Dissolved organic carbon leaching from plastics stimulates microbial activity in the ocean

Abstract

More than 5.25 trillion of plastic pieces have been estimated to be floating at the sea surface (Eriksen et al., 2014). Plastic marine debris on beaches and floating in seawater is exposed to solar UV radiation undergoing weathering degradation (Andrady, 2011). It can develop surface cracks and fragment into progressively smaller particles reaching microscopic sizes (< 5 mm, microplastics). Detrimental effects of plastics on marine organisms at different trophic levels have been widely reported, making plastic pollution a global environmental concern. However, the impacts of plastic debris on the lowest trophic levels, such as the microbial food web, remain enigmatic. Plastic is known to leach organic compounds to the aquatic media (Suhrhoff et al., 2016). The smaller the piece, the higher its surface to volume ratio and its potential for leaching. However, the contribution of plastic leaching to the dissolved organic carbon (DOC) pool in the ocean and its impact on the lowest trophic levels, such as the microbial food web, is still unknown. In this work we present experimental evidence that plastics release dissolved organic carbon (DOC) into the ambient seawater stimulating the activity of heterotrophic microbes. About 60% of the DOC leached from plastics is available to microbial utilization in less than 5 days. It is predicted that plastic waste entering the ocean will increase by 10-fold over the next decade (Jambeck et al., 2015), resulting in an increase in plastic-derived DOC that could have unaccounted consequences for the activity of marine microbes and for the ecosystem