Summer drought enhances diurnal amplitude of CO in two German rivers of different size.

Drought is becoming increasingly prevalent globally, stimulating research into its effects on river ecosystems. However, our understanding of how droughts affect riverine CO dynamics on a daily scale remains limited, particularly considering the likelihood of future drought occurrence. Here, we seize the opportunity to compare daily CO cycles between a non-drought summer and an unprecedented drought summer.

Dissolved organic matter quality, hydrological connectivity and microbial activity shape phosphorus buffering in river-floodplain systems.

High loads of nutrients like phosphorus (P) persistently degrade water quality in floodplain waterbodies and cause eutrophication, i.e., elevated algae production.

Anaerobic degradation of excess protein-rich fish feed drives CH ebullition in a freshwater aquaculture pond.

Aquaculture is a climate-relevant source of greenhouse gases like methane. Methane emissions depend on various parameters, with organic matter playing a crucial role. Nevertheless, little is known about the composition of organic matter in aquaculture.

Metabolism and carbonate buffering drive seasonal dynamics of CO emissions from two German reservoirs.

Biological metabolism drives much of the variation in CO in terrestrial ecosystems but does not explain CO oversaturation and emission in net autotrophic lakes and reservoirs. The unexplained CO could be attributed to the equilibria between CO and the carbonate buffering system, which is seldom integrated into CO budgets, let alone its interplay with metabolism on CO emissions. Here, we perform a process-based mass balance modeling analysis based on an 8-year dataset from two adjacent reservoirs with similar catchment sizes but contrasting trophic states and alkalinity.

Large-scale sampling of the freshwater microbiome suggests pollution-driven ecosystem changes.

Freshwater microbes play a crucial role in the global carbon cycle. Anthropogenic stressors that lead to changes in these microbial communities are likely to have profound consequences for freshwater ecosystems. Using field data from the coordinated sampling of 617 lakes, ponds, rivers, and streams by citizen scientists, we observed linkages between microbial community composition, light and chemical pollution, and greenhouse gas concentration.

Fluvial CO and CH in a lowland agriculturally impacted river network: Importance of local and longitudinal controls.

Despite streams and rivers play a critical role as conduits of terrestrially produced organic carbon to the atmosphere, fluvial CO and CH are seldom integrated into regional carbon budgets. High spatial variability hinders our ability to understand how local and longitudinal controls affect underlying processes of riverine CO and CH and challenge the prediction and upscaling across large areas. Here, we conducted a survey of fluvial CO and CH concentrations spanning multiple stream orders within an agriculturally impacted region, the North China Plain.

Cross-continental importance of CH emissions from dry inland-waters.

Despite substantial advances in quantifying greenhouse gas (GHG) emissions from dry inland waters, existing estimates mainly consist of carbon dioxide (CO) emissions. However, methane (CH) may also be relevant due to its higher Global Warming Potential (GWP). We report CH emissions from dry inland water sediments to i) provide a cross-continental estimate of such emissions for different types of aquatic systems (i.

Disentangling multiple chemical and non-chemical stressors in a lotic ecosystem using a longitudinal approach.

Meeting ecological and water quality standards in lotic ecosystems is often failed due to multiple stressors. However, disentangling stressor effects and identifying relevant stressor-effect-relationships in complex environmental settings remain major challenges. By combining state-of-the-art methods from ecotoxicology and aquatic ecosystem analysis, we aimed here to disentangle the effects of multiple chemical and non-chemical stressors along a longitudinal land use gradient in a third-order river in Germany.

Terrestrial Vegetation Drives Methane Production in the Sediments of two German Reservoirs.

Inland waters and reservoirs in particular are significant sources of methane to the atmosphere. However, little information is available on the extent to which organic carbon from terrestrial vegetation or from internal photosynthesis fuels the methane production. This limits our ability to constrain methane emissions efficiently.

Hidden treasures: Human-made aquatic ecosystems harbour unexplored opportunities.

Artificial water bodies like ditches, fish ponds, weirs, reservoirs, fish ladders, and irrigation channels are usually constructed and managed to optimize their intended purposes. However, human-made aquatic systems also have unintended consequences on ecosystem services and biogeochemical cycles. Knowledge about their functioning and possible additional ecosystem services is poor, especially compared to natural ecosystems.

Redox Conditions Affect Dissolved Organic Carbon Quality in Stratified Freshwaters.

The quality of dissolved organic carbon (DOC) affects both carbon cycling in surface waters and drinking water production. Not much is known about the influence of environmental conditions on DOC quality. We studied the effect of redox conditions on the chemical composition of DOC in a drinking water reservoir by Fourier transform ion cyclotron resonance mass spectrometry in combination with sediment core incubation experiments under manipulated redox conditions.

Methane storage and ebullition in monimolimnetic waters of polluted mine pit lake Vollert-Sued, Germany.

Reliable gas measurements from supersaturated deep waters still remain a challenge. However, good information is mandatory to investigate the limnic carbon cycle, assess the endangerment through limnic eruptions and evaluate a potential source of exploitable energy. We addressed these three points in a heavily polluted mine pit lake in Germany.

CO emissions from German drinking water reservoirs.

Globally, reservoirs are a significant source of atmospheric CO. However, precise quantification of greenhouse gas emissions from drinking water reservoirs on the regional or national scale is still challenging. We calculated CO fluxes for 39 German drinking water reservoirs during a period of 22years (1991-2013) using routine monitoring data in order to quantify total emission of CO from drinking water reservoirs in Germany and to identify major drivers.

