Microplastic Abundance, Size Distribution, and Polymer Composition in the Open Ocean Surface Layer: A Multi-Gyre Manta Trawl Survey

This study investigates microplastic particle abundance, size distribution, and polymer composition across five major ocean gyres sampled by standardized manta surface trawls within the context of marine pollution science and oceanography, an area of growing scientific importance given its implications for global marine pollution monitoring, source attribution, and plastic pollution treaty science support. Using standardized 335 um mesh manta trawl sampling with ATR-FTIR polymer identification of 24,840 confirmed microplastic particles from 248 stations, we examine plastic debris UV photodegradation and mechanical fragmentation accumulating in convergence gyre convergence zones, with particle abundance inversely scaling with size per power-law fragmentation kinetics in 248 manta trawl stations (48-54 per gyre) collecting 24,840 confirmed microplastic particles sized 0.3-10 mm with FTIR polymer type identification drawn from surface trawls at 248 stations within five major ocean convergence gyres at latitudes 20-45 deg N/S during 2016-2019 research cruises. Results indicate that mean abundance 128,400 pieces/km2 across all gyres with North Pacific highest (284,000 pieces/km2) and Indian Ocean lowest (48,400 pieces/km2); 72.4% of particles are secondary fragments <1 mm with polyethylene (48.4%) and polypropylene (28.4%) dominant polymers (p < 0.001), with 128,400 pieces/km2 mean; North Pacific 284,000; 72.4% fragments <1mm as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to marine pollution science and oceanography and carry actionable implications for the design of programs and policies targeting global marine pollution monitoring, source attribution, and plastic pollution treaty science support.