Estimations of densities of marine litter on the fringing reefs of Mayotte (France – South Western Indian Ocean) - impacts on coral communities

Abstract

The present study was carried out at 22 stations located on the fringing reefs of the island of Mayotte inside the perimeter of the Marine Natural Park of Mayotte (PNMM). The average assessment of the number of samples of marine litter (ML) collected at these stations was 3.9 ± 1.3 ML per 500 m2 in winter and 3.8 ± 1.1 ML per 500 m2 in summer. Plastic ML was dominant, representing approximately 92% of the litter collected at the stations for the two seasons. The majority was plastic ML from fishing gear (lines, nets etc.). Station 18 presented remarkable average densities of 39 ± 4.2 ML per 500 m2 for the two seasons and differed from the other stations in that the ML came solely from the catchment areas, with a majority of aluminium ML (56%). Approximately half the coral colonies coming into contact with ML presented an impact dominated by the category of “Broken or abraded colonies”, with 25% of the colonies being impacted. The colonies most severely impacted by ML were branch or table corals, with the greatest majority for the present study being of the genus Acropora.