Investigating the carbon isotope composition and leaf wax n-alkane concentration of C3 and C4 plants in Stiffkey saltmarsh, Norfolk, UK. (June 2016)

• Record Type: Journal Article
• Authors: Eley, Yvette; Dawson, Lorna; Pedentchouk, Nikolai
• Is Part Of: Organic geochemistry. Volume 96(2016:Jul.)
• Page Start: 28
• Page End: 42
• Publication Date: 2016-06
• Subjects: C3 vegetation -- C4 vegetation -- Carbon isotopes -- n-Alkanes -- Fractionation -- Saltmarsh; Organic geochemistry -- Periodicals; Biogeochemistry -- Periodicals; Géochimie organique -- Périodiques; 553.205
• DOI: 10.1016/j.orggeochem.2016.03.005
• Languages: English
• ISSNs: 0146-6380

Abstract

Highlights: Seasonal variation in C3 n -alkane δ 13 C (< 10‰) exceeded that in bulk tissue (< 7‰). Seasonal trends in bulk and n -alkane δ 13 C diverge for C3 dicots and succulents. Fractionation between plant bulk and n -alkane δ 13 C reached 13‰. Plants varied by > 2 orders of magnitude in the amount of n -alkanes they produced. C3 /C4 reconstruction in temperate salt marshes has a potential uncertainty of ∼11%. Abstract: The carbon isotope composition of terrestrial plants records valuable ecophysiological and palaeoecological information. However, interspecies variability in 13 C/ 12 C, at both the bulk and compound-specific (CS) level, requires further exploration across a range of ecosystem types. Here, we present bulk and n -alkane δ 13 C values, and n -alkane concentrations, from seven plants (C3 and C4 ) growing in a temperate UK saltmarsh. Inter- and intra-species variation in n -alkane δ 13 C values among C3 plants ranged from 8‰ ( n -C31 ) to 10‰ ( n -C27 ) across the 2011 and 2012 growing seasons, exceeding variability in bulk tissue (7‰). In contrast, the C4 monocot showed < 2‰ seasonal shifts in bulk and CS values. As a result of the variability in our CS data, we calculate that n -alkane based C3 /C4 reconstructions in temperate saltmarshes have a maximum uncertainty of ∼11%. For dicots and succulents, seasonal bulk and CS δ 13 C trends diverged, while for C3 and C4 monocots, bulk and CS values followed similar temporal patterns. Fractionation between bulk and n -alkane carbon isotope values varied from −4 to −10‰ for C3 plants, and reached −13‰ for the C4 monocot. We explain discrepancies between bulk and n -alkane δ 13 C values by referring to possible interspecies variation in salinity adaptation, which may influence the partitioning of pyruvate, shifting the isotopic composition of lipid biomarkers. These findings open new avenues for empirical studies to further understand the metabolic processes fractionating carbon during the synthesis of n -alkanes, enhancing interpretation of the biomarker signal from the geological record.