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Article
Spatial distribution and photosynthetic activity of phytoplankton in the Rybinsk Reservoir in the summer period of 2018-2020
Ivan V. Semadeni
Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok 109, Nekouz District, Yaroslavl Region, 152742 Russia
semadeni14@mail.ru
Received: 14.04.2022 Revised: 24.06.2022 Accepted: 01.07.2022 Published online: 12.04.2023
DOI: 10.23859/estr-220414 UDC 574.583(28):581
Translated by D.M. Martynova
Abstract. The spatial distribution of chlorophyll a (Chl a) and photosynthetic activity coefficient (PAC) of phytoplankton in the Rybinsk Reservoir was studied using fluorescent analysis in July-August 2018-2020. Under various hydrometeorological conditions, the content of Chl a varied as 0.26-116 ^g/L, averaging 16.7-21.2 ^g/L. The spatial distribution of Chl a in 2019 was characterized by moderate patchiness, in 2018 and 2020, by highly pronounced randomity (coefficients of variation Cv = 69, 91, and 140%, respectively). The PAC varied from 0.01 to 0.58, averaging 0.30-0.42. PAC below 0.3 were noted in 8-47% of cases, reflecting the development of phytoplankton under stressful conditions. The spatial distribution of PAC was more uniform than that of Chl a (Cv = 18-130%). PAC depended on Chl a content non-linearly (R2 = 0.50).
Key words: chlorophyll, PAC, quantum yield, monitoring, fluorescence, Upper Volga River, algocoenosis state, pigments
To cite this article. Semadeni, I.V., 2023. Spatial distribution and photosynthetic activity of phytoplankton in the Rybinsk Reservoir in the summer period of 2018-2020. Ecosystem Transformation 6 (2), 19-32. https://doi.org/10.23859/estr-220414
Научная статья
Пространственное распределение и фотосинтетическая активность фитопланктона Рыбинского водохранилища в летний период 2018-2020 гг.
И.В. Семадени
Институт биологии внутренних вод им. И.Д. Папанина РАН, 152742, Россия, Ярославская обл., Некоузский р-н, пос. Борок, д. 109
semadeni14@mail.ru
Поступила в редакцию: 14.04.2022 Доработана: 24.06.2022 Принята к печати: 01.07.2022 Опубликована онлайн: 12.04.2023
РСН: 10.23859^г-220414 УДК 574.583(28):581
Аннотация. В июле-августе 2018-2020 гг. с использованием флуоресцентной диагностики исследовано пространственное распределение хлорофилла a (Хл а) и коэффициента фотосинтетической активности (КФА) фитопланктона Рыбинского водохранилища. При различных гидрометеорологических условиях содержание Хл а изменялось в диапазоне 0.26-116 мк-г/л при средних значениях 16.7-21.2мкг/л. Пространственное распределение Хл а в 2019 г. характеризовалось умеренной, в 2018, 2020 гг. - высокой неоднородностью при коэффициентах вариации ^ = 69, 91 и 140% соответственно. Величины КФА варьировали от 0.01 до 0.58 при средних значениях 0.30-0.42. В 8-47% случаев отмечены КФА ниже 0.3, отражающие развитие фитопланктона в стрессовых условиях. Пространственное распределение КФА более однородно, чем распределение Хл а = 18-130%). Эмпирически выведена нелинейная зависимость КФА от содержания Хл а (№ = 0.50).
Ключевые слова: хлорофилл, КФА, квантовый выход, мониторинг, флуоресценция, Верхняя Волга, состояние альгоценоза, пигменты
Для цитирования. Семадени, И.В., 2023. Пространственное распределение и фотосинтетическая активность фитопланктона Рыбинского водохранилища в летний период 2018-2020 гг. Трансформация экосистем 6 (2), 19-32. https://doi.org/10.23859/estr-220414
Introduction
The Rybinsk Reservoir is studied by hydrologists and ecologists for many years (Struktura..., 2018). Planktonic algae, which produce the bulk of organic matter and transform the incoming energy of solar radiation into the ordered energy of bonds of organic molecules during photosynthesis (Todorenko, 2016), are sensitive to external factors (Elizarova, 1999; Suggett et al., 2010). Various indicators and methods are used to assess the state of algocenoses, including chlorophyll a concentration, primary production,
abundance and biomass of phytoplankton (Korneva, 2015; Metody... 1975; Mineeva, 2004, 2009, 2021; Sigareva, 2012). Nowadays, instrumental measurements for chlorophyll concentration (including fluorescence) are becoming widespread, the methods for measuring the photosynthetic activity and the efficiency of the quantum yield of photosystem II (PS II) getting much development (Gaevsky et al., 1993; Goltsev et al., 2014; Ivanova et al. et al., 2014; Matorin and Rubin, 2012; Popik, 2015).
The spatial heterogeneity of the environment is one of the important stabilizing factors in the functioning of any ecosystem. When studying large water areas, researchers are faced with heterogeneity in the phytoplankton distribution (Koreneva, 2017; Mineeva, 2004; Piirsoo et. al., 2008). This peculiarity is associated with various hydrodynamic processes, vital activity of aquatic organisms, nutrient limitation, etc. (Ekologicheskie..., 1993; Mineeva, 2021; Tesfay, 2007). Large-scale phytoplankton heterogeneity provides a number of competitive advantages; it is characterized by large-scale both space and time (dozens of days and thousands of kilometers). This work continues the series of long-term extended studies on the development of phytoplankton in the Rybinsk Reservoir and its horizontal distribution (Struktura..., 2018).
The study aims to assess the spatial heterogeneity and photosynthetic activity of phytoplankton in the Rybinsk Reservoir during periods with different hydroclimatic conditions.
