## 3 Results  
### Water and Sediment Characteristics  
The temperature of the littoral waters of Lake Iseo ranged from 15 \({}^{\circ}\)C in April to 28 \({}^{\circ}\)C in midsummer. The chemical characteristics of near-bottom waters differed between sites (Table 2). DSi concentrations were highest at the VS site and lowest at the RS site. While DSi concentrations were constant at the VS site, they increased throughout the season, reaching the same level as those at the BS site, and to a much lesser extent at the RS site. SRP concentrations were \(<\)5 \(\mu\)g P L\({}^{-1}\) and no differences were found between sites. DIN concentrations and their seasonal trends were similar in the three sites, and were mainly driven by N-NO\({}_{\mathrm{x}}\) which accounted for more than 80% of DIN on average. The DSi:DIN and DSi:SRP ratios conformed to the DSi concentration pattern, the ratios being VS\(>\)BS\(>\)RS. At both BS and RS, DSi:DIN and DSi:SRP increased throughout the season. At BS, values attained those measured at VS, while at RS, values remained nearly two times lower. On average, molar ratios DSi:DIN = 0.28, DSi:SRP = 132 and DIN:SRP = 37 evidenced that DSi concentrations in the water column were low compared to DIN. SRP was deficient with respect to both DIN and DSi, especially at RS. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Water**} & \multicolumn{3}{c}{**RS**} & \multicolumn{3}{c}{**VS**} & \multicolumn{3}{c}{**BS**} \\ \cline{2-10}  & **Early** & **Mid** & **Late** & **Early** & **Mid** & **Late** & **Early** & **Mid** & **Late** \\ \hline DSi & 57 & 130 & 225 & 404 & 400 & 494 & 137 & 238 & 490 \\ (\(\mu\)g Si L\({}^{-1}\)) & (1) & (5) & (24) & (20) & (39) & (13) & (10) & (10) & (13) \\ \hline SRP & 2 & 5 & 2 & 4 & 4 & 2 & 5 & 5 & 2 \\ (\(\mu\)g P L\({}^{-1}\)) & (0) & (1) & (0) & (1) & (0) & (0) & (1) & (1) & (0) \\ \hline N-NO\({}_{\mathrm{x}}\) & 592 & 509 & 538 & 426 & 376 & 442 & 497 & 420 & 485 \\ (\(\mu\)g N L\({}^{-1}\)) & (4) & (3) & (6) & (7) & (2) & (8) & (8) & (6) & (8) \\ \hline N-NH\({}_{4}\)\({}^{+}\) & 56 & 85 & 63 & 100 & 94 & 89 & 74 & 55 & 54 \\ (\(\mu\)g N L\({}^{-1}\)) & (4) & (3) & (3) & (4) & (6) & (3) & (4) & (3) & (5) \\ \hline DIN & 648 & 595 & 601 & 526 & 470 & 531 & 571 & 476 & 539 \\ (\(\mu\)g N L\({}^{-1}\)) & (5) & (4) & (6) & (4) & (6) & (9) & (9) & (6) & (10) \\ \hline DSi:DIN & 0.04 & 0.11 & 0.19 & 0.39 & 0.42 & 0.47 & 0.12 & 0.25 & 0.46 \\ (mol:mol) & (0.00) & (0.00) & (0.02) & (0.02) & (0.04) & (0.01) & (0.01) & (0.01) & (0.01) \\ \hline DSi:SRP & 38 & 31 & 109 & 148 & 155 & 309 & 36 & 65 & 262 \\ (mol:mol) & (3) & (4) & (13) & (20) & (26) & (29) & (5) & (5) & (32) \\ \hline DIN:SRP & 863 & 293 & 596 & 395 & 348 & 664 & 307 & 262 & 564 \\ (mol:mol) & (88) & (38) & (42) & (55) & (44) & (57) & (40) & (18) & (56) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Dissolved silica (DSi), soluble reactive phosphorus (SRP), ammonium (N-NH\({}_{4}\)\({}^{+}\)), nitrate and nitrite (N-NO\({}_{\mathrm{x}}\)) and dissolved inorganic nitrogen (DIN) concentration and DSi:DIN, DSi:SRP and DIN:SRP molar ratios in the water column at the three investigated sites (RS = rocky shores; VS = vegetated sediments; BS = bare sediments). All data represents the mean of three replicates (standard error in parenthesis). The surface sediment was similar at the VS and BS sites--soft and homogenous--although OM, N, and P were slightly greater at VS than at BS (Table 3). The percent of OM and nutrient content was comparatively higher at station RS, where the sediment was probably enriched by the biomass growing on stones. Accordingly, the average sedimentary BSi concentration was higher at RS (1.00 \(\pm\) 0.17%) compared to VS (0.79 \(\pm\) 0.03%) and BS (0.46 \(\pm\) 0.02%). Similar patterns were also found for total N (0.50 \(\pm\) 0.08% at RS, 0.33 \(\pm\) 0.01% at VS, and 0.21 \(\pm\) 0.00% at BS), and organic P (ranging from 0.11% at RS to 0.01% at both VS and BS).