Satellite Monitoring of Marine Litter in the Adriatic-Ionian Basin during 2015-2021

Abstract

Aim: To analyze the spatiotemporal distribution and accumulation patterns of floating marine litter in the Adriatic Sea from 2015 to 2021 using satellite observations, with particular focus on identifying regional variability and dominant transport mechanisms.

Methods: In this observational study, we used satellite data from the Copernicus Sentinel-2/MultiSpectral Instrument L1C system to estimate marine litter presence across the Adriatic Sea from July 2015 to September 2021. The dataset includes records of pixels per litter windrow (PLW), representing spectral reflectance indicators of floating plastic-like debris. We performed analyses on annual and monthly scales, focusing on four zones: Italy (zones A and B), Croatia (zone C), and Albania (zone D). We assessed variability using boxplot metrics and interpreted spatiotemporal patterns in the context of oceanographic features, wind patterns, and riverine inputs.

Results: Zone A had consistently higher PLW values across the study period, making it the most polluted area. Litter was probably transported along the western Adriatic coast by the Western Adriatic Current (WAC) toward the south, with partial redistribution toward the eastern coast. Zones B and D showed pronounced annual and seasonal variability, with peaks in 2017, 2019, and 2021, while zone C showed less consistent patterns. Monthly trends revealed increased litter presence in warmer months, coinciding with higher tourist activity and riverine discharges. There was a marked increase in the PLW difference between zones A and B in two periods, 2015–2017 and 2018–2021, potentially due to litter sinking, WAC meandering, or cleanup efforts.

Conclusions: Satellite remote sensing can help us identify marine litter hotspots and understand their seasonal and spatial dynamics. Our findings highlight persistent pollution in the northern Adriatic and the role of currents and riverine inputs in shaping litter distribution. Long-term monitoring and integrated waste management strategies are essential for effective mitigation.