Materials and methods
The Rybinsk Reservoir (N 58°22'30" E 38°25W) is located in the southern taiga subzone; it is large (4580 km2) and relatively shallow (average depth of 5.6 m) water body. About 20% of its total area is occupied by shallow waters with the depths of less than 2.0 m, about 25%, by the depths exceeding 8 m. The reservoir is divided into four sections (Rybinskoe..., 1972): Volga, Sheksna, and Mologa reaches, located along flooded riverbeds, and the Main Reach, which occupies the vast central part of the reservoir (Fig. 1).
Fig. 1. Schematic map of the Rybinsk Reservoir with the location of sampling stations. I -stations, II - boundaries.
Table 1. Meteorological conditions in a week before sampling in 2018-2020.
Y Average wind speed Cloudiness, Precipitation, Share of still Average air
(gusts), m/s % mm days, % temperature, °C
2018 2.2 (5) 50 12 17.2 18.4
2019 1.7 (5) 40 29 35.9 12.5
2020 3.1 (9) 60 78 12.5 17.0
The material was collected at 30 deep-water (channel) and at 17 shallow-water (at the mouths of small rivers and coastal) stations (Fig. 1) in July-August 2018-2020 (the warmest period of the year). Samples were taken with an Elgmork bathometer in the euphotic zone (0-2 m).
The content of chlorophyll a (Chl a) was determined, equal to its total amount in the three main divisions of freshwater algae (cyanobacteria, diatoms, and green: ChlCyan ChlBac and ChlChl), and the coefficient of photosynthetic activity (PAC), or effective quantum yield of photosystem II. Both indicators were measured using the PFL-3004 fluorimeter according to the methodology developed at the Krasnoyarsk State University (Gaevsky et al., 2005). In order to determine Chl a, the fluorescence yield at wavelength ~680 nm was measured upon excitation of natural water by light with the wavelengths of 410, 490, and 540 nm before and after the addition of simazine (electron transport chain (ETC) inhibitor) to the sample. The Chl a concentration was calculated using the system of equations developed by V.M. Gol'd et al. (1986). In order to calculate PAC, the fluorescence yield of natural water was determined upon excitation with white light at an intensity of 150 W/m2 before and after the addition of simazine to the sample cuvette, then PAC was calculated by the equation:
K0A = F /F -F
max max t
where F' is the maximum fluorescence of the
max
sample adapted to light after ETC inhibitor was added; Ft is the stationary fluorescence in the light (Gol'd et a l., 1986).
PAC is a dimensionless value that ranges 0-0.83, where 0.83 is the maximum value obtained for a healthy culture (Gol'tsev et al., 2014). When assessing photosynthetic activity based on PAC, the following ranges are used (Kurochkina, 2019): 0-0.3 refers to low photosynthetic activity (at which inhibition of solar energy absorption processes and damage to the integrity of photosystems can be observed); 0.3-0.5, to normal photosynthetic activity; > 0.5, to high photosynthetic activity (observed under optimal conditions, when algae develop (grow) actively).
The STATISTICA 10 (Statsoft, Russia), PAST 4.03 (Oyvind Hammer, Norway), and Excel 2016 (Microsoft, USA) software packages were used for statistical
data processing. Meteorological data (air temperature, wind speed, and direction) were downloaded from the online archives of weather forecast website www.rp5.ru for the station Cherepovets1. Water characteristics of the reservoir (level, inflow, flow) were obtained from the RusHydro website2 and from published data (Struktura..., 2018).
Results and discussion
Growing seasons of 2018-2020 were characterized by different hydrometeorological conditions (Table 1). In each growing season, the westerly, southerly, and northerly winds prevailed, their total average share reached up to 61-65%. Calm conditions were noted in 6-8% of cases. The easterly and northeasterly winds were least of all recorded. In 2020, the larger share of southerly winds (up to 10%) and smaller, of westerly ones, was observed compared to the other years under consideration. The average wind speed was 2.7 m/s in each study year.
The growing season of 2018 was characterized by the highest average air temperature (12 °C). In the week prior to sampling date, northerly and northeasterly winds prevailed (> 52%) with the share of calm hours amounting to 17% (Fig. 2). The year of 2019 was the coldest year (average air temperature of the growing season was 10.6 °C), windless year (average wind speed 2.3 m/s, calm days were 20% of total), and low-water year. A week before the material was collected, southwesterly winds prevailed (27% of cases) with a high share of calm weather. In 2020, the growing season was characterized by higher wind speed (2.9 m/s) and heavy precipitation. The hydro-meteorological situation in late July-early August was unfavorable for phytoplankton vegetation. There was a change in seasonal weather conditions with a change in the prevailing winds from the westerly ones to the northerly ones. Wind speeds reached 9 m/s; precipitation was observed daily for two weeks.
According to previously obtained data (Semadeni and Mineeva, 2019), the bulk of phytoplankton in the daytime is concentrated in the photic layer (> 80% of the recorded maximum Chl a and PAC values), which for the Rybinsk Reservoir is 0-2 m. At low wind
1 https://rp5.ru/Archive_weather_in_Cherepovets (accessed: 10.09.21)
2 http://www.rushydro.ru/hydrology/informer / (accessed: 12.09.21)
speed, elevated Chl a concentration is confined to the southern part of the reservoir and shallow water areas. At steadily directed winds (exceeding 2 m/s), the photic layer may be subjected to intense wind action, changing the photosynthetic activity of phytoplankton (Mosharov and Sergeeva, 2018). In the reservoir, a horizontal displacement of algae in the direction of the dominant winds was noted (Mineeva, 2004).
