Impact of microplastics on aquatic flora: Recent status, mechanisms of their toxicity and bioremediation strategies.

Abstract

The accumulation of microplastics (MPs) in aquatic environments has occurred pervasively. The MPs affect almost all the aquatic plants including the aquatic microorganisms, ultimately disturbing the food chain. Aquatic flora attracts MPs due to the formation of several chemical bonds and interactions, including hydrogen bonds, electrostatic, hydrophobic, and van der Waals. Consequently, they hinder plant growth when adsorbed to the plant surfaces. Moreover, the major metabolic processes, including photosynthesis, reproduction, and nutrient uptake, get affected due to the pore-filling of plant tissues and the blockage of sunlight. Subsequently, prolonged exposure to MPs inflicts excessive generation of reactive oxygen species (ROS), ultimately accelerating programmed cell death. However, it has been realized that bioremediation techniques, including phytoremediation, can effectively mitigate MPs pollution by adsorbing or accumulating MPs by 25-80% at the laboratory scale. In this connection, several microorganisms play a vital part in deteriorating MPs due to their ability to form biofilm over the MPs' surface. Additionally, the secretion of extracellular enzymes such as styrene monooxygenase, styrene oxide isomerase, phenylacetaldehyde dehydrogenase, PETase, etc., facilitates the degradation of MPs. Moreover, the inherent ability of plants to adsorb and accumulate MPs can be utilized to manage the MPs in aquatic ecosystems. However, there is a dearth of literature and comprehensive reviews highlighting the potential of bioremediation strategies. Therefore, apart from addressing the impact of MPs on aquatic flora, this article attempts to elucidate the physical and chemical basis of plant-plastic interaction and the potential strategies aquatic flora including microorganisms employ to mitigate plastic pollution.