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

GONZÁLEZ SAGRARIO M. A.; CARROZZO, DAVID; LAMI, ANDREA; MUSAZZI S.; SANTAMANS, CARLA; CÓRDOBA, FRANCISCO E.

Berlin

Congreso; 36th Congress of the International Society of Limnology: The next 100 years: Sensing and safeguarding inland waters; 2022

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

Climate change and humanactivities are main drivers affecting lake functioning. Using a multi-proxypaleolimnological approach we investigated long-term changes in lake KakelHuincul (Argentina, South America) to evaluate the impact of climate change.Age-Depth model was based on a combined  210Pb, 137Cs, and 14Cdating. According to Generalized Additive Models on principal curve scores, twodistinct 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 onchlorophyll and carotenoid pigments) characterized lake conditions during theturbid regime. Halophilic diatoms and cladocerans (Daphnia spinulata) dominated. The shift to a clear lake occurred atthe end of the Little Ice Age (LIA) (ca.1860), changing from pelagic to littoral-benthic primary production, i.e., from Cyclotella meneghiniana andAulacoseira granulata to benthic-epiphytic diatoms and submergedmacrophytes dominance from 1862 AD to the present. Overall primary productionand 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 shiftto littoral-benthic lake pathways and clear conditions. A reduction in luteinand the increment in alloxanthin, cyanobacteria-related pigments, and benthicdiatoms suggest a decrease in plant cover since the 1990 AD. Main changes inlake functioning were principally climate-driven; dry and cold conditionsprevent macrophyte development, implying diversity loss and turbid scenariosfor lakes under dry conditions.