A microplastic meal: a baseline assessment of microplastic polymer presence within manta-ray (Mobula alfredi) feeding grounds at D'Arros Island and the St. Joseph Atoll

Abstract

Microplastic ingestion by reef manta rays ( Mobula alfredi ) is a threat to their health and population stability. Seychelles' outer islands are vital habitats for M. alfredi but nothing is known about marine microplastic pollution in the area. Using plankton tows from D'Arros Island and St. Joseph Atoll – a key aggregation site, we quantified microplastic polymer type and relative abundance from locations where reef manta rays were actively feeding. We found polybutylene terephthalate (PBT, 1079 particles, 66%) to be the most abundant polymer using our screening technique. A polymer concern assessment identified polyurethane (PU), polyacrylonitrile (PAN), polyvinyl chloride (PVC) and PBT as “Very High” concern polymers that warrant further attention. We find no significant relationship between total microplastic abundance and zooplankton biomass indicating M. alfredi does not ingest relatively greater quantities of MPs while feeding at this aggregation site.