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Seasonal and spatial variations in shoreline plastic debris in Cenderawasih Bay National Park, Indonesia: A risk to ecologically sensitive areas

Marine Pollution Bulletin 2026
Ridwan Sala, Duaitd Kolibongso, Luki Sembel

Summary

Researchers found plastic trash (mostly common food-packaging plastics like polypropylene and polystyrene) washing up on beaches inside a protected marine park in Indonesia at similar or even higher levels than beaches outside it, showing that simply drawing park boundaries on a map doesn't stop pollution from drifting in. This matters because plastic that accumulates in these waters breaks down over time into microplastics, which can enter the seafood people eat and have been linked to potential health concerns — meaning protecting fish and shellfish sources requires broader coastal cleanup efforts, not just protected-zone labels.

Study Type Environmental

Marine protected areas (MPAs) face persistent challenges from mobile plastic pollutants. This research quantified the spatial and seasonal patterns of shoreline plastic debris within Cenderawasih Bay National Park (CBNP), Indonesia, and analyzed the polymer composition. Surveys of macro- and mesoplastics were conducted at 13 beach sites (inside vs. outside MPA boundaries) across two seasons, and FTIR spectroscopy was applied to 64 particles. Results revealed substantial spatial heterogeneity, with densities ranging from 0.01 to 4.98 items.m. A significant season × beach zone interaction (χ = 18.30, p < 0.001) indicated reduced vertical gradients during the wet season. Polymer analysis identified polypropylene (PP, 40.6%), polyethylene (PE, 26.6%), and expanded polystyrene (EPS, 20.3%) as the dominant types. Mean densities inside the MPA (0.13 ± 0.06 items.m) were numerically lower than outside (0.48 ± 0.36 items.m), though not statistically significant (p = 0.185). These findings indicate that spatial variability within this semi-enclosed bay system is high, and MPA administrative boundaries alone did not correspond to measurable reductions in plastic accumulation. Results underscore the importance of integrated land-sea management approaches in tropical coastal systems.

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