## 3 Results
### Oxidative Stress Biomarkers Indexes  
To evaluate the applicability of these biomarkers in multivariate indexes, towards a better communication of the overall effect of each tested compound, three index approaches were undertaken: the Integrated biomarker response (IBR) index; the principal component analysis (PCA)-based index; and the bioeffect assessment index (BAI). The IBR index applied to biomarker results on propranolol and SDS contaminant exposure gradient, showed no significant variance between the exogenous concentrations tested (Figure 2A,D respectively). Nevertheless, a trend can be noticed for both pollutants, as the highest index values reflected higher concentrations. For the glyphosate exogenous concen  
Figure 1: Canonical analysis of principal components plots of the diatom cells exposed to propranolol (**A**), fluoxetine (**B**), Ibuprofen (**C**), glyphosate (**D**), and SDS (**E**) at different exogenous concentrations, having the biomarker values as classifying variables. Data sources are available in Table 1.  
tration gradient, IBR scores showed significant increases on index values at 250 \(\mathrm{\SIUnitSymbolMicro g}\) L\({}^{-1}\) and 500 \(\mathrm{\SIUnitSymbolMicro g}\) L\({}^{-1}\) exposure concentrations (Figure 2B), akin to fluoxetine (Figure 2C) delivering a significantly higher index value at 80 \(\mathrm{\SIUnitSymbolMicro g}\) L\({}^{-1}\) concentration, suggesting a significant dose-response tendency for both pollutants. Concerning exposure to ibuprofen (Figure 2E), the IBR index revealed a significantly higher score at the maximum tested concentration of 300 \(\mathrm{\SIUnitSymbolMicro g}\) L\({}^{-1}\), and in fact, this increase reflects a high significant positive trend alongside the exogenous ibuprofen gradient. Regarding PCA-based index results for propranolol exposure, a significantly lower value was found in cultures exposed to 0.3 \(\mathrm{\SIUnitSymbolMicro g}\) L\({}^{-1}\), whilst the highest significant value was verified at 150 \(\mathrm{\SIUnitSymbolMicro g}\) L\({}^{-1}\) of propranolol concentration (Figure 3A). For glyphosate and fluoxetine exposure (Figure 3B,C respectively), the PCA-based index attributes a  
Figure 2: Integrated biomarker response (IBR) index of _Phaeodactylum tricornutum_ cells exposed to different contaminants and concentrations. (**A**) Propranolol. (**B**) Glyphosate. (**C**) Fluoxetine. (**D**) SDS. (**E**) Ibuprofen. Average \(\pm\) standard deviation, n = 3, different letters indicate significant differences at \(p<0.05\). significantly higher score at the maximum concentrations of 500 \(\upmu\)g L\({}^{-1}\) and 80 \(\upmu\)g L\({}^{-1}\), respectively, evidencing a positive correlation with both exogenous concentrations of these contaminants. Concerning SDS detergent (Figure 3D), PCA-based index scores did not show any significant variance under the increasing contaminant exposure gradient. On the other hand, in relation to ibuprofen (Figure 3E), significant and approximate high index values are presented for cultures exposed to 0.8 \(\upmu\)g L\({}^{-1}\) ibuprofen and all the concentrations above. For the propranolol exposure gradient, the BAI index provided similar results as the abovementioned PCA-based index, where a significant low index value is attributed to the minimum exogenous concentration of 0.3 \(\upmu\)g L\({}^{-1}\), and a significant index value increase was registered under the application of 150 \(\upmu\)g L\({}^{-1}\) of propranolol, underlining a positive trend for dose-response (Figure 4A). Regarding glyphosate, BAI was unsuccessful to provide significant values for the evaluation of antioxidant stress response under this  
Figure 3: Principal component analysis (PCA)-based index of _Phaeodactylum tricornutum_ cells exposed to different contaminants and concentrations. (**A**) Propranolol. (**B**) Glyphosate. (**C**) Fluoxetine. (**D**) SDS. (**E**) Ibuprofen. Average \(\pm\) standard deviation, n = 3, different letters indicate significant differences at \(p<0.05\). contaminant exposure gradient (Figure 4B).