Are mangroves hotspots for marine litter among selected coastal ecosystems of Mauritius, an oceanic island in Western Indian Ocean?

Abstract

Marine litter is a growing threat and its impacts are much more consequent on oceanic states. This study investigated the status of marine macro- and meso-litter in selected mangrove, seagrass and coral ecosystems of Mauritius island. The objective was to comparatively analyse the abundance and composition of marine macro- and meso-litter among the ecosystems and to determine their potential sources, contributing causative factors and identify any hotspot of litter pollution. Snapshot study was carried out in summer months from September 2020 to March 2021 in six sites situated in the north and south-west coastlines of Mauritius. 100 m2 quadrats were surveyed for macro-litter along 70 m transects placed in the three inundation zones of the mangrove ecosystems, while triplicate 800 m2 underwater belt transects were surveyed in benthic seagrass and coral ecosystems. For meso-litter sampling in mangroves, sediment samples were collected from nine 0.25 m2 quadrats along transect lines in each of the three inundation zones, while the coring technique was used for sampling in seagrass and coral ecosystems. Mean macro-litter density was highest at Melville mangrove ecosystem (5.60 ± 0.07 items/100 m2). Melville was also the only site where meso-litter was recorded. Plastics made up the highest composition for macro-litter (58%) and meso-litter (79%) in all coastal ecosystems studied. Mangrove ecosystems were found to be the main hotspot for both macro- (89.2%) and meso-litter (100%) contamination. The findings of this study further contribute to the data available on marine litter in coastal ecosystems, and can be used for the development of more efficient ecosystem-adapted prevention and remedial strategies in an island context.