Figure 1

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Figure 5

Figure 6

Means (and ranges) of the water quality parameters in the Sestroretskiy Razliv reservoir in different years (1980, 2002, 2016 and 2018)_ The comparison of the means among different years was carried out using ANOVA with the Tukey–Kramer test_ The Tukey–Kramer test results are indicated by superscripts_
| Parameter | 1980 | 2002 | 2016 | 2018 | F | p |
|---|---|---|---|---|---|---|
| Σ ions (mg l−1) | 57 | 67 | 68 | 71 | 1.82 | 0.171 |
| (37–84) | (64–71) | (47–98) | (55–85) | |||
| HCO3− (mg l−1) | 16ab | 12a | 22ab | 27b | 7.22 | < 0.01 |
| (10–23) | (9–15) | (14–32) | (18–41) | |||
| Secchi depth (m) | 0.76a | 0.34b | 0.36b | 0.44b | 8.14 | < 0.001 |
| (1.00–0.60) | (0.50–0.18) | (0.50–0.15) | (0.75–0.15) | |||
| Color (Pt-Co) | 130a | 128a | 178b | 107a | 10.05 | < 0.0001 |
| (103–152) | (112–144) | (121–240) | (77–140) | |||
| pH | 7.8a | 8.6a | 6.8b | 7.0b | 14.48 | < 0.0001 |
| (7.2–8.8) | (7.3–9.8) | (6.7–7.0) | (6.1–8.1) | |||
| TP (μg l−1) | 73a | 163b | 96a | 106a | 7.85 | < 0.001 |
| (32–158) | (94–233) | (49–150) | (42–170) | |||
| PO4-P (μg l−1) | 10a | 31b | 43b | 51b | 25.83 | < 0.0001 |
| (4–38) | (19–52) | (13–77) | (26–80) | |||
| TN (mg l−1) | 1.18a | 0.72b | 0.62b | 0.70b | 19.10 | < 0.0001 |
| (0.82–1.54) | (0.45–0.86) | (0.44–0.92) | (0.39–0.95) |
Means (and ranges) of phytoplankton biomass (B), chlorophyll a (Chl a) and relative biomass of diatoms (% Diatom) and cyanobacteria (% Cyanobacteria) in the Sestroretskiy Razliv reservoir in different years (1980, 2002, 2016 and 2018)_ The comparison of the means among different years was calculated using ANOVA with the Tukey–Kramer test_ The Tukey–Kramer test results are indicated by superscripts_
| Parameter | 1980 | 2002 | 2016 | 2018 | F | p |
|---|---|---|---|---|---|---|
| B (mg l−1) | 6.8a | 61.0b | 17.6c | 23.1c | 18.02 | < 0.0001 |
| (0.3–19.8) | (15.8–99.6) | (3.9–35.6) | (7.0–49.8) | |||
| Chl a (μg l−1) | 16.6a | 84.7b | 43.6ab | 66.6b | 6.87 | < 0.001 |
| (0.7–27.2) | (20.5–174.9) | (8.4–122.9) | (27.4–157.6) | |||
| % Diatom | 55.8a | 15.7b | 75.6a | 59.7a | 19.30 | < 0.0001 |
| (21.2–95.5) | (2.1–58.6) | (20.7–94.0) | (32.5–88.6) | |||
| % Cyanobacteria | 14.5aс | 75.9b | 2.4с | 26.2a | 23.94 | < 0.0001 |
| (0–46.2) | (26.9–96.4) | (0.3–6.7) | (1.2–62.1) |
Contribution of different species of helophytes, floating-leaved and submerged plants to the total plant coverage and the area of the Sestroretskiy Razliv reservoir in 1980 and 2016
| Ecological groups and species | Area, ha | % of plant cover | % of reservoir area | |||
|---|---|---|---|---|---|---|
| 1980* | 2016 | 1980* | 2016 | 1980* | 2016 | |
| Helophytes | ||||||
| Phragmites australis | 53.4 | 26.1 | 33.9 | 34.4 | 5.03 | 2.30 |
| Scirpus lacustris | 42.5 | 16.2 | 27.0 | 21.3 | 4.00 | 1.50 |
| Carex spp. | 0.3 | 9.5 | 0.2 | 12.5 | 0.03 | 0.90 |
| Equisetum fluviatile | 24.6 | 4.7 | 15.6 | 6.2 | 2.32 | 0.40 |
| Typha latifolia | (+) | 1.2 | (+) | 1.6 | (+) | 0.10 |
| Sparganium erectum + S. emersum + Butomus umbellatus | 5.6 | 3.6 | 3.6 | 4.7 | 0.53 | 0.30 |
| Total: | 126.4 | 61.3 | 80.4 | 80.8 | 11.91 | 5.50 |
| Floating-leaved plants | ||||||
| Nuphar lutea | 3.0 | 6.7 | 1.9 | 8.8 | 0.29 | 0.62 |
| N. pumila | 0.1 | (+) | 0.1 | (+) | 0.01 | (+) |
| Potamogeton natans | 3.4 | 3.2 | 2.2 | 4.2 | 0.32 | 0.30 |
| Persicaria amphibia | 6.3 | 2.4 | 4.0 | 3.2 | 0.60 | 0.22 |
| Sparganium gramineum | 0.1 | 0.7 | 0.1 | 0.9 | 0.01 | 0.07 |
| Nymphaea candida | 3.6 | 0.1 | 2.3 | 0.1 | 0.34 | 0.01 |
| Mixed beds | 11.9 | 0.9 | 7.6 | 1.2 | 1.13 | 0.08 |
| Total: | 28.4 | 14.0 | 18.1 | 18.4 | 2.70 | 1.30 |
| Submerged plants | ||||||
| P. perfoliatus | 2.5 | 0.6 | 1.6 | 0.8 | 0.20 | 0.10 |
| Total: | 157.3 | 75.9 | 100.0 | 100.0 | 14.81 | 6.80 |
Contribution of ecological groups of aquatic plants to the total aboveground biomass in the Sestroretskiy Razliv reservoir in 1980 and 2016
| Ecological group | Aboveground biomass | |||
|---|---|---|---|---|
| 1980* | 2016 | |||
| 103 kg | % | 103 kg | % | |
| Helophytes | 872.6 | 93.95 | 654.9 | 95.72 |
| Floating-leaved plants | 55.6 | 5.99 | 29.0 | 4.24 |
| Submerged plants | 0.6 | 0.06 | 0.2 | 0.03 |
| Total | 928.8 | 100 | 684.2 | 100 |
