Cornelia Blaga

Department of Earth Sciences - Geochemistry
Faculty of Geosciences
Utrecht University

Former position: Post-doc within project HYPER (Hypoxia mitigation for Baltic Sea Ecosystem Restoration)
Supervisors: Jaap Sinninghe Damsté and Gert-Jan Reichart  
Co-workers: Caroline Slomp, Tom Jilbert, Klaas Nierop ( Utrecht University )

Left 1 August 2011, working now at the NIOZ, Texel

Page is not updated since then

NEW mail address:
(geo)UU mail address nearly not available any more!!!
NEW phone number: +31 222 369.409



  • Nationality: Romanian
  • Date and Place of Birth: January 6 1981, Cluj-Napoca




  • Jul. 2010 present , PostDoc, Geochemistry, Utrecht University
  • Nov. 2005 - May 2010, Ph.D., Glycerol  dialkyl  glycerol  tetraether  membrane  lipids  in  lacustrine environments  and  their  application  as  proxies  for  palaeoclimate reconstructions
  • 2003 - 2005, Topmaster student, Ecology and Evolutionary Biology, Faculty of Natural Sciences and Mathematics, RUG, Groningen
  • 1999 - 2003, student, Faculty of Biology and Geology, Section Ecology and Environmental Protection, BBU, Cluj-Napoca
  • 1999 - 2003, student, Faculty of Sociology and Social Assistance, Section Sociology, BBU, Cluj- Napoca
  • 1999 - Baccalaureate Diploma, "Onisifor Ghibu" Theoretical High School, Cluj-Napoca




lake sediments, fine scale archives of climate change,

social behaviour, system organization, ethnology,
books, music




Romanian (mother tongue),
English, French, German, Italian, Dutch

PostDoc Project - HYPER (Hypoxia mitigation for Baltic Sea Ecosystem Restoration)

The Baltic Sea experiences strong latitudinal and vertical gradients in temperature and salinity, and the stratified water column is highly susceptible to hypoxia. Laminated anoxic sediments form in the hypoxic zones, providing archives of the interaction between climate and biogeochemical cycles. T he impact of modern climate change on the Baltic ecosystem requires a better understanding of the mechanisms by which climate affects the biogeochemistry of the basin and its susceptibility to hypoxia. Since the formation of the Baltic as a sea around 8000 years ago, natural climate variability has influenced hypoxia in the basin, with warmer intervals characterized by more severe and widespread hypoxia.

Fossil biomarkers have been shown to be useful paleo-tracers of algal and bacterial communities. Although previous work has shown that degradation of distinct classes of biochemical tracers (i.e. fatty acids, sterols, lipids, proteins, carbohydrates, pigments) is significantly higher in oxic than in anoxic unaltered biomarkers have been recovered from both freshwater and marine sediments. In this study, I shall investigate the presence of algal and bacterial biomarkers in order to reconstruct the historical trends of hypoxic events in the Baltic proper.


PhD Project - GDGT  membrane  lipids  in  lacustrine environments  and  their  application  as  proxies  for  palaeoclimate reconstructions

Lacustrine sediments often contain relatively high amounts of organic matter because of limited bottom water oxygenation and relatively high sedimentation rates. Molecular ecological analyses revealed that Archaea are not restricted to extreme environments but are also present in more temperate environments such as lakes. The membrane lipids of Crenarchaeota, a major group of the domain Archaea, consist of isoprenoid glycerol dialkyl glycerol tetraether (GDGTs) containing cyclopentane moieties, a characteristic generally considered as an adaptation mechanism to temperature of the membrane. Previously the analyses of core top sediments from different locations worldwide showed that the distribution of these isoprenoid GDGTs varies with sea surface temperature (SST), a relation expressed in the T etra E ther inde X of lipids with 86 carbon atoms (TEX 86 ). Besides isoprenoid GDGTs, branched GDGTs, whose potential biological origin is assigned to Bacteria, were also detected in peat bogs, soils, and coastal marine and lacustrine sediments. The branched GDGT abundance in marine sediments was shown to decrease relative to crenarchaeol (an isoprenoid GDGT) with increasing distance from river mouths, indicating fluvial transport of branched GDGTs from land to aquatic environments. This relation was expressed in the B ranched versus I soprenoid T etraether (BIT) index. The alkyl chains of branched GDGTs are composed of straight carbon chains containing a different number of cyclopentane moieties and also a different degree of methylation, which were shown to be related to air temperature and soil pH. This formed the basis for two newly developed proxies: CBT ( C yclisation ratio of B ranched T etraethers) showing the relation between the degree of cyclisation and soil pH; and MBT ( M ethylation index of B ranched T etraethers) expressing the correlation between the degree of methylation and annual mean air temperature and soil pH. This thesis describes the distribution and biological sources of GDGT membrane lipids in lacustrine environments, their potential use as temperature proxies and their application in reconstructing past continental temperatures.

