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Table 2 Descriptive statistics for the continuous predictor variables used to assess the occurrence and abundance of freshwater snail species in the Ethiopian Rift Valley

From: Environmental and biotic factors affecting freshwater snail intermediate hosts in the Ethiopian Rift Valley region

Predictor variable Tropical rainy climate zone Warm temperate rainy climate zone
Range Mean ± SD Median Range Mean ± SD Median
Altitude (m) 1655–1699 1678.9 ± 7 1681 1618–1645 1633.3 ± 5.3 1634
Water depth (m) 0.2–2.0 0.7 ± 0.4 0.6 0.1–1.2 0.5 ± 0.2 0.5
Transparency (m) 0.1–0.6 0.2 ± 0.1 0.2 0.1–0.8 0.3 ± 0.1 0.2
Ambient temperature (°C) 18–30 25 ± 2.9 26 16–30 23.7 ± 2.9 24
Water temperature (°C) 14.2–27.6 22 ± 3 22.2 15.2–30.2 21.9 ± 3.8 21.8
Dissolved oxygen (mg/l) 0.1–16 4.7 ± 2.7 4.5 0.3–21.5 6.5 ± 3.6 6.2
Oxygen saturation (%) 1.1–209 66 ± 38.7 60.4 4.4–349 96.1 ± 62.2 91.4
Chemical oxygen demand (mg/l) 7.9–50.4 19.8 ± 8.1 18.4 3.4–41.3 15.7 ± 7.3 16.2
Electrical conductivity (μS/cm) 137.3–2015 757 ± 431.1 902 233–3680 893 ± 590.7 700
pH 5.4–9.6 8.2 ± 0.9 8.9 3.1–9.8 7.5 ± 1.6 8.1
Turbidity (NTU) 2.8–247 24.6 ± 43.5 14.1 1.8–159 32 ± 34.8 13.9
Chlorophyll-a (µg/l) 12.7–41.4 15.5 ± 4.5 14.1 12.6–33.1 14.9 ± 2.8 13.9
Total suspended solids (mg/l) 90.8–687.2 268.8 ± 174 200.8 87.2–759.6 170.1 ± 111.7 145.6
Chloride (mg/l) 5–87 34.7 ± 18.7 38 16–252.9 37.1 ± 33.6 26
Nitrate (mg/l) 0–130.3 7 ± 17.3 0.5 0–95.3 8.4 ± 17.8 0.5
Ammonia (mg/l) 0–5.1 0.7 ± 0.9 0.4 0–5.1 0.8 ± 1.1 0.3
Total phosphorus (mg/l) 0–24.7 1.9 ± 3.4 1.0 0–11.1 1.2 ± 1.5 0.8
Orthophosphate (mg/l) 0–23.9 1.1 ± 2.8 0.4 0–7.8 0.5 ± 0.9 0.3
Alkalinity (mg/l) 78–896 381.4 ± 185.9 404 164–1414 376.1 ± 230.5 304
Total hardness (mg/l) 22–184 51.5 ± 23.4 46 52–316 116.4 ± 45.1 112
Calcium (mg/l) 14–114 32.4 ± 18.4 26 32–196 71.6 ± 34.6 60
Magnesium (mg/l) 0–76 19.1 ± 12.8 18 4–190 44.8 ± 29.9 44
Canopy cover (%) 0–100 21.5 ± 32.2 0 0–100 29.5 ± 35.7 10
Predator abundance (n) 0–153 19.4 ± 23.5 10 0–43 9.2 ± 9.4 1
Competitor abundance (n) 0–5 0.3 ± 0.8 0 0–79 2.9 ± 11.8 0
  1. Abbreviation: SD, standard deviation