# Mapping Subtidal Marine Forests in the Mediterranean Sea Using Copernicus Contributing Mission
## 4 Discussion  
### Capability of Earth Observation to Map Coastal Seascapes with Emphasis on Cystoseira s.l. Forests  
The utilization of the unique PlanetLabs SuperDove CubeSat sensors enabled the selection of optimal imagery during the growth period of _Cystoseira_ s.l. forests and temporal consistency with the field campaign for data collection. This flexibility, combined with a robust field dataset covering all the main habitat types, facilitated the production of accurate maps, surpassing the conventional 80% OA threshold. The spectral separability for _Cystoseira_ s.l. (TD = 1.69) confirmed their distinct spectral profile. In regard to the water quality, the SPM concentration ranged from 0 to 2 g per m\({}^{3}\), which indicates high water column transparency. The seascape classification yielded high thematic accuracy across all benthic classes, with F1 scores ranging from 0.87 to 1.00, demonstrating the effectiveness of the remote sensing workflow applied. Soft bottom habitats, both shallow and deep, were identified with perfect accuracy (UA = 1.00, PA = 1.00), likely due to their spectral uniformity and low structural complexity. _Cystoseira_ s.l. and _Seagrass_ also exhibited strong performance (F1 = 0.94 and 0.93, respectively), although some confusion occurred at habitat interfaces, potentially due to mixed pixels or spectral similarity with adjacent classes such as rocky reefs with other cover and shadows. Rocky reefs with other cover showed comparatively lower accuracy (F1 = 0.87), possibly influenced by substrate heterogeneity, relief-induced shadowing, and spectral overlap with macroalgal assemblages. Mapping accuracy was \begin{table}
\begin{tabular}{c c c c c c} \hline  & _Cystoseira_ s.l. & **Soft Bottoms (Deep)** & _Seagrass_ & **Rocky Reefs** & **Soft Bottoms (Shallow)** \\ \hline
**Mean absolute error (MAE)** & 0.06 & 0.0052 & 0.04 & 0.097 & 0.007 \\
**Root MSE (RMSE)** & 0.17 & 0.02 & 0.13 & 0.21 & 0.046 \\
**Ratio of performance to deviation (RPD)** & 2.37 & 18.66 & 3.005 & 1.87 & 8.72 \\
**Mean error (ME)** & \(-\)0.063 & 0 & 0.018 & 0.04 & \(-\)0.006 \\
**Mean squared error (MSE)** & 0.029 & 0.0005 & 0.018 & 0.046 & 0.002 \\
**Median absolute error (MedAE)** & 0 & 0 & 0 & 0 & 0 \\
**Squared Pearson correlation (r\({}^{2}\))** & 0.89 & 0.99 & 0.89 & 0.73 & 0.99 \\
**Explained variance score** & 0.85 & 0.99 & 0.89 & 0.73 & 0.99 \\
**Coefficient of determination (R\({}^{2}\))** & 0.82 & 0.99 & 0.89 & 0.71 & 0.99 \\ \hline \end{tabular}
\end{table} 
Table 6: Regression metrics from the fraction cover evaluation. \begin{table}
\begin{tabular}{c c c c c} \hline  & _Cystoseira_ spp. & **Soft Bottoms (Deep)** & _Seagrass_ & **Rocky Reefs** & **Soft Bottoms (Shallow)** \\ \hline _Cystoseira_ spp. & 18 & 0 & 0 & 0 & 0 \\
**Soft bottoms (deep)** & 0 & 20 & 0 & 0 & 0 \\ _Seagrass_ & 0 & 0 & 20 & 3 & 0 \\
**Rocky reefs** & 2 & 0 & 0 & 17 & 0 \\
**Soft bottoms (shallow)** & 0 & 0 & 0 & 0 & 20 \\ \hline \end{tabular}
\end{table} 
Table 4: Confusion matrix counts: predicted (rows) vs. observed (columns). \begin{table}
\begin{tabular}{c c c c} \hline  & _Cystoseira_ spp. & **Soft Bottoms (Deep)** & _Seagrass_ & **Rocky Reefs** & **Soft Bottoms (Shallow)** \\ \hline _Cystoseira_ spp. & 18 & 0 & 0 & 0 & 0 \\
**Soft bottoms (deep)** & 0 & 20 & 0 & 0 & 0 \\ _Seagrass_ & 0 & 0 & 20 & 3 & 0 \\
**Rocky reefs** & 2 & 0 & 0 & 17 & 0 \\
**Soft bottoms (shallow)** & 0 & 0 & 0 & 0 & 20 \\ \hline \end{tabular}
\end{table} 
Table 4: Confusion matrix counts: predicted (rows) vs. observed (columns). highest for soft bottom habitats, while _Seagrass_es demonstrated comparable performance to that reported in previous studies utilizing the same satellite constellation [29; 54; 55; 56]. In this study, \"_Seagrass_\" primarily referred to _Posidonia oceanica_. However, the possibility of concomitant occurrence of other species typically found in the periphery of _Poccanica_ meadows, such as little Neptune grass (_Cymodocea nodosa_) or dwarf eelgrass (_Zostera nolteii_), cannot be ruled out. The dominance of _Cystoseira_ s.l.