Isotopic paleolimnology of Lake Kinneret
Y. Dubowski, J. Erez, M. Stiller
Limnol. Oceanogr., 48(1), 2003, 68–78

The carbonate, organic C, and N contents and their respective ¹³C were measured in four cores from Lake Kinneret, Israel. Using these data and the isotopic difference between coexisting carbonate and organic C, ¹³C, we attempted to reconstruct the lake’s productivity and regional climatic conditions during the late Holocene. The sedimentary record of the last 120 yr (for which climatological data are available) demonstrates that during periods of intense productivity, organic C content and its ¹³C_org are high, whereas the ¹³C values are low. During wet periods, characterized by intense input of particulates and nutrients from external sources, the CaCO₃ content, its ¹³Ccar and ¹⁸O_car, and the organic C:N ratios are low. Based on these correlations, the longer sedimentary record of the last ca. 3,300 yr was divided into five stages, which differ in productivity and/or climatic characteristics. This longer sedimentary record indicates that the primary production in Lake Kinneret has varied in the past over a range similar to that observed presently, but the rate of these changes was much slower. The rainiest period recorded in the sediments was from about 200 B.C. to A.D. 200, i.e. during the Roman period, when the region was heavily populated. The recent decrease in ¹³C of atmospheric CO₂ that accompanies the global anthropogenic CO₂ rise seems to be recorded by a commensurate decrease in ¹³Ccar of the sediments. The concomitant increase in D ¹³C expresses an increase in the isotopic fractionation of the lake’s primary producers, which may also be related to the atmospheric CO₂ rise.