The relationship of water transparency, the degree of overgrowth of different types of lakes of the Ivano-Arakhleya system as a basis for monitoring and forecasting the ecological situation of the Baikal natural territory

. Previously, a hypothesis was put forward about a change in the degree of hydrophicity of lakes under the influence of fluctuations in the level. At the same time, the direct abiotic factors leading to ecosystem changes are the illumination of the soil and the level of its wind resuspending. At the same time, there were no empirical correlations between these indicators in relation to the lakes of the Ivano-Arachley system. In this work, based on the study of the lakes of the Ivano-Arakhley system, during the period of extremely low water content, a correlation is shown between the depth of macrophyte growth and the transparency of water at a damage of 0.96 (p=0.002). Factor analysis by the method of principal components showed a high positive relationship with the morphometric parameters of the ecosystem and the degree of openness of the reservoir. The relationship between the depth of vegetation distribution, water transparency, the ratio of depth, lake area expressed in terms of the coefficient of openness must be taken into account when planning activities on lakes that can affect vegetation or water transparency.


Introduction
In order to predict and prevent adverse environmental phenomena on the water bodies of the eastern periphery of the Baikal natural territory, it is necessary to digitalize the accumulated arrays of environmental data.The Ivano-Arakhley Lakes are a model group of lakes on which long-term hydrobiological studies of the dynamics of the structural and functional organization of aquatic ecosystems in an ultracontinental climate are carried out in Eastern Siberia [1].On the example of diverse lakes of Transbaikalia B.A. Shishkin [2], formulated a hypothesis about the cyclicity of lake ecosystems.The hypothesis of B.A. Shishkin is based on the idea of changing the degree of hydrophicity of lakes under the influence of fluctuations in the level.At the same time, the direct abiotic factors leading to ecosystem changes are the illumination of the soil and the level of its wind resuspending.At the same time, there are no empirical correlations between these indicators in relation to the lakes of the Ivano-Arachley system.The decrease in the level of lakes, the penetration of alien species, and the increasing anthropogenic influence are accompanied by undesirable changes in the communities and ecosystems of the Ivano-Arakhley lakes, the state of the quality of their waters.The most popular lake among Transbaikalians, Arachley, belongs to the deep ones, whose ecosystems are characterized by spatial complexity and non-synchronicity of the response of coastal and deep-water communities to changes, which makes it difficult to apply the theory of shallow lakes to such lakes and predict changes in their states [3,4].Currently, in conditions of increasing recreational load and water quality requirements, knowledge is needed about the relationship between water quality, the degree of water overgrowth and water transparency in lakes of different types.The aim of the study is to identify the relationship between water transparency and the maximum depth of plant growth in different types of lakes of the Ivano-Arachlea system and the factors that cause them.

Materials and methods
The lakes of the Ivano-Arakhley system include lakes Tasey, Ivan, Arakhley, Shakshinskoye, Bolshoy Undugun and Irgen -a chain of lakes in the forest-steppe zone of the Trans-Baikal Territory in the Beklemishevskaya intermountain depression at the junction of the Lena and Yenisei River catchments (Fig. 1).

Fig 1. Location of the Ivano-Arakhlei Lakes
The climate of the district is sharply continental with long-term cyclical fluctuations in precipitation, frosty and snowless winters.The surroundings of the lakes are used in forestry and agriculture.The lakes themselves are a popular recreation place for Transbaikalians, are used in fish farming, industrial fishing was carried out on the lakes using 500-meter or less tractor-drawn seines [5].The lakes are the core of the nature park.Lakes are characterized by cyclical fluctuations in the water level.During the period from the 1950s to 2021, lake levels in 2016 reached extremely low values.The area of lakes in high-water years ranges from 14.5 to 55 km2.Fresh lakes from weakly eutrophic (Arakhley) to eutrophic (Shaksha, Ivan) and hypertrophic (Irgen, Bol´shoy Undugun, Tasey) [1].
Field studies of macrophytes were carried out in August 2016.The research stations were evenly distributed over the entire depth range in the western part of the lakes.Sampling was carried out by a Petersen dredger (DCH-0.025)with overlapping side flaps.A total of 33 samples were taken, of which 7 samples were taken in Arachley Lake, in the lake.Shakshinsky -5, in oz.Ivan -5, in oz.Tasey -4, in Lake Bol´shoy Undugun -6, in Lake.Irgen -6 samples.The transparency of the water is measured by the Secchi disk.
The maximum depth of growth of aquatic plants is defined as the average value between the maximum depth of detection of permanent macrophyte thickets and the depth of the station following it, where macrophytes were absent or were represented by parts of them removed from the coast.The influence of wind resuspending is traced through the coefficient of lake openness, which is calculated as the ratio of the area of the reservoir to its average depth.
Statistical data analysis was performed in Excel, Excel Stat and Statistica 7.0 programs, morphometric indicators of lakes in high-water years were used [6].

