Characterization of biogeochemical self-purification processes in the Vjosa River network focusing on different spatial and temporal scales

The Vjosa River and its tributaries represent a large and dynamic river network characterized by a near natural flow regime and largely undisturbed hydromorphological dynamics. Due to the high connectivity (e.g. the lack of dams and regulation in the main river stem), the Vjosa River is a hotspot of natural biodiversity and may serve as an ecological reference system.

The self-purification potential of an ecosystem describes the resistance and resilience to contamination (disturbances). In rivers, the contaminants are attenuated and degraded not only in the visible river channels, but most importantly in the hyporheic zone and the riparian corridor. The subsurface is a vital bioreactor, that hosts an immense river- and groundwater-borne biodiversity.

Here we target the key biogeochemical processes involved in the cycling of carbon and nutrients in a qualitative and quantitative manner. The spatio-temporal distribution and transformation of different carbon (e.g. DOC, DIC, CO₂, CH₄), nitrogen (e.g. NO₃^-, NO₂^-, NH₄⁺), and phosphorus (e.g. PO₄^3-, P_tot) species are studied in detail at different spatial scales. Extrapolation from flow-through sediment microcosms to natural river sections of various dimensions (mesoscale to macroscale) will allow a good estimation of material import, transformation, attenuation, and export. The role of the microbial community, in the water and attached to the sediments, will be analyzed via high throughout sequencing to determine its composition and functions.

The outcome of this study will help to better understand the functioning river ecosystems from the micro to the catchment scale as a basis for in-depth evaluation of future sustainable management options. The Vjosa River has been proclaimed a national park recently, and options for ecotourism are currently developed by its management authorities. In the light of global change, the Vjosa River network shall serve as a reference system for other rivers in Europe and a unique field laboratory for assessing biogeochemical processes in an intact environment.