Polystyrene nanoplastics trigger changes in cell surface properties of freshwater and marine cyanobacteria

Abstract

Anthropogenic pressures on aquatic ecosystems have led to threats, including nanoplastics, defined as plastic particles less than 1 μm in diameter. This is concerning as cyanobacterial abundance is expected to increase under rising temperatures and carbon dioxide levels. Cyanobacterial cell surfaces are significant in nutrient and metal uptake and cycling; negatively charged functional groups and extracellular polymeric substances (EPS) help promote calcium carbonate formation along cell surfaces. Yet, the impacts of nanoplastics on cyanobacterial physiology and surface properties remain unclear. Here, we investigated the effects of polystyrene nanoplastics on cell growth, morphology, and surface properties of marine Synechococcus sp. PCC8806 and freshwater Spirulina platensis, crucial primary producers and players in many biogeochemical processes, under environmentally relevant nanoplastic concentrations. Nanoplastic aggregation and elevated secretion of EPS minimized negative impacts on growth and morphology by reducing potential nanoplastic–cell interactions. Polystyrene nanoplastics modified cell surface compositions by increasing polysaccharide and lipid contents by up to 35% and 37% in Synechococcus and Spirulina, respectively. Additionally, cell wall thickness increased by 15–20 nm for both cyanobacterial species. Together, these findings demonstrated the impacts of nanoplastics on cell surfaces and the coping mechanisms cyanobacteria employ against polystyrene nanoplastics.