Uptake, growth, and oxidative stress responses of Rhizophora mucronata (Poir. in Lam.) propagules exposed to high-density polyethylene microplastics

Abstract

The plastic revolution's contribution to global pollution gives rise to microplastics (MPs), bearing a toll on the marine environment. Knowledge of mangrove exposure to MPs causing adverse effects has yet to be elucidated. Hence, the physiological responses of R. mucronata propagules exposed to ubiquitous High-Density Polyethylene Microplastics (HDPE-MPs) were investigated. The set-up consists of a control (0 mg/L) and an environmentally relevant treatment group (32.65 mg/L), acclimatized and exposed for three months. Scanning Electron Microscopy (SEM) shows agglomeration of HDPE-MPs on root surfaces and translocation to the shoot system of smaller MPs (< 50 μm). Attenuated Total Reflectance Fourier Transform-Infrared Spectroscopy (ATR FT-IR) confirmed uptake in the roots. Root length, count, plant height, foliar area, and oxidative stress biomarkers (carbonyl protein and total chlorophyll) all show significant differences (p < 0.05). Indeed, plastic pollution has detrimental effects on mangroves that may consequently affect mangrove forest diversity and productivity.