Identifying the river sources and the ocean dynamics of floating plastic in the Galápagos Archipelago

Abstract

The increase of ocean plastic in the Gal ́apagos Archipelago receives more and more attention in recent years. However, the sources and the potential processes that cause the locally found plastic remain unknown. In previous research, the emerged plastic on Gal ́apagos coastlines is proved to be more likely from external sources. Among all the land-based plastic sources, riverine plastic inputs to the ocean are considered the main sources. In this research, we attribute the Gal ́apagos plastic to the major riverine sources on the west coastlines of America based on a Bayesian inference framework. Rivers in Panama Bight and Surrounding Regions are the most likely sources. We also found that most of the particles from the Panama Bight and Surrounding Regions only arrive in the Gal ́apagos from January to April. Particles from North Humboldt Current System also show an episodic nature of arrivals, but the arrival time is more spread throughout the years. Using a high-resolution ocean surface currents model, we simulate the pathways of virtual floating plastic particles from the river sources to the Gal ́apagos region. We analyzed the pathways and potential ocean dynamics that cause the episodic arrivals. A Panama Jet Current is first defined in this research and is considered to be responsible for most of the plastic arriving in the Gal ́apagos from the Panama Bight and Surrounding Regions. Humboldt Current is expected to transport most of the particles from North Humboldt Current System sources to the Gal ́apagos. Attributing the riverine sources and identifying the ocean transporting dynamics help to better understand the episodic nature of arriving particles in the Gal ́apagos Archipelago. Eventually, we are one step closer to predicting the arrival time of plastic in the Gal ́apagos Archipelago.