Seaweed farming pressure affects seagrass and benthic macroalgae dynamics in Chwaka Bay (Zanzibar, Tanzania)

Abstract Farming of Eucheuma denticulatum is a major activity in Zanzibar affecting seagrass ecosystems primarily through shading and trampling. The aim this study was to test the impacts trampling during seaweed farming on meadows composed by Halophila stipulacea Thalassia hemprichii their associated benthic macroalgae. Areas covered these species were selected for building farms three treatments: farm plots (with effects), effects only), control no or effects). Reduction light within recorded over 9 weeks. Percentage cover seagrasses macroalgae shoot density measured 12 weeks assess impact activities. Light significantly reduced 75 90% end growth cycle. H. , despite its capacity rapid growth, affected combination under treatment, while climax T. unaffected. Due decline increased suggesting change community dynamics. In contrast, had negative effect as an isolated disturbance, which suggests that are more resistant than would likely dominate macrophyte conditions.