COASTAL FRONTS AS INDICATORS FOR HOTSPOTS OF FLOATING MARINE DEBRIS

Abstract

Floating marine debris (FMD) pollution is a considerable concern due to its negative impacts on valuable coastal marine environments. Frontal zones formed through various oceanographic processes are known to drive FMD distribution and abundance. Since fronts serve as aggregators of both FMD and marine organisms, the identification of coastal FMD accumulation zones in relation to fronts is imperative. Building on previous research on the relationship between frontal frequency and FMD density, this research aims to identify coastal FMD hotspots by examining not only frontal frequency but also processes influencing frontogenesis through statistical modelling of remote sensing data. This 10-year study (2002-2012) was conducted in the coastal waters of the northeast USA because of concurrent availability of real time FMD and satellite imagery datasets. The FMD dataset was collected by the Sea Education Association (North Atlantic), and sea surface temperature (SST) fronts were derived from daily MODIS nighttime SST (1 km x 1 km) using the Cayula and Cornillon histogram method. Concurrent remote sensing data on currents (direction and speed), Finite-size Lyapunov exponents (convergence) and bathymetry were also acquired. Of the nine logistic regression models, the four best fit models indicate that coastal fronts and their frontogenesis, including convergence, current directions and velocity, have a significant influence on FMD accumulation. FMD hotspots are identified as areas with the highest average probability of high density (above 500 pieces/km²) FMD accumulation. Results highlight feasible application of statistical model development based on the premise that fronts are used as indicators of FMD hotspots in coastal regions, areas of high biodiversity and economic value around the globe.