Isoprenoid GDGTs were detected in variable amounts in particulate matter and the top 5 cm of the sediment from 47 European lakes, along a latitudinal transect from southern Italy to the northern part of Scandinavia . In many of the lakes, soil input affects the distribution of isoprenoidal GDGTs and prevents the reliable application of the TEX 86 temperature proxy for lake water temperature, which is based on in situ crenarchaeotal GDGTs production. The results presented in this thesis show that not only large lakes but also smaller size lakes with high in situ productivity of isoprenoid GDGTs are suited for the use of TEX 86 . After excluding lakes not suited for a TEX 86 based temperature reconstruction the winter temperatures correlate better with TEX 86 . This indicates that the isoprenoid GDGT producing organisms probably have their peak abundances during this season.

Because branched GDGTs dominate in many of the lake sediments, as indicated by high BIT values, t he potential of the MBT/CBT as a continental palaeothermometer in lacustrine environments was investigated. The set of surface sediments from the European lakes was extended by including a series of lake sediments from North and South America , as well as some sediments from Equatorial Africa. We observed that the distribution of branched GDGTs as expressed in the MBT and CBT indices varied substantially among the lake sediments and that the MBT/CBT-reconstructed temperatures using the global soil calibration were consistently below annual mean air temperature of the catchment of the lake. It seems that the branched GDGTs in lake sediments are derived from both erosion of soil and in situ production and that the existing soil calibration cannot be used for lake sediments.

In order to determine where and when the GDGT signal is produced in the water column of lakes, we collected descending particles using sediment with a monthly resolution from January 2008 to late March 2009 in Lake Lucerne . Suspended particulate matter (SPM) was monthly filtered from the water column at three different depths. The results of this study show that fluxes of GDGTs and concentrations in the water column vary according to a seasonal pattern, with a similar trend in SPM and sediment traps. Fluxes and concentrations of isoprenoid GDGTs increase with depth, maximum values being observed in the deeper part of the water column, indicating production of isoprenoid GDGTs in the deep, aphotic zone. Temperature profiles of the water column were also measured and at this depth the values fluctuate over the year between 5 and 8 °C. This is consistent with the low values of the TEX 86 proxy and with the inferred temperatures.

To reconstruct temperature changes during the Late Glacial Interstadial, the Younger Dryas and the Early Holocene ( ~14,600 to 10,600 cal. yr BP) the relative distribution of GDGTs in a sediment core from the same location as the seasonal study was determined. The Late Glacial period was characterized by large and rapid changes in temperature and precipitation marking the transition from the Last Glacial Maximum (LGM) to the Early Holocene. The shifts in temperature for this interval are believed to range between 3 and 6 °C with a decrease in temperature at the onset of Younger Dryas and an abrupt increase at the onset of Early Holocene. The TEX 86 record suggests a sequence of temperature shifts strongly resembling the d 18 O values recorded in the Greenland ice core. Reconstructed lake temperatures indicate a step-wise pattern of climate change, with a warming at the onset of the late-glacial interstadial , followed by an abrupt cooling at the onset of Younger Dryas and a rapid warming from 5.5 to 9°C at the Younger Dryas/Holocene transition within less than 200 years.


J.W.H. Weijers, C.I. Blaga, J.P. Werne, J.S. Sinninghe Damsté (2009)

Microbial membrane lipids in lake sediments paleothermometer. PAGES News, 17:102-104

C.I. Blaga, G-J Reichart, O. Heiri, J.S. Sinninghe Damsté (2009) Tetraether membrane lipid distributions in water-column particulate matter and sediments: a study of 47 European lakes along a north-south transect. Journal of Paleolimnology 41:523-540

C.I. Blaga, G-J Reichart, A.F. Lotter, S. Schouten, J.P. Werne, J.S. Sinninghe Damsté Branched glycerol dialkyl glycerol tetraethers in lake sediments: Can they be used as temperature and pH proxies? (in press Organic Geochemistry)

C.I. Blaga, G-J Reichart, L.W. Vissers, F. Anselmetti, J.S. Sinninghe Damsté Seasonal changes in glycerol dialkyl glycerol tetraether concentrations and fluxes in an alpine lake: Implications for the use of the TEX86 and BIT proxies (submitted to Geochimica et Cosmochimica Acta)

C.I. Blaga, G-J Reichart, A.F. Lotter, F. Anselmetti, J.S. Sinninghe Damsté Late Glacial to Holocene temperature variability of Lake Lucerne (Vierwaldstättersee, Switzerland) (in prep.)

F. Verbruggen, O. Heiri, G.J. Reichart, C.I. Blaga, A.F. Lotter Stable oxygen isotopes in aquatic invertebrate remains (chironomids, cladocerans) from deep European lakes (in prep.)



May 2-7, 2010, EGU General Assembly, Vienna

April 21-23, 2010, Darwin Days and NAC 10, Veldhoven

September 6-11, 2009, the 24th International Meeting on Organic Geochemistry, Bremen

April 19-24, 2009, EGU General Assembly, Vienna

April 6-7, 2009, Darwin Days, Veldhoven

March 27, 2009, EAWAG, Kastanienbaum

August 3-8 2008, Gordon Research Meeting - Organic Geochemistry, Holderness, NH

April 13-18 2008, EGU General Assembly, Vienna

September 9-15, 2007 the 23rd International Meeting on Organic Geochemistry, Torquay

July 25-29, 2006, 10th International Paleolimnology Symposium, Barcelona

May 17, 2006 PhD Geochemistry Meeting series, Utrecht