## 3 Results
### Nutrient Depletion  
A general reduction of nutrients concentration was observed in media where _Ulva_ spp. was cultivated, whatever the season and the cultivation system used (lab-system or IMTA system). The nutrient load of fresh collected effluent varied during each experiment and among experiments (d0 and medium change (MC) in Tables 3 and 4 and Figure 1 and Figure 3), depending on the functioning of the aquaculture. \begin{table}
\begin{tabular}{c c c c c} \hline  & \multicolumn{2}{c}{**SGR**} & \multicolumn{2}{c}{**YIELD**} \\ \hline
**AQUAI** & \multicolumn{2}{c}{_Estuarine_} & \multicolumn{2}{c}{_Coastal_} & \multicolumn{2}{c}{_Estuarine_} & \multicolumn{2}{c}{_Coastal_} \\ _d 4_ & 11.70 \(\pm\) 1.83 & \(-\)0.63 \(\pm\) 5.97 & 4.32 \(\pm\) 0.71 & \(-\)0.16 \(\pm\) 5.97 \\ _d 7_ & 7.84 \(\pm\) 3.83 & 10.52 \(\pm\) 2.94 & 1.77 \(\pm\) 0.95 & 2.15 \(\pm\) 1.30 \\ _d 11_ & 14.48 \(\pm\) 3.52 & 15.33 \(\pm\) 2.87 & 9.00 \(\pm\) 2.93 & 6.30 \(\pm\) 1.46 \\ _d 14_ & \(-\)13.79 \(\pm\) 7.63 & \(-\)5.20 \(\pm\) 4.32 & \(-\)9.19 \(\pm\) 4.99 & \(-\)2.45 \(\pm\) 2.04 \\ _d 18_ & 6.37 \(\pm\) 8.15 & 4.29 \(\pm\) 4.00 & 3.63 \(\pm\) 4.19 & 1.57 \(\pm\) 1.52 \\ _d 22_ & \(-\)6.19 \(\pm\) 4.16 & \(-\)10.17 \(\pm\) 3.74 & \(-\)3.35 \(\pm\) 2.17 & \(-\)3.53 \(\pm\) 0.63 \\ \hline
**AQUAI2** & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ _d 8_ & 3.91 \(\pm\) 0.67 & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ _d 14_ & 2.32 \(\pm\) 1.81 & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ _d 20_ & 1.30 \(\pm\) 1.03 & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ _d 26_ & 1.45 \(\pm\) 1.00 & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \hline \end{tabular}
\end{table} 
Table 2: Specific growth rate (SGR, % day\({}^{-1}\)) and yield (g wet weight/m\({}^{2}\)/day) of _Ulva_ spp. cultivated in fish effluent, for 22 (AQUAI) and 26 days (AQUAI2), in an IMTA-pilot system. In AQUAI, _Ulva_ spp. was collected in _Mondego_ estuary and _Figueira da Foz_ coast in late spring. In AQUAI2, _Ulva_ spp. from _Mondego_ estuary (late autumn) was used. Values are presented as mean \(\pm\) standard deviation, n = 3. \begin{table}
\begin{tabular}{c c c c c} \hline  & \multicolumn{2}{c}{**NO\({}_{3}\)\({}^{-}\)**} & \multicolumn{2}{c}{**NO\({}_{2}\)\({}^{-}\)**} & \multicolumn{2}{c}{**NH\({}_{4}\)\({}^{+}\)**} & \multicolumn{2}{c}{**Si**} \\  & & **(ug N-NO\({}_{3}\)\({}^{-}\)/L)** & **(ug N-NO\({}_{2}\)\({}^{-}\)/L)** & **(ug N-NH\({}_{3}\)/L)** & **(ug Si/L)** \\ \hline _d 0_ & Effluent & 350 \(\pm\) 100 \({}^{\,\text{a}}\) & 51 \(\pm\) 7 & 226 \(\pm\) 24 \({}^{\,\text{a}}\) & 515 \(\pm\) 28 \({}^{\,\text{a}}\) \\ \hline _d 6_ & Control & 50 \(\pm\) 5 \({}^{\,\text{b}}\) & \textless{}12 \({}^{\,\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\texttexttexttexttexttexttexttexttext    }}}}}}}}}}}}}\) & 289 \(\pm\) 11 \({}^{\,\text{b}}\) & 296 \(\pm\) 73 \({}^{\,\text{b}}\) \\  & _Ulva_ spp. & \textless{}40 \({}^{\,\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\texttexttexttexttexttext   }}}}}}}}}}}}}\) & 171 \(\pm\) 4 \({}^{\,\text{c}}\) & 108.6 \(\pm\) 0.1 \({}^{\,\text{c}}\) \\ MC & Effluent & 159 \(\pm\) 91 \({}^{\,\text{a}}\) & \textless{}40 \({}^{\,\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\texttexttexttexttexttext   \texttext{\texttexttexttexttexttexttexttexttexttexttexttexttexttexttexttexttexttexttexttexttexttexttext        \texttexttexttexttexttexttexttexttext     \texttexttexttexttexttexttexttexttext    \texttexttexttexttexttexttexttexttext   { \text  
On experiment LU2, the concentration of nutrients was daily monitored to better understand the removal rate vs removal timing of nutrients. Figure 1 clearly demonstrates the gradual removal of NO3\({}^{-}\), NO2\({}^{-}\) and NH4\({}^{+}\) in media with _Ulva_ spp. in comparison to freshly collected effluent and control. A natural depletion of nutrients can occur as observed in Figure 1 (Control), but the presence of _Ulva_ spp.