Microplastic accumulation in Halophila ovalis beds in the Swan-Canning Estuary, Western Australia

Small ephemeral seagrass (Halophila ovalis) beds in the Swan-Canning Estuary, Western Australia, were sampled to determine if microplastics attach to seagrass blades and accumulate in higher concentrations in seagrass sediment compared to bare sediment. Three microplastics were observed attached to sampled seagrass blades (n = 108). Microplastics had a mean concentration in seagrass sediments of 1000 ± 100.37se particles kg and in bare sediment of 972 ± 92.19se particles kg. ATR FTIR further verified 64.2 % of subsample particles as plastic (n = 28). This is the first known study to identify microplastics within the leaf canopy of H. ovalis however we could not support our hypothesis that this seagrass species acts as a sink for microplastic particles in sediments, as seen in studies on other seagrass species. The ability for seagrass habitats to trap and accumulate microplastics in sediments is likely influenced by species morphology, seagrass canopy density and life history.