Analysis of the contaminant “microplastics” in marine and freshwater ecosystems in the world heritage site Cocos Island National Park, Costa Rica

Microplastics (MPs) defined as ‘small’ pieces of plastic < 5 mm have been found everywhere scientists have looked: in deep oceans; in Arctic snow and Antarctic ice; in shellfish, table salt, drinking water and honey; and drifting in the air or falling with rain over mountains and cities. Nevertheless, considering that oceanic insular environments such as Coco’s Island, are even more vulnerable to plastic pollution because they could retain plastics from the adjacent ocean currents by different meteoceanographic mechanisms; ecologically, they are unique ecosystems in terms of biodiversity and endemism, and, the limited human activity and its remoteness from the mainland, the question arises about the status of contamination in Cocos Island National Park. The purpose of the project was to analyse the presence of MPs in the marine and freshwater ecosystem by comparing samples of biota, sediments and water. Two phases have been carried out; in 2018 the first phase was carried out and the presence of the contaminant in both ecosystems was analysed. The detection of MPs in the marine ecosystem samples was expected due to exposure by marine currents, tourism activities, and discarded fishing gear from illegal fishing activities; however, the presence in the freshwater ecosystem were not expected and the sources of contamination were unclear, also the first phase only focused the survey close to the human activity. In the second phase developed in 2022, an analysis was conducted around the island, with the intention of compare the areas with human presence and areas without human presence to determine if the presence of ranger parks was a significant source of contamination in the freshwater ecosystem and also to determine if the distribution of MPs is consistent around the island or if there are accumulation sites in the two ecosystems. The results obtained indicate that the distribution of MPs in the marine and freshwater ecosystem was consistent around the island; therefore, human activity by staff is not a significant source of MPs. These results prove that issue most be viewed as a planetary boundary threat, therefore, governance strategies must be implemented. Also, a Global Plastic Waste Partnership must be established to determine the path to move forward.