Influence of energy sources on biofilm phosphorus entrapment pathways in fluvial ecosystems

• Applicant: Dr. Nuria Perujo
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 514547471

In aquatic ecosystems, nutrient cycling is a crucial ecosystem function. Both, nitrogen (N), and phosphorus (P) are essential nutrients for aquatic biota but in excess, nitrogen and phosphorus cause eutrophication. Eutrophication represents a global ecosystem impairment, whereby excess of nutrients modify the structure and function of freshwater ecosystems. Main impacts of eutrophication are an excessive increase of algal biomass and productivity; impairment of water physicochemical quality (i.e. increase in colour, odour and turbidity); anoxic waters, fish death and water use restriction for recreational purposes. Eutrophication has been recognized as a significant environmental concern across Europe since the late 1980s and continues to be a challenge nowadays. For a healthy ecosystem, phosphorus levels in water should be controlled. Phosphorus is not completely removed from the aquatic ecosystem but it is immobilized from one compartment (i.e., water) to another (i.e., riverbed substrates and/or biota). In this P immobilization, microbial biofilms play a key role by entrapping dissolved phosphorus from water. This entrapment can occur in two different pools (i.e. intracellularly or extracellularly). However, the knowledge behind the biological mechanisms of biofilm P entrapment in aquatic ecosystems is still limited. Furthermore, the ability of biofilm to entrap P may depend on their metabolic profiles. More specifically, C-related metabolism determine the ability of biofilms to mineralize and use organic compounds for growth and P-related metabolism is linked to their ability to uptake different sources of P. For this reason, I expect that the ability of aquatic ecosystems to entrap P from aquatic ecosystems will depend on the structure and activity of biofilms. The main objective of this project is to understand how energy sources in river ecosystems modulate within-biofilm P entrapment pathways. And specifically (i) to disentangle how the combination of autotrophic and heterotrophic energy sources (i.e., light and DOM) determine the dominance of intracellular P and extracellular P entrapment in biofilms, (ii) to test the effect of autotrophic and heterotrophic energy sources on C and P metabolism in biofilms and their link to P entrapment pools, and (iii) to link patterns of intracellular P and extracellular P entrapment pathways in biofilms and metabolic profiles with longitudinal gradients of light and dissolved OM quality in river ecosystems.

• DFG Programme: Research Grants