Darwin?s paradise contaminated by marine debris. Understanding their sources and accumulation dynamics.

Plastic pollution is a global environmental threat. Remote and pristine islands are not safe from this threat. Here, we estimated beach macro-(>25 mm), meso-(5-25 mm) and microdebris (<5 mm) levels in Galapagos and studied the role of environmental variables determining their accumulation. The vast majority of beach macro-and mesodebris were plastic, while most microdebris were cellulosic. The levels of beach macro-, meso-and microplastics were notably high and comparable with exceptional levels reported in contaminated areas. Oceanic currents and the anthropic pressure of use of the beach were the main factors that determined the level of macro-and mesoplastics, as well as the diversity of items, with more types of items in the beaches facing the pre-dominant current. Microplastic levels were mainly driven by the slope and, to some extent, the grain size of the sediment in the beach. The absence of relationship between the levels of large size debris and the level of microplastics suggests that secondary microplastics that accumulated in the beaches were previously fragmented before arriving to the beach. This differential influence of environmental factors in the accumulation of marine debris according to their size should be taken into account when developing strategies to mitigate plastic pollution. Additionally, this study reports high levels of marine debris reported in a remote and protected area such as Galapagos, which are comparable to areas with direct sources of marine debris. This is especially worrying for Galapagos since the sampled beaches are cleaned at least annually. This fact highlights the global dimension of this environmental threat that demands further extensive international commitment to conserve some of the last paradises on Earth.

Automated summary

Plastic pollution poses a global environmental threat, even to remote and pristine islands such as Galapagos. This study assessed the levels of beach debris in Galapagos and identified the environmental factors influencing their accumulation. The levels of plastic debris on the beaches were alarmingly high and comparable to those in highly contaminated areas. Macro- and mesoplastics were mainly affected by oceanic currents and human activities, while microplastics were influenced by the slope and sediment grain size. The study highlights the urgent need for international commitment in mitigating plastic pollution and protecting pristine habitats.