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Reproductive parameters of amphipod species during the study
| 2017 | 2018 | 2019 | |
|---|---|---|---|
| G. varsoviensis | |||
| n | 34 | 68 | 32 |
| Average size of ovigerous females, mm | 11.2 ± 1.1 SD | 11.3 ± 1.2 SD | 11.4 ± 1.3 SD |
| Average number of eggs per brood | 26 ± 11 SD | 30 ± 13 SD | 37 ± 14 SD |
| P. robustoides | |||
| n | ovigerous females were not obtained | 22 | 17 |
| Average size of ovigerous females, mm | - | 11.6 ± 1.3 SD | 10.9 ± 1.5 SD |
| Average number of eggs per brood | - | 25 ± 16 SD | 31 ± 22 SD |
| G. pulex | |||
| n | 8 | only two ovigerous females were obtained | only one ovigerous female was obtained |
| Average size of ovigerous females, mm | 10.7 ± 0.5 SD | - | - |
| Average number of eggs per brood | 27 ± 5 SD | - | - |
Air temperature and precipitation in Latvia during the study*
| 2017 | 2018 | 2019 | Latvian norm | |
|---|---|---|---|---|
| Annual mean air temperature, °C | +6.9 | +7.6 | +8.2 | +6.4 |
| Annual total precipitation (mean in Latvia), mm | 809.8 | 472.7 | 629.2 | 685.6 |
| Spring | ||||
| Average air temperature, °C | +5.6 | +6.9 | +7.2 | +5.6 |
| Precipitation, mm | 116.3 | 80.7 | 100.5 | 122.7 |
| Summer | ||||
| Average air temperature, °C | +15.4 | +18.1 | +17.2 | +16.2 |
| Precipitation, mm | 237.0 | 162.4 | 176.7 | 225.7 |
| Autumn | ||||
| Average air temperature, °C | +7.6 | +8.6 | +8.3 | +6.7 |
| Precipitation, mm | 313.5 | 124.3 | 236.7 | 201.0 |
Background characteristics of the sampling sites during the study
| Characteristics | “Daugavpils” | “Jēkabpils” | “Veczeļki” | “Gostiņi” |
|---|---|---|---|---|
| Position | 55°52′04″N | 56°29′52″N | 56°31′50″N | 56°36′56″N |
| Gammarids | G. varsoviensis | G. varsoviensis | G. varsoviensis | P. robustoides |
| G. pulex | ||||
| G. pulex | P. robustoides | |||
| 2018 no sampled | ||||
| Substrate | sand, silty sand covered by detritus, some pebble and boulders, emergent and submerged macrophytes | sand, silty sand covered by detritus, emergent and submerged macrophytes | sand, fine gravel, pebble and some boulders covered by detritus, emergent macrophytes | sand, silty sand covered by detritus, some pebble and boulders, emergent and submerged macrophytes |
| 2017, month | V–X | V–IX | V–IX | V–IX |
| average (range) | ||||
| T (°C) | 16.03 (9.76–20.45) | 18.14 (15.75–20.47) | 17.86 (15.38–20.25) | 17.42 (14.14–20.52) |
| Cond. (μS cm−1) | 306 (251–335) | 313 (280–337) | 311 (274–334) | 317 (274–375) |
| DO (mg l−1) | 7.67 (6.09–9.19) | 7.45 (6.31–8.83) | 8.20 (9.57–7.19) | 7.74 (5.11–9.94) |
| pH | 7.96 (7.72–8.24) | 8.05 (7.84–8.14) | 8.16 (7.98–8.47) | 8.12 (7.51–8.60) |
| CHL (μg l−1) | 3.89 (2.84–5.45) | 4.98 (3.38–8.30) | 3.23 (2.97–3.65) | 4.68 (3.20–5.61) |
| 2018, month | V–X | V–X | V–X | |
| average (range) | ||||
| T (°C) | 18.62 (11.79–21.97) | 17.16 (6.42–23.01) | 2018 | 17.86 (6.56–23.62) |
| Cond. (μS cm−1) | 382 (233–467) | 367 (280–404) | 404 (390–427) | |
| DO (mg l−1) | 9.60 (7.51–13.75) | 8.48 (6.19–11.16) | 9.63 (6.62–11.71) | |
| pH | 8.73 (8.16–9.22) | 8.81 (8.45–9.06) | 9.00 (8.92–9.41) | |
| CHL (μg l−1) | 3.26 (1.77–6.69) | 3.99 (3.06–5.19) | 4.56 (3.96–5.30) | |
| 2019, month | IV–IX | IV–IX | VI–IX | VI–IX |
| average (range) | ||||
| T (°C) | 18.13 (11.42–22.18) | 18.28 (13.05–22.68) | 19.68 (13.27–23.22) | 20.79 (14.61–23.12) |
| Cond. (μS cm−1) | 354 (216–512) | 316 (227–378) | 341 (289–374) | 342 (288–377) |
| DO (mg l−1) | 8.13 (6.39–10.64) | 7.83 (5.91–9.94) | 8.20 (6.33–10.19) | 10.18 (8.00–13.67) |
| pH | 7.73 (7.38–8.20) | 7.80 (7.41–8.19) | 8.09 (7.77–8.29) | 8.40 (8.06–8.95) |
| CHL (μg l−1) | 4.39 (3.03–8.26) | 4.39 (2.16–6.89) | 2.96 (2.11–4.29) | 4.21 (2.95–6.60) |