Student Project Figures Figure 12 Figure 12: Average optical density (absorption) of algae cells present within artificial water (± standard error (SE)) over time (minutes), for three different treatments and one artificial seawater control (blue line). Three concentrations of microbeads were pipetted into the inhalant siphon of the ascidian, Pyura stolonifera (n=4/treatment) to test for an effect on feeding activity. The low (red line), medium (green line) and high (purple line) concentration of microplastics used in this study corresponded to 0.05g/ml, 0.1g/ml and 0.15g/ml, respectively. Water samples were taken every 30 minutes (including time zero) and optical density was measured. There was a significant correlation between the density of algae cells present (optical density) in the water and the concentration of microplastics pipetted directly into the ascidian (ANCOVA, n=4/treatment: treatment x time F 1, 12 = 2.062, P = 0.0337). Figure 12