Post-depositional alteration of stable isotope signals by preferential degradation of algae-derived organic matter in reservoir sediments

Liu X, Wendt-Potthoff K, Barth J, Friese K (2022)

Publication Type: Journal article

Publication year: 2022

Journal

Biogeochemistry Springer Verlag (Germany)

DOI: 10.1007/s10533-022-00930-y

Abstract

Post-depositional degradation of organic matter (OM) in freshwater sediments is crucial for driving the biogeochemical dynamics and influencing the carbon burial. This process also often causes diagenetic alteration on paleoenvironmental proxies. Yet, mechanisms behind degradation of sedimentary OM and depth-related variations in stable isotope ratios can so far only be explained in part. Degradation of sedimentary OM in two drinking water reservoirs with contrasting eutrophic and mesotrophic states and different catchment land use (agriculture versus forestry) was studied. A 4-step procedure was used to chemically separate sedimentary OM in terms of biochemical composition. Here we presented depth profiles of biochemical composition of sedimentary OM that helped to quantify preferential degradation of aquatic proteins and carbohydrates and the following removal of aquatic lipids. Sediment in the eutrophic reservoir, which reflected a larger contribution of algal-derived OM than the mesotrophic reservoir with a forest dominated catchment, was therefore subject to more intensive degradation of sedimentary OM along with delta C-13 and delta N-15 alterations. In addition, changes in the relative proportions of biochemical components in sedimentary OM had more pronounced impact on delta N-15 values relative to delta C-13. Our findings suggest that the lability of algae-derived OM leads to uncertainties for the estimation of carbon burial in water bodies and obscures paleo-limnological information derived from isotopic proxies. Post-depositional modifications are more pronounced in eutrophic freshwaters that accumulated more readily degradable OM of algal origin in their sediments. Recognition of these modifications will help constrain carbon burial rates of productive lakes and reservoirs and assess the role of reservoirs in carbon cycling.

Authors with CRIS profile

Johannes Barth Lehrstuhl für Angewandte Geologie

Involved external institutions

Sun Yat-Sen University CN China (CN) Helmholtz-Zentrum für Umweltforschung (UFZ) / Helmholtz Center for Environmental Research DE Germany (DE)

How to cite

APA:

Liu, X., Wendt-Potthoff, K., Barth, J., & Friese, K. (2022). Post-depositional alteration of stable isotope signals by preferential degradation of algae-derived organic matter in reservoir sediments. Biogeochemistry. https://dx.doi.org/10.1007/s10533-022-00930-y

MLA:

Liu, Xiaoqing, et al. "Post-depositional alteration of stable isotope signals by preferential degradation of algae-derived organic matter in reservoir sediments." Biogeochemistry (2022).

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