Different response of bulk and n-alkane δ13C signatures to seasonal shifts in environmental conditions in a temperate coastal ecosystem

Yvette Eley; Nikolai  Pedentchouk; Lorna  Dawson

Different response of bulk and n-alkane δ¹³C signatures to seasonal shifts in environmental conditions in a temperate coastal ecosystem

Yvette Eley, Nikolai Pedentchouk, Lorna Dawson

Archaeology

Research output: Contribution to conference › Abstract › peer-review

Abstract

The carbon isotope signal recorded in land plants represents an important reservoir of information for reconstructing climatically driven shifts in plant ecophysiology and biochemistry. Analytical advances have led to widespread usage of compound-specific (CS) carbon isotope analysis of leaf wax biomarkers, such as n−alkanes, in addition to traditional bulk isotope methods, to identify shifts in the relative percentage of C₃ and C₄vegetation contributing to the sedimentary record. Recent studies, however, have extended the application of leaf wax biomarkers, using bulk and n−alkane δ¹³C values interchangeably to derive information about plant-environment relations, both in modern ecosystems and throughout the geological past. Even though previous work on C₃ plants has shown a clearlink between climatically influenced plant physiology and bulk δ¹³C values, further research is needed to establish whether the same link can be seen in leaf wax biomarkers.

To address this question, we collected bulk and n−alkane δ¹³C data from plants growing at Stiffkey marsh on thenorth Norfolk coast, UK over a period of 15 months. Maximum interspecies variation in weighted average (WA) n−alkane δ¹³C among C₃ species was typically 2-3‰ greater than in bulk. We observed a close correlation in the bulk and WA n−alkane δ¹³C seasonal trends from C₃ grasses and reeds (R²=0.9, P <0.05). However, for other species (including C₃ and C₄ plants), no statistically significant relationship was observed between their respective bulk and WA n−alkane carbon isotope values. This variation in δ¹³C trends resulted in considerable intra- and inter-species variability (ranging from -4 to -13 per mil) in the offset between bulk and WA n−alkane δ¹³C values. In addition, we identified a positive correlation (R²=0.7, P <0.05), for all species (with the exception of the evergreen succulent Suaeda vera) between the relative abundance of the n−C₂₅and n−C₂₇ n−alkane homologues and n−C₂₉ alkane δ¹³C values.

We explain the discrepancy between bulk and n−alkane δ¹³C signatures by referring to possible interspecies variation in post-photosynthetic carbon isotope fractionation. Our data imply that for some species, seasonal changesin the abundance of n−alkane homologues might be an important biochemical process influencing n−alkane δ¹³C signatures. We further theorise that interspecies variation in n−alkane δ¹³C values may arise from biochemical differences in salinity adaptation - in plants adapted to salt stress, production of osmoregulatory solutes (amino acids and/or carbohydrates) may influence the partitioning of pyruvate to fates other than acetyl-CoA, shifting the isotopic composition of lipid biomarkers. Mechanisms controlling metabolic fluxes through these biochemical processes may potentially exert an additional important control over the δ¹³C signal of lipid biomarkers.We therefore conclude that it may not be valid to use bulk and n−alkane δ¹³C data interchangeably to examine plant-environment interactions. These findings open new avenues for empirical studies to further understand the metabolic processes fractionating carbon during the synthesis of leaf wax lipids, enhancing interpretation of the biomarker signal from the geological record.

Original language	English
Publication status	Published - 2014
Event	European Geophysical Union - Vienna, Austria Duration: 27 Apr 2014 → 2 May 2014

Conference

Conference	European Geophysical Union
Country/Territory	Austria
City	Vienna
Period	27/04/14 → 2/05/14

