TY - JOUR
T1 - Impact of human activities and vegetation changes on the tetraether sources in Lake St Front (Massif Central, France)
AU - Martin, Céline
AU - Ménot, Guillemette
AU - Thouveny, Nicolas
AU - Davtian, Nina
AU - Andrieu-Ponel, Valérie
AU - Reille, Maurice
AU - Bard, Edouard
N1 - Funding Information:
We thank C. De Jonge and an anonymous reviewer for their constructive comments which improved the manuscript. We thank the CEREGE-SETEL coring team, Sébastien Marguerite and Samuel Meulé, who provided engineering and technical assistance and manpower during the coring operation with the UWITEC equipment at Lake St Front. We also thank the coring team: Guillaume Jouve, Christine Paillès, Emmanuel Chapron, Bertil Hebert and Thierry Courp. Jean Goedert is acknowledged for assisting with fieldwork during the soil sampling campaign. Sébastien Pivot and Frauke Rostek are also acknowledged for their assistance during core sampling, Guillaume Jouve for his help with core opening and sedimentological description, and Yoann Fagault and Frauke Rostek for analytical support in the laboratory. We also thank Bassam Ghaleb for the 210 Pb activity measurements and advice regarding data interpretation. The ARTEMIS program and J.P. Dumoulin provided 14 C measurements using the Accelerator Mass Spectrometer located in Saclay, France (Laboratoire de Mesure du 14 C). We are also grateful to Yannick Garcin for his help with the Bacon program and to Claude Mante for his help with the compositional analysis and Codapack program. Yunping Xu is acknowledged for kindly supplying data and insightful discussions. The work at CEREGE was supported by the Collège de France . Additional financial support was provided by the BNP Paribas Foundation (Climate Initiative – project CPATEMP).
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/9
Y1 - 2019/9
N2 - The distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) has been shown to correlate with mean annual air temperature and is increasingly used for paleoclimate reconstructions, in particular in lakes. Numerous studies have reported in situ production of brGDGTs in lakes. These brGDGTs have different distributions compared with those produced in soils and their mixing hampers paleoclimate reconstructions. Very few tools exist to determine brGDGT sources in the present and to trace their changes in the past linked with environmental changes of climatic or anthropogenic origin. While human activities are known to affect both soil and aquatic ecosystems, particularly bacterial communities, the specific impacts on brGDGT distributions are poorly investigated. High resolution analyses of brGDGTs were carried out on Holocene sediments and catchment soils of Lake St Front (Massif Central, France) in association with sedimentological, palynological, and geochemical analyses. Comparison of brGDGT distributions in sediments and soils revealed their mixed origin. For the first time, we tested the reliability of the ΣIIIa/ΣIIa ratio in lakes which indicated a gradual shift from aquatic to terrigenous brGDGT sources over the Holocene. This shift was supported by sedimentological and geochemical indices. Three events with a high proportion of terrigenous brGDGTs (6–5.5, 2.8–2.5, and 2–0.2 kyr cal BP) coincide with changes in vegetation in the catchment area, driven by climate and/or human activities. This suggests that vegetation modifications in the watershed impact brGDGT distributions and may thus bias brGDGT-based paleoclimatic reconstructions.
AB - The distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) has been shown to correlate with mean annual air temperature and is increasingly used for paleoclimate reconstructions, in particular in lakes. Numerous studies have reported in situ production of brGDGTs in lakes. These brGDGTs have different distributions compared with those produced in soils and their mixing hampers paleoclimate reconstructions. Very few tools exist to determine brGDGT sources in the present and to trace their changes in the past linked with environmental changes of climatic or anthropogenic origin. While human activities are known to affect both soil and aquatic ecosystems, particularly bacterial communities, the specific impacts on brGDGT distributions are poorly investigated. High resolution analyses of brGDGTs were carried out on Holocene sediments and catchment soils of Lake St Front (Massif Central, France) in association with sedimentological, palynological, and geochemical analyses. Comparison of brGDGT distributions in sediments and soils revealed their mixed origin. For the first time, we tested the reliability of the ΣIIIa/ΣIIa ratio in lakes which indicated a gradual shift from aquatic to terrigenous brGDGT sources over the Holocene. This shift was supported by sedimentological and geochemical indices. Three events with a high proportion of terrigenous brGDGTs (6–5.5, 2.8–2.5, and 2–0.2 kyr cal BP) coincide with changes in vegetation in the catchment area, driven by climate and/or human activities. This suggests that vegetation modifications in the watershed impact brGDGT distributions and may thus bias brGDGT-based paleoclimatic reconstructions.
KW - Altitude lake
KW - Anthropogenic impact
KW - Branched GDGTs
KW - Holocene
KW - Soil erosion
KW - Vegetation dynamics
UR - http://www.scopus.com/inward/record.url?scp=85068534381&partnerID=8YFLogxK
U2 - 10.1016/j.orggeochem.2019.06.005
DO - 10.1016/j.orggeochem.2019.06.005
M3 - Article
AN - SCOPUS:85068534381
SN - 0146-6380
VL - 135
SP - 38
EP - 52
JO - Organic Geochemistry
JF - Organic Geochemistry
ER -
