When algae meet plastic: An invisible crisis in aquatic ecosystems

Aquatic ecosystems are particularly vulnerable to microplastics (MP) pollution, with an estimated 70–80% of MPs in water bodies originating from terrestrial sources. Among aquatic organisms, algae play a crucial role as primary producers, contributing to approximately 45% of global primary production and forming the base of many aquatic trophic chains. However, MPs pose a significant ecological threat to algae, potentially disrupting ecosystem homeostasis. MP interactions with algae occur through surface adsorption, biofouling, and cellular uptake mechanisms, leading to several physiological and biochemical impacts. These include reduced photosynthetic efficiency, increased reactive oxygen species production, altered endocytosis pathways, and the potential for hydrophobic toxins to enter algal cells. While some algae may exhibit resilience, more sensitive species face growth inhibition and reduced diversity, which could have cascading effects throughout the food web. Current methodologies for studying MP-algae interactions rely on microscopic and spectroscopic techniques, including optical microscopy, scanning electron microscopy, atomic force microscopy, Fourier transform infrared, and Raman spectroscopy. However, many of these methods lack standardization and sensitivity when applied to complex biological matrices, highlighting the need for improved detection techniques. Despite being impacted by MP pollution, algae also present a promising avenue for MP mitigation. Their bioindicative properties could support novel approaches for monitoring water quality and pollution levels, including MP contamination. Additionally, algae-based phycoremediation strategies offer potential solutions for removing MPs from aquatic environments. Addressing the identified knowledge gaps, we highlight the potential of algae in protecting and managing aquatic ecosystems in the face of increasing plastic pollution.