Cite this

@conference{4419c23fc0c24a8fbe3b0709288b7d1a,

title = "Different response of bulk and n-alkane δ13C signatures to seasonal shifts in environmental conditions in a temperate coastal ecosystem",

abstract = "The carbon isotope signal recorded in land plants represents an important reservoir of information for reconstructing climatically driven shifts in plant ecophysiology and biochemistry. Analytical advances have led to widespread usage of compound-specific (CS) carbon isotope analysis of leaf wax biomarkers, such as n−alkanes, in addition to traditional bulk isotope methods, to identify shifts in the relative percentage of C3 and C4 vegetation contributing to the sedimentary record. Recent studies, however, have extended the application of leaf wax biomarkers, using bulk and n−alkane δ13C values interchangeably to derive information about plant-environment relations, both in modern ecosystems and throughout the geological past. Even though previous work on C3 plants has shown a clearlink between climatically influenced plant physiology and bulk δ13C values, further research is needed to establish whether the same link can be seen in leaf wax biomarkers.To address this question, we collected bulk and n−alkane δ13C data from plants growing at Stiffkey marsh on thenorth Norfolk coast, UK over a period of 15 months. Maximum interspecies variation in weighted average (WA) n−alkane δ13C among C3 species was typically 2-3‰ greater than in bulk. We observed a close correlation in the bulk and WA n−alkane δ13C seasonal trends from C3 grasses and reeds (R2=0.9, P <0.05). However, for other species (including C3 and C4 plants), no statistically significant relationship was observed between their respective bulk and WA n−alkane carbon isotope values. This variation in δ13C trends resulted in considerable intra- and inter-species variability (ranging from -4 to -13 per mil) in the offset between bulk and WA n−alkane δ13C values. In addition, we identified a positive correlation (R2=0.7, P <0.05), for all species (with the exception of the evergreen succulent Suaeda vera) between the relative abundance of the n−C25 and n−C27 n−alkane homologues and n−C29 alkane δ13C values. We explain the discrepancy between bulk and n−alkane δ13C signatures by referring to possible interspecies variation in post-photosynthetic carbon isotope fractionation. Our data imply that for some species, seasonal changesin the abundance of n−alkane homologues might be an important biochemical process influencing n−alkane δ13C signatures. We further theorise that interspecies variation in n−alkane δ13C values may arise from biochemical differences in salinity adaptation - in plants adapted to salt stress, production of osmoregulatory solutes (amino acids and/or carbohydrates) may influence the partitioning of pyruvate to fates other than acetyl-CoA, shifting the isotopic composition of lipid biomarkers. Mechanisms controlling metabolic fluxes through these biochemical processes may potentially exert an additional important control over the δ13C signal of lipid biomarkers.We therefore conclude that it may not be valid to use bulk and n−alkane δ13C data interchangeably to examine plant-environment interactions. These findings open new avenues for empirical studies to further understand the metabolic processes fractionating carbon during the synthesis of leaf wax lipids, enhancing interpretation of the biomarker signal from the geological record. ",

author = "Yvette Eley and Nikolai Pedentchouk and Lorna Dawson",

year = "2014",

language = "English",

note = "European Geophysical Union ; Conference date: 27-04-2014 Through 02-05-2014",

}

TY - CONF

T1 - Different response of bulk and n-alkane δ13C signatures to seasonal shifts in environmental conditions in a temperate coastal ecosystem

AU - Eley, Yvette

AU - Pedentchouk, Nikolai

AU - Dawson, Lorna

PY - 2014

Y1 - 2014

N2 - The carbon isotope signal recorded in land plants represents an important reservoir of information for reconstructing climatically driven shifts in plant ecophysiology and biochemistry. Analytical advances have led to widespread usage of compound-specific (CS) carbon isotope analysis of leaf wax biomarkers, such as n−alkanes, in addition to traditional bulk isotope methods, to identify shifts in the relative percentage of C3 and C4 vegetation contributing to the sedimentary record. Recent studies, however, have extended the application of leaf wax biomarkers, using bulk and n−alkane δ13C values interchangeably to derive information about plant-environment relations, both in modern ecosystems and throughout the geological past. Even though previous work on C3 plants has shown a clearlink between climatically influenced plant physiology and bulk δ13C values, further research is needed to establish whether the same link can be seen in leaf wax biomarkers.To address this question, we collected bulk and n−alkane δ13C data from plants growing at Stiffkey marsh on thenorth Norfolk coast, UK over a period of 15 months. Maximum interspecies variation in weighted average (WA) n−alkane δ13C among C3 species was typically 2-3‰ greater than in bulk. We observed a close correlation in the bulk and WA n−alkane δ13C seasonal trends from C3 grasses and reeds (R2=0.9, P <0.05). However, for other species (including C3 and C4 plants), no statistically significant relationship was observed between their respective bulk and WA n−alkane carbon isotope values. This variation in δ13C trends resulted in considerable intra- and inter-species variability (ranging from -4 to -13 per mil) in the offset between bulk and WA n−alkane δ13C values. In addition, we identified a positive correlation (R2=0.7, P <0.05), for all species (with the exception of the evergreen succulent Suaeda vera) between the relative abundance of the n−C25 and n−C27 n−alkane homologues and n−C29 alkane δ13C values. We explain the discrepancy between bulk and n−alkane δ13C signatures by referring to possible interspecies variation in post-photosynthetic carbon isotope fractionation. Our data imply that for some species, seasonal changesin the abundance of n−alkane homologues might be an important biochemical process influencing n−alkane δ13C signatures. We further theorise that interspecies variation in n−alkane δ13C values may arise from biochemical differences in salinity adaptation - in plants adapted to salt stress, production of osmoregulatory solutes (amino acids and/or carbohydrates) may influence the partitioning of pyruvate to fates other than acetyl-CoA, shifting the isotopic composition of lipid biomarkers. Mechanisms controlling metabolic fluxes through these biochemical processes may potentially exert an additional important control over the δ13C signal of lipid biomarkers.We therefore conclude that it may not be valid to use bulk and n−alkane δ13C data interchangeably to examine plant-environment interactions. These findings open new avenues for empirical studies to further understand the metabolic processes fractionating carbon during the synthesis of leaf wax lipids, enhancing interpretation of the biomarker signal from the geological record.

