## 3 Results
### Primary Producer Biomass and Elemental Composition
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Primary Producer**} & \multirow{2}{*}{\begin{tabular}{c} **Seasonal** \\ **phase** \\ \end{tabular} } & \multirow{2}{*}{**B**} & \multirow{2}{*}{**BSi**} & \multirow{2}{*}{**N**} & \multirow{2}{*}{**P**} & \multirow{2}{*}{**BSi:N**} & \multirow{2}{*}{**BSi:P**} & \multirow{2}{*}{**N:P**} \\ \hline \multirow{5}{*}{Filamentous algae} & \multirow{2}{*}{Early} & 62 & 3.36 & 0.86 & 0.07 & & & \\  & & (19) & (1.03) & (0.26) & (0.02) & 0.98 & 62 & 63 \\ \cline{2-10}  & \multirow{2}{*}{Mid} & 48 & 1.41 & 0.23 & 0.01 & & & \\  & & (21) & (0.40) & (0.06) & (0.00) & 1.54 & 141 & 91 \\ \cline{2-10}  & \multirow{2}{*}{Late} & 30 & 0.75 & 0.19 & 0.01 & & & \\  & & (22) & (0.20) & (0.05) & (0.00) & 0.98 & 106 & 108 \\ \hline \multirow{5}{*}{\
\begin{tabular}{c} **Vallisneria spiralis** \\ \end{tabular} } & \multirow{2}{*}{Laves} & 99 & 99 & 3.64 & 0.22 & 0.10 & 4 & 37 \\  & & (36) & 1.00 & 2.35 & 0.13 & 0.21 & 9 & 40 \\ \cline{2-10}  & \multirow{2}{*}{Late} & 117 & 0.91 & 2.45 & 0.10 & 0.19 & 10 & 54 \\ \cline{2-10}  & & \multirow{2}{*}{Early} & 60 & 0.48 & 2.92 & 0.16 & 0.08 & 3 & 40 \\ \cline{2-10}  & & & (22) & 0.50 & 2.61 & 0.17 & 0.10 & 3 & 34 \\ \cline{2-10}  & & & (13) & 0.33 & 3.32 & 0.16 & 0.05 & 2 & 46 \\ \hline \multirow{5}{*}{
\begin{tabular}{c} **Vallisneria** \\ \end{tabular} } & \multirow{2}{*}{Laves} & \multirow{2}{*}{Lately} & 4 & n.a. & n.a. & n.a. & n.a. & n.a. & n.a. \\ \cline{2-10}  & & & (27) & 0.64 & 2.82 & 0.27 & 0.11 & 3 & 23 \\ \cline{2-10}  & \multirow{2}{*}{Late} & 54 & 0.85 & 1.95 & 0.15 & 0.22 & 6 & 29 \\ \cline{2-10}  & & & (17) & 0.89 & 1.95 & 0.15 & 0.22 & 6 & 29 \\ \cline{2-10}  & \multirow{2}{*}{Roots} & \multirow{2}{*}{Early} & n.a. & n.a. & n.a. & n.a. & n.a. & n.a. & n.a. \\ \cline{2-10}  & & & (15) & 0.61 & 1.83 & 0.12 & 0.17 & 6 & 34 \\ \cline{2-10}  & & & & & & & & & \\ \cline{2-10}  & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Biomass (B, g DW m\({}^{-2}\)), biogenic silica (BSi, %), nitrogen (N, %) and phosphorus (P, %) content and BSi:N, BSi:P and N:P molar ratios in filamentous algae and macrophytes (leaves and roots). All data represents mean \(\pm\) standard error (standard error in parenthesis), n.a. = not available. Concurrently, the N:P molar ratio increased from 29 in spring to 49 in late summer. At VS, both BSi:N and BSi:P in macrophytes biomass were much lower, i.e., 0.06 to 0.19 (BSi:N) and 2.5 to 9.2 (BSi:P). Furthermore, the BSi:P ratio was greater in the leaves than in the roots of _V. spiralis_. The standing stocks of BSi, N and P (Figure 2) retained by primary producer biomass varied between sites and throughout the season. The BSi stock was greater at RS than at VS. At RS, BSi underwent an abrupt decrease in midsummer, attaining a value similar to VS in late summer. In contrast, at the BS site, BSi associated with MPB progressively increased and was much greater than at RS and VS, especially from midsummer onwards. At the VS site, BSi was mostly retained by the leaves, while only a small fraction accumulated in the roots. Both N and P stocks followed a different pattern, i.e., VS \(>\) BS \(>\) RS. However, while biomass-N decreased throughout the summer at both RS and VS, it remained steadily constant at BS. In addition, at VS, the nitrogen decrease was mainly accounted for by leaves, while it accumulated in roots in late summer. The P stocks accounted for by the different primary producer assemblages was always low and often negligible, when compared to BSi and N.