Abstract
Low-density polyethylene (LDPE) is broadly utilized worldwide, increasing more dramatically during the COVID-19 pandemic, and the majority ends up in the aquatic environment as microplastics. The influence of polyethylene microplastics (LDPE-MPs) on aquatic ecosystems still needs further investigation, especially on microalgae as typical organisms represented in all aquatic systems and at the base of the trophic chain. Thereby, the biological and toxicity impacts of LDPE-MPs on Chaetoceros calcitrans were examined in this work. The results revealed that LDPE-MPs had a concentration-dependent adverse effect on the growth and performance of C. calcitrans. LDPE-MPs contributed the maximum inhibition rates of 85%, 51.3%, 21.49% and 16.13% on algal growth chlorophyll content, φPSII and Fv/Fm, respectively. The total protein content, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities were significantly increased at 25 mg L−1 LDPE-MPs by 1.37, 3.52, 2.75 and 1.84 folds higher than those of the controls to sustain the adverse effects of LDPE-MPs. Extracellular polymeric substance (EPS) and monosaccharides contents of C. calcitrans were improved under low concentration of LDPE-MPs, which could facilitate the adsorption of MPs particles on the microalgae cell wall. This adsorption caused significant physical damage to the algal cell structure, as observed by SEM. These results suggest that the ecological footprint of MPs may require more attention, particularly due to the continuing breakdown of plastics in the ecosystem.
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•Studying the interactive effect of LDPE-MPs on Chaetoceros calcitrans has never been done previously.•LDPE-MPs significantly reduced the growth and photosynthetic efficiency of this diatom.•The advert effect of LDPE-MPs on C. calcitrans is concentration-dependent.•Antioxidant enzyme activities of C. calcitrans were improved under LDPE-MPs treatments.•Various physiological and biochemical changes were recorded in the algal cells exposed to LDPE-MPs concentrations.