Results
The results of field measurements and calculations are presented in Table 1.Note: S -area, V-volume, Wm -average width, L -length of the lake, T -water transparency, D -maximum depth, Dm -average depth, Dmacr -depth of macrophyte distribution, K -the coefficient of openness of the lake.
Correlation analysis of the data showed a regular relationship between water transparency and the maximum depth of macrophyte growth (Fig. 2).The correlation of the depth of macrophyte distribution and water transparency in the Arachley lakes in 2016 was 0.96 (p=0.002).Factor analysis by the method of principal components (Fig. 3), allowed us to identify 2 groups of components, collectively explaining 94.01% of the variance.The first component is characterized by a high positive relationship with the volume (0.99), average (0.98) and E3S Web of Conferences 462, 03043 (2023) AFE-2023 https://doi.org/10.1051/e3sconf/202346203043maximum (0.94) depth, area (0.82), average length (0.78) and width (0.73) of lakes, water transparency (0.72) and depth of macrophyte growth (0.62) in lakes Arachley and Shakshinskoe.The second component is characterized by a high connection with the coefficient of water openness (0.90).The greatest openness is characteristic of the lakes Irgen and Shakshinskoe.The scaled biplot of the mutual arrangements of the studied variables shows that the parameters of the lakes Tasey, Bol´shoy Undugun and Ivan are characterized by a negative relationship (Fig. 3).Fig. 3. Orientation of the parameters of the Ivano-Arachley lakes in the space of the first two main components of the PCA: D -the maximum depth of the lake, Dm -the average depth of the lake, Dmacr -the depth of distribution of macrophytes in the lake, K -the coefficient of openness of the lake, L is the length of the lake, S is the area of the lake, Tr is the transparency of the water in the lake, V is the volume of the lake, Wm is the average width of the lake

