Mémoire

Abstract

Every year, 14 million tons of plastic reach the ocean, where they threaten ecosystems and human health. The Black Sea, a semi-enclosed basin with strong riverine inputs, offers a unique setting to investigate microplastic transport. Using the NEMO-BAMBHI model and Lagrangian simulations, we explored four scenarios: homogeneous releases (2D and 3D with sinking) and riverine releases with different sinking velocities. In the 2D simulation, accumulation hotspots appear along the southwestern coast, with particles largely following the Rim Current. Adding sinking (3D) significantly alters dispersion: particles display clustered trajectories, reduced beaching, and oscillations likely linked to vertical dynamics. Riverine scenarios reveal strong local retention near river mouths. Across all cases, accumulation consistently overlaps with ecologically sensitive areas such as the northwestern shelf and the Turkish coast. Sinking strongly reduces lateral transport, riverine inputs dominate accumulation patterns, and vulnerable coastal regions remain key hotspots. Continued investigation of vertical processes is essential to refine predictions of microplastic fate in enclosed seas.