Quantifying the Connectivity of Microplastic Pollution in the Texas–Louisiana Coastal Area

Despite the Gulf of Mexico having one of the world’s highest microplastic concentrations, there is a paucity of information regarding the impact of microplastic pollution on its coastal systems. Using a Lagrangian particle-tracking model coupled with a validated 3D hydrodynamic model, we examined the retention and transport pathway of microplastic particles released from major rivers and bayous in Texas and Louisiana to the Gulf of Mexico. Emphasis was placed on retention time within estuaries and connectivity of particles along the coastline past the initial release location. Magnitude of river inflow has significant impacts on how long particles are retained in estuaries, with high flows (within Galveston Bay and eastward) flushing particles out in less than a year while low flows (west of Galveston Bay) often have the majority of particles still retained after the two-year simulation. Single, high flow events are found to decrease the retention time, highlighting the potential of storms to flush microplastics out of estuaries and into the Gulf. Seasonality of shelf current impacts where along the coast microplastics travel and other estuaries they enter. Settling behavior of particles results in increased retention time within estuaries but a comparable impact on coastal areas.