Stable oxygen and carbon isotopes in modern benthic foraminifera from the Laptev Sea shelf: implications for reconstructing proglacial and profluvial environments in the Arctic

• Published in: Marine Micropaleontology
• Main Authors: Bauch, Henning, Erlenkeuser, Helmut, Bauch, Dorothea, Müller-Lupp, Thomas, Taldenkova, Ekaterina
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2004
• Subjects: Arctic; Laptev Sea; Foraminifera*; laptev; lena river
• Online Access: https://oceanrep.geomar.de/id/eprint/7660/; https://oceanrep.geomar.de/id/eprint/7660/1/2004_BauchH-etal-Arctic_MarMic.pdf; https://doi.org/10.1016/j.marmicro.2004.01.002

Measurements of δ18O and δ13C isotopes in three benthic foraminiferal species from surface sediments of the eastern Laptev Sea are compared to water δ18O values and δ13C values of dissolved inorganic carbon (DIC). Samples investigated originate from two environmentally contrasting core locations, which are influenced by riverine freshwater runoff to a varying degree. At the river-distal site, located within relatively stable marine conditions on the outer shelf, Elphidiella groenlandica, Haynesina orbiculare and Elphidium excavatum forma clavata show a positive specific offset of 1.4‰, 1.5‰ and 1‰, respectively, in their δ18O values relative to the expected value for inorganic calcite precipitated under equilibrium conditions. At the site close to the Lena River confluence, with enhanced seasonal hydrographic contrasts, calculated δ18O offsets in E. groenlandica and in H. orbiculare remain about the same whereas E. e. clavata displays a distinctly negative offset of −1.8‰. The δ18O variation in E. e. clavata is interpreted as a vital effect, a finding which limits the potential of this species for reconstructing freshwater-influenced shelf paleoenvironments on the basis of oxygen isotopes. This interpretation gains support when comparing foraminiferal δ13C with the δ13CDIC of the water. While some of the difference in the carbonate δ13C seems to be controlled by a riverine-related admixture of DIC, clearly defined δ13C ranges in each of the three foraminifera at the river-proximal site shows that also the carbon isotopic signature in E. e. clavata is particularly affected by environmental factors.