DOWN-CORE BRGDGT BIOMARKER DISTRIBUTIONS FROM KONGRESSVATNET, SVALBARD: A DEEP, ANOXIC, AND MEROMICTIC ARCTIC LAKE

BrGDGTs (branched glycerol dialkyl glycerol tetraethers) are a suite of bacterial membrane lipids whose distributions have been shown to relate to environmental temperature in modern settings. As such, they have been used to reconstruct past temperatures in sedimentary archives across a wide range of environments. Numerous questions remain, however, about the influence of environmental parameters besides temperature on brGDGT distributions (such as conductivity, pH, and dissolved oxygen). Here, we analyzed brGDGTs in down-core sediments from Kongressvatnet, Svalbard, Norway. Kongressvatnet is a 55-meter deep lake, with anoxic conditions in the bottom five meters. During the 2022 and 2023 field seasons, multiple lake sediment cores were recovered from Kongressvatnet. Samples from Kongressvatnet suggest brGDGTs are likely reflecting a signal other than temperature (likely dissolved oxygen and/or conductivity), as down-core shifts in brGDGTs do not match local and regional paleoclimate trends. We investigated other possible controls on brGDGTs in Kongressvatnet and compared our results against modern sediment trap and soil samples from the lake and catchment. Although sediment type may be influencing the brGDGT-reconstructed temperatures, other environmental parameters, such as conductivity and dissolved oxygen, are likely reflected in the down-core brGDGT distributions from Kongressvatnet.