occurrence of juvenile and adult Acropora implies that self-seeding is occurring. In contrast, the lack of Acropora adults at Chunguu suggests that the site receives recruits from other reefs. On the eastern coast, Mnemba had the lowest survival rates of all three sites, supporting mainly faviids and massive Porites. The results suggest that the western reefs have a more significant potential to recover from disturbances than the eastern reefs.

Keywords
Juvenile corals, density, diversity, survival, Zanzibar, Tanzania.

Cite this paper
Ali M. Ussi, Christopher A. Muhando, Robert van Woesik, Density, diversity, and survival of juvenile corals on reefs of Zanzibar, Tanzania , SCIREA Journal of Geosciences. Volume 7, Issue 1, February 2023 | PP. 1-23. 10.54647/geosciences170235

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