| Title | Recent environmental changes inferred from sediments in a shallow lake of the Argentinian pampas |
| Abstract | The Pampas are fertile lowland plains that extend across east-central Argentina and are renowned for their agricultural importance. The low geomorphologic relief of the region accounts for the occurrence of numerous shallow lakes whose sediments constitute paleoenvironmental archives of the outcomes of natural processes and human activities in the Pampas. We identified the main forcing factors behind hydrological shifts during the past ca. 200 years in La Barrancosa, a shallow lake located in the southeastern Pampas. The data provide a historical context to better understand environmental changes in the area during the twentieth century. Variations in biological (ostracods, chironomids and pigments), geochemical and sedimentological variables were interpreted in terms of lake level and trophic state changes. The low diversity of biological assemblages and the autoecology of the ostracod and chironomid taxa suggest that during parts of the record assigned to the nineteenth century, near the end of the Little Ice Age, La Barrancosa was a shallow, ephemeral, subsaline wetland, indicating drier-than-present conditions. Thereafter, a hiatus from ca. AD 1860-1940 is attributed to denudation processes during the Pampas Dust Bowl drought of the 1930s. The onset of wetter conditions around 1940 brought higher lake levels and establishment of a perennial shallow lake, inferred mostly from shifts in sedimentological and geochemical variables. Marked variations in fossil pigments and in ostracod and chironomid assemblages reveal that the basin shifted from being endorheic to arheic around 1970, in spite of increased precipitation, forced by changes in global circulation patterns. This shift coincided with an inferred increase in primary production and was coeval with profound land use changes and technological innovations in the region. Further changes in sedimentological, geochemical and biological variables indicate that eutrophication accelerated from 1990 onwards, most likely as a consequence of the increase in planted area around the lake, massive application of fertilizer, and cultivation of pesticide-intensive transgenic soybeans. This study provides an historical perspective into ongoing environmental deterioration of shallow lakes in the Argentinian Pampas. |
| Source | Journal of paleolimnology (Dordr., Online) 61 (1), pp. 37–52 |
| Keywords | Shallow lakesPampean plainsPaleolimnologyTwentieth centuryEnvironmental change |
| Journal | Journal of paleolimnology (Dordr., Online) |
| Editor | Kluwer, Dordrecht, Paesi Bassi |
| Year | 2019 |
| Type | Articolo in rivista |
| DOI | 10.1007/s10933-018-0043-y |
| Authors | Plastani M.S.; Laprida C.; Montes de Oca F.; Massaferro J.; Panarello H.O.; Ramon Mercau J.; Lami A. |
| Text | 399600 2019 10.1007/s10933 018 0043 y Scopus 2 s2.0 85050342418 Shallow lakes Pampean plains Paleolimnology Twentieth century Environmental change Recent environmental changes inferred from sediments in a shallow lake of the Argentinian pampas Plastani M.S.; Laprida C.; Montes de Oca F.; Massaferro J.; Panarello H.O.; Ramon Mercau J.; Lami A. Instituto de Estudios Andinos Don Pablo Groeber Universidad de Buenos Aires CONICET , Ciudad Autonoma de Buenos Aires, Argentina; Instituto de Estudios Andinos Don Pablo Groeber Universidad de Buenos Aires CONICET , Ciudad Autonoma de Buenos Aires, Argentina; CENAC Administracion de Parques Nacionales CONICET , Bariloche, Argentina; CENAC Administracion de Parques Nacionales CONICET , Bariloche, Argentina; Instituto de Geocronologia y Geologia Isotopica Universidad de Buenos Aires CONICET , Ciudad Autonoma de Buenos Aires, Argentina; Instituto de Geocronologia y Geologia Isotopica Universidad de Buenos Aires CONICET , Ciudad Autonoma de Buenos Aires, Argentina; Instituto de Geocronologia y Geologia Isotopica Universidad de Buenos Aires CONICET , Ciudad Autonoma de Buenos Aires, Argentina; Istituto per lo Studio degli Ecosistemi CNR , Verbania Pallanza, Italy The Pampas are fertile lowland plains that extend across east central Argentina and are renowned for their agricultural importance. The low geomorphologic relief of the region accounts for the occurrence of numerous shallow lakes whose sediments constitute paleoenvironmental archives of the outcomes of natural processes and human activities in the Pampas. We identified the main forcing factors behind hydrological shifts during the past ca. 200 years in La Barrancosa, a shallow lake located in the southeastern Pampas. The data provide a historical context to better understand environmental changes in the area during the twentieth century. Variations in biological ostracods, chironomids and pigments , geochemical and sedimentological variables were interpreted in terms of lake level and trophic state changes. The low diversity of biological assemblages and the autoecology of the ostracod and chironomid taxa suggest that during parts of the record assigned to the nineteenth century, near the end of the Little Ice Age, La Barrancosa was a shallow, ephemeral, subsaline wetland, indicating drier than present conditions. Thereafter, a hiatus from ca. AD 1860 1940 is attributed to denudation processes during the Pampas Dust Bowl drought of the 1930s. The onset of wetter conditions around 1940 brought higher lake levels and establishment of a perennial shallow lake, inferred mostly from shifts in sedimentological and geochemical variables. Marked variations in fossil pigments and in ostracod and chironomid assemblages reveal that the basin shifted from being endorheic to arheic around 1970, in spite of increased precipitation, forced by changes in global circulation patterns. This shift coincided with an inferred increase in primary production and was coeval with profound land use changes and technological innovations in the region. Further changes in sedimentological, geochemical and biological variables indicate that eutrophication accelerated from 1990 onwards, most likely as a consequence of the increase in planted area around the lake, massive application of fertilizer, and cultivation of pesticide intensive transgenic soybeans. This study provides an historical perspective into ongoing environmental deterioration of shallow lakes in the Argentinian Pampas. 61 Published version http //www.scopus.com/inward/record.url eid=2 s2.0 85050342418 partnerID=q2rCbXpz Articolo 2019_J_Paleolimnol_61_37_52.pdf Articolo in rivista Kluwer 1573 0417 Journal of paleolimnology Dordr., Online Journal of paleolimnology Dordr., Online J. paleolimnol. Dordr., Online Journal of paleolimnology. Dordr., Online andrea.lami LAMI ANDREA |