During the study period, Chl a concentration corresponded to values typical of high summer (Struk-tura..., 2018). In the summer of 2018, the content of Chl a varied within 4.5-80 ^g/L. As calm weather and low wind (2.5 m/s) predominated, the spatial distribution of Chl a was non-uniform (Cv = 91%). The highest concentration of Chl a was noted in the central and southern parts of the reservoir (Fig. 3). This pattern of pigment distribution in the reservoir is typical for the summer period of maximum water heating (Mineeva, 2021). High Chl a (> 60 ^g/L) was recorded in the southern part of the Main Reach in the zone of the local ecotone, where various water masses were confluencing and mixing. High values of Chl a (> 40 ^g/L) were also noted in the upper Sheksna Reach near the city of Cherepovets and in the Sheksna River. The pigment concentration was significantly lower in the other parts of the reservoir, with minimal values registered in the Mologa Reach (< 5 ^g/L).
The biomass ratio of the main taxonomic groups of phytoplankton is similar to the data published earlier (Korneva, 2015; Struktura..., 2018;): ChlCyan and ChlBac contribute the most to total Chl a At the Volga Reach, the contribution of ChL reaches 78%, while
Cyan
that of ChlBac is the lowest. At the Main and Mologa reaches, the contribution of ChL and ChL is close
Cyan Bac
to the average, 63-67% and 24-31%, respectively (Table 2). At the Sheksna Reach, more than a half of Chl a is represented by ChlBac (57%), only a third (32%), by ChlCyan The contribution of ChlChl is low, varying from 5% at the Volga Reach up to 10% at the Sheksna Reach. Generally, average relative content of ChlCyan and ChlBac is 62 and 31%, respectively, in the Rybinsk Reservoir.
The highest average content of Chl a (28 ^g/L) has been recorded at the Volga and Sheksna reaches; at the Main Reach, it did not exceed 18 ^g/L. Such values are typical for eutrophic waters. At the Mologa Reach, the content of Chl a (10.1 ^g/L) is close to that observed in mesotrophic waters (Table 2). In the entire reservoir, the average value (21.2 ^g/L) is the highest over three years of observations. This is due to weak mixing of the water column and the ascending of the blue-green algae into the surface water layer.
In 2019, Chl a distribution over the water area of the Rybinsk Reservoir was moderately heterogeneous (Cv = 69%). The range of values was shifted leftwards compared to 2018 (2.2-68.0 ^g/L). Active vegetation of phytoplankton was noted in the northern part of Main Reach and at the Sheksna Reach, as
well as in the southeastern part of the reservoir. Maximum Chl a (35-68 ^g/L) were registered at the Main Reach. Chl a concentration did not exceed 24 ^g/L at three other reaches. Minimum values (< 5 ^g/L) were noted at the Mologa Reach and in the eastern part of the Main Reach (Fig. 3).
The chlorophyll ratio of the main divisions of algae differed from the values obtained in 2018. Chl-Cyan predominated (50-56%), but the share of ChlBac decreased down to 35% at the Main and Sheksna reaches, while the share of ChlBac increased up to 44-51% at the Volga and Mologa reaches compared to the previous year. The relative content of ChlChl at the Main and Volga reaches was the highest for the study period (15-22%). The average relative content of ChL and ChL in the reservoir was 47 and 40%,
Cyan Bac
respectively.
The average concentration of Chl a at the Volga, Main, and Sheksna reaches were 18.4, 19.2, and 20.3 ^g/L, respectively; this corresponded to eutrophic waters. At the Mologa Reach, the value of this indicator was almost two times lower (11 ^g/L), i.e., moderately eutrophic waters (Table 2). In 2019, the average Chl a concentration in the entire reservoir was lower than in 2018 (17.6 ^g/L). In the coastal zone of the Sheksna Reach, Chl a concentration was 36% higher than at deep-water stations; in the Mologa Reach near the shore, it decreased by 15%. No significant differences were found in the other two reaches.
The year of 2020 is characterized by the widest range of values (from 0.26 to 116 ^g/L) and the most heterogeneous spatial distribution of Chl a (Cv = 140%). The maximum concentration of Chl a were noted in the southern part of the Volga Reach and at the Sheksna Reach (116 and 91 ^g/L, respectively). High values were also registered in the western part of the Mologa Reach (66 ^g/L). There were no large accumulations of algae in the open areas: the lowest Chl a (< 5 ^g/L) was recorded in the center of the reservoir (Fig. 3).
In total Chl a, ChlBacdominated at the Mologa and Sheksna reaches (81% and 50%), while ChlCyan dominated at the Main and Volga reaches (53% and 59%). The contribution of ChlChl was low (5-10%). The average relative content of Chl and Chl in contrast
° Cyan Bac,
to the two previous years, was characterized by an increase in the share of the latter up to 48%.
Average concentration of Chl a at the Volga, Sheksna, and Mologa reaches (25, 15.6, 18.3 ^g/L) correspond to the eutrophic waters, while the Main Reach (12.4 ^g/L) is moderately eutrophic (Table 2). Lower water temperature, constant wind activity with heavy precipitation led to a decrease in photosynthet-ic activity due to the competitive advantage of small-sized algae with lower productivity (Winder and Summer, 2012). This is expressed in a decrease in the average Chl a concentration down to 16.7 ^g/L, the lowest for the entire study area over the entire study
2018 2019 2020
c
10 10 10
Fig. 2. Wind rose: winds prevailing a week before sampling in 2018-2020.
Fig. 3. Spatial distribution of Chl a (|jg/L) in the Rybinsk Reservoir in the summer period of 2018-2020.
Fig. 4. Spatial distribution of PAC in the Rybinsk Reservoir in the summer period of 2018-2020.
Table 2. Average content of chlorophyll a and share of chlorophyll of main algae taxa. ChlCyan - chlorophyll of cyanobacteria; ChlBac - chlorophyll of diatoms; ChlChl - chlorophyll of green algae.
