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Unlocking the methane cycling archives from Arctic lakes: a biological fingerprint

Periodic Reporting for period 1 - ArCH4ives (Unlocking the methane cycling archives from Arctic lakes: a biological fingerprint)

Reporting period: 2016-03-01 to 2018-02-28

Arctic landmasses and lakes release significant amounts of methane (CH4), a greenhouse gas with an atmospheric warming potential 25 times higher than CO2 that contributes heavily to global climate change. Yet the effect of rapid warming in the Arctic on the fate of natural CH4 emissions from lakes is poorly understood. The recent advance of high-throughput sequencing to analyse ancient environmental DNA, or paleogenomics, from Arctic lake sediment has tremendously heightened analytical sensitivity and thus unlocked a wealth of new information on past ecosystems and their processes, especially on decadal to millennial timescales.

ArCH4ives combines an innovative metagenomic approach on ancient environmental DNA from Holocene lake sediment cores to determine the impact of long-term climate change on microbial CH4 cycling in Arctic lakes.

While providing the Fellow with new expertise in cutting-edge paleogenomics and microbial ecology in world-leading research facilities at the Centre for GeoGenetics, Copenhagen University, ArCH4ives set out to advance paleoecology, gain significant new insights into the global carbon cycle and improve our understanding of the sensitivity of polar ecosystems.
ArCH4ives built and expanded on a unique set of Holocene lake sediment cores spreading along major environmental gradients in Arctic landscapes, a design which aimed to control for the different catchment-specific processes that may have influenced microbial communities in the past, and isolate the influence of climate on their ecology. This interdisciplinary approach was supported by the analysis of complementary paleoecological proxies for other important components of the carbon cycle in Arctic watersheds via collaborations with international partners.

At all selected sites, including newly acquired sequences from the Godthåbsfjord region, Southwest Greenland, we used an optimised 'shotgun' sequencing approach to acquire the microbial community profiles. So far, this strategy yielded ecologically relevant information on the diversity and function of major groups of both CH4 producers (Archaea) and consumers (Bacteria: methanotrophs Type I and Type II), but also on other groups of microbes (Cyanobacteria) and higher organisms including zooplankters (Copepods, Ostracods and Cladocerans), plants (aquatic and terrestrial) and fish (Atlantic salmon, Three-spined stickleback). Changes in the community structure of CH4-microbes effectively reflected major environmental changes that occurred at the sites over the Holocene, however additional analyses are required to determine the impact of climate change alone on these changes.

These results were presented at two well-attended international conferences in the field (IAL-IAH and ArcticNet ASM2018).
ArCH4ives led to (1) scientific innovation by ancient metagenomics being successfully applied on multiple sites across the Arctic and over extended timescales to determine the effects of long-term climate change on an important yet understudied greenhouse-related biogeochemical process, (2) advanced training in the emerging field of paleogenomics and (3) significant career advancement for the Fellow to continue developing the field of paleogenomics to solve long-standing ecological questions and address global environmental problems such as climate change.
ArCH4ives paleogenomic workflow