Anthropogenic Influence on the ¹⁴C Activity and Other Constituents of Recent Lake Sediments: A Case Study¹

Abstract

ABSTRACT. Anthropogenic activities that introduce an excess of nutrients and other pollutants into rivers and lakes are causing significant changes in their aquatic environment. Excessive nutrients greatly accelerate eutrophication, and lake marl formed during eutrophication differs from that formed in oligotrophic water.We analyzed recent sediment cores from Prone and Kozjak lakes located in Plitvice National Park, central Croatia.Analyses consisted of 14C activity of calcareous lake marl, the ratio of stable isotopes (b13C, 5180), organic compounds in the sediment and the distribution of diatoms. Previous 14C activity measurements helped to determine the sedimentation rate and thus the time period of increased input of nutrients into lakes. We determined the increased 14C activity in lake sediments caused by nuclear bomb effect in recent depth profiles. We attributed the sudden increase in diatom species, Cyclotella operculata unipuctata andAchnanthes clevei rostrata, in the uppermost 5-cm layer, to eutrophication of the lake water.We performed a molecular characterization of hydrocarbons isolated from the sediments, and applied computer-assisted high-resolution gas chromatography/mass spectrometry to estimate contributions of biogenic, fossil and pyrolytic hydrocarbons.

Experimental Determination of the 14C Initial Activity of Calcareous Deposits

“…Pazdur, Pazdur & Szulc (1988) Several shallow sediment cores were retrieved from Lake Kozjak (see Fig. 1A) to study anthropogenic influences on lakes and lake sediments, as described by Srdoc et al (1992). The uppermost 9 cm of the core showed a non-linear increase of 14C activity compared to layers immediately below 9 cm.…”

Study of Pollution of the Plitvice Lakes by Water and Sediment Analyses

“…Moreover, the lakes are located in mostly deciduous forest, and huge amount of leaves are transported into the lakes every year. Anthropogenic influence on 14 C activity and some aliphatic and polycyclic aromatic hydrocarbons of recent lake sediment in lakes Kozjak and Prošće were published in Srdoč et al (1992). Additionally, some preliminary measurements of dissolved organic carbon (DOC) in water in this area showed that increase of DOC can disturb or even stop the process of tufa precipitation (Srdoč et al, 1985a).…”

Defining centric diatoms of most relevant phytoplankton functional groups in deep karst lakes

“…Alongside diatoms, chrysophytes frequently constitute a significant component of phytoplankton assemblages of karst lakes (Srdoč et al, 1992;Morata et al, 2003;Gligora et al, 2007;Ž utinić et al, 2014;Gligora Udovič et al, 2015). The major representative, Dinobryon spp.…”