Changes in accumulation of organic matter and stable carbon and nitrogen isotopes in sediments of two Slovenian mountain lakes (Lake Ledvica and Lake Planina), induced by eutrophication changes

Abstract

We measured accumulation rates of organic carbon (OC) and total nitrogen (TN) and stable carbon (␦ 13 C org ) and nitrogen isotopes (␦ 15 N) in the sediments of two mountain lakes (Lake Ledvica and Lake Planina, northwest Slovenia). Marked variations of these parameters were observed in both sediments. OC accumulation rates ranged from 4 to 23 g m Ϫ2 yr Ϫ1 in Lake Ledvica, whereas in Lake Planina they were one order of magnitude higher and increased substantially in the upper sediments. ␦ 13 C org and ␦ 15N decreased upward in Lake Ledvica, from Ϫ25.5‰ to Ϫ28.4‰, and from ϩ2.1‰ to Ϫ3.4‰, respectively. In contrast, substantial variations in the ␦ 13 C org profile, ranging from Ϫ30.9‰ to Ϫ37.4‰, but a quite uniform ␦ 15

A 1600 year multiproxy record of paleoclimatic change from varved sediments in Lake Xiaolongwan, northeastern China

“…In paleolimnological studies, one difficulty with reconstructing palaeoclimate from stable isotopic analyses is to determine whether changes occurred in temperature, precipitation or trophic state. For example, stable organic carbon isotopic compositions have been interpreted as an indicator of relative humidity [Hong et al, 2001;Xu et al, 2006], trophic state and primary productivity [Brenner et al, 1999;Teranes and McKenzie, 1999;Hodell and Schelske, 1998], and isotopic composition of atmospheric CO 2 [Vreca and Muri, 2006]. Nitrogen isotope signals in lake sediments are more complex to interpret due to the confounding effects of nitrogen biogeochemical cycling processes [Meyers and Teranes, 2001;Talbot, 2001;Lehmann et al, 2002Lehmann et al, , 2004.…”

Towards a Deeper Understanding of How Carbonate Isotopes (14C, 13C, 18O) Reflect Environmental Changes: A Study with Recent 210Pb-Dated Sediments of the Plitvice Lakes, Croatia

“…induced calcite precipitation (Schelske and Hodell 1991;Hodell et al 1998;Brenner et al 1999Brenner et al , 2001Brenner et al , 2006Herczeg et al 2001;Wan et al 2003;VreËa 2003;Mayr et al 2005;VreËa and Muri 2006).…”

The effect of fish stocking on mountain lake plankton communities identified using palaeobiological analyses of bottom sediment cores

“…The trend towards more negative d 13 C values in surface sediments can be related to the consumption of 13 C-depleted CO 2 formed during the degradation of sinking organic matter by aquatic biota (Vreca and Muri 2006). However, from the 1960s to the present, the magnitude of these changes in d 13 C was small (approximately 1 %), and the introduction of fish did not provide a clear signal in the isotopic composition.…”