Year Reach Chl a, ^g/L ChlC , % Cyan' ChlBa, % ChlCh. %
Volga 28.5 ± 12.2 78 17 5
Main 18.9 ± 5.1 67 24 9
2018 Mologa 27.9 ± 7.1 63 31 6
Sheksna 10.1 ± 1.4 33 57 10
Total for Rybinsk Reservoir 21.2 ± 3.51 62 30 8
Volga 18.4 ± 3.2 34 44 22
Main 19.2 ± 4.5 50 35 15
2019 Mologa 20.2 ± 3.4 42 51 7
Sheksna 11.1 ± 2.6 56 35 9
Total for Rybinsk Reservoir 17.6 ± 2.03 47 40 13
Volga 25.2 ± 9.9 59 34 7
Main 12.4 ± 2.4 53 37 10
2020 Mologa 15.6 ± 0.9 15 81 4
Sheksna 18.3 ± 7.2 40 50 10
Total for Rybinsk Reservoir 16.7 ± 3.4 43 48 9
period. Under such conditions, the vegetation of algae in the semi-closed parts of the reservoir is more intense (Pyrina et al., 1976). A significant difference in the content of Chl a has been registered at deep-water and shallow-water coastal stations of each reach: in shallow waters, the values were 2-4 times higher than in the open part of the reservoir.
The effective quantum yield of fluorescence is one of the parameters assessing the state of the pho-tosynthetic apparatus of phytoplankton (Goltsev and Kaladzhi, 2016; Hartig et al., 1998; Mosharov and Sergeeva, 2018). The photosynthetic activity coefficient (PAC) characterizes the proportion of light quanta used in photosynthetic reactions of PS II (Maxwell and Johnson, 2000), and reflects the efficiency of solar energy absorption.
In 2018, PAC values in the Rybinsk Reservoir varied from 0.19 to 0.51 (Cv = 22%). The pattern of PAC distribution (Fig. 4) was similar to that of Chl a (Fig. 3). PAC values above 0.40 were noted in the northern part of the water area in the Sheksna Reach (PACav = 0.41) and in the Sheksna River, as well as at theavVolga Reach (PACav = 0.38). Low PAC (< 0.30) were observed singly at the Mologa Reach and in the eastern part of the reservoir. The predominance of certain division of algae did not affect the overall photosynthetic activity. Thus, at the Mologa, Main, and Volga reaches, ChlCyan dominated in total Chl a, at the Sheksna Reach, this was ChlB with approximately
equal PAC values. At seven stations, PAC < 0.3 were noted, which indicated the inhibition of photosynthetic processes (Rubin, 2005). PAC exceeding 0.50 was noted only at one station (Table 3). We argue that the mass development of phytoplankton organisms leads to intercompetition for light and nutrients, which is expressed by a decrease in the efficiency of solar energy absorption at chlorophyll concentrations of more than 40 ^g/L. The average PAC at the Main and Mologa reaches (0.33) is close to the critical low value; at the Sheksna and Volga reaches, they are higher (0.41 and 0.39, respectively) and correspond to the normal functioning of phytoplankton community (Table 4). The average PAC for the entire reservoir was 0.36.
In 2019, a range of PAC was close to that observed in 2018 (0.26-0.58), with low variability (Cv = 18%). The spatial distribution of PAC also differed little comparing to 2018 (Fig. 4), but did not coincide with the distribution of Chl a (Fig. 3). High values of PAC (> 0.50) were noted in different areas of the Volga, Main, and Sheksna reaches, while the minimum values (< 0.30) were recorded in the Mologa Reach. The maximum average PAC (0.49) was registered at the Volga Reach, where the ChlBac share reached 72% in the total Chl a, accompanied by high share of ChlChl (25%). Similar data were obtained by other researchers (Darchambeau et al. al., 2014; Ratan, 2017). The highest average PAC (0.46) was also noted here. At the Main, Sheksna, and Mologa reaches, lower mean
Table 3. Frequency of occurrence of PAC value range in the Rybinsk Reservoir in 2018-2020.
PAC
Year
< 0.3 0.3-0.5 0.5-0.7
2018 23% 71% 3%
2019 8% 76% 16%
2020 47% 53% 0% Total 26% 67% 6%
Table 4. PAC values (mean ± error of mean) at the reaches of the Rybinsk Reservoir.
Reach
Year
2018 2019 2020
Volga 0.39 ± 0.03 0.49 ± 0.03 0.23 ± 0.06
Main 0.33 ± 0.06 0.42 ± 0.02 0.30 ± 0.03
Mologa 0.33 ± 0.07 0.36 ± 0.02 0.41 ± 0.02
Sheksna 0.41 ± 0.06 0.43 ± 0.02 0.27 ± 0.04
values were obtained (0.42, 0.43, and 0.36, respectively). The first two were characterized by the ChlCyan to ChlBac ratio typical for the summer period (~60% to ~30%, respectively); at the Mologa Reach, more than half of the total Chl a was represented by ChlBac. The photosynthetic activity of algae from deep-water and shallow-water stations differed insignificantly in most cases. At the Mologa Reach, the average PAC at the riverbed stations was 11% higher than in the coastal zone. In 8% of cases, PAC was below 0.30, in 16%, exceeded 0.5. Compared to 2018, phytoplankton vegetated under more favorable conditions in 2019. The average PAC was 0.41 for the entire reservoir.
In 2020, under unstable hydrometeorological conditions, the PAC range was the widest (0.02-0.47), and the spatial distribution was characterized by the highest heterogeneity observed for all the considered years (Cv = 143%). High PAC (> 0.40) were noted locally at all reaches of the reservoir (Fig. 5). The minimum values (< 0.30) were registered in the open areas of the Main and Volga reaches. In these zones, ChlCyan dominated in the total Chl a (53-58%). A higher concentration of ChlBac was recorded in the semi-closed part of the reservoir. The average PAC (0.23, 0.27, and 0.30) reflected the development of phytoplankton under stress conditions at the Volga, Sheksna, and Main reaches, respectively. At the semi-closed Mologa Reach, PAC = 0.41. The maximum
° ' av
PAC was noted in the shallow semi-closed areas of the reservoir and in the river mouths. The PAC was higher in the coastal zone comparing to the channel
stations: at the Volga Reach, by 36%, at the Mologa Reach, by 6%. PAC < 0.3 was noted in 47% of cases, PAC exceeding 0.5 was not registered. The average PAC for the entire reservoir was 0.30, the lowest for
av
the entire study period.
