Overall, across trial 1, MP addition had an overall marginally significant effect on protist abundance (repeated measures ANOVA F_2,27=0.24, P<0.0540). In addition, protist abundance varied significantly over the course of the trial (F_6,22=1.50, P<0.0013) (Figure 3A). The treatment with the highest concentration of MPs tended to have the smallest number of protists after day 6 since the onset of the trial. In trial 2, there was no overall difference between the two MP addition treatments throughout the course of the trial (F_1,18=0.081, P<0.2433) (Figure 3B). However, time had a significant effect on abundance as demonstrated by the significant decline in abundance after day 10 (F_8,11=59.36, P<0.0001) (Figure 3B).