| Title | Paleolimnological reconstruction of the centennial eutrophication processes in a sub-tropical South American reservoir |
| Abstract | Reservoirs hold a detailed record of the changes in the input of sediments and nutrients over decades to centuries. Paleolimnological multi-proxy analysis makes it possible to reconstruct baseline conditions to infer early evidence of environmental change. Our study aims to reconstruct historical human impacts derived from urban development on the San Roque reservoir (Córdoba, Argentina) related to the centennial dynamics of sedimentary and eutrophication processes. A paleolimnological record, dated by Pb and Cs, made it possible to identify two stages during the environmental evolution of the San Roque reservoir. Physical processes, such as fluvial discharge and water level variation, dominantly ruled stage 1 (Unit C) during the initial infilling of the reservoir. Nutrient load and eutrophication processes controlled stage 2 (Units B and A). Stage 1 (77-55 cm; AD 1921 to 1965) occurred before and after the second dam was built and while the level of water increased by ? + 8 m; it displayed a high variation in mean grain size and maximum values of magnetic susceptibility. Stage 2 (AD 1965-2017) records a new reservoir base level and the maintenance of high water levels and comparatively more stable conditions. Regarding the eutrophication process throughout stage 2, three sub-stages were defined: a) Sub-stage I (AD 1965-1985) is a period of incipient eutrophication; b) Sub-stage II (AD 1985-2005) is an interval of increase of eutrophication as shown by the increase in several organic proxies related to the abundance of phytoplankton. Echinenone, zeaxanthin and myxoxanthophyll indicate that cyanobacteria increased concentration by three-to four-fold in comparison with the previous sub-stage. c) Sub-stage III (AD 2005-2017) shows the transition to a hypereutrophic state. Diatomea (fuco and diato), dinophyceae (diadino), chlorophyta (lut) and cryptophyta (allo) groups show a comparatively higher contribution. Our results mostly highlight that during the last century the main drivers of changes in the environmental state of the San Roque reservoir were trophic, fluvial and hydrometeorological. These results might provide tools for anticipating future scenarios for water management plans under increasing anthropic pressure. |
| Source | Journal of South American earth sciences 103 |
| Keywords | AnthropoceneCentral ArgentinaFossil pigmentSan Roque reservoirTrophic state |
| Journal | Journal of South American earth sciences |
| Editor | Earth Sciences and Resources Institute, University of South Carolina., [S.l.], Regno Unito |
| Year | 2020 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.jsames.2020.102707 |
| Authors | Halac, S.; Mengo, L.; Guerra, L.; Lami, A.; Musazzi, S.; Loizeau, J. L.; Ariztegui, D.; Piovano, E. L. |
| Text | 454291 2020 10.1016/j.jsames.2020.102707 Scopus 2 s2.0 85087003903 Anthropocene Central Argentina Fossil pigment San Roque reservoir Trophic state Paleolimnological reconstruction of the centennial eutrophication processes in a sub tropical South American reservoir Halac, S.; Mengo, L.; Guerra, L.; Lami, A.; Musazzi, S.; Loizeau, J. L.; Ariztegui, D.; Piovano, E. L. Consiglio Nazionale delle Ricerche; Universidad de Chile; Universite de Geneve; Consejo Nacional de Investigaciones Cientificas y Tecnicas Reservoirs hold a detailed record of the changes in the input of sediments and nutrients over decades to centuries. Paleolimnological multi proxy analysis makes it possible to reconstruct baseline conditions to infer early evidence of environmental change. Our study aims to reconstruct historical human impacts derived from urban development on the San Roque reservoir Cordoba, Argentina related to the centennial dynamics of sedimentary and eutrophication processes. A paleolimnological record, dated by Pb and Cs, made it possible to identify two stages during the environmental evolution of the San Roque reservoir. Physical processes, such as fluvial discharge and water level variation, dominantly ruled stage 1 Unit C during the initial infilling of the reservoir. Nutrient load and eutrophication processes controlled stage 2 Units B and A . Stage 1 77 55 cm; AD 1921 to 1965 occurred before and after the second dam was built and while the level of water increased by 8 m; it displayed a high variation in mean grain size and maximum values of magnetic susceptibility. Stage 2 AD 1965 2017 records a new reservoir base level and the maintenance of high water levels and comparatively more stable conditions. Regarding the eutrophication process throughout stage 2, three sub stages were defined a Sub stage I AD 1965 1985 is a period of incipient eutrophication; b Sub stage II AD 1985 2005 is an interval of increase of eutrophication as shown by the increase in several organic proxies related to the abundance of phytoplankton. Echinenone, zeaxanthin and myxoxanthophyll indicate that cyanobacteria increased concentration by three to four fold in comparison with the previous sub stage. c Sub stage III AD 2005 2017 shows the transition to a hypereutrophic state. Diatomea fuco and diato , dinophyceae diadino , chlorophyta lut and cryptophyta allo groups show a comparatively higher contribution. Our results mostly highlight that during the last century the main drivers of changes in the environmental state of the San Roque reservoir were trophic, fluvial and hydrometeorological. These results might provide tools for anticipating future scenarios for water management plans under increasing anthropic pressure. 103 Published version http //www.scopus.com/record/display.url eid=2 s2.0 85087003903 origin=inward Halac et al. 2020 Paleolimnological reconstruction of the centennial.pdf articolo pdf Halac et al. 2020 Paleolimnological reconstruction of the centennial.pdf Articolo in rivista Earth Sciences and Resources Institute, University of South Carolina. 0895 9811 Journal of South American earth sciences Journal of South American earth sciences J. South Am. earth sci. Journal of South American earth sciences. andrea.lami LAMI ANDREA simona.musazzi MUSAZZI SIMONA |
