Abstract
The drivers of organic carbon (OC) burial efficiency are still poorly understood despite their key role in reliable projections of future climate trends. Here, we provide insights on this issue by presenting a paleoclimate time series of sediments, including the OC contents, from Lake Veliko jezero, Croatia. The Sr/Ca ratios of the bulk sediment are mainly derived from the strontium (Sr) and calcium (Ca) concentrations of needle-like aragonite in Core M1-A and used as paleotemperature and paleohydrology indicators. Four major and six minor cold and dry events were detected in the interval from 8.3 to 2.6 calibrated kilo anno before present (cal ka BP). The combined assessment of Sr/Ca ratios, OC content, carbon/nitrogen (C/N) ratios, stable carbon isotope (δ13C) ratios, and modeled geochemical proxies for paleoredox conditions and aeolian input revealed that cold and dry climate states promoted anoxic conditions in the lake, thereby enhancing organic matter preservation and increasing the OC burial efficiency. Our study shows that the projected future increase in temperature might play an important role in the OC burial efficiency of meromictic lakes.
Highlights
Lakes have disproportionally large annual amounts of buried organic carbon (OC) compared to oceans[1] and are of great importance for the global carbon budget and cycle; they might have a vast impact on climate change in the future
Lake Veliko jezero, with a surface area of 1.44 km[2], consists of three basins; core M1-A is derived from the deepest basin, with a maximum depth of 46 m (Fig. 1)
The data presented here demonstrate that temperature changes may have a significant impact on OC burial efficiency
Summary
Lakes have disproportionally large annual amounts of buried organic carbon (OC) compared to oceans[1] and are of great importance for the global carbon budget and cycle; they might have a vast impact on climate change in the future. Compared with numerous paleoclimate studies of biogenic aragonite, the paleoclimate potential of inorganic aragonite in marine/lake sediments needs to be explored, which is mainly because sedimentary environments in which inorganic aragonite precipitates are rare, and studies show that the Sr/Ca ratio of inorganic aragonite is much less sensitive to temperature changes than the Sr/Ca ratio of coral aragonite skeletons[21]. Despite this obstacle, the main advantage of inorganic aragonite is the lack of vital effects. The significance of the Sr/Ca ratio as a paleotemperature proxy was confirmed by correlation with other previously published studies, including the main Holocene climatic events from the wider Mediterranean r egion[26,27,28,29,30,31]
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