## 4 Results
### Coefficient of Determination  
The coefficient of determination, R\({}^{2}\), was used as a measure of the fit of the mathematical model with the data obtained from Tables 1-5 for both species and in both breeding variants. This coefficient indicates what proportion of the variance in the data coincides with the correlation of the variables that are described in the model. Thus, we can say that it is a determinant of the fit of the sample to the model, described in the range of values between 0 and 1, with values close to unity corresponding to a higher model fit. \[\text{R}^{2}=1-\frac{SS_{\text{res}}}{SS_{tot}}\]  
where  
\((SS_{\text{res}})\) is the sum of the squares of the residuals, that is, the sum of the squares of the differences between the actual values and the values predicted by the model:  
\[SS_{\text{res}}=\sum_{i=1}^{n}\left(y_{i}-\hat{y}_{i}\right)^{2}\]  
\((SS_{\text{tot}})\) is the total sum of squares, that is, the sum of the squares of the differences between the actual values and the average value of the actual data:  
\[SS_{tot}=\sum_{i=1}^{n}\left(y_{i}-\overline{y_{i}}\right)^{2}\]  
The value of R\({}^{2}\) ranges from 0 to 1, where a value closer to 1 indicates a better fit of the model to the data. Using all the data, which are the variables of concentrations and types of plastics, we initially performed a determination analysis for the linear function and quadratic function, but with such a number of variables, the function was not sufficient, and the determination index at each analysis indicated 1. For a better and more accurate depiction of the statistical fit of the model, a third-degree power polynomial and fourth-degree polynomial analysis were performed and are presented in the tables (Tables 6-9) and figures below (Figures 15-18). To increase the clarity of the results, the authors used the abbreviation of the third-degree polynomial as (R\({}^{2}\))\({}^{3}\) and the fourth-degree polynomial as (R\({}^{2}\))\({}^{4}\). Figure 15 rearranges the coefficient of determination for _D. veneta_ in the micro-culture, based on the data in Table 2.  
Figure 14: Characteristic peaks for polystyrene 3060, 3026, 2913, 2844,1601, 1492, 1450, 1027, 751, and 694. The function values for each plastic in the concentration correlation are shown in Table 6. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **(R2)3** & **(R2)4** \\ \hline PA & 0.995 & 1 \\ \hline PET & 0.9983 & 1 \\ \hline PS & 0.9451 & 1 \\ \hline PE & 0.9971 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Values of the third-degree (R2)3 and fourth-degree (R2)4 polynomial coefficients of \(D\). _veneta_—micro-culture. Figure 16: Determination coefficient for \(L\). _terrestris_ from micro-culture. Figure 15: Determination coefficient for \(D\). _veneta_ from micro-culture. Figure 17 rearranges the coefficient of determination for _D. veneta_ in the macro-culture, based on the data presented in Table 4.  
Figure 18 rearranges the coefficient of determination for _L. terrestris_ in the macro-culture, based on the data presented in Table 5.  
Figure 17: Determination coefficient for _D. veneta_ from macro-culture. \begin{table}
\begin{tabular}{c c c} \hline  & **(R2)3** & **(R2)4** \\ \hline PA & 0.9957 & 1 \\ \hline PET & 0.9920 & 1 \\ \hline PS & 0.9453 & 1 \\ \hline PE & 0.8514 & 1 \\ \hline \end{tabular}
\end{table} 
Table 7: Values of the third-degree (R2)3 and fourth-degree (R2)4 polynomial coefficients of _L. terrestris_—micro-culture. \begin{table}
\begin{tabular}{c c c} \hline  & **(R2)3** & **(R2)4** \\ \hline PA & 0.9956 & 1 \\ \hline PET & 0.9957 & 1 \\ \hline PS & 0.9956 & 1 \\ \hline PET & 0.9102 & 0.9102 \\ \hline PS & 0.9643 & 1 \\ \hline PE & 0.9405 & 0.9405 \\ \hline \end{tabular}
\end{table} 
Table 8: Values of the third-degree (R2)3 and fourth-degree (R2)4 polynomial coefficients of _D. veneta_—macro-culture.