This dataset contains a list of epiphytic macroalgae species and their percentage of coverage on the penumatophores of the mangroves in Gazi Bay, Kenya, sampled during August-September 1989. Also the particle size distribution data from the different transects is noted. The data were digitized by VLIZ from the original report: De Schryver, T. (1990). Epifytische wieren (Bostrychietum) in de mangrove van Gazi Bay (Kenia)= Epiphytic algae (Bostrychietum) in the mangroves of Gazi Bay (Kenya). MSc Thesis. Rijksuniversiteit Gent. Faculteit Wetenschappen: Gent. 99, appendix pp.