Marine Water and Sediment Quality Assessment of Mainland Kedah and Langkawi Island Shorelines: A Case Study

Abstract Coastal areas are ecologically, economically, socially, and culturally significant but face environmental challenges that demand sustainable management. This study assessed water and sediment quality along 440 km of shorelines in mainland Kedah and Langkawi Island. Water quality was analyzed through 22 samples collected across the study area, evaluating 24 parameters compared to Malaysian Marine Water Quality Standards (MWQS). Sediment quality was assessed at two sites (S1 and S2) based on heavy metal concentrations, including Nickel (Ni), Copper (Cu), Chromium (Cr), Lead (Pb), Arsenic (As), Cadmium (Cd), and Zinc (Zn). Results showed that the marine water quality ranged from moderate to good along mainland Kedah and good to excellent along Langkawi Island. Faecal coliform levels exceeded 70 cfu/100ml at all stations along mainland Kedah shoreline, indicating pollution concerns. Sediment quality met standards set by Washington Ecology Department, suggesting no major issues. Average Nickel, Lead, and Cadmium concentrations were 41.2, 53.2, and 4.34 mg/kg, respectively, at both sites, while Copper, Arsenic, and Zinc were higher at S1, with maximum values of 72.4, 27.4, and 274.9 mg/kg, respectively. By identifying pollution hotspots and areas of high environmental quality, this study promotes sustainable practices to protect the long-term health of these vital coastal zones.