Sedimentary DNA identifies modern and past macrophyte diversity and its environmental drivers in high‐latitude and high‐elevation lakes in Siberia and China

Abstract

Arctic and alpine aquatic ecosystems are changing rapidly under recent global warming, threatening water resources by diminishing trophic status and changing biotic composition. Macrophytes play a key role in the ecology of freshwaters and we need to improve our understanding of long‐term macrophytes diversity and environmental change so far limited by the sporadic presence of macrofossils in sediments. In our study, we applied metabarcoding using the trnL P6 loop marker to retrieve macrophyte richness and composition from 179 surface‐sediment samples from arctic Siberian and alpine Chinese lakes and three representative lake cores. The surface‐sediment dataset suggests that macrophyte richness and composition are mostly affected by temperature and conductivity, with highest richness when mean July temperatures are higher than 12°C and conductivity ranges between 40 and 400 μS cm−1. Compositional turnover during the Late Pleistocene/Holocene is minor in Siberian cores and characterized by a less rich, but stable emergent macrophyte community. Richness decreases during the Last Glacial Maximum and rises during wetter and warmer climate in the Late‐glacial and Mid‐Holocene. In contrast, we detect a pronounced change from emergent to submerged taxa at 14 ka in the Tibetan alpine core, which can be explained by increasing temperature and conductivity due to glacial runoff and evaporation. Our study provides evidence for the suitability of the trnL marker to recover modern and past macrophyte diversity and its applicability for the response of macrophyte diversity to lake‐hydrochemical and climate variability predicting contrasting macrophyte changes in arctic and alpine lakes under intensified warming and human impact.

Environmental DNA of aquatic macrophytes: the potential for reconstructing past and present vegetation and environments

“…Moreover, Alsos et al (2018) demonstrated that lake sediment eDNA from recent samples largely matches the extant vegetation with 88% of dominant and common taxa and 60% of rare taxa detected, and additionally records taxa missing in the survey that are likely true positives such as plants growing in deep water. Detection is also highly related to environmental conditions, especially temperature and water conductivity (Stoof-Leichsenring et al, 2022). Macrophyte communities constitute a good indicator of environmental conditions, especially in regions with high aquatic plant diversity which allows sensitivity to the spatial heterogeneity of the ecosystem, and can distinguish land use in river sections (Ji et al, 2021).…”

“…In sum, macrophyte-based P6 loop metabarcoding supports reconstructions for a wide array of important freshwater metrics. From sed aDNA-derived macrophyte turnover and community composition, we can infer lake level changes (Heinecke et al, 2017) and conductivity and temperature changes (Stoof-Leichsenring et al, 2022) on millennial time scales. Our study extends environmental reconstructions for northern Fennoscandian lakes over the last twelve thousand years to thermal range, continentality, nutrient availability, light conditions, and water pH.…”

“…This suggests that even their early occurrences can be used confidently for environmental reconstruction. Indeed, the temporal compositional and richness changes could be observed across Siberia and Tibet for the Pleistocene and Holocene (Stoof-Leichsenring et al, 2022). Combining the modern dataset with the core metabarcoding data would allow to use the macrophyte community signal for the reconstruction of past environments, such as conductivity and temperature.…”

“…SedaDNA has been shown to enhance such reconstructions, as it can provide higher consistency in detection of species than plant macrofossils (Alsos et al, 2016) and higher taxonomic resolution than pollen (Clarke et al, 2020;Courtin et al, 2021;Niemeyer et al, 2017), and can also be used as the sole proxy for the reconstruction of past terrestrial environments (Alsos et al, 2022). Therefore, it holds great potential for studies of past and present aquatic ecosystems (Stoof-Leichsenring et al, 2022), which would in turn expand the applicability of sedaDNA for abiotic reconstructions.…”

Sedimentary ancient DNA reveals past ecosystem and biodiversity changes on the Tibetan Plateau: Overview and prospects

“…A pronounced change from emergent to submerged taxa combined with an increase in macrophyte richness in Lake Naleng is found at 14 ka BP. Based on the modern results described above, this important turnover could be explained by an increase in temperature and water conductivity due to glacial runoff and high evaporation during the deglaciation (Stoof-Leichsenring et al, 2022).…”