Macronutrients (carbon (C), nitrogen (N), and phosphorous (P)) are substances that all organisms require to survive, grow and reproduce. While C, N, and P are naturally present in all aquatic ecosystems, human activities have significantly increased their concentrations and changed their dynamics in rivers. This lead to widespread degradation of water quality. Meaningfully reversing those consequences requires understanding how anthropogenic activities have changed macronutrient dynamics. This approach is still hindered by the availability of long-term data which covers periods of pollution and recovery. In this thesis, I investigated long-term changes by collecting, combining, and interpolating time series of many different ecological variables. Particularly, I developed a conceptual model that linked a 65-year long time series of in-stream N concentrations in the Elbe to changed anthropogenic N sources, which I, in turn, explained with a characteristic succession of human needs. To understand the sources and the sinks of N in rivers, I developed a mass balance model that quantifies how much N has been retained by organisms in the Elbe over the last 42 years. Using an inverse Bayesian model approach, I estimated the daily importance of bacterial and algal activity over 36 of these 42 years. Apart from N, macronutrient ratios (C:N:P) are a crucial determinant of the integrity of aquatic ecosystems. To comprehend the effects of anthropogenic activities on C:N:P ratios, I analyzed C, N, and P data from 574 German catchments spanning a large gradient of agricultural and urban activities. Over the last 65 years, I discovered multiple regime shifts in the N dynamics of the Elbe. Before ∼ 1970, the Elbe experienced constant N concentrations across the seasons. Afterwards, a distinct seasonal pattern emerged with high concentrations during winter and low concentrations during summer. After the collapse of the German Democratic Republic in 1989, water quality in the Elbe improved drastically as many pollutant sources ...


    Access

    Download


    Export, share and cite



    Title :

    Anthropogenic changes in seasonality and stoichiometry of the macronutrient regime in catchments of Central Europe



    Publication date :

    2023-06-12


    Type of media :

    Theses


    Type of material :

    Electronic Resource


    Language :

    English



    Classification :

    DDC:    550 / 551 / 627