First spatio-temporal study of macroinvertebrates in the Santa Cruz River: a large glacial river about to be dammed without a comprehensive pre-impoundment study

Abstract

The Santa Cruz River is the last free flowing river in Patagonia Argentina. Two dams are projected and no pre-impoundment study has been undertaken. The present research studies macroinvertebrate communities along three different hydrological periods and at three river areas; located upstream and downstream of future dams. 53 macroinvertebrate taxa were identified, with the most abundant orders being Ephemeroptera, Plecoptera, Coleoptera, and Crustacea (particularly amphipods). Ordnination methods (CCA) and generalized linear mixed models (GLMM) were applied: according to the CCA, main environmental variables related to macroinvertebrate density were temperature, suspended solids, depth and substrate size; and using GLMM main factors associated with macroinvertebrates were the location and hydrological period, and variables with higher influences were temperature, substrate size, current speed and depth. We anticipate changes in the structure of macroinvertebrates and, consequently, in trophic webs by the modification of the habitat that will be provoked by the two dams.