Research projects

Ecological interactions between phytoplankton and bacteria arguably represent the most crucial and complex inter-organism association in marine environments. For decades, researchers have investigated the association between bacteria and phytoplankton through the assimilation and remineralization of phytoplankton-derived organic matter into inorganic nutrients by heterotrophic bacteria. Notwithstanding, there are a variety of phytoplankton-bacteria interactions, spanning from beneficial (mutualism and commensalism) to negative (parasitism, predation or competition) relationships. Many of these interactions are mediated by the production and exchange of volatile organic components (VOCs). VOCs are a diverse bioactive molecules of low molecular weight and high vapor pressures. These VOCs are also very important in atmospheric chemistry as are main biogenic precursors of ozone, which is a greenhouse gas and a toxic air pollutant. Even though, the interactions between phytoplankton-bacteria and VOCs strongly influence in biochemical cycles, regulate the productivity of aquatic food webs, and affect ocean-atmosphere fluxes of climatically relevant chemical. There is still a lack of information about the role of phytoplankton and bacteria interactions in the production and composition of VOCs in marine environments.

Biogenic Volatile Organic Compounds (bVOCs) are reactive compounds produced by a wide range of organisms. They are used for various purposes such as interspecies communication and resistance to abiotic stressors. In addition, bVOCs influence the atmospheric chemistry, the climate, and play a part in the carbon cycle. BVOC dynamics in freshwater ecosystems are understudied, and little is known about the totality of compounds emitted (volatilome) from freshwater lakes as well as the organisms that produce and consume bVOCs in these ecosystems. This PhD project aims to advance the understanding of freshwater lake volatilomes, gaining insight into the active consumer and producers by focusing on the bacterio- and phytoplankton communities. Furthermore, this project will investigate the impact of environmental factors on the bVOC emissions, to improve the prediction of future freshwater bVOC dynamics and emissions in a changing climate.

Recent studies highlight the vital roles of VOCs in atmospheric processes, including the formation of tropospheric ozone and secondary organic aerosols, as well as their influence on greenhouse gas lifetimes and ecological interactions. Although extensively researched in terrestrial environments, our understanding of VOCs in aquatic ecosystems remains limited. This project focuses particularly on the exchange of these organic compounds between the sea and the atmosphere. Previous oceanic flux measurements have primarily concentrated on selected sulfur compounds (mainly DMS), oxygenated VOCs, and isoprene. These studies have been restricted to a few compounds, often lacking comprehensive temporal coverage, leaving many VOCs unexplored. By utilizing high-frequency VOC measurements, specifically PTR-TOF-MS, this study aims to conduct direct flux measurements at a coastal site to investigate the temporal variability of exchanges across a range of VOCs and their relationship to changes in environmental forces and ecological variations.

Terrestrial vegetation and soil take up and emits different organic molecules called volatile organic compounds (VOCs), which in case of the latter, contributes to the production of aerosol particles, which affect cloud formation and climate. Due to global change, it is expected that the global temperature will significantly increase, and droughts will become more prevalent and severe, in certain regions. These altered environmental conditions not only changes the VOC emissions and consumption. It has previously been shown that warming, as well as drought, affect the plant and soil microbiota composition. It has been shown that drought influence microbial soil biomass and relative abundance, depending on the soil type, due to resource limitations. The correlation between soil and plant associated microbial communities and VOC emission and consumption, during global change, has yet to be investigated further. 

This project aims to investigate the effects of global change events on the relationship between soil VOC emissions and consumption, and plant and soil associated microbiota.

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Since primary production in the Arctic Ocean (AO) is limited by nitrogen (N) availability, knowledge about sources and sinks of N is of critical importance. Surprisingly, a few recent studies have presented sporadic data suggesting N2 fixation in the AO. This import of bioavailable N could be of fundamental importance for N and carbon biogeochemistry in the AO, but data are scarce. This cross-disciplinary and international project aims to quantify pelagic N₂ fixation in the AO – a biological process hitherto unaccounted for. In situ measurements, experiments, and use of cutting-edge methodology will provide unprecedented data on fixation rates, identity of the active organisms, and insights into controlling factors in a cross-Arctic Ocean survey. This information is essential for prediction of primary production in the future AO, particularly in the face of climate change.

Plant productivity in pristine ecosystems like boreal and tropical cloud forests is limited by soil nutrients, primarily nitrogen (N). Mosses are major contributors to ecosystem productivity in these habitats, and most of them are colonized by N₂-fixing cyanobacteria, thereby providing N to the ecosystem. Despite this key role, critical knowledge gaps exist. In particular, the climatic controls of moss-associated N₂ fixation remain unclear, limiting our ability to quantify and project climate change effects on this fundamental ecosystem function. Further, it is unknown whether mosses and associated cyanobacteria share a mutualistic (both partners benefit) or parasitic (one partner benefits at the expense of the other) relationship. Yet, the balance of this association is crucial for maintaining ecosystem productivity. In SYMBIONIX, we will combine field, laboratory and modelling approaches to fill these knowledge gaps by addressing 4 objectives. We will (1) identify the climatic controls of N₂ fixation in mosses from contrasting ecosystems: boreal forests and tropical cloud forests, (2) ascertain the degree of mutualism or parasitism between moss and cyanobacteria using transcriptomics, (3) determine nutrient exchange rates between moss and cyanobacteria using nanoSIMS. The ultimate goal is (4) to model ecosystem N input via N₂ fixation in boreal and tropical ecosystems.

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Our atmosphere is constantly influenced by volatile organic compounds (VOCs). Emitted by biological organisms and various anthropogenic activities, these gases can lead to ozone creation or depletion. But in the Arctic, the driver of the emission and absorption of many common VOCs is still unknown. The EU-funded ELATE project seeks to shed light on these sources and sinks and use modelling to quantify how increased atmospheric CO2 and biological factors impact them. Understanding the changes in common VOCs, like light alkenes, could help researchers better interpret their impact on the climate and raise public awareness of EU’s climate neutrality goals.

IndiVOCtual investigates the sources (genetics, dendroecology, insect herbivory stress) of within-species variation and their influence on volatile emissions from widespread mountain birch forests in the Subarctic. Currently, these factors are unaccounted for in the models, and are necessary to improve our ability to predict volatile emissions from high-latitude ecosystems.