High-resolution genomics to reveal changes in microbial biodiversity across space and time in the warming Arctic Ocean

Moreover, as the environmental change in the Arctic is accelerating, it has become the main focus of geopolitical interests because the Arctic is not only regulating global climate but is used for extracting biological and geological resources. Thus, the Arctic provides significant ecosystem services on biodiversity that is largely unknown, particularly for the most inaccessible geographic areas such as the central Arctic Ocean. Understanding how the largest of all aquatic ecosystems in the Arctic changes is therefore crucial for different key disciplines of the 21st century including climate research, conservation, and sustainable economic development. Aquatic microbes in sea ice and seawater play pivotal roles in climate feedbacks and in sustaining food webs (marine primary production), which are central for conservation and ecosystem services. Microbes also serve as biological indicators due to their fast adaptive response following environmental change. Although genomic approaches have provided transformative insights into responses of microbial communities to environmental change, their application is limited in polar ecosystems and especially the central Arctic Ocean mainly due to issues of access and the extreme nature of this ecosystem. To overcome these challenges, a Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) has been conducted in 2020. MOSAiC is the largest polar expedition in history including over 20 countries with more than 400 researchers, studying a drifting surface habitat while it crosses the central Arctic Ocean via the transpolar drift current. Hence, the ice-breaker RV ‘Polarstern’ spent a year drifting across the central Arctic Ocean and locked up into the sea ice. This expedition, therefore, enabled for the first time to sample the same surface-ocean habitat (mainly sea ice and co-drifting water directly underneath) while it was carried across the Arctic Ocean by the transpolar drift current. Thus, the MOSAiC drift expedition has created a time series of samples reflecting the seasonal cycle of environmental changes in a drifting surface ocean habitat (e.g. a sea-ice floe from its formation to thaw), which is unprecedented but will help to reveal how the environmental change in the Arctic Ocean impacts the Arctic climate system. This new NERC project is not only built on the unique time-series data and samples, it capitalizes on a subsequent microbial genomics project funded by the DOE Joint Genome Institute (JGI, USA). The latter is providing sequence data including their basic analyses (e.g. assembly, annotations) of microbial metagenomes and metatranscriptomes for over 400 time-series samples from the drifting sea-ice floe. Bespoke bioinformatics and community ecology analyses will be applied to those sequence data for revealing how habitat-specific genomic diversity of ocean microbes and their microbiomes is changing throughout time (complete seasonal cycle) and in relation to changing habitat characteristics (e.g. formation of sea ice in autumn and thaw in spring and summer). Thus, this project will provide a baseline for assessing how microbes as a biological bellwether respond to the changing Arctic Ocean, which is essential for making predictions about how warming in the Arctic impacts ecosystem services underpinned by microbes such as sustaining the marine food web and driving the carbon cycle in the Arctic Ocean.