The content of Chl a is considered to be a universal ecological and physiological characteristic of the pho-tosynthetic activity of algae; this indicator reflects the amount of synthesized biomass under the prevailing environmental conditions and the physiological state of organisms. In pristine, anthropogenically undisturbed ecosystems, the relationship between the quantum yield and Chl a is most often positive (Mosharov and Sergeeva, 2018; Popik, 2015). In the Rybinsk Reservoir in 2018, the relationship between PAC and Chl a is moderate (r = 0.55), the relationship with the relative amount of ChL and ChL. is closer (r = 0.66 and 0.76,
Bac Chl
respectively). In 2019, a significant relationship is observed only with the share of ChlChl (r = 0.59). In 2020, the closest correlation of PAC with Chl a is obtained (r = 0.78), less pronounced with the shares of ChlBac and ChlChl (r =0.61 and 0.66, respectively). For the entire period of studies (2018-2020), the relationship between PAC and Chl a is characterized by moderate tightness (r = 0.64). If one excludes the Chl a values exceeding 40 ^g/L from the dataset, which are characteristic of eutrophic and hypereutrophic water bodies, the correlation coefficient increases (r = 0.73).
In general, Chl a is related to PAC non-linearly. When ranking PAC values by chlorophyll content, an approximation equation with a high coefficient
Fig 5. Dependence of PAC on Chl a content in 2018 (A) and in 2018-2020 (B).
of determination has been obtained both for certain years (Fig. 5A) and for the entire dataset (Fig. 5B):
K0A = -0.00005xX^2 + X^ + 0.148 (n = 114, R2 = 0.50).
For the entire data series, the relationship is non-linear; a logarithmic increase of PAC up to 0.5 occurs along an increase of Chl a concentration up to 40 ^g/L. The maximum activity of the photosynthetic apparatus (PAC = 0.58) is observed at Chl a concentration of 20 to 40 ^g/L. As Chl a content increases further, PAC decreases (Fig. 5). In 2018, the relationship between PAC and Chl a at > 40 ^g/L has a shape of logarithmic curve except two stations.
Conclusions
The spatial distribution of chlorophyll in the Rybinsk Reservoir in summer is characterized by a high degree of heterogeneity, when coefficients of variation range from 69% at prevailing calm weather and low wind speed up to 140% at strong winds and heavy precipitation. Chlorophyll concentration is generally higher in coastal areas and in semi-closed shallow water areas than at deep (open) riverbed stations.
PAC, determined for the phytoplankton of the Rybinsk Reservoir for the first time, ranges 0.3-0.5 in most of cases (66%), which indicates a normal physiological state of algae. PAC less than 0.3 makes up a significant share at unstable hydrometeorological conditions.
The spatial distribution of PAC and Chl a do not coincide with each other. High PAC is observed throughout the entire water area of the reservoir, depending on the conditions of a certain year; high PAC is registered most often in the southern and northern parts of the reservoir. In 2018 and 2019, a horizontal displacement of algae along the wind direction has been noted, which did not affect PAC. The relationship between PAC and Chl is not linear. The maximum activity of the photosynthetic apparatus is observed in the range of chlorophyll concentrations from 20 to 40 ^g/L. At Chl a above 40 ^g/L, PAC decreases.
ORCID
l.v. Semadeni 0000-0003-2381-4587 References
Darchambeau, F., Sarmento, H., Descy, J.-P., 2014. Primary production in a tropical large lake: The role of phytoplankton composition. Science of the Total Environment 1 (473-474), 178-188. http://www. doi.org/10.1016/j.scitotenv.2013.12.036
Elizarova, V.A., 1999. Populyatsionnyi rost vodoroslei v vodoeme [Population growth of algae in a pond]. In: Pautova, V.N., Rozenberg, G.S.
(eds.), Ekologiya fitoplanktona Rybinskogo vodokhranilishcha [Ecology of phytoplankton in the Rybinsk Reservoir]. Institute of Ecology of the Volga River Basin RAS, Tol'yatti, Russia, 51-68. (In Russian).
Primary production in a tropical large lake: The role of phytoplankton composition. Science of the Total Environment 1 (473-474), 178-188. http://www. doi.org/10.1016/j.scitotenv.2013.12.036
Gaevsky, N.A., Kolmakov, V.l., Anischenko, O.V., Gorbaneva, T.B., 2005. Using DCMU-fluorescence method for identification of dominating phytoplankton groups. Journal of Applied Phycology 17 (6), 483-494. http://www.doi. org/10.1007/s10811-005-2903-x \
Gaevsky, N.A., Shatrov, I.Yu., Gol'd, V.M., 1993. Fluorestsentnyi analiz pigmentov fitoplanktona [Fluorescent analysis of phytoplankton pigments]. In: Pyrina, I.L. (ed.), Metodicheskie voprosy izucheniya pervichnoi produktsii vnutrennikh vodoemov [Methodological issues of studying the primary production of inland water bodies]. Gidrometeoizdat, St. Petersburg, Russia, 101109. (In Russian).
Gol'tsev, V.N., Kaladzhi, H.M., 2016. Ispol'zovanie peremennoi fluorestsentsii khlorofilla dlya otsenki fiziologicheskogo sostoyaniya fotosinteticheskogo apparata rastenii [Use of variable chlorophyll fluorescence to assess the physiological state of the photosynthetic apparatus of plants]. Fiziologiya rastenii [Plant Physiology] бз(б), 881-907. (In Russian).