Discussion
The results of correlation and factor analysis of the data showed the presence of an empirical relationship between the transparency of water, the depth of overgrowth and the coefficient of openness of the reservoir.This is confirmed by the observed changes in the lakes.The extreme decrease in the water level (2016) led to the drainage of the sandy-pebble shallow waters of the lakes and an increase in the proportion of silts, including in the deep-water lake Arachley.At the same time, there is a decrease in the degree of overgrowth of the littoral from depths of 10-11 m in the 1960s to 4.5 m in 2016.As a result, a decrease in water transparency to 4.5 m was revealed in Lake Arachley from the end of July to the beginning of May in 2016-2021.Whereas in July-August 1936 the water transparency reached 10-11 m [7].In the 70s, the transparency of water during the open water period ranged from 5 to 9 meters [2].Presumably, a decrease in the water level in Lake Shakshinsky also contributed to a decrease in water transparency due to an increase in wind impact on water masses and churning of silty sediments.The connection between the decrease in water level and the increase in the proportion of fine bottom sediments is also observed in other lakes of Transbaikalia, for example, in the lakes of the Onon-Torey plain [8,9].
The color of muddy sediments in lakes Ivan, Tasey and Undugun according to the study materials was gray, in Lake Irgen -gray-black and only in Lake Shakshinsky -black.In shallow Arachleian lakes, silty precipitation in 2016 was predominantly gray, which indicates their oxidation as a result of wind mixing.In Bol´shoy Undugun and especially Irgen, the silt is lumpy, which is also due to the mixing of the water column and bottom sediments.I.e., the formation of plant groups in Lakes Irgen and Bol´shoy Undugun is under the special influence of wind mixing.A feature of Shakshinsky was black silts, indicating anaerobic conditions at the bottom.The great openness of the Irgen and Shakshinskoe lakes determines the low transparency and degree of overgrowth.In terms of water surface area, Lake Shakshinskoe is comparable to Lake Arakhley, and in depth -with Lake Ivan.With a decrease in depth and an increase in the area of the lake, the churning of bottom sediments increases, thus, the parameters of Lake Shakshinsky allow for less transparency of the lake's waters in comparison with lakes Arakhley and Ivan.With an increase in the area of the reservoir or a decrease in its depth, the openness of the reservoir increases, which leads to an increase in wind effects on water masses, the turbidity of bottom sediments and, as a result, a decrease in transparency and deterioration of the habitat conditions of macrophytes.It is possible that the low values of water transparency and the depth of macrophyte distribution in the lake in 2016 were under the determining negative influence not only of the lake area, but also of other factors, including fishing activities.
Currently, when implementing fisheries management measures, they do not consider the possibility of a negative impact on the transparency and quality of water, as well as on the components of ecosystems involved in maintaining the quality and transparency of water.Non-water fishing was carried out on Lake Shakshinskoye, during which vegetation was removed, especially communities of bottom-dwelling algae, and large filter shellfish.The introduction of carp can affect the transparency of water, stirring up bottom sediments or eating benthic filtrators.
Vegetation performs an environment-forming function, muddy precipitation stabilizes and affects turbidity, transparency and water quality.When carrying out activities on lakes, the presence of a mutual relationship between the transparency of water quality and bottom vegetation is not always taken into account.When proposing methods of restoration or biological reclamation of the Ivano-Arachley lakes by removing macrophytes in some way, it is necessary to take into account possible negative effects on water quality due to the multifactorial influence of macrophytes on the state of the water column.In addition, bottom macrophytes are an important factor in the distribution of bottom animals and have a diverse impact on the state of aquatic ecosystems.With regard to the economic use of lakes, the overgrowth of lakes with macrophytes is accompanied by undesirable effects: it hinders navigation, fishing and recreational use of reservoirs.On the other hand, by now there is an idea of the important function of macrophytes in maintaining the (hydrobiological regime) alternatively stable state of "clean" water, because they stabilize bottom sediments and prevent the transfer of nutrients from them to pelagic communities [3,4].
The introduction of Elodea canadensis Michx in the lakes of the Ivano-Arachley system also had an impact on plant communities, on the state of the ecosystem of lakes and water quality.In lakes, its distribution is also due to the amount of water transparency -in Lake Shakshinskoe, it did not form a belt along the shore at depths up to 0.5 m.It is locally distributed in the Arakhley Lake.In the lakes Tasey, Bol´shoy Undugun, Ivan all over the lake.
The relationship between the depth of vegetation distribution, water transparency, the ratio of depth, lake area expressed in terms of the coefficient of openness must be taken into account when planning activities on lakes that can affect vegetation or water transparency.It is necessary to pay increased attention to all activities carried out both in the water area of lakes and in the water protection zone.At the project level, provide for the possibility of a negative impact on bottom vegetation, water transparency and ways to reduce them.It is necessary to monitor the ecological situation in the ecosystem of the lake, to predict a decrease in water transparency and the degree of overgrowth.This will prevent undesirable unexpected negative effects in the ecosystems of the lakes of the Ivano-Arakhlei Natural Park, which perform a significant social function and are a promising direction for the development of tourism in the Baikal natural territory.

Conclusion
The results of correlation and factor analysis of the data showed the presence of an empirical relationship between the transparency of water, the depth of overgrowth and the coefficient of openness of the reservoir.This is confirmed by the changes observed in lakes during the period of extremely low water content.
Based on the study of the lakes of the Ivano-Arachley system, during the period of extremely low water content, a correlation between the depth of macrophyte growth and the transparency of water at a damage of 0.96 (p=0.002) is shown.Factor analysis by the method of principal components showed a high positive relationship with the morphometric parameters of the ecosystem and the degree of openness of the reservoir.
With an increase in the area of the reservoir or a decrease in its depth, the openness of the reservoir increases, which leads to an increase in wind effects on water masses, the turbidity of bottom sediments and, as a result, a decrease in transparency and deterioration of the habitat conditions of macrophytes.

Fig. 2 .
Fig.2.The relationship between the depth of overgrowth and the transparency of water in the Ivano-Arakhley lakes in 2016.

Table 1 .
The maximum depth of growth of aquatic plants, % overgrowth, water transparency and the coefficient of openness of different types of lakes of the Ivano-Arakhleya system at extremely low water levels in 2016.