Isotopic paleolimnology of Lake Kinneret

Abstract

The carbonate, organic C, and N contents and their respective ␦ 13 C were measured in four cores from Lake Kinneret, Israel. Using these data and the isotopic difference between coexisting carbonate and organic C, ⌬␦ 13 C, 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 ␦ 13 C org are high, whereas the ⌬␦ 13 C values are low. During wet periods, characterized by intense input of particulates and nutrients from external sources, the CaCO 3 content, its ␦ 13 C car and ␦ 18 O 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 ␦ 13 C of atmospheric CO 2 that accompanies the global anthropogenic CO 2 rise seems to be recorded by a commensurate decrease in ␦ 13 C car of the sediments. The concomitant increase in ⌬␦ 13 C expresses an increase in the isotopic fractionation of the lake's primary producers, which may also be related to the atmospheric CO 2 rise.During the last decade it has been well established that the C isotopic fractionation of marine and freshwater phytoplankton is controlled by their rate of growth, the ambient concentration of dissolved CO 2 (CO 2(aq) ), and the phytoplankton size and shape (e.g, Degens 1969; Goericke et al. 1994;Laws et al. 1995;Rau et al. 1996). Thus, the fractionation of C isotopes is becoming an important tool for deciphering paleoenvironmental changes in aquatic systems (e.g., Hollander et al. 1993;Jasper et al. 1994) Because of their smaller size and higher sedimentation rates, lakes are more sensitive than oceans to climatic and environmental changes. Their sedimentary records therefore allow finer time resolution and direct comparison with known historic and climatic records on nearby land. Lake Kinneret (35Њ31ЈE, 32Њ53ЈN) is a warm monomictic lake characterized by an annual winter-spring bloom of Per-1 To whom correspondence should be addressed. Present address: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 54-1320, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (yaeldu@mit.edu). AcknowledgmentsThis research was supported by the Belfer Foundation for Energy Research, by grant DISUM-BMBF 0033-01421 from the Israeli Ministry of Science and the German Ministry of Science and Technology, and by the Moshe Shilo Minerva Center for Marine Biogeoc...

Quantifying rates of methanogenesis and methanotrophy in Lake Kinneret sediments (Israel) using pore‐water profiles

“…Acetate concentrations in the sediment are 3-5% (Nü sslein et al 2001). Dubowski et al (2003) showed that the C : N value ranged between 10 and 14 in the sediments.…”

Species-specific imprint of the phytoplankton assemblage on carbon isotopes and the carbon cycle in Lake Kinneret, Israel

“…The compiled sediment trap data from 1990 to 1995 also exhibited no δ 13 C alteration with trap depths (data not shown). The notion of lack of δ 13 C-POM alteration is widely accepted (Meyers 1994); it enables the application of δ 13 C-POM from sediment cores to reconstruct past environmental conditions (Brenner et al 1999, Dubowski et al 2003. The lack of alteration in isotopic composition is validated in turn by the little to no carbon isotopic fractionation when organic matter is consumed (DeNiro and Epstein 1978), which would leave the remaining organic matter intact in terms of its δ 13 C. To explore the possible causes for the significantly higher spring δ 13 C peaks in Peridinium years than in nonPeridinium years (Fig.…”

“…The freeze-dried material was subsampled to obtain both organic (POM traps ) and inorganic (mostly CaCO 3 ) material separately. The organic subsample was treated with 1 N HCl to remove CaCO 3 , dried in the hood to remove the excess acid, and stored at room temperature in a desiccator until δ 13 C analysis was performed (Dubowski et al 2003). The inorganic subsample was treated with diluted (1:5) NaOCl for 24 h to oxidize the organic matter.…”

Hydrological and Ecological Controls on Autochthonous Carbonate Deposition in Lake Systems: A Case Study From Lake Wuliangsu and the Global Perspective

“…Circles denote shallow lakes, including Lake Wuliangsu (this study), and lakes from the Songnen Plain (Ou & Zhang, 2009), the Kajemarum Oasis (Holmes et al, 1997), and the Christmas Island (Trichet et al, 2001). Squares denote large and deep lakes, including Lakes Erie , Ontario , Mendota (Hollander et al, 1992), Qinghai (Xu et al, 2006), Pyramid (Meyers et al, 1998;Tenzer et al, 1997), Kivu (Botz et al, 1988), and Kinneret (Dubowski et al, 2003). Squares denote large and deep lakes, including Lakes Erie , Ontario , Mendota (Hollander et al, 1992), Qinghai (Xu et al, 2006), Pyramid (Meyers et al, 1998;Tenzer et al, 1997), Kivu (Botz et al, 1988), and Kinneret (Dubowski et al, 2003).…”