G. edulis was collected from canals at Brackishwater Culture Research Centre, Gelang Patah, Johor Bahru, Malaysia and U. lactuca collected during low tide at Danga Estuary, Johor Bahru, Malaysia. Healthy thalli of the macroalgae were collected and transported to the laboratory in a polystyrene box filled with water samples from the respective site. In the laboratory the macroalgae were washed under running water and cleaned of epiphytes. Healthy thalli of macroalgae were separated to reduce the risk of contamination during the experiments. Snapshots of the outdoor experimental setup are displayed in Fig. 2.