Anaerobic metabolism of two hydro‐morphological similar pre‐dams under contrasting nutrient loading (Rappbode Reservoir System, Germany)

Abstract

Anaerobic microbial processes in reservoirs have a strong influence on water quality, and these processes are influenced by inputs from the catchment. Two morphologically similar pre‐dams of the large Rappbode reservoir system in Germany were studied for oxygen consumption, carbon dioxide production, nitrate reduction, manganese and iron reduction, sulfate reduction, and methanogenesis. Rates were obtained by calculations from hypolimnion size and hypolimnetic water chemistry and from incubation of sediment samples (manganese and iron reduction, sulfate reduction, and methanogenesis only). Length of anoxic conditions (anoxic factor) and anaerobic process rates were generally higher for Hassel pre‐dam, a water body with 58% grasslands and agriculture in its catchment. Rappbode pre‐dam had higher iron reduction rates. Oxygen consumption and sulfate reduction (and nitrate reduction for Hassel pre‐dam) were the most important respiratory processes. While hypolimnion chemistry was similar and showed mainly temporal differences in seasonal development, the pre‐dam sediments differed considerably with roughly twofold higher microbial biomass and 102–104 fold higher counts of sulfate‐reducing prokaryotes in Hassel pre‐dam compared to Rappbode pre‐dam. These differences can be explained by the higher nutrient input, longer water retention time, and consequently higher biomass production in Hassel pre‐dam. The view of microbial activities against known loads of solutes also implies that the quality of allochthonous organic matter and particulate fluxes likely governs respiratory processes in the pre‐dams by providing electron donors and acceptors.

Enhancement of sediment phosphorus release during a tunnel construction across an urban lake (Lake Donghu, China)

“…Besides, DO concentration in water column in construction area (3.7 mg L −1 ) was significantly lower than that in the other lakes (6.0 mg L −1 ) at the end of the construction (24th May). This difference may attribute to the cofferdam events since it can prolong water retention time (Wendt-Potthoff et al 2014) and limit oxygen availability (Windham-Myers et al 2013), thereby enhancing formation of anaerobic condition. Thus, construction in lake could greatly enhance phosphorus releasing from sediment with anaerobic desorption of Fe(OOH)∼P being a main pathway.…”

Ecological response of two hydro‐morphological similar pre‐dams to contrasting land‐use in the Rappbode reservoir system (Germany)

“…In the hypolimnion, vertical gradients of nitrate indicated losses by diffusion probably caused by microbial denitrification in the sediment (e.g., Nizzoli et al, 2010) and probably by nitrate reduction in the bottom waters due to arising anoxia (Wendt-Potthoff et al, 2014). In epilimnetic waters, nitrate depletion proceeded as well, probably due to assimilative uptake by algae and microbes.…”

“…In epilimnetic waters, nitrate depletion proceeded as well, probably due to assimilative uptake by algae and microbes. In the hypolimnion, vertical gradients of nitrate indicated losses by diffusion probably caused by microbial denitrification in the sediment (e.g., Nizzoli et al, 2010) and probably by nitrate reduction in the bottom waters due to arising anoxia (Wendt-Potthoff et al, 2014).…”

Trajectories of Sediment-Water Interactions in Reservoirs as a Result of Temperature and Oxygen Conditions

“…Furthermore, modelling of climate change effects already shows increasing risk of anoxia in lakes [18] and hence, the recovery of lakes from eutrophication will become more difficult [19].Redox condition is another major determinant of sediment-water interactions [20,21], which affects the dominant biogeochemical redox reactions and solubility of some metals and ions. At low redox potential, which occurs at low oxygen and nitrate conditions, iron and manganese are reduced and released into the water [2,22]. This reductive dissolution of Fe causes the release of P and DOC [2,3], making the oxygen conditions of a lake's hypolimnion a key issue in lake management.The effects of temperature and oxygen conditions on benthic solute fluxes have been extensively studied, but only separately [7,11,[23][24][25].…”

“…Redox condition is another major determinant of sediment-water interactions [20,21], which affects the dominant biogeochemical redox reactions and solubility of some metals and ions. At low redox potential, which occurs at low oxygen and nitrate conditions, iron and manganese are reduced and released into the water [2,22]. This reductive dissolution of Fe causes the release of P and DOC [2,3], making the oxygen conditions of a lake's hypolimnion a key issue in lake management.…”