## 4 Discussion
For example, for the Kara and Laptev Seas, where the volume of river runoff occupies a very large part, and the difference in nutrients concentrations is large (for example, silicon concentrations), it is necessary to constantly evaluate the maximum concentration of a nutrients. The nutrient supply decreases when one water changes to another. The same state of affairs also applies to the content of meltwater in the surface layer, and the content of nutrients which is much less. If the initial concentrations are underestimated due to the influence of meltwater, then it can lead to overestimations of their consumption, and, consequently, to overestimations of primary production. Determination of the amount of nutrient consumption, i.e., the difference between the reference point and the measured value of nutrient concentrations, allows moving from average stoichiometric ratios to veritable ratios for a given point of research and a given period of the year. Usually the stoichiometric Redfield-Richards ratio is used, which in molar form is C:Si:N:P = 106:23:16:1, which is 41.1:20.9:7.2:1 by mass. The average stoichiometric ratios calculated from the results of this study (by mass) for the entire Barents Sea in the euphotic layer during the period of maximum nutrient consumption (July-September) are reported in Table 5:  
Based on the results obtained from the measured values, the stoichiometric mass ratio for the Barents Sea can be written as follows: C:Si:N:P = 56.6:13.2:10.1:1 or in the atomic form 146:15:22:1. In addition, it becomes possible to evaluate the change in stoichiometric ratios for the studied water area (Figure 14). The work [7] shows the change in the stoichiometric ratio in the Arctic Ocean. For the Barents Sea, the ratio POC:PON (particulate organic carbon (POC) and nitrogen (PON)) in atomic form was 8.5 \(\pm\) 1.8, while the Redfield-Richards ratio was 6.62. However, it cannot be constant, because the classical ratio is an average ratio, and the real ratio is determined by the specific composition of phytoplankton, the formation of which consumes a different amount of nutrients. The average C:N ratio in the Barents Sea is 7.97 \(\pm\) 0.14, which is quite close to the values presented in [7]. The technique described in this paper makes it possible to trace the change in both stoichiometric ratios and changes in primary production in various water areas, as well as in the annual cycle. Since it was shown above that 94% of the Barents Sea phytoplankton consists of diatoms and dinoflagellates, then, consequently, the stoichiometric ratios should also vary in the range between the ratios for these two systematic groups. This is observed from the presented results with a shift of values from the ratios Redfield-Richards toward dinoflagellates. The C:P and C:N ratios in the Barents Sea are shifted by 29% and 23% accordingly. The N:P ratio falls out of this pattern in the Barents Sea, the value of which is outside the range of this value between diatoms and dinoflagellates by 25% which is still difficult to explain and requires further research. Perhaps this is due to the need to revise the values of the content of biogenic elements in various systematic groups of phytoplankton. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Ratio**} & **Redfield–Richards** & \multicolumn{2}{c}{**Average at the**} & \multirow{2}{*}{**Diatom \({}^{**}\)**} & \multirow{2}{*}{**Peridinium \({}^{**}\)**} \\  & **Richards** & & & \\  & [13; 14] & & & \\ \hline C:P & 41.1 & 56.6 \(\pm\) 3,3 & 37.0 & 58.8 \\ \hline Si:P & 20.9 & 13.2 \(\pm\) 0.9 & 34.4 & 3.8 \\ \hline Si:N & 2.9 & 1.4 \(\pm\) 0.8 & 5.1 & 0.4 \\ \hline N:P & 7.2 & 10.1 \(\pm\) 4.9 & 6.7 & 8.1 \\ \hline \hline \end{tabular} Note: * calculated by Equation (13); **[13; 26] (Table 2).  
\end{table} 
Table 5: Nutrient ratios and their content in different area and species (by mass). The presented technique using the isotope parameter currently has its limitations.