Asian Journal of Environment & Ecology

Sedimentation can hinder coral recruitment and early survival, but its variation across Zanzibar reefs is poorly quantified for restoration planning. We assessed the temporal and spatial variability of sedimentation rates at three reef sites on Unguja Island, Zanzibar (Chumbe, Changuu, and Mnemba reefs), and their relationships with juvenile coral density and juvenile coral survival, during five seasonal periods in 2011–2012 using sediment traps and repeat juvenile coral surveys. During the study period, sedimentation rates at Chumbe ranged from 0.97 mg cm^-2 day^-1 in November 2011-January 2012 and 9.07 mg cm^-2 day^-1 in May-July 2011, from 1.69 mg cm^-2 day^-1 in May-July 2011 to 5.47 mg cm^-2 day^-1 in February-April 2011 at Changuu, and from 0.7 mg cm^-2 day^-1 in September-November 2011 to 1.4022 mg cm^-2 day^-1 in November 2011-January 2012 at Mnemba. On average, sedimentation rates were higher at Chumbe reef (4.67 mg cm^-2 day^-1) relative to Changuu (3.67 mg cm^-2 day-¹) and were lowest at Mnemba reef (1.22 mg cm^-2 day^-1). Sedimentation rates were highest and lowest on reef slopes and crests, respectively. High sedimentation rates at Chumbe were observed from May-July 2011, and low rates were measured from November 2011 to May 2012. At Changuu, high sedimentation rates were recorded between January and May 2012 and a low rate between May and October 2011. At Mnemba, high sedimentation rates were recorded between January 2012 and May 2012, and low rates were recorded between July 2011 and November 2011. There were no relationships between sedimentation rates, juvenile coral densities, and survival in reef sites. The results suggest that sedimentation was low and did not negatively impact juvenile coral densities or survival. Furthermore, the May-July period is not suitable for coral transplants at Chumbe, as is February-May at Changuu reef. The findings provide actionable guidance for scheduling reef restoration.