Aquatic and Terrestrial Plant Contributions to Sedimentary Plant Waxes in a Modern Arctic Lake Setting. Issue 8 (11th August 2022)

• Record Type: Journal Article
• Authors: Hollister, Kayla V.; Thomas, Elizabeth K.; Raynolds, Martha K.; Bültmann, Helga; Raberg, Jonathan H.; Miller, Gifford H.; Sepúlveda, Julio
• Is Part Of: Journal of geophysical research. Volume 127:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-11
• Subjects: leaf wax -- modern plants -- Arctic lake -- leaf wax isotopes; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2022JG006903
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Sedimentary plant wax δ 2 H values are common proxies for hydrology, a poorly constrained variable in the Arctic. However, it can be difficult to distinguish plant waxes derived from aquatic versus terrestrial plants, causing uncertainty in climate interpretations. We test the hypothesis that Arctic lake sediment mid‐ and long‐chain plant waxes derive from aquatic and terrestrial plants, respectively. We compare n ‐alkanoic acid and n ‐alkane chain‐length distributions and n ‐alkanoic acid δ 2 H and δ 13 C values of the 29 most abundant modern plant taxa to those for soils, water filtrates, and lake sediments in the Qaupat Lake (QPT) catchment, Nunavut, Canada. Chain length distributions are variable among terrestrial plants, but similar and dominated by mid‐chain waxes among submerged/floating aquatic plants. Sedimentary wax distributions are similar to those in submerged/floating aquatic plants and to Salix spp., which are among the most abundant terrestrial plants in the QPT catchment. Mid‐chain n‐ alkanoic acid δ 2 H values are similar in sediments and submerged/floating aquatic plants, but 50‰ lower than Salix spp. In contrast, sedimentary long‐chain n ‐alkanoic acid δ 2 H values fall between those for submerged/floating aquatic plants and Salix spp. We therefore infer that mid‐chain waxes in QPT are primarily from aquatic plants, whereas long‐chain waxes are from a mix of terrestrial and aquatic plants. In Arctic lakes like QPT, terrestrial wax transport via leaf litter and surface flow is limited by low‐lying topography and sparse vegetation. If these lakes also have abundant aquatic plants growing near the sediment‐water interface, the aquatic plants can contribute large portions of sedimentary waxes. Plain Language Summary: Plant leaves produce straight‐chain hydrocarbon compounds called leaf waxes that are affected by changes in climate. Leaf waxes are abraded off of leaves and deposited in lake sediments, creating a natural archive of climate change. However, it can be difficult to distinguish leaf waxes created by aquatic versus terrestrial plants, as they are mixed together during transport and deposition. Leaf waxes produced by aquatic and terrestrial plants reflect different environments, so identifying the source of sedimentary waxes is important for interpreting past climate. We test an outstanding hypothesis that mid‐ and long‐chain‐length waxes in Arctic lake sediments are derived from aquatic and terrestrial plants, respectively. We test this hypothesis by vegetation mapping and analyzing the leaf waxes in the most abundant aquatic and terrestrial plant taxa in an Arctic lake catchment, as well as the waxes preserved in soils, lake water filtrates, and lake sediments. We find that mid‐chain‐length waxes preserved in lake sediments likely reflect aquatic plant production, while long‐chain‐length waxes likely reflect a mix of aquatic and terrestrial plant production. The sedimentary wax sources in this lake are controlled by the landscape and climate of this particular catchment, which favor the transport and deposition of aquatic over terrestrial plant leaf waxes. Key Points: Vegetation maps and analysis of leaf wax chain length distributions and isotopes characterize modern plant wax sources to an Arctic lake Submerged aquatic plants are the primary source of mid‐chain waxes in a lake located on southeastern Baffin Island Submerged aquatic and terrestrial plants both contribute to long‐chain sedimentary waxes