A note on the trophic structure of alpine streams in the Wind River Mountains, Wyoming, USA
Robinson, C.T.; Alther, R.; Leys, M.; Moran, S.; Thompson, C.
published: Sep 1, 2015
ArtNo. ESP141018701002, Price: 29.00 €
We investigated environmental characteristics and macroinvertebrate trophic structures of alpine streams in the glaciated Dinwoody catchment of the Wind River Range, Wyoming, USA. Study sites were above 3100 m a.s.l. and all above treeline except for one site representing a forested headwater stream. Physico-chemistry grouped sites by sub-basin and glacial influence. Seston levels were higher in the forested stream and a side-slope tributary (> 227 mg m–3) than the other streams (< 100 mg m–3). Periphyton levels were higher (> 2.7 mg m–2) in streams in the Heap Steep sub-basin fed by a remnant hanging glacier (active ice field) than in the other streams (< 1.0 mg m–2). Macroinvertebrate abundances (range = 140–2400 individuals per 5-min kick sample) and taxa richness were generally low (2–8 taxa at most sites), although being higher in lower-basin sites and the forested stream than at sites nearest the glaciers. Macroinvertebrate trophic structures were simple, consisting of primary consumers and predators, including two riparian spiders. Macroinvertebrate δ15N values ranged from ca. –2.54 to –5.41, whereas δ13C values ranged from –24.23 to –16.08. Individual taxa varied widely in δ13C among sites, suggesting carbon sources differed among sites. Carbon isotope ratios also increased from upper sites to lower sites in the same sub-basin, suggesting a glacial carbon source at sites near the glacier to an instream carbon source at lower glacial sites lacking substantial riparian inputs. The upper glacial sites also had carbon isotope ratios similar to that of the forested headwater stream. These data suggest a highly heterogeneous spatial structure in alpine landscapes concomitant with the longitudinal development of glacial streams that is reflected in the trophic structure of local macroinvertebrates.