Micro/nanoplastic-induced stress in microalgae: Latest laboratory evidence and knowledge gaps

Pollution by micro- and nanoplastics (MNPs) is a major concern today, with direct consequences for human health and the environment. Microalgae, among the main primary producers in aquatic ecosystems, suffer from MNPs contamination due to the worrying amount of plastic waste and its persistence in the environment. This problem has mobilized international organizations and raised awareness among the scientific community for the identification of effective solutions. Policies aimed at reducing plastic products, waste management, and recycling are attempting to limit this problem; however, plastic pollution appears to be irreversible. Therefore, a critical analysis of the effects of MNPs on various microorganisms (e.g., microalgae) is urgently needed. Therefore, the objective of this review was to identify the impact of micro- and nanoplastics on microalgal populations, based on the currently available literature. Particular attention was paid to available laboratory studies on MNPs effects on microalgae physiology - as growth rate, pigment content, photosynthetic activity, oxidative stress - and morphology, with the aim of providing an update on the state of the art.