Holocene changes in trophic states of shallow lakes from the Pampa plain of Argentina

STUTZ, S.; BOREL, C M; FONTANA, S L; TONELLO, M. S.

Tokyo

Congreso; XIII International Palinological Congress; 2012

The Palynological Society of Japan, The International Federation of Palynological Societies, The International Organisation of Palaeobotany, Association of Pollen Information

Changes in trophic status of shallow lakes from the south-eastern Pampa plain of Argentina are evaluated based on the relative presence of submerged macrophytes and phytoplankton algae. The evolution of lake Lonkoy is reconstructed for the last 5000 years, using pollen, non-pollen palynomorphs (NPPs) and macro fossil remain analyses, revealing three main lake stages. A macrophyte dominated clear lake prevailed until 670 cal yr BP. Afterwards, the lake changed to a turbid phytoplankton dominated state. Recently, the lake has turned to an inorganic-turbid phase, with suspended inorganic material. These results are compared with two other paleolimnological records from the region, lakes Hinojales and Nahuel Rucá revealing a similar late Holocene evolution, with a shift from a macrophyte to phytoplankton dominated lake, occurring at broadly the same time. The shift of states could be attributed to a shift in climate after 1000 cal yr BP towards wetter conditions during the Medieval Climate Anomaly.