Organic matter in sediment layers of an acidic mining lake as assessed by lipid analysis. Part II: Neutral lipids.

Natural neutralization of acidic mining lakes is often limited by organic matter. The knowledge of the sources and degradability of organic matter is crucial for understanding alkalinity generation in these lakes. Sediments collected at different depths (surface sediment layer from 0 to 1 cm and deep sediment layer from 4 to 5cm) from an acidic mining lake were studied in order to characterize sedimentary organic matter based on neutral signature markers.

No nitrification in lakes below pH 3.

Lakes affected by acid mine drainage (AMD) or acid rain often contain elevated concentrations of ammonium, which threatens water quality. It is commonly assumed that this is due to the inhibition of microbial nitrification in acidic water, but nitrification was never directly measured in mine pit lakes. For the first time, we measured nitrification by (15)NH4Cl isotope tracer addition in acidic as well as neutral mine pit lakes in Spain and Germany.

Organic matter in sediments of an acidic mining lake as assessed by lipid analysis. Part I: fatty acids.

Fatty acid (FA) patterns of sediments collected from the bottom of an acidic mine pit lake (AML) at different depths (surface sediment: 0 to 1cm; deep sediment: 4 to 5 cm) were studied to characterize microbial communities and the sources of sedimentary organic matter (SOM). Studies were performed on the molecular level utilizing source-specific, diagnostic FA biomarkers. The biomarker-based approach has been used widely in marine sediment studies, but has not been applied for sediments from AMLs so far.

Structure and function of the microbial community in an in situ reactor to treat an acidic mine pit lake.

Sulfate-reducing bioreactors are a promising option for the treatment of acid mine drainage. We studied the structure and function of a biofilm in a methanol-fed fixed-bed in-lake reactor for the treatment of an acidic pit lake by a combination of laboratory incubations, chemical and molecular analyses and confocal laser scanning microscopy to determine whether competition by different groups of microorganisms as well as the precipitation of minerals affect reactor performance negatively. The biofilm growing on the surface of a synthetic carrier material consisted of dense microbial colonies covered by iron-sulfide precipitates.

Occurrence and role of algae and fungi in acid mine drainage environment with special reference to metals and sulfate immobilization.

Passive remediation of Acid Mine Drainage (AMD) is a popular technology under development in current research. Roles of algae and fungi, the natural residents of AMD and its attenuator are not emphasized adequately in the mine water research. Living symbiotically various species of algae and fungi effectively enrich the carbon sources that help to maintain the sulfate reducing bacterial (SRB) population in predominantly anaerobic environment.

Microbial sulphate reduction at a low pH.

It is now well established that microbial sulphate-reduction can proceed in environments with a pH<5. This review summarizes existing reports on sulphate reduction at low pH and discusses possible pH effects on sulphate-reducing bacteria. Microbial sulphate reduction has been observed in acidic lakes, wetlands, mesocosms, acidic sulphate soils and bioreactors.

Natural alkalinity generation in neutral lakes affected by acid mine drainage.

Lakes in surface mining areas are often subject to continuous loads of acid mine drainage. The knowledge of internal alkalinity generation in a lake is necessary to predict if the lake will stay circumneutral or may acidify. The most important processes of alkalinity production in lakes are sulfate reduction, denitrification, and the burial of N in the sediment.

Processes at the sediment water interface after addition of organic matter and lime to an Acid Mine Pit Lake mesocosm.

A strategy to neutralize acidic pit lakes was tested in a field mesocosm of 4500 m(3) volume in the Acidic Pit Mine Lake 111 in Germany. Carbokalk, a byproduct from sugar production, and wheat straw was applied near to the sediment surface to stimulate in lake microbial alkalinity generation by sulfate and iron reduction. The biogeochemical processes at the sediment-water interface were studied over 3 years by geochemical monitoring and an in situ microprofiler.

Nitrogen turnover in drying sediments of an Amazon floodplain lake.

In the Amazon floodplain large areas are subject to annual cycles of drying and rewetting. The turnover of nitrogen in the periodically drying sediments is an important regulator of floodplain fertility. In the present study the transition of a lake sediment from flooded to dry conditions was studied with respect to microbial nitrogen turnover.

Community structure and photosynthetic activity of epilithon from a highly acidic (pH < or = 2) mountain stream in Patagonia, Argentina.

We explored a benthic community living on stones in an acidic (pH< or =2) stream of active volcanic origin from Patagonia, Argentina, by combining in situ measurements (temperature, pH, conductivity, dissolved oxygen), photosynthesis of intact biofilms (measured with microsensors by the light-dark shift method), pure-culture experiments on isolated algae, and confocal laser scanning microscopy on the biofilms. The epilithon of the Agrio River was dominated (99% of total biomass) by one species: Gloeochrysis (Chrysophyceae). This species was observed as brown, mucilaginous, 200-microm-thick films on stones, growing in clumps in a dense matrix of fungal hyphae, bacteria, and inorganic particles held together by extracellular polymeric substances.

Microbial sulfate reduction at low pH in sediments of an acidic lake in Argentina.

We measured sulfate reduction in the acidic (pH < or = 3) sediment of an Argentinean lake influenced by volcanism. Sulfate reduction rates of 2.04 mmol m(-2) d(-1) were determined with a 35SO4(2-) core injection method and confirmed by batch incubations and from H2S measurements in the sediment.