Glacier and ice sheet host diverse communities of microorganisms who thrive on the ice surface despite numerous stresses including freeze-thaw cycles, high UV irradiance, resource limitation and freezing temperatures. Some microbes become 'dormant' to cope with stress - persisting in a reversible state of low metabolic activity. But despite dormancy being common in nature, its prevalence is largely unknown on glaciers. In 2019 we went to Greenland & Iceland to study melting glacier surfaces, their microbes, and measured dormancy responses. We used BONCAT incubations, amplicon and metatranscriptomic sequencing, and ecological modelling to investigate active and dormant microbes and state-switching responses. We found that glacier surface microbial communities are comprised of both active and inactive organisms, which are capable of state-switching on timescales similar to the freeze–thaw cycles experienced on glacier surfaces. The fast state-switching responses may be particularly important considering future climate change - since short but extreme warming events (e.g. during winter) might trigger reactivation of dormant microbes & alter the structure, functioning and carbon cycling of these systems.

Read the paper here:
Bradley J, Trivedi C, Winkel M, Mourot R, Lutz S, Larose C, Keuschnig C, Doting E, Halbach L, Zervas A, Anesio A, Benning L. (2023) Active and dormant microorganisms on glacier surfaces. Geobiology. doi: 10.1111/gbi.12535

How much of Earth's organic carbon is buried in ocean sediments? And how much stays 'buried'?

Quantifying the organic carbon sink in marine sediments is crucial for assessing how the marine carbon cycle regulates Earth’s climate. We argue that Burial efficiency (BE) – the commonly-used metric reporting the percentage of organic carbon that becomes 'buried', is loosely defined, misleading, and inconsistent. We use a global diagenetic model to highlight vastly different BE’s depending on sediment depth or age horizons used to calculate BE. Instead, we propose using transfer efficiencies (Teff’s) for quantifying sediment OC burial. This metric requires precise specification of spatial or temporal references, and emphasizes that OC degradation continues beyond these horizons. Ultimately, quantifying OC burial with precise sediment-depth and sediment-age-resolved metrics will enable a more consistent and transferable assessment of OC fluxes through the Earth system.

The open access paper is available here:

Bradley J° Hülse D°, LaRowe D, Arndt S (2022) Transfer Efficiency of Organic Carbon in Marine Sediments. Nature Communications. doi:10.1038/s41467-022-35112-9 (°co-first authors)

James is co-author on a new study led by Laura Halbach (Aarhus University) investigating pigment signatures of algal communities and their implications for glacier surface darkening.

Halbach L, Chevrollier L, Doting E, Cook J, Jensen M, Benning L, Bradley J, Hansen M, Lund-Hansen L, Markager S, Sorrell B, Tranter M, Trivedi T, Winkel M, Anesio A. (2022) Pigment signatures of algal communities and their implications for glacier surface darkening. Scientific Reports. doi: 10.1038/s41598-022-22271-4

James and Margaret are in Svalbard, together with Carlo Cardellini (University of Perugia, Italy) and Francesco Montemagno (University of Naples Frederico II, Italy), to study the impact of permafrost thaw on ecosystem functioning and biogeochemical fluxes. We are focussing on seven sites spanning Bayelva river to Midtre Lovénbreen glacier forefield, near the settlement of Ny-Ålesund. The project is in collaboration with Donato Giovannelli (University of Naples Frederico II, Italy) and funded by the Natural Environment Research Council's Arctic Access Scheme.

James is co-author on a paper 'The biogeography of relative abundance of soil fungi versus bacteria in surface topsoil' published in Earth System Science Data investigating the fungal to bacterial ratio in terrestrial settings globally. 

Yu K, Hoogen J, Wang Z, Averill C, Routh D, Smith G, Drenovsky R, Scow K, Mo F, Waldrop M, Yang Y, Vries F, Bardgett R, Manning P, Bastida F, Baer S, Bach E, García C, Wang Q, Ma L, Chen B, Ye J, Teurlincx S, Heijboer A, Bradley J, Crowther T. (2022) The biogeography of relative abundance of soil fungi versus bacteria in surface topsoil. Earth System Science Data. doi: 10.5194/essd-14-4339-2022

We are looking for a PhD student to join the group! This is a fully-funded 3-year position based in the Bradley lab in London, UK.

