Diatom responses to natural and anthropogenic environmental changes in a Patagonian river, Argentina

The Chubut River is a Patagonian river that flows from the Andes to the Atlantic Ocean, and is interrupted by a dam built at the middle valley. To investigate the sedimentary history of the lower river basin, a sediment core was collected from the floodplain. Fossil diatom assemblages contained within the core obtained at Gaiman village have been applied to a diatom-based inference model of conductivity. Two phases in the evolution of the Chubut River lower basin were identified through diatomological and sedimentological analyses, in which multivariate analysis were included, assisted by radiocarbon dating. Phase 1 representing natural conductivity and depth changes during the Early Holocene and Phase 2 the infilling of the lotic environment in recent times influenced by the anthropogenic effects, nutrients input and dam construction.