Gol'tsev, V.N., Kaladzhi, M.H., Kuzmanova, M.A., Allakhverdiev, S.I., 2014. Peremennaya i zamedlennaya fluorescentsiya khlorofilla a -teoreticheskie osnovy i prakticheskoe prilozhenie v issledovanii rastenii [Variable and delayed fluorescence of chlorophyll a - theoretical foundations and practical application in plant research]. Institute of Computer Studies, Moscow -Izhevsk, Russia, 220 p. (In Russian).
Gol'd, V.M., Gaevsky, N.A., Shatrov, I.Yu., 1986. Opyt ispotezovaniya fluorestsentsii dlya differentsial'noi otsenki soderzhaniya khlorofilla u planktonnykh vodoroslei [Experience in using fluorescence for differential assessment of chlorophyll content in planktonic algae]. Gidrobiologicheskii zhurnal [Hydrobiological Journal] 22 (3), 80-85. (In Russian).
Hartig, P., Wolfstein, K., Lippemeier, S., Colijn, F., 1998. Photosynthetic activity of natural microphytobenthos populations measured by
fluorescence (PAM) and 14C-tracer methods: a comparison. Marine Ecology Progress Series 166, 53-62. http://www.doi.org/10.3354/meps166053
Ivanova, E.A., Anishhenko, O.V., Gaevsky, N.A., Glushhenko, L.A., Kolmakov, V.I., 2014. Vklad raznykh grupp avtotrofov v pervichnuyu produktsiyu gornogo ozera Oiskoe [The contribution of different groups of autotrophs to the primary production of the mountain lake Oiskoe]. Sibirskii ekolologicheskii zhurnal [Siberian Ecological Journal] 4, 531-546. (In Russian).
Ekologicheskie faktory prostranstvennogo raspredeleniya i peremeshcheniya gidrobiontov [Ecological factors of spatial distribution and movement of hydrobionts], 1993. Poddubny, A.G. (ed.). Gidrometeoizdat, St. Petersburg, Russia, 333 p. (In Russian).
Koreneva, T.G., 2017. Otsenka ekologicheskogo sostoyaniya zaliva Aniva (Okhotskoe more) po fitopigmentnym kharakteristikam [Assessment of the ecological state of the Aniva Bay (Sea of Okhotsk) according to phytopigment characteristics]. Biological sciences PhD thesis abstract. Yuzhno-Sakhalinsk, Russia, 24 p. (In Russian).
Korneva, L.G., 2015. Fitoplankton vodokhranilishch basseina Volgi [Phytoplankton of reservoirs of the Volga River basin]. Kostroma Printing House, Kostroma, Russia, 284 p. (In Russian).
Kurochkina, V.A., 2019. Intrapopulation variability of functional and morphological parameters of algae Conticribra weissflogii and Attheya ussurensis under osmotic stress. Biological sciences PhD thesis abstract. Moscow, Russia, 26 p. (In Russian).
Matorin, D.N., Rubin, A.B., 2012. Fluorestsentsiya khlorofilla vysshikh rastenii i vodoroslei [Fluorescence of chlorophyll in higher plants and algae]. Institute of Computer Studies, Moscow, Russia, 256 p. (In Russian).
Maxwell, K., Johnson, G.N., 2000. Chlorophyll fluorescence - a practical guide. Journal of Experimental Botany 51 (345), 659-668. http:// www.doi.org/10.1093/jexbot/51.345.659
Metodika izucheniya biogeotsenozov vnutrennikh vodoemov [Methodology for studying biogeocenoses of inland water bodies], 1975. Mordukhai-Boltovskoy, F.D. (ed.). Nauka, Moscow, USSR, 240 p. (In Russian).
Mineeva, N.M., 2004. Rastitel'nye pigmenty v vode volzhskikh vodokhranilishch [Plant pigments in the water of the Volga reservoirs]. Nauka, Moscow, Russia, 156 p. (In Russian).
Mineeva, N.M., 2009. Pervichnaya produktsiya planktona v vodokhranilishchakh Volgi [Primary production of plankton in the reservoirs of the Volga River]. Printhaus, Yaroslavl', Russia, 279 p. (In Russian).
Mineeva, N.M., 2021. Mnogoletnyaya dinamika khlorofilla v planktone razlichnykh uchastkov krupnogo ravninnogo vodokhranilishcha [Long-term dynamics of chlorophyll in plankton in various parts of a large lowland reservoir]. Biologiya vnutrennikh vod [Inland Water Biology] 6, 574585. (In Russian).
Mosharov, S.A., Sergeeva, V.M., 2018. Otsenka funkcional'nogo sostoyaniya morskogo fitoplanktona po fluorestsentnym pokazatelyam i sootnosheniyu kontsentratsii feofitina i khlorofilla a [Assessment of the functional state of marine phytoplankton by fluorescent indicators and the ratio of the concentrations of pheophytin and chlorophyll a]. Voprosy sovremennoj al'gologii [Issues of Modern Algology] 1 (16). (In Russian).
Piirsoo, K., Pall, P., Tuvikene, A., Viik, M., 2008, Temporal and spatial patterns of phytoplankton in a temperate lowland river (Emajogi, Estonia). Journal of Plankton Research 30 (11), 1285-1295. http://www.doi.org/10.1093/plankt/fbn082
Popik, A.Ju., 2015. Dinamika spektrov lazernoi indutsirovannoi fluorestsentsii khlorofilla a fitoplanktona v usloviyakh menyayushchikhsya parametrov vneshnei sredy [Dynamics of the laser-induced fluorescence spectra of phytoplankton chlorophyll a under changing environmental parameters]. Physical and Mathematical Sciences PhD thesis abstract. Vladivostok, Russia, 145 p. (In Russian).
