Deciphering the behavior and fate of microplastics in coastal aquatic environments: A comprehensive review illuminating coastal dynamics and driving mechanisms

The coastal zone is a highly complex and dynamic interface connecting terrestrial, riverine, and marine ecosystems. Furthermore, the intricate interplay of physical, geochemical, biological, and hydrological processes in coastal aquatic environments adds to the complexity of the environmental behavior of microplastics (MPs). This review provides a comprehensive overview of the main features of coastal zones related to the behavior and fate of MPs at first. The recently reported MP fluxes from different watersheds to the coastal ocean are summarized, and the controversy in estimating riverine MP fluxes is discussed. It then summarizes the present knowledge of the environmental dynamics, eventual fate, interaction with other particles and organisms, and natural weathering of MPs in three types of highly distinctive coastal aquatic environments (coastal waters, estuarine waters, and coastal lagoons), along with their driving mechanisms. These findings are discussed by combining insights from the major coastal features related to hydrology, meteorology, topography, and geochemistry. The role of MP properties on the environmental behavior and fate of MPs is also addressed. Data-based analyses of changes in research trends, research types, and research perspectives were conducted to identify potential research gaps. Five existing knowledge gaps and future perspectives in terms of research subjects and research approaches are proposed to improve the evaluation of the coastal fate of MPs and develop potential mitigation strategies for MP pollution. • Riverine MP fluxes are summarized and estimation controversies are discussed. • Mechanisms of MP behavior are distilled with highlights for each study identified. • Most studies focus on coastal and estuarine waters, while few lagoon explorations. • Hydrological, meteorological, topographical, and geochemical features are critical. • Dataset analyses have identified potential research gaps and future perspectives.