The role of the atmosphere in shaping and sustaining microbial communities on glaciers

The atmosphere forms a bridge between Earth’s major biomes, linking terrestrial, aquatic, and glacial systems. The continual exchange, transport and dispersal of microorganisms between the atmosphere and it’s adjacent habitats shapes these environments via processes that are not yet fully understood. The cryosphere shares many of the same characteristics as the atmosphere, for example: low substrate availability, freezing temperatures, and high UV radiation. This PhD project will examine the ecological links between the atmosphere and the cryosphere – in particular, glacier surfaces in polar regions. Using state-of-the-art genomic and biogeochemical techniques, the student will investigate the role of the atmosphere in shaping microbial communities in snow and ice habitats, as well as in sustaining them by providing sources of energy. There will be opportunities for fieldwork in Svalbard and/or other polar environments to collect atmospheric samples, as well as samples of snow and glacier ice for analyses. The student will collaborate across multi-disciplinary teams in London (Queen Mary University of London and the Natural History Museum) and internationally (Australia, Canada, and the USA), and be embedded into a wider project that investigates the atmosphere as a microbial ecosystem. This PhD project would suit a student with interests in environmental microbiology, biogeochemistry and polar environments.

Main supervisor:
James A. Bradley

Co-supervisors:
Anne Jungblut, Natural History Museum, UK
Chris Greening, Monash University, Australia
Jackie Goordial, University of Guelph, Canada
Elizabeth Trembath-Reichert, Arizona State University, USA

Location:
Queen Mary University of London, and The Natural History Museum, London, UK.

Application Deadline:
3rd October 2022

Start-date:
January 2023 or as soon as possible thereafter. 

How to apply:
To apply, please click here: https://mysis.qmul.ac.uk/urd/sits.urd/run/siw_ipp_lgn.login?process=siw_ipp_app&code1=RFQM-L8ZM-01&code2=0014

Your application must include a Personal Statement (2 pages max), Research Proposal (1 page max), Curriculum Vitae (2 pages max), and the names and contact details of up to three academic references. In your personal statement, please identify your research interests, outline relevant skills, training, experience and qualifications, and explain why you are interested in this programme and how it fits your career development plans. In your research proposal, please briefly outline how your research will address one or more of the themes described in the project summary above.

Please also email James (james.bradley@qmul.ac.uk) prior to the deadline to confirm your intention to apply.

James is in Greenland with Donato Giovannelli and Matteo Selci (University of Naples Federico II) for their INTERACT-funded project GHOST: Greenland Homeothermic Springs.

Below is an overview of the trip written by Matteo.

Today we took a day off so I thought it would be a good idea to share with you what we are doing here in Greenland. We are at the Arctic Station in the south of Disko Island.

Our main purpose here is find and sample as many geothermal springs as possible.
​
But why Disko Island and why geothermal springs? ​

“The Arctic is a beautiful but unforgiving environment. Climate change is an ever-felt presence here at the top of the world, and whilst the Arctic is the first to feel its impacts, the rest of the world waits perilously in the firing line.”

James wrote a piece for Arc’teryx describing some of the science and personal sentiments of his work in the Arctic – with a focus on thawing permafrost. Thanks Arc’teryx for your backing, and for the feature!

Click here to read the piece!

James is lead-author on a new paper in Frontiers in Microbiology on the characteristics of global marine sediments as a microbial habitat. Following our 2020 Science Advances study, we use global models to assess how variations in marine sediment physicochemical properties impact microorganisms, organic carbon,  bioenergetics and cell power availability on a global scale.

Bradley J, Arndt S, Amend J, Burwicz-Galerne E, LaRowe D (2022) Sources and fluxes of organic carbon and energy to microorganisms in global marine sediments. Frontiers in Microbiology. 13:910694. doi: 10.3389/fmicb.2022.910694

James is in Svalbard with Ian Stevens and Eva Doting (Aarhus University) to study the sources, sinks and viability of microbes on the surface of High-Arctic glaciers. The project is funded by ​INTERACT (EU Horizon-2020).