Are mangroves hotspots of marine litter for surrounding beaches? Hydrodynamic modeling and quali-quantitative analyses of waste in southeastern Brazil

Abstract

The present study investigated the hypothesis that the marine litter found on the beaches of Santos, in Brazil, may have originated from the mangrove located in the adjacent estuary, acting as a hotspot. To this end, we performed quali-quantitative analyses of the waste found in the beach environments (beached and discarded litter) and the mangrove, as well as hydrodynamic modeling, to verify the influence of the tides on waste transport and the level of contamination according to the Clean Coast Index (CCI). The beached waste presented a similar composition to the items found in the mangrove, corroborated by multivariate analyses and Spearman’s correlation. The hydrodynamic conditions revealed that tidal currents transport waste from the interior of the mangrove to the beaches through the Santos Channel, therefore indicating that the mangrove itself acts as a marine litter hotspot. This problem needs to be managed on a macro-scale by public management agencies, not just locally.