Heavy Metal Contamination (Cu and Pb) in Rhizophora apiculata Ecosystems: A Comparative Study between Two Coastal Areas in North Sumatra

Abstract

Mangrove ecosystems are increasingly threatened by heavy metal pollution resulting from rapid industrialization and urbanization. This study aims to analyze and compare the concentrations of Copper (Cu) and Lead (Pb) in the water, sediment, and tissues of Rhizophora apiculata in two distinct coastal areas of North Sumatra: Sicanang Island, Belawan (representing an industrial site) and Sembilan Island, Langkat (representing a conservation site). Samples were analyzed using Atomic Absorption Spectrophotometry (AAS) to determine the distribution and accumulation patterns of these metals. The results revealed that Pb concentrations in the water at both sites ranged from 0.25 to 0.26 mg/l, significantly exceeding the Indonesian national seawater quality standard of 0.008 mg/l. Within the plant tissues, the highest Cu concentration was found in the fibrous roots (up to 1.33 mg/kg), followed by the stilt roots and bark. This distribution pattern suggests that R. apiculata functions as a biological "metal barrier," effectively sequestering pollutants in its root system to protect its physiological functions. These findings underscore the critical state of heavy metal contamination in Belawan’s mangrove ecosystems and highlight the potential of R. apiculata as a bio-indicator for environmental monitoring and a candidate for phytoremediation in contaminated tropical coasts.