Aquatic macrophyte dynamics in Lake Karakul (Eastern Pamir) over the last 29 cal ka revealed by sedimentary ancient DNA and geochemical analyses of macrofossil remains
Due to methodological challenges there are only a few studies that focus on macrophyte dynamics in large lakes despite their notable role in a lake’s ecosystem functioning. This study investigates composition and productivity changes of the submerged vegetation of Lake Karakul, Pamir Mountains (Tajikistan), using sedimentary ancient DNA metabarcoding and elemental (C/N) and isotopic (δ13C, δ15N) measurements of Stuckenia cf. pamirica (Baagøe) Z. Kaplan (Potamogetonaceae) leaf remains. No Stuckenia cf. pamirica leaf remains were found for 28.7–26.1 cal ka BP, when both Potamogetonaceae and Chara (L.) DNA sequences were recorded, suggesting sparse submerged vegetation at the coring site. This agrees with the inference of a deep lake reached using geochemical proxies. From 26.1 to 17.5 cal ka BP a few macrophyte remains and high numbers of Potamogetonaceae sequences were recovered: lake level was probably low, as suggested by other studies on the lake. Another phase of increased numbers of Chara sequences and the absence of Stuckenia cf. pamirica leaf remains was found between 17.5 and 12.2 cal ka BP, which coincides with a lake-level transgression at Lake Karakul as indicated by paleo-shoreline investigations. Analyses of macrophyte remains reveal intermediate paleo-productivity from 6.9 cal ka BP and high paleo-productivity from 2.2 cal ka BP onwards. From comparisons with other studies, we suggest that lake-level changes are the main driver for the submerged vegetation composition and productivity at the coring site in Lake Karakul and underline our conclusions by depicting the present-day distribution of Stuckenia cf. pamirica and Chara within the lake.
KeywordsPotamogeton/Stuckenia Arid central Asia Paleo-productivity Submerged vegetation composition Metabarcoding Chara/Characeae
We thank Ilhomjon Rajabov for logistical support in Tajikistan during the 2008 and 2012 expeditions and Thomas J. Whitmore and two anonymous reviews for their comments, which helped to improve this manuscript. We appreciate the financial support of the DFG (PhD scholarship for LH in the DFG Graduate School 1364, grants Mi 730/15-1 and 15-2 to SM, as well as grant EP 98/2-1 to LSE).
The paleo-genetic dataset, macrophyte measurement results and the raw data of the Ilumina HiSeq sequencing run are available at Pangaea (https://doi.pangaea.de/10.1594/PANGAEA.877361).
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