## 4 Discussion  
### Discussion of the Lake Markakol MP Analyses  
This initial study on plastics, including mesoplastics and microplastics, in the Lake Markakol environment, including the tributary rivers and the only outflow, illustrated both the plastic load of the tributaries and the plastic sink of the lake. Data on high concentrations of MPs in different areas of Lake Markakol indicate serious pollution problems. For the 0.315-1.0 mm particle size, the highest MP content of the tributaries to the lake was found in the Tishushka River (30.2 \(\upmu\)m/m\({}^{3}\)), decreasing in the order of the Topolevka River, Zhirelka River, Malaiba River, Yelovka River and Urunhaika River (11.5 \(\upmu\)m/m\({}^{3}\)). For the 1.0-5.0 mm particle size, the highest MP content of the tributaries to the lake was found in the Topolovka River (130.9 \(\upmu\)m/m\({}^{3}\)), decreasing in the order of the Tishushka River, Malaiba River, Urunhaika River and Zhirelka River (43.8 \(\upmu\)m/m\({}^{3}\)) (Figure 3). The highest MP contents within the lake zones for the 0.315-1.0 mm particle size were found in zone 1 (165.5 \(\upmu\)m/m\({}^{3}\)), decreasing in the order of zone 4, zone 5, zone 2 and zone 3 (37.6 \(\upmu\)m/m\({}^{3}\)). The corresponding MP contents for the 1.0-5.0 mm particle size for the lake zones were 147.2 \(\upmu\)m/m\({}^{3}\) in zone 2, followed by zone 1, zone 5, zone 4 and zone 3 (4.0 \(\upmu\)m/m\({}^{3}\)) (Figure 3). High MP concentrations were found in the northern, northeastern and southern zones (Figure 2 and Tables 1 and 2) of the lake, especially in the confluence areas of the Topolevka, Urunhaika and Matabai rivers, indicating that these areas are active MP pollution hotspots. The total concentration of macro- and microplastics contributed by the tributaries was 482.1 \(\upmu\)g/m\({}^{3}\), while the lake water area had a higher concentration of 837.5 \(\upmu\)g/m\({}^{3}\). These results, together with the non-plastic loaded effluent of the Kazhyr River, indicate that Lake Markakol is a significant MP sink, while the tributaries significantly contribute to the overall pollution pattern. The indications of possible reasons for the detection of MPs in lake and river areas, such as poaching and unconstructive tourism, emphasize the importance of the anthropogenic  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Sampling Location**} & **Trawling** & \multirow{2}{*}{**Weather Conditions**} & **Air Temperature** & **Types of Plastic** & **Plastic Size** & **Quantity of Plastic** \\  & **Time/Distance** & **(min/m)** & & **(C)** & **Discovered** & **(mm)** & **(Yes)** \\ \hline \multicolumn{6}{c}{The Main Tributaries Flowing into Lake Markakol} \\ \hline Urunhaika River & & cloudy & 26 & 0.5–300 & 125 \\ \hline Tikhushka River & & clear, no & 29 & 0.5–3.8 & 143 \\ \hline Zhirelka River & & precipitation & & fishing line nets, & 0.4–3.6 & 117 \\ \hline Topolevka River & \multirow{2}{*}{15} & slightly cloudy, no & & wrapers, labels, & 0.5–4.2 & 178 \\ \cline{2-6} \cline  
influence on the pollution of aquatic systems. Polyamide fiber nets, monofilament and other plastic materials left behind can create significant pollution and harm to ecosystems, including endemic fish species. According to our observations, the majority of the plastic was associated with local pollution sources, as larger fractions were found in the inflowing rivers of the lake. Also, some of the plastic found in the lake water was of polymer origin, typical of monofilament nets used in fishing activities. These findings suggest that much of the plastic in the lake came from local pollutants and unsustainable fishing practices. At the same time, the transfer of plastic particles from places of unorganized collection of household waste could not be ruled out. Some of the detected MP particles of the ecosystem of the high-mountain Lake Markakol are probably associated with the increasing tourism in this area.