## 3 Results
### Experiment 1  
The main objective of this experiment was to evaluate the response of _Phaeocystis antarctica_ and _Prorocentrum_ sp. to iron and vitamin B\({}_{12}\) limitation. In the case of the _Prorocentrum_ sp., the Chl-a content increased from 16.56 \(\upmu\)g L\({}^{-1}\) (\(\pm\)0.40) on Day 1 to 89.71 \(\upmu\)g L\({}^{-1}\) (\(\pm\)2.81) on Day 16 of the DFB treatment (Figure 3). The Fv/Fm ratio was recorded as 0.56 (\(\pm\)0.02) on Day 1 and remained high until Day 8, before decreasing to 0.26 (\(\pm\)0.02) on Day 16. An opposite trend was observed for \(\sigma\)PSII at 440 nm, which increased from 8.48 nm\({}^{2}\) (\(\pm\)0.18) on Day 1 to 10.10 nm\({}^{2}\) (\(\pm\)0.20) on Day 8, and then decreased slightly to 8.82 nm\({}^{2}\) (\(\pm\)0.19) on Day 16. In the -B12 treatment, the Chl-a content was maintained around 16.77 \(\upmu\)g L\({}^{-1}\) (\(\pm\)0.55) for the first seven days, before exhibiting a sharp increase to 132.22 \(\upmu\)g L\({}^{-1}\) (\(\pm\)2.78) on Day 16. The Fv/Fm ratio showed a similar trend to that of Chl-a, presenting a value of 0.57 (\(\pm\)0.02) on Day 1 and remaining around \(\sim\)0.54 until Day 8, before decreasing to 0.30 (\(\pm\)0.02) at the end of the experiment (Figure 3). The \(\sigma\)PSII at 440 nm increased from 8.22 nm\({}^{2}\) (\(\pm\)0.18) on Day 1 to 10.20 nm\({}^{2}\) (\(\pm\)0.20) on Day 11, and then decreased slightly to 9.33 (\(\pm\)0.19) on Day 16. The Chl-a content and Fv/Fm in the CTRL treatment exhibited the same trend as in the -B12 treatment. The Chl-a content exhibited the lowest value of 14.59 \(\upmu\)g L\({}^{-1}\) (\(\pm\)0.52) on Day 1 and the highest value of 131.24 \(\upmu\)g L\({}^{-1}\) (\(\pm\)2.67) on Day 16, whereas Fv/Fm ranged from 0.54 (\(\pm\)0.02) on Day 1 to 0.29 (\(\pm\)0.02) on Day 16. The \(\upsigma\)PSII at 440 nm ranged from 8.20 nm\({}^{2}\) (\(\pm\)0.18) on Day 1 to 10.05 nm\({}^{2}\) (\(\pm\)0.20) on Day 16 of this treatment (Figure 3). The total cell number increased from 15,000 to 58,000 cells mL\({}^{-1}\), 18,000 to 50,000 cells mL\({}^{-1}\), and 21,000 to 62,000 cells mL\({}^{-1}\) in the DFB, -B12, and CTRL treatments, respectively, from the beginning to the end of the experiment. The pigment/Chl-a ratios for each treatment are presented in Table 1. The most significant differences were observed for the Chl-c\({}_{2}\)/Chl-a ratio among treatments, which were 0.36 (\(\pm\)0.05), 0.34 (\(\pm\)0.03), and 0.01 in the DFB, -B12, and CTRL treatments, respectively. The Perid/Chl-a ratio also differed among treatments, exhibiting values of 1.40 (\(\pm\)0.02), 1.30 (\(\pm\)0.05), and 1.27 (\(\pm\)0.02) in the DFB, -B12, and CTRL treatment, respectively. Figure 3: Experiment 1. Changes in chlorophyll-a (Chl-a) concentration (\(\upmu\)g L\({}^{-1}\)), maximum PSII photochemical efficiency (Fv/Fm), and maximum PSII effective absorption cross-section (\(\upsigma\)PSII) (nm\({}^{2}\)) in _Prorocentrum_ sp. under different treatments. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline  & **Lines** & **Chl-c/** & **Chl-c/** & **Perid/** & **Bu/** & **Fuco/** & **Hex/** & **Viola-like/** & **Luf/** & **\(\mathbf{\beta}\)-car/** & **Hex** & **Hex** & **Period:** & **D/(D4 + D0** \\  & **Growth** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-a** & **Chl-c** & **Hex** & **\(\mathbf{\times}\mathbf{100}\)** \\ \hline _Proenctrum sp._ & **DFB** & 0.00 & 0.36 & 1.40 & - & - & - & 0.02 & - & 0.01 & - & - & - & - & 5.55 \\  & **-B12** & 0.00 & 0.34 & 1.30 & - & - & - & 0.03 & - & 0.01 & - & - & - & 4.75 \\  & **-B12** & 0.00 & 0.34 & 1.30 & - & - & - & 0.03 & - & 0.01 & - & - & - & 4.62 \\  & **-B12** & 0.00 & 0.34 & 1.27 & - & - & - & 0.03 & - & 0.01 & - & - & - & 4.62 \\ \hline _P.