Both lakes and oceans are important for the global carbon cycle and thus the regulation of climate processes. Due to climate change and human activities, aquatic systems are subject to increasing pressure with changes already observed at multiple levels affecting their functioning. It is therefore urgent to understand the dynamic of aquatic systems, if one wants to predict their response to changing conditions.

Schematic representation of the interactions between microorganisms, nutrients and carbon in aquatic systems

Phytoplankton, act as engineers, initiating the incorporation of terrestrial and atmospheric compounds into the food chain and driving their biogeochemical cycling. They not only respond rapidly to their environment, they also profoundly alter aquatic chemistry, affecting the reactivity, recycling, remineralisation and therefore fate of many elements. As such, phytoplankton affect the dynamics of aquatic systems with effects at both local and global scales. Phytoplankton can thus be used as sentinel to assess the dynamics and changes in aquatic systems.

One of the most prominent reported controls of phytoplankton biomass, biodiversity and productivity is nutrient limitation, reported in most of the ocean and numerous lakes. Iron (Fe), nitrogen (N) and phosphorous (P) are the main limiting nutrients in aquatic systems. Nutrient limitation affects the functioning of aquatic systems and their contribution to the global carbon cycle. Despite numerous studies, the parameters controlling nutrient limitation and their accessibility to phytoplankton remain largely unknown.

In the marine and lake biogeochemistry group we aim to better understand the impact that nutrient distribution and chemistry has on phytoplankton biomass, biodiversity and productivity. Our research also characterises the feedback interactions that microorganisms exert (microbial loop) on the biogeochemical cycle of these nutrients, with associated impact on their potential limitation to phytoplankton and carbon cycle. For this purpose we use a multidisciplinary approach using parameters ranging from subcellular processes, chemical speciation to ecosystem-wide response.