Plastic contamination in commercially valuable decapods caught near a major Australian urban centre

Plastic contamination can have adverse impacts on marine biota, yet broad assessments are lacking in many species and regions globally, including decapod crustaceans in Western Australia (WA). This study examined microplastics in the digestive tracts, and plasticisers (phthalate esters and bisphenols) in muscle tissue and hepatopancreas of four commercially valuable species of decapods: Portunus armatus (blue swimmer crab, n =20), Panulirus cygnus (western rock lobster, n =10), Hypothalassia acerba (champagne crab, n =10) and Chaceon albus (crystal crab, n =9). Decapods were caught at depths between 9 and 677 m at five locations within ∼50 km of the shoreline of a large urban centre (Perth, WA) in 2022. Approximately 49 % of individuals examined contained microplastics with a total of 43 microplastics 700 μm (median) in length found. There were, on average, 0.88 ± 0.20 (standard error) microplastics per individual (MPs individual⁻¹) and 0.20 ± 0.04 microplastics per wet weight (g) of digestive tract. Hypothalassia acerba had a significantly higher occurrence (90 %) and abundance of microplastics (2.30 ± 0.70 MPs individual⁻¹) compared to the other species examined despite being caught in deeper offshore waters. Conversely, higher concentrations of phthalate esters (di-n-butyl phthalate/di-(2-ethylhexyl) phthalate) were detected in muscle tissue of P. armatus collected from two nearshore locations. Microplastic contamination was within lower limits of reports from other decapod studies and may be more influenced by species-specific feeding ecology and plastic in capture methods rather than environmental contamination. However, phthalate esters may accumulate in muscle tissue of nearshore species from environmental exposure rather than ingested microplastics. This study is the first to assess plastic contamination in commercially valuable wild-caught decapods in WA. Although contamination levels might be considered low compared to other seafood globally, the emerging spatial patterns of contamination warrant further investigation, particularly to better understand differences in exposure pathways between microplastics and chemical additives.