Linking microbial genomics and greenhouse gas saturation in high Arctic freshwaters

Climate change is causing temperatures in the Arctic to rise faster than in any other region of the world. This rapid warming leads, among other effects, to the massive loss of ice masses, development of thermokarst features when permafrost thaws, intensification of the hydrological cycle, and increasing loads of nutrients and organic carbon to surface waters. Freshwaters are highly sensitive to these changes, which affect microbial community composition and diversity. Therefore, these ecosystems are good sentinels to study processes in primary ecological succession related to ecosystem processes such as productivity and greenhouse gas emissions.

We aim to contribute to a deeper understanding of the linkages between biogeochemistry, microbiology and hydrology in high Arctic freshwaters. To do so, we conducted several fieldwork campaigns in Arctic and sub-Arctic localities (Svalbard, Finnmark, Finse, Northwest Territories) to unravel microbial diversity and metabolism in such unique ecosystems.

Effects of permafrost thaw on the global nitrogen cycle: the role of thermokarst systems (NITROKARST)

Global changes are modifying the Arctic regions' climate, where temperatures have risen faster than anywhere else on Earth. These regions store vast amounts of soil organic matter (SOM) in permafrost soils that rapidly release nutrients and greenhouse gases when they thaw. The thawing yields thermokarst processes that occur abruptly, leading to ground surface collapse and to the development of ecosystems (ponds and lakes) where anaerobic environments enhance microbial activity. With Arctic warming, permafrost thawing and thermokarst processes will increase, releasing soluble nitrogen into the environment, thus enhancing microbial decomposition of SOM. 

Through the EU-funded NITROKARST project, we explored the underlying mechanisms of the nitrogen cycle in thermokarst systems from the Northwest Territories (Canada), examining how microbial pathways promote nitrogen transformation and how thawing controls the operation of these processes.

ARCTIC-BIODIVER – filling gaps in Arctic freshwater biodiversity knowledge

Arctic freshwater ecosystems are under increasing threat from stressors such as climate change, land-use changes, introduced species, increased UV-radiation and exploitation of natural resources. Climate change is predicted to cause direct and indirect effects to these ecosystems and the biodiversity they support, including the fish used by people inhabiting the Arctic.

Through the ARCTIC-BIODIVER project, we aim to facilitate development of biodiversity scenarios at national and circumpolar scales. These include freshwaters from remote locations within Norway, Sweden, Greenland, Canada and Alaska. Within each region, selection of data focused on maximizing spatial and temporal coverage to ensure that the data covered the variability in Arctic lakes and rivers. A primary focus is to develop strong links between climate change predictions, biodiversity scenarios, and the consequences for ecosystem services in Arctic freshwaters. I personally also contribute to circumpolar harmonization of microbial sampling methods and large-scale analysis of microbial biodiversity change.

Microbial gene pool driving nitrogen cycling in hypersaline lakes

Saline and hypersaline lakes are heavily impacted by human activities such as mining, drainage, and pollution. Primarily found in arid and semi-arid regions within endorheic basins, these lakes experience pollutant accumulation due to low precipitation and high evaporation rates characteristic of these areas. Contamination primarily results from agricultural wastewater and organic and inorganic waste from domestic and industrial sources. Excessive nutrient inputs, particularly nitrogen, lead to eutrophication of these ecosystems.

Despite the vital role of saline lakes in nitrogen cycling, little attention has been given to understanding their functionality. My goal is to clarify how salinity shapes the structure and function of microbiomes across saline lake gradients, primarily located in the Iberian Peninsula, testing the hypothesis that microbial community taxonomic and functional diversity shifts significantly with changes in salinity. Advances in sequencing technologies have greatly enhanced our ability to study microbial diversity, though these methods have rarely been applied to saline lake ecosystems. 

Microbial nitrogen processing in wildfire-affected Mediterranean catchments through multi-omics

Wildfires act as positive feedback mechanisms to global change by altering biogeochemical cycles, especially impacting nitrogen availability, which is crucial for ecosystem productivity. Fires remove or transform nitrogen through volatilization, conversion to pyrogenic organic matter, or ash formation, with runoff transporting available nutrients, including nitrogen, to freshwaters, and potentially leading to ecosystem risks like eutrophication. Post-fire conditions favor fire-adapted microbes, which can be transferred to streams, altering ecosystem functioning.

We investigate the microbial nitrogen cycle across wildfire-impacted catchments in Castilla-La Mancha (Central Spain), integrating field sampling, microcosm experiments, and multi-omic analyses to assess short- and long-term shifts in nitrogen cycling and microbiome composition. This research will deepen our understanding of wildfire-driven changes in aquatic microbial and functional diversity, as well as nitrogen cycle gene expression in such fragile environments.