Seegrass cover and shoot density and benthic macroalgae cover during the experiment in Chwaka Bay (Unguja Island, Zanzibar Archipelago, Tanzania)

Percentage cover and shoot density of seagrasses were measured taking three random points in each plot at each sampling time with 0.25 m2 and 0.01 m2 quadrats, respectively. Percentage cover was included as the only variable for the measurement of benthic macroalgae as macroalgae could not be assessed by shoot density. The Braun-Blanquet scale was used for the cover measurements (Mueller-Dombios and Ellenberg 1974), consisting of a scale of 8 numbers each one referring to an interval of percentage cover. The scale goes as follows: 0.1 = < 5% solitary, 0.5 = < 5% sparse, 1 = < 5% numerous, 2 = cover ≥ 5% - ≤ 25%, 3 = cover > 25% - ≤ 50%, 4 = cover > 50 - ≤ 75%, and 5 = cover > 75%. The cover categories were transformed into the midpoint cover range (Braun-Blanquet 1964). The final units is the percentage cover (%) of each seagrass species and macrolalgae in the quadrat. Shoot density was measured counting the individual shoots of the two seagrass species within the 0.01 m2 quadrat (Number of shoots per 0.01 square meters). The number of shoots were then standarized by square meter to obtain the final shoot density (number of shoots/m2).