Biomarkers and their applications in ecosystem research

Abstract

Biomarkers are biogenic organic compounds that carry the chemical structures specific to their biological sources and survive long-term preservation in environmental and geological systems. The abundance of biomarkers may indicate the relative contribution of specific biological sources to the natural organic matter while their chemical and isotopic compositions may also inform on the transformation stage of organic matter and the environmental settings. Compared with conventional bulk analysis, biomarkers offer highly specific and sensitive tools to track the sources, transformation and dynamic changes of natural organic matter components and have therefore been widely used in ecological and biogeochemical studies in the past decades. In particular, combined with ecosystem observations and control experiments, biomarkers have shown great potentials in revealing changes in microbial activity and carbon sources, soil organic matter dynamics, stabilization mechanisms and response to global changes. The recently-developed biomarker-specific isotope analysis also exhibits a great promise in revealing ecosystem carbon and nitrogen turnover and food web structures. This review summarizes several major catego-ries of commonly used biomarkers, their analytical methods, applications in ecosystem studies and existing pit-falls, and discusses future directions of research to provide guidance for biomarker users in ecology and environmental sciences. Otto et al ., 2005). Micorbial-derived biomarkers: phospholipid fatty acids (PLFAs) such as linoleic acid (VII; Frostegård & Bååth, 1996); glycerol dialkyl glycerol tetraethers (GDGTs) such as GDGT-2 (VIII; Schouten et al ., 2013); amino sugars, including α -D-glucosamine (IX) and α -D-galactosamine (X), etc. (Joergensen, 2018). In addi-tion, neutral sugars such as α -D-glucose (XI) and amino acids with side chain (R group; XII) can be synthesized by both plants and microbes.