Seafloor Biogeochemistry
Short description
Our research group studies biogeochemical processes in marine surficial sediments.The main objective is to increase our knowledge of sediments’ roles in ocean biogeochemical cycles – how these processes lead to or influence fluxes of solutes such as nutrients, inorganic carbon, metals, methane, nitrogen gas, nitrous oxide, etc., across the sediment-water interface.
Recently, our focus has been on the quantification of climate forcing trace gases such as methane and nitrous oxide. We measure and quantify these fluxes both ex situ with state-of-the-art core incubation and in situ using autonomous benthic landers. We also carry out complex incubation experiments with stable isotope tracers.
We have studied most of Earth’s oceans, including the deep sea, but our focus is on the North Sea, the Baltic Sea, and the North Atlantic fjords.
Research themes
1) Overlooked biogeochemical processes
Our team is interested in understanding how seafloor biogeochemistry is affected by eutrophication, climate change, and pollution by emerging contaminants.
Specifically, we quantify rates of microbial nitrogen cycling processes, including denitrification, nitrification, DNRA, and anammox, as well as long-term nitrogen burial and dissolved nitrogen fluxes.
We quantify processes and components of the oxygen, carbon, phosphorus, and silica cycles. We combine laboratory experiments and in situ benthic lander deployments, focusing on seafloor areas with strong gradients (e.g., oxygen fluctuations).
2) Coastal oceanic greenhouse gas exchanges
Our research focuses on the distribution and the dynamics of greenhouse gases beyond CO₂, including methane and nitrous oxide, in the coastal ocean.
For example, we investigate whether nitrous oxide is produced during seafloor deoxygenation cycles, and whether methane emissions can partly offset CO₂ uptake in coastal ecosystems.
Ongoing projects focus on fjords and aquaculture-impacted coastal settings.
3) Role of infauna in shaping biogeochemical cycles
Our work investigates how sediment infauna (i.e., macro- and meiofauna) regulate sediment biogeochemical processes such as organic matter mineralization, denitrification, and so on.
For example, we showed that nematodes can enhance oxygenation and increase nitrogen loss, helping limit eutrophication.
We are interested in quantifying meiofauna's ability to function in extreme environments, such as in oxygen-depleted, euxinic conditions.
4) Environmental impacts of sediment disturbance, remediation, and geoengineering
We study how human activities (such as geoengineering, seafloor trawling, and sediment remediation) affect benthic biogeochemical processes and ecosystem functioning.
We are interested in testing potential solutions to remediate polluted sediments, such as sediment capping with activated carbon.
These approaches may potentially reduce contamination in the long-term, but may come with unwanted alterations of sediment chemistry and ecology.
Publications
For lists of publications, please visit the individual researcher’s personal webpage.
Per Hall, Professor Emeritus
Stefano Bonaglia, Senior Lecturer
