Marine debris in a World Heritage Listed Brazilian estuary

• Spatio-temporal benthic marine debris variability was studied in a Brazilian estuary.
• Most (93%) debris was plastic; mainly shopping-bag fragments >21 mm.
• There was no significant temporal variability in benthic debris accumulation.
• The most contaminated areas were closest to urban and drainage areas.
• Minimizing marine debris requires integrating local government and civil society.

Using monthly otter-trawl deployments, spatial and temporal variability among the relative densities of marine debris were assessed in the Paranaguá estuarine complex; a subtropical World Heritage Listed area in southern Brazil. During 432 deployments over 12 months, 291 marine debris items were identified; of which most (92%) were plastic, and more specifically shopping bags, food packages, candy wrappers and cups typically >21 mm long. The most contaminated sectors were those closest to Paranaguá city and the adjacent port, and had up to 23.37 ± 3.22 pieces ha−1. Less urbanized sectors had between 12.84 ± 1.49 and 9.32 ± 1.10 pieces ha−1. Contamination did not vary between dry or wet seasons, but rather was probably affected by consistent urban disposal and localized hydrological processes. Marine debris might be minimized by using more environment friendly materials, however a concrete solution requires adequately integrating local government and civil society.