## 4 Discussion  
### Temperature as the Main Driver of Seedling's Trait Responses  
Temperature was the dominant driver of _E. acoroides_ seedling's trait responses within this experiment, and there were no synergistic effects in the interaction of both factors. Therefore, our initial hypothesis was rejected. In general, our results showed that seedlings of seagrass _E. acoroides_ perform better at the higher temperature treatments, as bigger leaves with high maximum leaf lengths, leaf SA, and weight were always observed. This is in accordance with what was observed in the field in previous studies with adult individuals, as the temperature was also the major factor influencing the growth rate with increasing values above 30 \({}^{\circ}\)C [27]. This pattern of an enhanced size of leaves under an increasing temperature has also been observed in seedlings of _Zostera marina_[19] while detrimental or no changes were observed in above-ground traits of other persistent species with big-size seedlings, such as _P. oceanica_, at sub-lethal temperatures [15,17]. The optimum temperature for photosynthesis in adult _E. acoroides_ from Philippines ranged between 24 and 33 \({}^{\circ}\)C, with an optimal temperature set at 27 \({}^{\circ}\)C [35] or 33 \({}^{\circ}\)C [30]. Thus, based on the photosynthetic potential of PSII (_Fv/Fm_) observed in this study, seedlings are still within the species' optimal range. However, \(rETR_{\max}\) (photosynthetic capacity) and Ek (saturation irradiance) values were higher in the seedlings' grown at regimes of 27 \({}^{\circ}\)C than in the ones grown \begin{table}
\begin{tabular}{c c c c c} \hline
**Dependent Variable** & **Factor** & **TSS** & _F-Value_ & _p-Value_ \\ \hline
**Leaves** & & & & \\ \hline Sucrose & Temperature & 0.000 & 0.051 & 0.87 \\  & CO\({}_{2}\) & 0.000 & 2.030 & 0.197 \\  & Interaction & 0.000 & 0.170 & 0.692 \\ \hline Starch & Temperature & 0.036 & 2.363 & 0.168 \\  & CO\({}_{2}\) & 0.027 & 1.785 & 0.224 \\  & Interaction & 0.069 & 4.558 & 0.069 \\ \hline Seeds & & & & \\ \hline Sucrose & **Temperature** & **0.012** & **7.464** & **0.013** \\  & CO\({}_{2}\) & 0.002 & 1.470 & 0.239 \\  & Interaction & 0.000 & 0.017 & 0.897 \\ \hline Starch & Temperature & 0.088 & 1.781 & 0.197 \\  & CO\({}_{2}\) & 0.031 & 0.633 & 0.436 \\  & Interaction & 0.013 & 0.270 & 0.609 \\ \hline \end{tabular}
\end{table} 
Table 6: Results of analysis of variance (two-way ANOVA test) of the effects of temperature and CO\({}_{2}\) on the sucrose and starch content of the leaves and seeds (Figure 6). _p_-Values in bold are statistically significant (<0.05) (TSS: Total sum of squares). at 31 \({}^{\circ}\)C, showing that some down-regulating mechanism might be potentially initiated at high target temperatures. These detrimental effects on photo-physiology were also observed in _P. oceanica_ seedlings at increasing temperatures [14; 17]. Even though, _rETR_ values were higher than in younger seedlings of the same species [18], which indicates a higher independence in maternal reserves in comparison to the younger leaves. Leaf nitrogen content under regimes of 27 \({}^{\circ}\)C was within the range observed in adult _E. acoroides_ plants under natural conditions in South-East Asia meadows [34]. Contrary to this, carbon content was lower than in younger _E. acoroides_ seedlings [18] showing that internal reserves were being used. This has also been observed in _P. oceanica_ seedlings of a similar age [20]. Both leaf nitrogen and carbon contents, however, were also significantly affected by an increasing temperature. Lower leaf nutrient content under regimes of 31 \({}^{\circ}\)C was observed, which was likely related to nutrient reabsorption, often occurring under higher growth rates due to dilution of nutrients in leaf tissue [54; 55]. On the contrary, higher carbon content in below-ground tissues were detected at the high target temperature, which has been shown in previous studies with _P. oceanica_ and _E. acoroides_ seedlings [17; 18].