## 4 Results and Discussion
### Effects at Biological Level: ROS  
The enzymatic activity in terms of the superoxide dismutase (SOD) was measured after magnetic field exposure and shown in Figure 6a for species 1 and in Figure 6b for species 2. For Species 1 (_S. obliquus_), the application of SMFs resulted in 26 and 50% less SOD activity relative to the control values for the north and south configurations, respectively. On the contrary, in the case of Species 2 \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Flux Density, \(B_{0}\) (T)**} & **Normalized \(P\),** & **Power, \(P(0)\)** & **Time Constant, \(\tau_{P}\) (s)** & **Coefficient of** \\  & **P(t = 0)/\(P_{0}\)** & **(W) at \(W_{0}=10\) cm/s** & **Time Constant, \(\tau_{P}\) (s)** & **Determination** \\ \hline
0.125 & 0.0156 & \(3.5\times 10^{-4}\) & 387.6 & 0.99864 \\
0.25 & 0.0625 & \(1.4\times 10^{-3}\) & 339.0 & 0.99898 \\
0.375 & 0.1406 & \(3.1\times 10^{-3}\) & 280.1 & 0.99928 \\
0.5 & 0.25 & \(5.0\times 10^{-3}\) & 223.2 & 0.99943 \\
0.75 & 0.5625 & \(1.3\times 10^{-2}\) & 139.1 & 0.99941 \\
1 & 1 & \(2.2\times 10^{-2}\) & 89.8 & 0.99937 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary for the magnitude of the power dissipation, time constant, and the corresponding coefficient of determination for different magnetic flux density values applied to Medium 2. Figure 5: Normalized power dissipation \(P/P_{0}\) in Medium 1 (a) and Medium 2 (b) as a function of the time constant \(\tau_{P}\) for different \(B_{0}\) values. (c) Time constant \(\tau_{P}\) as a function of the magnetic flux density \(B_{0}\) for Medium 1 and 2. (_N. Gaditana_), SOD increased significantly with the SMF treatment reaching a maximum of 1.22 mUmg\({}^{-1}\) with the north and 1.593 mUmg\({}^{-1}\) with the south configuration, meaning significant relative differences of, respectively, 78 and 115% above their control values. In terms of the catalase (CAT) in Figure 7, Species 1 showed 14 and 7.6% less CAD activity compared to the control values for the north and south configurations, respectively. Conversely, Species 2 experimented with changes under SMFs as the CAT levels increased up to 0.13 mUmg\({}^{-1}\) with the north and 0.13 mUmg\({}^{-1}\) with the south configuration, meaning, respectively, relative differences of 29 and 23% with respect to their control conditions. The quantification of metabolites of interest was measured after 96 h of SMF exposure. Figure 8A shows a slight decrease in the production of violaxanthin and lutein with respect to the control (<1%). Figure 8B shows that the abundance of violaxanthin increased by 40.9% compared to the control. Figure 6: Superoxide dismutase activity. (**A**) North and (**B**) south magnet configurations for Species 1. (**C**) North and (**D**) south magnet configuration for Species 2. The * symbol stands for statistical significance \(p<0.005\) with 95% confidence. Figure 7: Catalase activity. (**A**) North and (**B**) south configurations for Species 1. (**C**) North and (**D**) south configuration for Species 2. The * symbol stands for statistical significance \(p<0.005\) with 95% confidence. The results obtained in terms of the enzymatic activity show a clear difference between both microalgae species. In the case of Species 2, SOD increases significantly with respect to the control in both magnet configurations. This behavior can be associated to the oxidative stress that SMFs are causing to the cell culture [59]. Medium 2, being \(\sim\)50 times more conductive than Medium 1, could promote a more effective electron transfer and allowing for a more pronounced ROS formation. In addition, a very important aspect is the structure of the cell. Since it has a rigid wall, it becomes less susceptible to the damage caused by ions, which are driven by magnetic field gradients. The antioxidant defense machinery counteracts the damage by activating antioxidant enzymes such as SOD first and then the non-enzymatic antioxidants such as pigments.