Light intensity on the water surface and at the bottom of the water column during the experiment in Chwaka Bay (Unguja Island, Zanzibar Archipelago, Tanzania)

A Li-Cor 1500 with a PAR (photosynthetically active radiation) sensor was used to measure the degree of shading by the seaweed growing over the seagrass meadow at each sampling time. Three random points were chosen within the seaweed farm plots and outside the farmed plots (control). The underwater PAR sensor (μmol photons m−2 s−1) was placed just below the water surface and at the seagrass canopy, while recording also the water depth at the canopy.