Microalgae–microplastics interactions at environmentally relevant concentrations: Implications toward ecology, bioeconomy, and UN SDGs

Microplastics (MPs) are one of the emerging pollutants, causing potential harm to aquatic ecosystems and serious concern in achieving UN Sustainable Development Goals (SDGs). Realizing the occurrence of varying concentrations of MPs in the environment, this investigation presents multi-dimensional insights into the ecological and bioeconomic implications at environmentally relevant concentrations. We pursued a multi-step approach to gain a comprehensive understanding on the effects of microalgae‒MPs interactions and their expansive implications toward SDGs. Baseline data generated using a model microalga, Raphidocelis subcapitata, and three MPs (polyethylene terephthalate, PET; polyvinyl chloride, PVC; and polystyrene, PS) indicated 10‒15 % reduction in microalgal growth rate relative to the control, pointing to a heightened energy demand. The biochemical impacts displayed concentration-dependent variability. Using the baseline data, we developed a linear regression model to dissect the interaction effects around the primary dimensions of Ecology and Bioeconomy. Notably, a correlation matrix for carbon allocation pinpointed PET as having a more pronounced impact compared to PVC and PS, with the model accounting for 33.72 % of the observed variance. Extending our insights from the model, we adopted an evidence-based methodology to outline the broader implications across the Ecology and Bioeconomy domains, and subsequently identified their associations with specific SDGs. Further probing into microalgae‒MPs interaction effects at environmentally relevant concentration, our model revealed that the selected MPs perturbed the ecological variables. Interestingly, when carbon allocation was assessed to study bioeconomic implications, there were contrasting effects on starch synthesis (beneficially) and lipid synthesis (detrimentally). The present combined analysis revealed that MPs, beyond their traditional association with SDG 14 (Life Below Water), directly and indirectly affect five other SDGs through their interactions with microalgae. This study thus underscores the complex and interconnected nature of MPs pollution at environmentally relevant concentrations and their impacts on ecological and bioeconomic aspects of SDGs, thereby highlighting the urgent need for additional research and effective mitigation strategies.