Mangrove forest: An important coastal ecosystem to intercept river microplastics.

The research on transportation of river microplastics (MPs) mainly focuses on the estimations of the total contents of river MPs entering the ocean, while the related transportation processes and influence factors were still largely unknown. In our study, the role of mangrove forest, a special tropical ecosystem in the estuary, on the transportations of MPs from rivers to ocean was explored. Except for the ND river with the absence of mangrove forest, the MPs collected from the water sample of the river upstream were much higher than their corresponding downstream (p < 0.05), with the interception rate of riverine MPs by mangrove forests ranging from 12.86% to 56% in dry season and 10.57%-42% in rainy season. The MPs with the characteristics of high density, larger size and regular shape were more easily intercepted. Furthermore, the combined effects of ecological indicators, the properties of mangrove and the hydrodynamic factors jointly determined the interception rates of MPs. This study provides a new perspective and data support for quantifying mangrove forests intercepting MPs in rivers as a factor of MPs retention in global rivers.

Distribution and retention of microplastics in plantation mangrove forest sediments.

Microplastics (MPs) in ocean tides can be effectively intercepted by mangroves, especially sediments, which are considered to be effective sinks. However, the retention of plantation mangrove forests on MPs is still unclear. In this study, the spatial distribution and its implication factors of MPs in surface sediments of plantation mangrove forests were investigated for the first time. In plantation forests, MPs were detected with abundances ranging from 67 ± 21 to 203 ± 25 items/kg, and plantation forests were significantly lower than natural forests at the CJ sampling site (p < 0.05). Plantation forests had fewer fibrous MPs than natural forests (p < 0.05). Furthermore, the MPs abundance showed strong linear relationships with the sand content (p = 0.002, R2 = 0.86) and Aegiceras corniculata biomass (p = 0.001, R2 = 0.84). Partial least squares path modeling analysis (PLS-PM) indicated that these two factors influenced MPs abundance by retaining MPs with fibrous, fragmented, denser and larger-sized characteristics. Our results revealed the differences in MPs abundance and characteristics between plantation and natural mangrove forests, and it is necessary to monitor MPs pollution to provide significant guidance for the restoration of constructed wetlands.