Climate change as the major driver of changes in shallow lake functioning during the last 1600 years.

GONZÁLEZ SAGRARIO, M.A.; CARROZZO, D.; LAMI, A.; MUSAZZI, S.; SANTAMANS, C.; CÓRDOBA, F.

Berlín

Congreso; 36th Congress of the International Society for Limnology.; 2022

SIL- International Society of Limnology, IGB- Leibniz Institute of Freshwater Ecology and Inland Fisheries.

Climate change and human activities are main drivers affecting lake functioning. Using a multi-proxy paleolimnological approach we investigated long-term changes in lake Kakel Huincul (Argentina, South America) to evaluate the impact of climate change. Age-Depth model was based on a combined Pb-210, Cs-137, and C-14 dating. According to Generalized Additive Models on principal curve scores, two distinct periods occurred in this shallow lake: 1- a turbid (ca. 1653-1862 AD) and 2- a clear regime (1862 AD- present). Low nutrient load and primary productivity (based on chlorophyll and carotenoid pigments) characterized lake conditions during the turbid regime. Halophilic diatoms and cladocerans (Daphnia spinulata) dominated. The shift to a clear lake occurred at the end of the Little Ice Age (LIA) (ca.1860), changing from pelagic to littoral-benthic primary production, i.e., from Cyclotella meneghiniana and Aulacoseira granulata to benthic-epiphytic diatoms and submergedmacrophytes dominance from 1862 AD to the present. Overall primary production and nutrients increased. Cladocerans shifted from large-bodied Daphnia to small Ceriodaphnia. Dry and cold conditions persisted during the LIA, favoring a turbid regime with high water conductivity; however, the incrementin temperature and precipitation after this climatic event promoted the shift to littoral-benthic lake pathways and clear conditions. A reduction in lutein and the increment in alloxanthin, cyanobacteria-related pigments, and benthic diatoms suggest a decrease in plant cover since the 1990 AD. Main changes in lake functioning were principally climate-driven; dry and cold conditions prevent macrophyte development, implying diversity loss and turbid scenarios for lakes under dry conditions.