Microplastic in Sediments and Ingestion Rates in Three Edible Bivalve Mollusc Species in a Southern Philippine Estuary

Plastics are now a major environmental concern worldwide with their widespread contamination and accumulation. Microplastic particle (< 5 mm) is an emerging pollution issue as it is being detected worldwide in aquatic and terrestrial ecosystems, but relatively little is known in tropical regions. This study determined the (1) abundance of microplastics in sediment and (2) in situ and laboratory ingestion rates of microplastics in three scarcely studied tropical bivalve mollusc species ( Donax sp., Meretrix meretrix , and Katelysia hiantina ) in Panguil Bay, Southern Philippines. A total of 2258 microplastic particles (62.72 ± 18.31 items/m 2 ) were found on the sediment samples. Filament/fiber is the most abundant type of microplastic in terms of morphology, while black and blue are the dominant colors of microplastic particles. There were 1495 microplastic particles (4.15 ± 3.37 particles/clam) present in the clam tissues, of which polypropylene (PP) and rayon (RY) polymers are the most common, whereas K. hiantina (707 particles) showed the highest amount of microplastics. The number of ATR-FTIR-confirmed polymer types in the wild clams is greater than that in the sediments. The study reveals abundant microplastics in sediments and in the three species of bivalve individuals from the wild. All clams ingested low-density polyethylene (LDPE) microplastic particles in the laboratory. The mean number of LDPE microplastic particles ingested by clams is 4.62 ± 2.40 particles/clam/7days, with the highest value observed in K. hiantina . Additionally, Donax sp., M. meretrix , and K. hiantina could ingest high densities of 40–60-μm microplastic particles.