Investigating microplastic contamination and biomagnification in a remote area of South Australia

Context Microplastics are widespread in aquatic ecosystems and are commonly recorded in water, sediment and a broad spectrum of marine biota. Yet, the extent to which organisms ingest microplastics directly or indirectly by trophic transfer is largely unknown. Aims This study characterises microplastic abundance across intertidal water, sediment, and marine biota species of different trophic levels, and investigates whether biomagnification occurs. Methods Water, sediment, molluscs, crustaceans and fish were sampled from a single area in southern Australia. Key results Microplastics were recorded in 35% of water, 45% of sediment and 39% of biota samples. Plastic load was 0.36 ± 0.08 microplastics g-1 DW for sediment, 0.50 ± 0.17 microplastics L-1 for water, and 0.70 ± 0.25 microplastics individual-1 for biota. Biomagnification was not found, although similarities in plastic characteristics across biota may imply trophic transfer. Most of the microplastics were fibres (97.5%) of blue, black and transparent colour. Spectral analysis (µ-FTIR) indicated that polyester (50%) and polyethylene (42.3%) dominated the polymer compositions. Conclusions There were no significant differences in microplastic contamination among biota species, with no biomagnification identified. Implications We provide information on biomagnification of microplastics alongside a still uncommon characterisation of contamination in water, sediment and biota.