## 4 Discussion  
The applicability of global algorithms to the waters off of the Baja California Peninsula was assessed. Both CI and OCx algorithms exhibit similarities for waters with mChl-\(a\) values less than 0.3 mg m\({}^{-3}\) (\(\log_{10}\)(mChl-\(a\)) \(\sim-0.5\)) and a blue/green reflectance ratio of \(\mathfrak{R}\geq 2.5\) (F \(\geq 0.4\)), as depicted in Figure 2. CI is deemed superior for retrievals below 0.15 mg m\({}^{-3}\), while OCx is more effective for higher mChl-\(a\) concentrations (Chl-\(a\geq 0.2\) mg m\({}^{-3}\)) [25]. The CI algorithm includes information on reflectance at 670 nm [10], and therefore, the retrieved Chl-a values show more dispersion than the OCx. Ref. [39] stated that regionalizing the algorithms diminishes the bias, but uncertainties are still important because of the natural variation of the optical properties of phytoplankton, the presence of other optically active components, and the atmospheric correction. These authors found that removing the 443 nm band improved the performance of the Ocx algorithm. However, given that the natural data dispersion surpasses the difference between CI and OCx for mChl-\(a<0.3\) mg m\({}^{-3}\), OCx was deemed more suitable for the region, leading to its selection for regionalization. The proposed regional algorithm has a slightly better fit for the area as compared to Ocx (Table 2). However, the metrics shown in Table 2 analyze the whole of the algorithm. As shown in Figure 3, the divergence between the algorithms is in the extreme conditions of oligotrophic (high R or F, low mChl-\(a\)) and eutrophic waters (low \(\mathfrak{R}\) or \(F\), high mChl-\(a\)). For these conditions, the regional algorithm outperforms the OCx, yielding results with a lower specific SSE for the oligotrophic and eutrophic areas. This discrepancy suggests that the IMECOCAL region's oligotrophic waters possess a higher pigment concentration than the global database used to derive OCx parameters. As Ref. [28] posits, the presence of small cells (cyanobacteria), typical of tropical and subtropical waters in warm waters off of the Baja California Peninsula, could explain this variation. While other factors like particulate matter or continental debris might influence this difference, their sporadic occurrence \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Error** & **CalCOFI 2** & **CI** & **OCx** & **Regional** & \
\begin{tabular}{c} **Bio-Optical** \\ **Properties** \\ \end{tabular} &
\begin{tabular}{c} **Climatic** \\ **Condition** \\ \end{tabular} \\ \hline \(R^{2}\) & 0 * & 0.2640 & 0.4054 & 0.4441 & 0.4473 & 0.4585 \\ \(R^{2}_{a}\) & 0 * & 0.2637 & 0.4046 & 0.4434 & 0.4465 & 0.4579 \\ SSE & 156,141.81 & 450.60 & 364.03 & 340.33 & 338.39 & 331.52 \\ RMSLE & 7.1715 & 0.3853 & 0.3463 & 0.3348 & 0.3339 & 0.3304 \\ AIC & 25,949.82 & 8195.45 & 7553.75 & 7349.37 & 7332.03 & 7267.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The coefficient of determination (\(R^{2}\)), the adjusted coefficient of determination (\(R^{2}_{a}\)), the sum of square error (SSE), the root mean squared logarithmic error (RMSLE), and the Akaike information criterion (AIC) for each of the tested and proposed algorithms. The \(R^{2}\) and \(R^{2}_{a}\) marked with an asterisk were outside of the expected range of \([0,1]\). means their impact is limited to specific situations and data points. As per Ref. [5], OCx is effective in eutrophic areas due to its higher mChl-\(a\) output. However, the IMECOCAL region's data indicates lower mChl-\(a\) values for smaller \(\mathfrak{R}\) values, leading the regional algorithm to produce reduced mChl-\(a\) results. This suggests that the eutrophic zone in the IMECOCAL region has a lower pigment concentration than the global database. The regional algorithm, tailored to the unique oceanographical and optical properties of the area, offers improved predictions for both eutrophic and oligotrophic zones. The segmentation of the database resulted in models with minimal complexity (Equations (10)-(12)).