Plastic pellets: understanding their dynamics and impacts on the coastal environment

Abstract

Plastics are materials that have been widely used in modern society. Among them, microplastics (plastics smaller than 5 mm in diameter) have been raising concerns due to their high capacity for dispersion and accumulation, which can be widely found in coastal regions worldwide. Plastic pellets are raw materials for plastic products. Pellets are small in size and have a granular shape. They can be lost during industrial and transportation processes. Several studies have reported the presence of these materials in the coastal environment, their capacity for sorption of chemical contaminants, and the impacts of ingestion and exposure of pellets on marine organisms. This study aimed to test the toxic effects of plastic pellets on benthic macrofauna organisms on sandy beaches under natural conditions. It also contributed to the understanding of their dispersion and accumulation patterns in the coastal zone and their ability of sorbing hydrophobic chemical contaminants. For this, in situ and laboratory experiments were conducted to expose Excirolana armata to plastic pellets. Chemical contributions were made through an oil spill simulation experiment in the laboratory, followed by chemical analyses and passive sampling of pellets on beaches using aerial drone images. Under environmental conditions, mortality was observed at the pellet’s lowest densities and increased intraspecific interactions of cannibalism and aggressiveness of the organisms tested. However, organisms with fast life cycles tend to acquire resistance to these stressors. Furthermore, plastic pellets can transport hydrophobic contaminants, especially PAHs. Naphthalene, phenanthrene, and chrysene were the main PAHs adsorbed and potentially carried by pellets. Finally, we proved that it is possible to use aerial drone images to monitor plastic pellets on sandy beaches, which is a thousand times more effective than the traditional active field methods.