Figure 4. Scatter graph of the mea  optical density (OD) values over time (minutes) of the negative ("seawater" [squares]) and positive ("algae" [circles], "microplastics" [crosses]) controls. Purple markers represent OD600 means. Black markers represent OD690 means. Error bars represent the standard deviations of those means. OD values one or more standard deviations from the mean were excluded from analysis as outliers. Dashed black and purple lines represent OD690 and OD600 trendlines. For "seawater", OD600= -1.00 x 10E-05 minutes + 0.0013 (R²= 0.600) and OD690= -1.50 x 10E-05 minutes + 0.0017 (R²= 0.100). For "microplastics", OD600= -1.15 x 10E-04 minutes + 0.0187 (R²= 0.808) and OD690= -1.35 x 10E-04 minutes + 0.0123 (R²=0.748). For "algae", OD600= -7.00 x 10E-05 minutes + 0.0281 (R²= 0.980) and OD690= -6.50 x 10E-05 minutes + 0.0312 (R²= 0.966).