Pyrina, I.L., Bashkatova, E.L., Sigareva, L.E., 1976. Pervichnaya produktsiya fitoplanktona v melkovodnoi zone Rybinskogo vodokhranilishcha v 1971-1972 gg. [Primary production of phytoplankton in the shallow waters of the Rybinsk Reservoir in 1971-1972]. In: Butorin, N.V (ed.), Gidrobiologicheskii rezhim pribrezhnykh melkovodii verkhne-volzhskikh vodokhranilishch [The hydrobiological regime of the coastal shallow waters of the upper Volga River reservoirs]. Institute for Biology of Inland Waters, Yaroslavl, Russia, p. 106-132. (In Russian).
Rattan, K.J., 2017. Comparative analyses of physiological assays and chlorophyll a variable fluorescence parameter: investigating the
Rubin, A.B., 2005. Biofizika fotosinteza i metody ekologicheskogo monitoringa [Biophysics of photosynthesis and methods of ecological monitoring]. Tehnologii zhivykh system [Technologies of Living Systems] 1 (2), 425-453. (In Russian).
Rybinskoe vodokhranilishche i ego zhizn' [Rybinsk reservoir and its life] 1972. Kuzin, B.S. (ed.). Nauka, Leningrad, USSR, 364 p. (In Russian).
Semadeni, I.V., Mineeva, N.M., 2019. Soderzhanie khlorofilla kak pokazatel' kachestva vody vodokhranilishch Verkhnei Volgi v gody s razlichnymi gidroklimaticheskimi usloviyami [Chlorophyll content as an indicator of water quality in reservoirs of the Upper Volga in years with different hydroclimatic conditions]. Materialy II Mezhdunarodnoi konferentsii "Ozera Evrazii: Problemy i puti ikh resheniya". Ch. 2 [Materials of the 2nd International conference "Lakes of Eurasia: Problems and ways to solve them". P. 2]. Kazan', Russia, 327-331. (In Russian).
Sigareva, L.E., 2012. Chlorophyll v donnykh otlozheniyakh volzhskikh vodoemov [Chlorophyll in the bottom sediments of the Volga River reservoirs]. KMK, Moscow, Russia, 217 p. (In Russian).
Struktura i funktsionirovanie ekosistemy Rybinskogo vodokhranilishcha v nachale XXI veka [Structure and functioning of the ecosystem of the Rybinsk Reservoir at the beginning of the XXI century], 2018. Lazareva, V.I. (ed.). Russian Academy of Sciences, Moscow, Russia, 457 p. (In Russian).
Suggett, D.J, Moore, C.M., Geider, R.J., 2010. Estimating aquatic productivity from active fluorescence measurements. In: Sugget, D.J, Borowotzka, M.A., Prasil, O. (eds.), Chlorophyll a Fluorescence in Aquatic Sciences: Methods and Applications, 103-127. http://www.doi. org/10.1007/978-90-481-9268-7_6
Tesfay, H., 2007. Spatio-temporal variations of the biomass and primary production of phytoplankton in Koka Reservoir. Candidate of Biological Sciences thesis. Addis Ababa, Ethiopia, 92 p.
Todorenko, D.A., 2016. Kharakteristiki svetovykh reaktsii fotosinteza pri vozdeistvii toksicheskikh veshchestv [Characteristics of light reactions of photosynthesis under the influence of toxic
substances.]. Biological Sciences PhD thesis abstract. Moscow, Russia, 129 p. (In Russian).
Winder, M., Sommer, U., 2012. Phytoplankton response to a changing climate. Hydrobiologia 698, 5-16. http://www.doi.org/10.1007/s10750-012-1149-2
Список литературы
Гаевский, Н.А., Шатров, И.Ю., Гольд, В.М., 1993. Флуоресцентный анализ пигментов фитопланктона. В: Пырина, И.Л. (ред.), Методические вопросы изучения первичной продукции внутренних водоемов.
Гидрометеоиздат, СПб, Россия, 101-109.
Гольд, В.М., Гаевский, Н.А., Шатров, И.Ю., 1986. Опыт использования флуоресценции для дифференциальной оценки содержания хлорофилла у планктонных водорослей. Гидробиологический журнал 22 (3), 80-85.
Гольцев, В.Н., Каладжи, Х.М., 2016. Использование переменной флуоресценции хлорофилла для оценки физиологического состояния фотосинтетического аппарата растений. Физиология растений 63 (6), 881-907.
Гольцев, В.Н., Каладжи, М.Х., Кузманова, М.А., Аллахвердиев, С.И., 2014. Переменная и замедленная флуоресценция хлорофилла a - теоретические основы и практическое приложение в исследовании растений. Институт компьютерных исследований, Москва - Ижевск, Россия, 220 с.
Елизарова, В.А., 1999. Популяционный рост водорослей в водоеме. В: Паутова, В.Н., Розенберг, Г.С. (ред.), Экология фитопланктона Рыбинского водохранилища. Институт экологии Волжского бассейна РАН, Тольятти, Россия, 51-68.
Иванова, Е.А., Анищенко, О.В., Гаевский, Н.А., Глущенко, Л.А., Колмаков, В.И., 2014. Вклад разных групп автотрофов в первичную продукцию горного озера Ойское. Сибирский экологический журнал 4, 531-546.
Коренева, Т.Г., 2017. Оценка экологического состояния залива Анива (Охотское море) по фитопигментным характеристикам. Автореферат диссертации на соискание ученой степени кандидата биологических наук. Южно-Сахалинск, Россия, 24 с.
Корнева, Л.Г., 2015. Фитопланктон водохранилищ бассейна Волги. Костромской печатный дом, Кострома, Россия, 284 с.
