## 3 Material and Methods
The obtained classification results are presented graphically in the form of dendrograms, and in a more complex form as a combination of dendrograms and a heatmap. The research on macrophytes of Lake Piaseczno was conducted in 2007 and 2018 in July in four transects that correspond to sectors of the dominant land use in the catchment: PRF, R, RA and FR. The littoral zone was analysed from the shoreline to the maximum range of occurrence of macrophytes. The research covered all groups of macrophytes: emerging (EM), submerged (SM), floating (FM) and pleuston (PM). Their species composition was determined--with nomenclature after [PERSON] [49]--as well as the density of emerging macrophytes and their range of occurrence, biomass and dominance in biomass in particular groups [38; 50]. The productivity of the littoral of Lake Piaseczno was analysed based on the biological lake water trophy indicators gross primary production of phytoplankton, chlorophyll \(a\) concentration and calculated [PERSON]'s trophic state indices (TSIChl-_a_ and TSISD). The analyses were implemented in the summer season of 2015 and 2018 (two terms one month apart in each season) in the littoral zone adjacent to particular sectors of the catchment. Study sites were designated in the centre of the shoreline of each sector at a distance of approximately \(-10\) m from the shore, depending on the bottom slope inclination, to obtain sample immersion to a depth of approximately 0.75 m. For sectors 2 and 3, due to their homogeneity, one study site was designated on their arbitrary boundary. The limnological status of Lake Piaseczno was determined based on the same research conducted in the deepest place in the lake (38.8 m) in the peatogenic zone (depths of 0.75 m and 2.5 m). The study results were averaged for the analysed profile and study season. Gross primary production of phytoplankton was measured by means of the aerobic method [51]. The concentration of dissolved oxygen in water was determined by means of the Winkler iodometric titration method [52]. The amount of released oxygen for subsequent study terms was converted to amounts of carbon assimilated from 1 m\({}^{2}\) per hour (mg C\({}_{\text{ass}}\cdot\)m\({}^{-2}\cdot\)h\({}^{-1}\)), assuming that 1 g of released oxygen corresponds to 0.312 g of assimilated carbon [53]. The obtained results after conversion to mgC\({}_{\text{ass}}\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\) (assuming that d = 12 h) described the level of trophy of lake waters (according to [2] and [54]). Concentration of chlorophyll \(a\), the most important photosynthetic pigment, was analysed by means of the spectrophotometric method [55] and expressed in mg Chl_a_\(\cdot\)m\({}^{-2}\). Based on chlorophyll \(a\) concentration values expressed in ug Chl_a_\(\cdot\)dm\({}^{-3}\), TSI CHLa was calculated [56]:  
\[\text{TSI CHLa}=9.81\text{ ln(Chl)}+30.6. \tag{4}\]  
The research on biological trophic status indicators was supplemented by measurements of the basic physical-chemical water properties, i.e., electrolytic conductivity (uS\(\cdot\)cm\({}^{-1}\)), reaction (pH), and oxygen concentration in mg O\({}_{2}\cdot\)dm\({}^{-3}\), by means of a certified field meter (HI 9811-5) or titration methods (oxygen concentration: control samples for gross primary production of phytoplankton). Based on measurements of Secchi visibility (m), which determines water transparency in the pelagial zone, the TSI SD was calculated [56]:  
\[\text{TSI SD}=60-14.41\text{ ln(SD)}. \tag{5}\]The obtained study results were analysed with unitary coefficients of export of surface loads of biogenic substances from catchment areas under different land uses according to [PERSON] [10]: 1 ha of arable fields in the lake's catchment generates 9 kg N and 0.3 kg P; 1 ha of meadows and pastures 3 kg N and 0.2 kg P; 1 ha of forests 1.5 kg N and 0.1 kg P; and loose building development (the equivalent of recreational plots) 9 kg N and 0.3 kg P (kg\(\cdot\)ha\({}^{-1}\cdot\)year\({}^{-1}\)).