TABLE 2.
Enrichment (δ 15N) of investigated taxa and two food sources at nine distances downstream of the isotope inlet.
| Class/order | Taxon | Feeding type | N | Reference | Distance downstream to isotope inlet (m) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 50 m | 100 m | 200 m | 300 m | 500 m | 750 m | 1000 m | 1500 m | 2000 m | |||||
| Mean δ 15N (‰) | |||||||||||||
| Crustacea: Amphipoda | Gammarus pulex (Linnaeus, 1758) | Shredder | 336 | 4.8 ± 1.3 | 44.8 ± 47.1 | 32.5 ± 33.9 | 33.5 ± 30.4 | 30.8 ± 28.2 | 17.7 ± 17.7 | 17.2 ± 15.8 | 13.4 ± 10.8 | 10.1 ± 7.6 | 7.3 ± 4.3 |
| Insecta: Ephemeroptera | Ephemera danica Muller, 1764 | Active filter feeder | 271 | 5.7 ± 1.1 | 42.7 ± 35.0 | 34.7 ± 29.6 | 28.8 ± 31.4 | 24.4 ± 20.1 | 31.6 ± 32.6 | 32.2 ± 36.4 | 25.9 ± 24.3 | 16.1 ± 16.0 | 11.3 ± 16.8 |
| Baetis sp. Leach, 1815 | Grazer | 169 | 5.4 ± 1.5 | 64.3 ± 72.4 | 59.7 ± 68.5 | 59.5 ± 54.6 | 83.4 ± 76.8 | 66.4 ± 38.5 | 100.2 ± 75.0 | 76.3 ± 50.9 | 16.7 ± 6.2 | 34.6 ± 22.0 | |
| Insecta: Megaloptera | Sialis sp. Latreille, 1802 | Predator | 65 | 7.5 ± 0.8 | 8.1 ± 1.0 | 9.4 ± 3.4 | 7.5 ± 2.0 | 12.9 ± 7.1 | 10.2 ± 5.3 | 14.1 ± 2.2 | 23.2 ± 20.2 | 7.0 ± 2.0 | 7.0 ± 1.7 |
| Insecta: Plecoptera | Nemoura sp. Latreille, 1796 | Shredder | 78 | 4.4 ± 0.8 | 109.0 ± 44.0 | 104.4 ± 38.6 | 98.3 ± 18.2 | 115.9 ± 24.2 | 95 ± 40.9 | 69.5 ± 20.8 | 67.3 ± 18.7 | 38.2 ± 7.6 | 25.1 ± 2.7 |
| Insecta: Trichoptera | Hydropsyche angustipennis (Curtis, 1834) | Passive filter feeder | 83 | 5.2 ± 0.9 | 49.3 ± 39.5 | 45.4 ± 27.5 | 42.0 ± 17.9 | 55.9 ± 16.9 | 48.9 ± 19.3 | 57.5 ± 18.8 | 39.2 ± 23.5 | 7.2 | 14.9 ± 3.6 |
| Polycentropus irroratus Curtis, 1835 | Predator | 22 | 7.2 ± 0.5 | 80.3 ± 7.0 | 81.1 | 76.3 ± 47.2 | 56.3 ± 20.9 | 33.8 ± 9.3 | 17.7 ± 1.2 | ||||
| Chaetopteryx villosa (Fabricius, 1798) | Shredder | 31 | 6.3 ± 0.1 | 13.0 ± 13.9 | 36.2 ± 30.7 | 32.5 | 10.9 ± 3.8 | 10.2 ± 2.4 | 9.1 ± 2.9 | 9.2 ± 6.5 | 7.9 ± 2.4 | ||
| Halesus radiatus (Curtis, 1834) | Shredder | 81 | 0.9 ± 1.7 | 12.0 ± 5.5 | 11.4 ± 5.4 | 7.2 ± 3.5 | 13.1 ± 7.9 | 13.5 | 11.0 ± 8.4 | 2.6 ± 1.5 | 1.0 ± 2.0 | 0 ± 2.4 | |
| Limnephilus lunatus Curtis, 1834 | Shredder | 53 | 6.1 ± 0.7 | 9.2 ± 3.2 | 17.9 ± 11.5 | 12.8 ± 7.2 | 12.7 ± 5.7 | 12.3 ± 3.5 | 11.4 ± 2.0 | 9.4 ± 3.5 | 9.8 ± 2.7 | 9.1 ± 2.2 | |
| Potamophylax cingulatus (Stephens, 1837) | Shredder | 14 | 1.5 ± 0.9 | 27.4 | 14.6 | 19.9 ± 7.0 | 11.2 ± 1.3 | 4.8 ± 1.6 | |||||
| Potamophylax rotundipennis (Brauer, 1857) | Shredder | 24 | 1.1 ± 0.7 | 9.2 | 4.4 ± 2.9 | 19.1 ± 25.9 | 5.2 | 5.6 ± 0.9 | 3.6 ± 0.7 | ||||
| Food source | |||||||||||||
| Particulate organic matter (POM) | 319 | 0.5 ± 1.2 | 2.3 ± 7.3 | 4.6 ± 8.5 | 2.6 ± 4.6 | 1.3 ± 4.8 | 1.9 ± 5.7 | 2.0 ± 3.7 | 0.8 ± 2.8 | 0.6 ± 2.4 | 1.1 ± 3.9 | ||
| Phytobenthos (PB) | 327 | 4.5 ± 2.2 | 16.6 ± 14.9 | 22.8 ± 17.0 | 14.8 ± 12.7 | 8.1 ± 8.1 | 11.1 ± 12.7 | 7.7 ± 5.2 | 7.5 ± 6.4 | 6.8 ± 6.1 | 5.9 ± 4.4 | ||
Note: Feeding types reflect the main assignment acc. to freshwaterecology.info (Schmidt‐Kloiber & Hering, 2015). Reference measurements were derived from samples taken 50 m upstream of the isotope inlet. N, number of specimens analysed for each taxon. Bold values indicate enrichment levels above Reference +2 SD (Macneale et al., 2004). Empty lines indicate that a species has not been detected at this distance.