Evaluating the Potential of Mangrove Phytoremediation for Mitigating Coastal Water Eutrophication in Macao SAR: A Field and Mesocosm Study

Eutrophication due to anthropogenic nutrient inputs is a serious issue in many coastal and marine environments. Mangrove plants form unique intertidal forests at the edge of the land and sea, forming multifunctional ecosystems that provide an array of services, such as the phytoremediation of pollutants. The purpose of this study was to evaluate the levels of nutrients (PO 4 3− , NO 2 − , NO 3 − , NH 4 + ) in the coastal waters around Macao SAR, in areas with and without mangroves, in order to assess their phytoremediation potential. The work was reinforced through a mesocosm experiment with various treatments with and without mangroves. The results of the field investigations indicated a high degree of eutrophication in the coastal waters of Macao, with average values of 0.30 mg/L, 0.09 mg/L, 23.8 mg/L, and 0.36 mg/L of phosphate, nitrite, nitrate, and ammonium, respectively. There were no apparent significant differences in the levels of nutrients in areas with and without mangroves, which was most likely caused by the conditions during sampling as well as the density of the mangrove forest. The mesocosm experiments, however, revealed a clearer effect of the presence of mangroves (and sediments) in the degradation of nutrients. Therefore, it is highly recommended to plant more mangroves to help mitigate coastal water eutrophication in the area as a phytoremediation approach.