AB - The carbon isotope signal recorded in land plants represents an important reservoir of information for reconstructing climatically driven shifts in plant ecophysiology and biochemistry. Analytical advances have led to widespread usage of compound-specific (CS) carbon isotope analysis of leaf wax biomarkers, such as n−alkanes, in addition to traditional bulk isotope methods, to identify shifts in the relative percentage of C3 and C4 vegetation contributing to the sedimentary record. Recent studies, however, have extended the application of leaf wax biomarkers, using bulk and n−alkane δ13C values interchangeably to derive information about plant-environment relations, both in modern ecosystems and throughout the geological past. Even though previous work on C3 plants has shown a clearlink between climatically influenced plant physiology and bulk δ13C values, further research is needed to establish whether the same link can be seen in leaf wax biomarkers.To address this question, we collected bulk and n−alkane δ13C data from plants growing at Stiffkey marsh on thenorth Norfolk coast, UK over a period of 15 months. Maximum interspecies variation in weighted average (WA) n−alkane δ13C among C3 species was typically 2-3‰ greater than in bulk. We observed a close correlation in the bulk and WA n−alkane δ13C seasonal trends from C3 grasses and reeds (R2=0.9, P <0.05). However, for other species (including C3 and C4 plants), no statistically significant relationship was observed between their respective bulk and WA n−alkane carbon isotope values. This variation in δ13C trends resulted in considerable intra- and inter-species variability (ranging from -4 to -13 per mil) in the offset between bulk and WA n−alkane δ13C values. In addition, we identified a positive correlation (R2=0.7, P <0.05), for all species (with the exception of the evergreen succulent Suaeda vera) between the relative abundance of the n−C25 and n−C27 n−alkane homologues and n−C29 alkane δ13C values. We explain the discrepancy between bulk and n−alkane δ13C signatures by referring to possible interspecies variation in post-photosynthetic carbon isotope fractionation. Our data imply that for some species, seasonal changesin the abundance of n−alkane homologues might be an important biochemical process influencing n−alkane δ13C signatures. We further theorise that interspecies variation in n−alkane δ13C values may arise from biochemical differences in salinity adaptation - in plants adapted to salt stress, production of osmoregulatory solutes (amino acids and/or carbohydrates) may influence the partitioning of pyruvate to fates other than acetyl-CoA, shifting the isotopic composition of lipid biomarkers. Mechanisms controlling metabolic fluxes through these biochemical processes may potentially exert an additional important control over the δ13C signal of lipid biomarkers.We therefore conclude that it may not be valid to use bulk and n−alkane δ13C data interchangeably to examine plant-environment interactions. These findings open new avenues for empirical studies to further understand the metabolic processes fractionating carbon during the synthesis of leaf wax lipids, enhancing interpretation of the biomarker signal from the geological record.

M3 - Abstract

T2 - European Geophysical Union

Y2 - 27 April 2014 through 2 May 2014

ER -