Biomarkers as proxies of climate change

© 2005 Taylor & Francis. All rights reserved. Common applications of biomarkers in palaeoclimate research are briefly reviewed, and the principles behind their use discussed. Biological marker compounds (or biomarkers) are geologicallyoccurring organic compounds with chemical structures that can be unambiguously linked to natural product precursors. They are thus considered to be molecular fossils. As such, these compounds preserve information regarding the contributions of different sources of biomass to sedimentary organic matter. The use of biomarkers as climate proxies is relatively recent. Their potential in palaeoclimatological reconstruction studies has been increasingly recognized during the last 20 years, but it is only since the 1990s that their application has taken off worldwide, with numerous groups investing in the technology to carry out biomarker measurements. This is probably due to the development of the UKKindex to estimate sea-surface temperature, arguably to date the most successful application of biomarkers. Judging by the publications in journals with highest impact factors, other applications have also generated a great deal of interest, particularly the reconstruction of past variations in atmospheric CO2, marine primary productivity, relative presence of C3versus C4plants, and anoxygenic photosynthesis. This information cannot easily be gained by non-geochemical techniques. Thus, biomarkers have earned their own niche in the Earth Sciences and palaeoclimate research.