Interactions between phytoplankton species and micro/nano-plastics and heavy metal contamination.

Micro/nanoplastics (MNPs) have attracted the attention of researchers because of their toxicity and increasing abundance in natural ecosystems, especially in marine ecosystems. Similarly, heavy metals pose a significant threat to living organisms due to their toxicity. Waste generated by anthropogenic activities, including heavy metals, MNPs, and other contaminants, is often discharged into water bodies or ends up there unintentionally. Recently, phytoplankton have shown promising results in water treatment for these pollutants, with an ability to adapt to and overcome the toxicity of MNPs and heavy metals, depending on the concentration of these contaminants. Microalgae can remove heavy metals through biosorption, bioaccumulation, and biotransformation, sometimes converting them into less toxic forms, making them useful for bioremediation applications. Additionally, microalgae can aggregate MNPs via adsorption, thus reducing their concentration in the medium over time. However, beyond a threshold concentration, these pollutants can cause lethal damage to microalgae, and it is necessary to limit the simultaneous exposure of microalgae to multiple pollutants as they can interact synergistically. Toxic effects of heavy metals and MNPs include inhibited photosynthesis, decreased population growth, cell deformation, as well as altered enzymatic and genetic activities. The relationship and interactions between MNPs, heavy metals, and phytoplankton are explored herein to deepen our understanding and enable better utilization of phytoplankton in bioremediation of aquatic ecosystems.