## 3 Results and Discussion  
The results of determining physicochemical factors in overlying waters in spring and summer are presented in Tables 1 and 2. The overlying water of Lake Jeziory Wielkie was characterized by a high pH, with an average pH of 8.17. This pH level was slightly higher in spring, averaging 8.19, compared to the summer when it averaged 8.49. In the spring, the highest pH values were observed in the northern part of the lake (specifically at points 13, 14, and 15), which may have been influenced by dissolved organic compounds originating from surface runoff from agricultural areas. The content of org-P in the overlying water of Lake Jeziory Wielkie revealed an average org-P content of 0.53 mg dm\({}^{-3}\). The org-P content was higher during the spring period (0.69 mg dm\({}^{-3}\)) compared to the summer period (0.38 mg dm\({}^{-3}\)). The higher org-P content in bottom waters in spring could be caused by the runoff of pollutants from the catchment (agroforestry catchment) during spring rains. The sum of precipitation in 1 month before sample collection was 60 mm (IMGW). This research examined the activity of phosphatases in the spring and summer, aligning with periods of heightened biological activity corresponding to phases of intense growth and potential environmental shifts. Other scholars exploring this subject similarly concentrate on these two study periods as indicative intervals [4; 10; 11; 12; 23; 24; 25; 31; 32; 33]. The average content of ALP and ACP enzymes in Lake Jeziory Wielkie was 637.57 and 745.41 \(\upmu\)g of p-nitrophenol g\({}^{-1}\) h\({}^{-1}\). The content of the ALP enzyme in bottom sediment samples of this lake in spring ranged from 119.34 to 407.23 \(\upmu\)g of p-nitrophenol g\({}^{-1}\) h\({}^{-1}\). However, the content of the ACP enzyme was slightly higher in this period, ranging from 144.68 to 866.51 \(\upmu\)g of p-nitrophenol g\({}^{-1}\) h\({}^{-1}\). In the summer, the content of both enzymes was slightly higher and ranged from 180.87 to 2852.25 \(\upmu\)g of p-p-nitrophenol g\({}^{-1}\) h\({}^{-1}\) and from 329.36 to 1793.01 \(\upmu\)g of p-nitrophenol g\({}^{-1}\) h\({}^{-1}\), respectively, for spring and summer (Figures 4 and 5). Moreover, the average ALP value for Lake Jeziory Wielkie in summer was four times higher than in spring. Additionally, the average value of ACP was twice  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Point**} & \multicolumn{3}{c}{**pH [-]**} & \multicolumn{3}{c}{**Org-P [mg dm\({}^{-3}\)]**} \\ \cline{2-5}  & **Spring** & **Summer** & **Spring** & **Summer** \\ \hline
1 & 7.89 & 8.99 & 0.72 & 0.61 \\ \hline
2 & 7.95 & 7.89 & 0.83 & 0.31 \\ \hline
3 & 7.72 & 7.81 & 1.26 & 0.39 \\ \hline
4 & 8.86 & 8.94 & 0.42 & 0.07 \\  
as high in the same period (Table 1). [PERSON] [31] emphasized in his research that the enzyme values in the summer period are higher than in the colder periods. Similar conclusions were reached by [PERSON] et al. [32], who confirmed that a greater amount of the ALP enzyme was observed in the summer. However, the study by [PERSON] et al. [33] proved that the values of ACP enzymes were approximately 25% higher than the values of ALP enzymes. Many studies prove that the activity of soil enzymes is positively correlated with the soil's nutrient content. Our research confirms this statement, and additionally, having information about the texture of bottom sediments (sand and loamy sand), we know that they can contribute to the easy transfer of substances at the water-sediment interface (Figure 6). Moreover, the research of [PERSON] et al. [27] shows that the catchment area of the Gluszynka river-like system comprises easily permeable formations with low retention capacity. This indicates that in the event of intensive fertilization of these soils, there exists a tangible risk of rapid substance transport to surface and groundwater, potentially posing an additional detrimental factor to the water quality of Lake Jeziory Wielkie.