Impact of human activities and vegetation changes on the tetraether sources in Lake St Front (Massif Central, France)
Martin, Céline (Aix-Marseille Université)
Ménot, Guillemette (Centre National de la Recherche Scientifique. Université de Lyon)
Thouveny, Nicolas (Aix-Marseille Université)
Davtian, Nina (Aix-Marseille Université)
Andrieu-Ponel, Valérie (Aix-Marseille Université)
Reille, Maurice (Venède)
Bard, Edouard (Aix-Marseille Université)

Data:	2019
Resum:	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.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	Altitude lake ; Anthropogenic impact ; Branched GDGTs ; Holocene ; Soil erosion ; Vegetation dynamics ; SDG 13 - Climate Action
Publicat a:	Organic Geochemistry, Vol. 135 (September 2019) , p. 38-52, ISSN 0146-6380

DOI: 10.1016/j.orggeochem.2019.06.005

Postprint 62 p, 5.8 MB

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