Курочкина, В.А, 2019. Внутрипопуляционная изменчивость функциональных и
морфологических параметров водорослей weissflogii и Attheya ussurensis при осмотическом стрессе. Автореферат диссертации на соискание ученой степени кандидата биологических наук. Москва, Россия, 26 с.
Маторин, Д.Н., Рубин, А.Б., 2012. Флуоресценция хлорофилла высших растений и водорослей. Институт компьютерных исследований, Москва, Россия, 256 с.
Методика изучения биогеоценозов внутренних водоемов, 1975. Мордухай-Болтовской, Ф.Д. (ред.). Наука, Москва, СССР, 240 с.
Минеева, Н.М., 2004. Растительные пигменты в воде волжских водохранилищ. Наука, Москва, Россия, 156 с.
Минеева, Н.М., 2009. Первичная продукция планктона в водохранилищах Волги. Принтхаус, Ярославль, Россия, 279 с.
Минеева, Н.М., 2021. Многолетняя динамика хлорофилла в планктоне различных участков крупного равнинного водохранилища. Биология внутренних вод 6, 574-585.
Мошаров, С.А., Сергеева, В.М., 2018. Оценка функционального состояния морского фитопланктона по флуоресцентным показателям и соотношению концентраций феофитина и хлорофилла а. Вопросы современной альгологии 1 (16).
Попик, А.Ю., 2015. Динамика спектров лазерной индуцированной флуоресценции хлорофилла а фитопланктона в условиях меняющихся параметров внешней среды. Диссертация на соискание ученой степени кандидата физико-математических наук. Владивосток, Россия, 145 с.
Пырина, И.Л., Башкатова, Е.Л., Сигарева, Л.Е., 1976. Первичная продукция фитопланктона в мелководной зоне Рыбинского водохранилища в 1971-1972 гг. В: Буторин, Н.В. (ред.), Гидробиологический режим прибрежных мелководий верхне-волжских водохранилищ. ИБВВ, Ярославль, Россия, 106-132.
Рубин, А.Б., 2005. Биофизика фотосинтеза и методы экологического мониторинга. Технологии живых систем 1 (2), 425-453.
Рыбинское водохранилище и его жизнь, 1972. Кузин, Б.С. (ред.). Наука, Ленинград, СССР, 364 с.
Семадени, И.В., Минеева, Н.М., 2019. Содержание хлорофилла как показатель качества воды водохранилищ Верхней Волги в годы с различными гидроклиматическими условиями. Материалы II Международной конференции «Озера Евразии: проблемы и пути их решения». Ч. 2, Казань, Россия, 327331.
Сигарева, Л.Е., 2012. Хлорофилл в донных отложениях волжских водоемов. Товарищество научных изданий КМК, Москва, Россия, 217 с.
Структура и функционирование экосистем Рыбинского водохранилища в начале XXI века, 2018. Лазарева, В.И. (ред.). РАН, Москва, Россия, 457 с.
Тодоренко, Д.А., 2016. Характеристики световых реакций фотосинтеза при воздействии токсических веществ. Диссертация на соискание ученой степени кандидата биологических наук. Москва, Россия, 129 с.
Экологические факторы пространственного распределения и перемещения гидробионтов, 1993. Поддубный, А.Г. (ред.). Гидрометеоиздат, СПб., Россия, 333 с.
Darchambeau, F., Sarmento, H., Descy, J.-P., 2014. Primary production in a tropical large lake: The role of phytoplankton composition. Science of the Total Environment 1 (473-474), 178-188. http://www. doi.org/10.1016/j.scitotenv.2013.12.036
Gaevsky, N.A., Kolmakov, V.I., Anischenko, O.V., Gorbaneva, T.B., 2005. Using DCMU-fluorescence method for identification of dominating phytoplankton groups. Journal of Applied Phycology 17 (6), 483-494. http://www.doi. org/10.1007/s10811-005-2903-x
Hartig, P., Wolfstein, K., Lippemeier, S., Colijn, F., 1998. Photosynthetic activity of natural microphytobenthos populations measured by fluorescence (PAM) and 14C-tracer methods: a comparison. Marine Ecology Progress Series 166, 53-62. http://www.doi.org/10.3354/meps166053
Maxwell, K., Johnson, G.N., 2000. Chlorophyll fluorescence - a practical guide. Journal of Experimental Botany 51 (345), 659-668. http:// www.doi.org/10.1093/jexbot/51.345.659
Piirsoo, K., Pall, P., Tuvikene, A., Viik, M., 2008, Temporal and spatial patterns of phytoplankton in a temperate lowland river (Emajogi, Estonia). Journal of Plankton Research 30 (11), 1285-1295. http://www.doi.org/10.1093/plankt/fbn082
Rattan, K.J., 2017. Comparative analyses of physiological assays and chlorophyll a variable fluorescence parameter: investigating the importance of phosphorus availability in oligotrophic and eutrophic freshwater systems. Aquatic Ecology 51 (3), 359-375. https://doi.org/10.1007/s10452-017-9622-7
Suggett, D.J, Moore, C.M., Geider, R.J., 2010. Estimating aquatic productivity from active fluorescence measurements. In: Sugget, D.J, Borowotzka, M.A., Prasil, O. (eds.), Chlorophyll a Fluorescence in Aquatic Sciences: Methods and Applications, 103-127. http://www.doi. org/10.1007/978-90-481-9268-7_6
Tesfay, H., 2007. Spatio-temporal variations of the biomass and primary production of phytoplankton in Koka Reservoir. Candidate of Biological Sciences thesis. Addis Ababa, Ethiopia, 92 p.
Winder, M., Sommer, U., 2012. Phytoplankton response to a changing climate. Hydrobiologia 698, 5-16. http://www.doi.org/10.1007/s10750-012-1149-2
