<p> Electronic Supplementary Material</p><p>Ocean acidification and rising temperatures may increase biofilm primary productivity but decrease grazer consumption: evidence from a mesocosm experiment</p><p>Bayden D. Russell, Sean D. Connell, Helen S. Findlay, Karen Tait, Stephen Widdicombe, Nova</p><p>Mieszkowska</p><p>1 Table S1. Summary of an ANOVA testing for the combined effects of time of pre-exposure </p><p> of Grazer to experimental conditions (2-week v. 5-month exposed), Temperature (14 v. </p><p>18 ºC) and CO2 (380 v. 750 v. 1000 ppm) on the percentage cover of biofilm consumed </p><p> during the experiment. Significant p-values in bold.</p><p>Source of variation Sum of squares df Mean squares F P Grazer 4824.38 1 4824.38 20.76 0.0001 Temperature 634.14 1 634.14 2.73 0.1072 CO2 3127.24 2 1563.62 6.73 0.0033 Grazer × Temperature 605.11 1 605.11 2.60 0.1153 Grazer × CO2 545.98 2 272.99 1.17 0.3204 Temperature × CO2 335.51 2 167.75 0.72 0.4927 Grazer × Temperature × CO2 229.42 2 114.71 0.49 0.6145 Residual 8365.45 36 232.37</p><p>2 Table S2. Summary of ANOVAs testing for the combined effects of Temperature (14 v. </p><p>18 ºC) and CO2 (380 v. 750 v. 1000 ppm) on the percentage cover of biofilm consumed by (a)</p><p>5-month and (b) 2-week pre-exposed grazers during the experiment. Significant p-values in </p><p> bold.</p><p>Source of variation Sum of squares df Mean squares F P (a) 5-month pre-exposed Temperature 1239.08 1 1239.09 4.68 0.044 CO2 3138.29 2 1569.15 5.92 0.011 Temperature × CO2 534.02 2 267.01 1.01 0.385 Residual 4768.72 18 264.93 (b) 2-week pre-exposed Temperature 0.17 1 0.17 0.00 0.977 CO2 267.47 2 267.47 1.34 0.287 Temperature × CO2 15.46 2 15.46 0.08 0.926 Residual 199.82 18 199.82</p><p>3 Table S3. Summary of an ANOVA testing for the combined effects of Temperature (14 v. 18</p><p>-1 -1 ºC) and CO2 (380 v. 750 v. 1000 ppm) on the metabolic rates (μmol O2.g .h ) of Grazers pre-</p><p> exposed for different times (2-week v. 5-month pre-exposed). Significant p-values in bold.</p><p>Source of variation Sum of squares df Mean squares F P Grazer 0.002 1 0.002 0.03 0.844 Temperature 0.233 1 0.233 4.25 0.047 CO2 0.021 2 0.105 0.19 0.827 Grazer × Temperature 0.005 1 0.005 0.09 0.758 Grazer × CO2 0.112 2 0.056 1.02 0.383 Temperature × CO2 0.150 2 0.075 1.37 0.265 Grazer × Temperature × CO2 0.005 2 0.002 0.04 0.953 Residual 1.532 28 0.055</p><p>4 Table S4. Summary of an ANOVA testing for the combined effects of Temperature (14 v. </p><p>18 ºC) and CO2 (380 v. 750 v. 1000 ppm) on the percentage cover of biofilm on ungrazed </p><p> settlement panels. Significant p-values in bold.</p><p>Source of variation Sum of squares df Mean squares F P (a) Acclimatized Temperature 7920.67 1 7920.67 48.22 <0.0001 CO2 700.00 2 350.00 2.13 0.1477 Temperature × CO2 208.44 2 104.22 0.63 0.5417 Residual 2956.89 18 164.27</p><p>5</p>