Modelled broad-scale shifts on seafloor ecosystem functioning due to microplastic effects on bioturbation

Abstract

Many studies have found that microplastic (MP) is increasing in marine sediments and threatening benthic species' health. However, the links to changes in ecosystem function have yet to be made. The study investigates this linkage between MP contamination and ecosystem functions using experimental observations to parametrize bioturbation coefficients (Db) in a simplified transport-reaction model. Bioturbating species play an essential role in regulating nutrient cycling in marine sediments, and their interaction with MP can be upscaled to an ecological level. In the MP-contaminated sediment, organic matter accumulates in the oxic sediment zone leading to a cascading effect that stimulates aerobic respiration by 18%. The composition of bioturbators modulates this shift in the ecosystem functioning. Maldanid worms, typically classified as deep burrowing upward-conveyor belt feeders, became less active, and the Db was reduced by 30% with the additive of 0.02 g MP cm− 2 at surface sediment. The tellinid bivalve, usually classified as a medium-depth burrower, surface deposit feeder, and bioirrigator, retained its particle mixing behaviour in MP-contaminated systems. This study provides a mechanistic insight into the impact of MP and indicates that the functional role of bioturbating species should be involved in assessing the global impact of MP.