# Mediterranean Aquaponics: Fasting and Refeeding in a Polyculture Aquaponic System
## 4 Discussion
### Plant Growth Performance  
Glasswort (_S. europaea_) is a halophytic plant that is particularly well suited to growth in saline environments. Halophytes employ a range of processes and metabolic adaptations that enable them to flourish in a diverse array of soil salinities, spanning the low levels characteristic of agricultural soils to the exceedingly high levels prevalent in coastal ecosystems [68]. The responses of different species to salinity levels vary, and the optimal level of salinity for growth is dependent on both genotype and environmental conditions. A number of halophytes are capable of attaining optimal growth under conditions of mild to moderate salinity, due to the presence of established physiological adaptations [69]. Additionally, glasswort is included in this category, exhibiting optimal growth at salinities between 12 and 25 g/kg. However, growth is negatively impacted when salinities fall below or exceed this range, for instance, at 0.55 and 72 g/kg [70]. Similarly, ref. [71] determined that glasswort exhibits optimal growth at salinities of 10-22 g/kg. Therefore, the salinity levels utilized in this study are within the optimal range for glasswort growth. The application of fish treatments resulted in notable impacts on the growth parameters of the plants.  
Notably, the glasswort cultivated with treatment B exhibited a greater height than the other two treatments. This increase in height can be attributed, at least in part, to the elevated levels of nitrate in the recycled water. In a greenhouse study conducted by [PERSON] et al. [72] on the related species _Salicornia neei_([PERSON], 1817), a similar number of branches was observed along with slightly taller plants than those in our study, despite the plants being subjected to a salinity of 11 g/kg. With regard to productivity, the yield observed in treatment B (42.38 \(\pm\) 5.66 kg/m\({}^{2}\)) was found to be significantly higher than the yields reported by [73] for the related species _Sarcocornia ambigua_ in co-culture with Pacific white shrimp at a salinity of 16 g/kg.  
The enhanced growth of plants in treatment B can be attributed to the higher nitrogen content observed in their branches, which exhibited statistically significant differences compared to the other treatments, with treatment B showing the highest values. The nitrogen levels measured in this study indicate that _S. europaea_ is a valuable source of protein. Similar nitrogen contents have been reported in _S. europaea_ by [74] and in _Arthrocennum macrostachyum_([PERSON], 1853) by [75].  
Moreover, treatments A and B exhibited markedly diminished ash content in comparison to treatment C. The total ash content observed in this study was significantly lower than the values reported by [74] for the same species (31.2%). A distinctive trait of halophytes is the accumulation of minerals in plant tissues, which is indicated by a high ash content.  
Regarding photosynthetic pigments, the findings revealed significantly elevated levels of chlorophyll A. The chlorophyll A findings were higher than those of [70]. The concentrations of chlorophyll B and carotenoids exhibited no discernible variation across the various treatments. The observed decreases in chlorophyll content are consistent with the findings of [70] at salinity levels exceeding 400 mM NaCl. Additionally, [76] observed that the chlorophyll and carotenoid content of cultivated glasswort is lower than that of glasswort harvested in the field.