Seagrass abundance in Changuu Island (Unguja Island, Zanzibar Archipelago, Tanzania)

We mapped the seagrass meadows in the study area to calculate the total area covered by each seagrass species and the extent of the overgrazing of T. gratilla. The mapping was performed in low tide with a Garmin GPSmap 78s and a transect tape, making a total of six transects parallel to the coast and 20 perpendicular to the coast to form a grid. We recorded patches of seagrass species directly in the GPS by marking the change in the benthic communities along each transect. The meadows were categorized by species and further sub-categorized as overgrazed or not-overgrazed. A meadow was defined as overgrazed when the shoots in the meadow were lacking leaves and meristems except for sparsely distributed ungrazed individual shoots. All data points were transferred to the software Quantum GIS (Version 2.10.1 Pisa). We constructed polygons over the seagrass meadows with the data and the plug-in Open Layers and calculated the total cover area per seagrass species (square meters) and the percentage of the total covered by each seagrass species.