title: Biogeochemical patterns in a river network along a land use gradient.
abstract: The Bode catchment (Germany) shows strong land use gradients from forested parts of the National Park (23% of total land cover) to agricultural (70%) and urbanised areas (7%). It is part of the Terrestrial Environmental Observatories of the German Helmholtz association. We performed a biogeochemical analysis of the entire river network. Surface water was sampled at 21 headwaters and at ten downstream sites, before (in early spring) and during the growing season (in late summer). Many parameters showed lower concentrations in headwaters than in downstream reaches, among them nutrients (ammonium, nitrate and phosphorus), dissolved copper and seston dry mass. Nitrate and phosphorus concentrations were positively related to the proportion of agricultural area within the catchment. Punctual anthropogenic loads affected some parameters such as chloride and arsenic. Chlorophyll a concentration and total phosphorus in surface waters were positively related. The concentration of dissolved organic carbon (DOC) was higher in summer than in spring, whereas the molecular size of DOC was lower in summer. The specific UV absorption at 254 nm, indicating the content of humic substances, was higher in headwaters than in downstream reaches and was positively related to the proportion of forest within the catchment. CO₂ oversaturation of the water was higher downstream compared with headwaters and was higher in summer than in spring. It was correlated negatively with oxygen saturation and positively with DOC concentration but negatively with DOC quality (molecular size and humic content). A principle component analysis clearly separated the effects of site (44%) and season (15%), demonstrating the strong effect of land use on biogeochemical parameters.
authors.affiliation: Department of River Ecology, Helmholtz-Centre for Environmental Research UFZ, Brückstraße 3a, 39114, Magdeburg, Germany, norbert.kamjunke@ufz.de.
authors.forename: Norbert
authors.initials: N
authors.lastname: Kamjunke
authors.forename: Olaf
authors.initials: O
authors.lastname: Büttner
authors.forename: Christoph G
authors.initials: CG
authors.lastname: Jäger
authors.forename: Hanna
authors.initials: H
authors.lastname: Marcus
authors.forename: Wolf
authors.initials: W
authors.lastname: von Tümpling
authors.forename: Susanne
authors.initials: S
authors.lastname: Halbedel
authors.forename: Helge
authors.initials: H
authors.lastname: Norf
authors.forename: Mario
authors.initials: M
authors.lastname: Brauns
authors.forename: Martina
authors.initials: M
authors.lastname: Baborowski
authors.forename: Romy
authors.initials: R
authors.lastname: Wild
authors.forename: Dietrich
authors.initials: D
authors.lastname: Borchardt
authors.forename: Markus
authors.initials: M
authors.lastname: Weitere
mesh_terms: D000383:Agriculture; D002244:Carbon / Q000032:analysis; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D004784:Environmental Monitoring; D005858:Germany; D006812:Humic Substances / Q000032:analysis; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D009566:Nitrates; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen; D000077194:Chlorophyll A