The distribution of epiphytic algae on three Kenyan seagrass species

Abstract

A survey of epiphytic algae attached on the leaves of the seagrasses Cymodocea rotundata Ehrenberg and Hemprich ex Ascherson, Thalassia hemprichii (Ehrenberg) Ascherson and Thalassodendron ciliatum (Forsskal) den Hartog was conducted in intertidal seagrass beds located in Vipingo and Nyali along the Kenyan coast. The aim of the survey was to determine the differences in epiphytic loading on these seagrass species between areas that have different nutrient levels. The study revealed a significant difference in the levels of nitrates, ammonia and phosphates in the water column at the two sites with Vipingo having lower levels of all nutrients. The biomass of T.hemprichii and T. ciliatum and their associated epiphytic algae was higher in Nyali. However the biomass of the C. rotundata was lower in Nyali, though the epiphytic biomass remained the same when the two sites were compared. Rhodophytes dominated in both sites and there were more cyanophytes found on the seagrasses of Vipingo. The data presented in this paper shows that nutrient loading has an influence on the composition and biomass of epiphytic algae growing on these intertidal seagrasses. Vipingo, which had a lower level of nutrient loading, had higher numbers of cyanobacteria while in Nyali, where nutrient loading was higher, there were fewer species of epiphytes seen on the seagrasses.