Distribution of Marine Debris in the Mangroves of a Semi-enclosed Lagoon System

In recent years, marine debris has become a serious environmental concern, particularly for coastal ecosystems such as mangroves. This chapter focuses on Setiu Wetlands (Malaysia), a semi-enclosed lagoon system with some luxuriant mangrove cover vulnerable to plastic entrapment. The assessment was conducted during low tide in dry and wet seasonal periods at three sites, from the upstream (Pulau Layat), midstream (Kampung Pengkalan Gelap), and downstream (Pulau Sutung). Three 25 m long parallel transects, at a distance of 5, 10, and 25 m from the water edge to the back mangrove, were established for each site. All marine debris within 1 m ¥ 1 m quadrats along each transect (25 plots/transect) were observed, collected, and identified. Plastic bags were the most dominant type of marine debris, followed by water bottles and Styrofoam blocks. Plastic bags and water bottles are largely associated with domestic usage (including the chances for a small fraction through tourism activities), while large-sized Styrofoam blocks belong to fishing activities. Notable differences, although not significant, were observed in the findings. Higher accumulation of marine debris in the dry season be linked to reduced water exchange, while its highest entrapment around 10 m inside the forest was due to mixed (Avicennia-Rhizophora) mangrove species with dense pneumatophores and prop root systems. Overall, the abundance of marine debris in Setiu Wetlands was rather low compared to other published reports from mangrove areas in Asia. Enhanced plastic waste management practices are still crucial for mitigating marine debris pollution and conserving the mangroves in Setiu Wetlands.