Biotic diversity of benthic macroinvertebrates at contrasting glacier-fed systems in Patagonia Mountains: The role of environmental heterogeneity facing global warming

MISERENDINO, M. L.; BRAND, CECILIA; EPELE, L.B.; DI PRINZIO, C.Y.; OMAD, G.H.; ARCHANGELSKY, M.; MARTÍNEZ, O.A.; KUTSCHKER, A.

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018 vol. 622 p. 152 - 163

0048-9697

Global warming is altering dynamics and integrity of glacier-fed systems and appears as a major threat for aquatic biodiversity. Patagonia is by far the largest glacierized area in South America, however little is known about ecology, functioning and biodiversity of these aquatic ecosystems. We investigated changes in environmental features and macroinvertebrate communities along a longitudinal gradient of glacier influence of two Patagonian systems (Torrecillas and Baggilt) that differ in glacier cover magnitude and the spatial sequence of lotic and lentic phases. Both glaciers, Torrecillas (~5.5 km2) and Cónico (~0.44 km2, Baggilt System), at present are retreating. The aim was to understand the complexity of the relationships of the communities with the environmental background and to identify useful taxa indicating effects of environmental change. Longitudinal distribution of benthic invertebrates partially fitted to predictions for glacierized temperate systems, with Diamesinae spp. dominating at closest sites to the Cónico, and Orthocladiinae increasing downstream, but patterns were unclear at Torrecillas. Generalized Linear Model identified chlorophyll a and conductivity as having significant effect on richness and density respectively at Torrecillas; detritus biomass and gravel influenced species richness, and boulder and water temperature affected density, at Baggilt. Canonical Correspondence Analyses integrating benthic biota and environmental variables revealed that a higher environmental heterogeneity at Baggilt related with spatial dimension (unshaded/shaded reaches, wetland reaches), local resources (detritus, bryophytes) and temperature probably explained the unexpected high richness in benthic assemblages (67 taxa). Environmental conditions imposed by the lake outlet (proglacial) at Torrecillas resulted in a less diverse community (31 taxa). Finally our results suggest that these isolated, small glacier-fed streams typical from the Patagonian landscape appear highly vulnerable to global warming. Endemic elements could disappear at upper segments being replaced by other species common at rhithral environments, which might increase local diversity (alfa diversity) but decrease regional diversity (gamma diversity).