VOLUME 19 (Supplement)

Microplastic distribution and polymer composition across seagrass-associated matrices in tropical seagrass ecosystems: Evidence from Banaybanay, Davao Oriental, Philippines

Microplastic pollution poses an escalating global threat to marine ecosystems, with coastal habitats such as seagrass beds being particularly vulnerable. Seagrass meadows provide critical ecological services, including carbon sequestration, nursery habitats for marine life, and shoreline stabilization, yet their integrity is increasingly compromised by plastic contamination. This study investigated the occurrence and environmental implications of microplastics in the seagrass beds of Barangay Mogbongcogon, Banaybanay, Davao Oriental. Sampling was conducted at low tide in November 2024 across four environmental matrices: seagrass blades, seagrass-bed sediments, water column, and beachline sediments. Microplastics were quantified and categorized by color and morphology using a stereomicroscope, while polymer types were identified with an Agilent Cary 630 FTIR spectrometer. Results revealed black microplastics as the most dominant, particularly in the water column (15.38%) and sediments (13.46%). Fibers were the most prevalent morphology (21.15%) in both sediments and water, while polyester was the dominant polymer type, notably in seagrass beds (SB) sediments (21.15%) and water (17.31%). Seagrass sediments recorded the highest microplastic abundance (n=19), whereas seagrass blades showed the highest density (0.056 particles per 10 blades). Statistical analysis indicated no significant associations between color or morphology and environmental matrices, although polymer type demonstrated a significant relationship (χ²(4, N=52) = 10.592, p = 0.032). The accumulation of microplastics within seagrass habitats highlights the vulnerability of coastal ecosystems to persistent plastic pollution. These findings highlight the urgent need for enhanced monitoring and stricter waste management to address plastic pollution in seagrass ecosystems. Community-based interventions are also essential to reduce plastic inputs and safeguard the ecological functions of coastal environments.