The effect of surface properties on the interactions of particles and marine mucous filters

Free-living suspended cells form the foundation of marine food webs, making suspension feeding a key mode in aquatic ecosystems. Suspension feeders across phyla use diverse filtration mechanisms, often relying on mucus and low-pressure pumps with high filtration efficiencies and self-cleaning capabilities. Traditionally, particle capture was thought to depend on size alone, but recent evidence highlights the importance of physicochemical surface interactions between prey cells and filtration apparatuses. In this study, we investigated the capture of 0.3-3 {micro}m particles by ascidians and found that coating particles with amphiphilic polymers altered their mobility within the mucous filter, affecting capture efficiency. Surface interactions, such as steric repulsion, significantly influence particle mobility and inversely correlate with capture success. Furthermore, we discovered that the mucous filter in ascidians is much thicker ([~]5 {micro}m) than previously believed, functioning as a continuous sheet. These findings suggest a need to reevaluate suspension feeding models, with implications for marine ecosystems and filtration technology development.