Response of testate amoebae assemblages to environmental and climatic changes during the last ~700 yrs in Laguna Polo, Patagonia, Argentina.

CHARQUEÑO CELIS, NORMA FERNANDA; MAYR, CHRISTOPH; DUBOIS NATHALIE; JULIETA MASSAFERRO

Simposio; ISTA 10; 2023

Little is known about the paleoecology of testate amoebae in Patagonia, especially in lakes. To fill this knowledge gap, our main goal is to document the paleoecological record of testate amoebae from Laguna Polo (49° 15' 59.4" S, 72° 53' 38.4" W) in Santa Cruz, southern Patagonia. We analyzed a 54-cm long sediment core and conducted paleoecological analyses on testate amoebae in combination with geochemical analyses to characterize the sediment composition (Ca, K, Ti, TOC, TIC, TN, δ15N, δ13C and C/N). The age model, based on radiocarbon dates and tephrochronology, indicates a basal age of ca. AD 1302. The testate amoebae assemblages are composed of Centropyxis with five morphotaxa, Difflugia with three, and Lagenodifflugia, Zivkovicia and Cyclopyxis with one, respectively. According to the redundance analysis (RDA), the assemblages are mainly related to Ca (Pr(>F)=0.007), TOC (Pr(>F)=0.038) and δ13C (Pr(>F)= 0.099). Then, a Detrended Correspondence Analysis (DCA) was performed using all species and their abundances to summarize environmental changes along the record. DCA axis 1 seems to correlate with the volcanic activity from Volcan Lautaro, whereas DCA axis 2 relates to lake productivity. Finally, the testate amoebae ecological turnover in the last 700 years allows identifying the effect of climate events such as the end of the Medieval Climate Anomaly (MCA, AD 1302-1419), the Little Ice Age (LIA, AD 1419-1722) and the most recent climate change (AD 1959-2018). This work highlights the usefulness of lacustrine testate amoebae for paleoenvironmental reconstructions and the need to understand the sensitiveness of these protists to different environmental drivers.