## 4 Discussion
### Comparison with Microplastics Studies of Other Water Bodies  
[PERSON] et al. [108] conducted a study which dealt with the MP content in the aquatic environment of mountain lakes in Siberia, particularly in Altai and the West Siberian Plain. The authors focused on six lakes: Talmen, Dzhulukul, Teletskoye, Zludyri, Degtyarka and Kuchuk. These lakes are located in the strictly protected Katunsky and Altai areas. These lakes are not affected by industrial activities. They are located in protected areas without permanent populations, and they contained MP particles, the concentrations of which ranged from 4 to 26 particles per liter of water, mainly from various human activities such as fishing, vehicles and waste disposal, especially by tourists. Even in such remote lakes where human activities are limited, high concentrations of MPs were observed. This emphasizes the need for increased attention to waste management and to careful water use in freshwater environments in order to maintain a basic level of environmental and health safety. Studies conducted in 2011-2013 by the Limnological Institute of the Siberian Branch of the Russian Academy of Sciences [109] and later by Greenpeace on Lake Baikal [110]revealed significant pollution in the lake from household waste, including plastics. Statistics show that up to 87% of the plastic found on the Lake Baikal coast is single-use plastics. In addition, the concentration of MPs in the lake water and on its shores turned out to be high, according to a study by Moscow State University's (MSU) specialists [111]. For samples taken from the water surface in the coastal zone of the most populated southeastern coast and in the so-called Small Sea near Olkhon Island, in terms of water surface area, the concentration of particles ranged from 19,000 to 75,000 plastic particles per 1 km\({}^{2}\), with an average value of 42,000 particles per 1 km\({}^{2}\), which corresponds to a high degree of plastic pollution [111]. Based on chemical composition, the particles were identified to be polyethylene, polypropylene and polystyrene. It is assumed that the MPs detected during this study were decomposition products of various household packaging materials [111]. According to our own long-term observations since 1987 (1988, 2000, 2002, 2003, 2006, 2007, 2009 and 2018) in these case study areas, both in the Altai Mountains (Russian part in West Siberia) and in and around Lake Baikal (East Siberia in Russia), the increasing number of tourists, including unguided and so-called \"wild\" tourism, is responsible for the huge deposition and distribution of plastic and MPs in these natural lake environments. Studies conducted by immunologists in the last decade have provided a broader picture of the MP content in lakes around the world and its impact on aquatic ecosystems. About 90 lakes in different regions of Asia, Europe, North and South America and Antarctica were analyzed regarding their plastic pollution [49; 112; 113; 114; 115]. Chinese scientists processed data from 66 lakes, emphasizing the study of urban influences on MP accumulation in water and sediments [115; 116]. Limnologists also found that large lakes have significantly lower MP contents in their mud compared with smaller water bodies. For example, in Lake Victoria, the concentration of MP particles was 6.5 granules per kilogram, while in a small pond in London, this value reached 540 particles per kilogram [114; 116]. In the sediments of large lakes, MPs are mainly represented by coarse debris and particles ranging in size from 1 to 5 mm. Light MP fibers easily migrate through the water column, moving upward, downward and horizontally. This allows them to spread over long distances and affect different areas of water bodies [117]. One study [118] was conducted to assess MP pollution in a large, remote mountain lake, namely Hovsgol Lake, located in the mountains of northern Mongolia, which despite its remoteness, protected status and low population density was also prone to MP pollution.