Functional Feeding Groups of Macrofauna and Detritus Decomposition along a Gradient of Glacial Meltwater Influence in Tropical High-Andean Streams

Tropical Andean glaciers are retreating rapidly, with possible consequences for trophic structure and ecosystem processes in high meltwater streams. Here, we measured the environmental characteristics, quantified pools of particulate organic matter (POM) periphyton (Chl. a), sampled benthic macroinvertebrates, determined functional feeding groups (FFG), performed mesh bag decomposition experiments Calamagrostis grass detritus at 17 stream sites along a gradient glacial influence (GI) 0–23% glacier cover catchment 4050–4200 m a.s.l. Andes Ecuador. POM was unrelated to GI while Chl. a. showed weak (non-significant) negative relationship GI. The macrofauna abundance decreased taxon richness number FFGs per site hump-shaped increasing Taxa an opportunistic generalist mode generally dominated assemblages were related levels low Only shredders negatively GI, but POM. Decomposition rates comparable those found temperate alpine streams, both fine (0.0010–0.0065; median 0.0028 d−1) coarse (0.0019–0.0088; 0.0048 bags, peaked intermediate values, difference between types small almost constant gradient. This indicates overall minor effect macroinvertebrate compared that microbes, particular It also suggests relatively average temperature these high-altitude equatorial streams (7–10 °C) does not produce higher than colder latitudes. results suggest that, lower end cover, tropical loss will change dominant microbial role decomposition, part physical abrasion could be partially replaced by biological shredding.