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

MARÍA DE LOS ÁNGELES GONZÁLEZ SAGRARIO; DAVID CARROZZO; ANDREA LAMI; SIMONA MUSAZZI; CARLA D. SANTAMANS; CÓRDOBA, FRANCISCO E.

Berlín

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

Climate change and human activities are the 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. AgeDepth model was based in a combined 210Pb, 137Cs, and 14C 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 Cyclotellameneghiniana and Aulacoseira granulata to benthic-epiphytic diatoms and submerged macrophytes dominance from 1862 AD to the present. Overall primary production and nutrients increased. Cladocerans shifted from large-bodied Daphnia to small-bodied Ceriodaphnia. Dry andcold conditions persisted during the LIA, favoring a turbid regime with high water conductivity; however, the increment in 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 coversince 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.