Publications - Publications

Borehole nuclear magnetic resonance as a promising 3D mapping tool in peatland studies

Reza Mashhadi, S., Grombacher, D., Zak, D., et al. — Fri, 01 Mar 2024 13:30:24 +0100

The potential and limitations of the Borehole Nuclear Magnetic Resonance (BNMR) technique as an in situ measurement for peatland soil characterization was tested in 163 boreholes at four selected peatlands in Denmark. The BNMR data effectively differentiated various geological units in peatland environments due to their distinct NMR responses. Moreover, field-scale variations of the porosity and pore size distribution (e.g., porosity variations within a single geological unit) were mapped to reveal possible trends reflecting geological or hydrogeological conditions in a peatland. Additionally, some of the NMR parameters were found to be correlated with peat decomposition or the degree of humification. The estimation of hydraulic conductivity (K) based on NMR data was also examined for various geological units and compared with slug test measurements. While NMR-based hydraulic conductivity estimations for sand and gyttja (fine-grained sediment with high organic matter) geological units fall within an acceptable range of error, we encountered challenges in achieving reliable estimations for peat. This study showed the potential of BNMR as a robust, rapid, and reliable in situ tool for soil characterization in peatland research.

Assessing groundwater denitrification spatially is the key to targeted agricultural nitrogen regulation

Hansen, B., Aamand, J., Blicher-Mathiesen, G., et al. — Sun, 01 Dec 2024 13:30:24 +0100

Globally, food production for an ever-growing population is a well-known threat to the environment due to losses of excess reactive nitrogen (N) from agriculture. Since the 1980s, many countries of the Global North, such as Denmark, have successfully combatted N pollution in the aquatic environment by regulation and introduction of national agricultural one-size-fits-all mitigation measures. Despite this success, further reduction of the N load is required to meet the EU water directives demands, and implementation of additional targeted N regulation of agriculture has scientifically and politically been found to be a way forward. In this paper, we present a comprehensive concept to make future targeted N regulation successful environmentally and economically. The concept focus is on how and where to establish detailed maps of the groundwater denitrification potential (N retention) in areas, such as Denmark, covered by Quaternary deposits. Quaternary deposits are abundant in many parts of the world, and often feature very complex geological and geochemical architectures. We show that this subsurface complexity results in large local differences in groundwater N retention. Prioritization of the most complex areas for implementation of the new concept can be a cost-efficient way to achieve lower N impact on the aquatic environment.

Borehole Nuclear Magnetic Resonance Studies at Four Danish Peatlands

Mashhadi, S. R., Grombacher, D., Pedersen, J. B., et al. — Sun, 01 Jan 2023 13:30:24 +0100

This study highlights the opportunities of Borehole Nuclear Magnetic Resonance (BNMR) technique for the investigation of peatlands. To achieve this goal, four Danish peatland sites were selected to do BNMR surveys. The data analysis showed that BNMR data can be used to differentiate between different geological units in peatland settings. Moreover, by mapping pore size distribution variability patterns at the field scale, BNMR data can provide invaluable insights into the local geological or environmental conditions of peatland environments.

Miljøeksperter: Udtagning af lavbundsjorde er ingen mirakelkur mod iltsvind - sådan får vi synergi mellem land og vand

Kronvang, B., Kristensen, E., Seslef, J., Grønnegaard, H. . — Mon, 19 Feb 2024 13:30:24 +0100

: Vurdering af placering af sugecellefelter for stationsmarker i LOOP-oplande

Thorsen, M., Blicher-Mathiesen, G., Houlborg, T. — Sun, 01 Jan 2023 13:30:24 +0100

Opdatering af baseline 2027

Andersen, H. E., Børsting, C. F., Christensen, J. H., et al. — Sun, 01 Jan 2023 13:30:24 +0100

Miljøeffekten af den danske undtagelse fra nitratdirektivet til brug for afrapportering til EU-Kommissionen i 2022

Rolighed, J., Thorsen, M., Blicher-Mathiesen, G. — Wed, 13 Dec 2023 13:30:24 +0100

Oparbejdning af landbrugsregisterdata og beregning af referenceudvaskning for nitrat med NLES5

Rolighed, J. — Wed, 06 Dec 2023 13:30:24 +0100

Varslingssystemet for udvaskning af pesticider til grundvand (VAP)

Badawi, N., Karan, S., Haarder, E. B., et al. — Tue, 01 Aug 2023 13:30:24 +0200

The Danish Pesticide Leaching Assessment Programme

Badawi, N., Karan, S., Haarder, E. B., et al. — Tue, 01 Aug 2023 13:30:24 +0200

Advances in Catchment Science, Hydrochemistry, and Aquatic Ecology Enabled by High-Frequency Water Quality Measurements

Bieroza, M., Acharya, S., Benisch, J., et al. — Tue, 28 Mar 2023 13:30:24 +0200

High-frequency water quality measurements in streams and rivers have expanded in scope and sophistication during the last two decades. Existing technology allows in situ automated measurements of water quality constituents, including both solutes and particulates, at unprecedented frequencies from seconds to subdaily sampling intervals. This detailed chemical information can be combined with measurements of hydrological and biogeochemical processes, bringing new insights into the sources, transport pathways, and transformation processes of solutes and particulates in complex catchments and along the aquatic continuum. Here, we summarize established and emerging high-frequency water quality technologies, outline key high-frequency hydrochemical data sets, and review scientific advances in key focus areas enabled by the rapid development of high-frequency water quality measurements in streams and rivers. Finally, we discuss future directions and challenges for using high-frequency water quality measurements to bridge scientific and management gaps by promoting a holistic understanding of freshwater systems and catchment status, health, and function.

Næringsstofbelastning, kildeopsplitning og kvælstofretention

Thodsen, H., Tornbjerg, H., Trolle, D., Erichsen, A. Chr., Larsen, T. C. — Fri, 01 Dec 2023 13:30:24 +0100

I denne rapport er anvendte metoder og diverse leverancer fra Arbejdspakke 1 i
projektet ”Second opinion” fase III, ”styrket modelgrundlag” beskrevet og
præsenteret.

Importance of small geological features for simulated spatial patterns in tile drain flow in Fensholt catchment of Denmark

Mahmood, H., Frederiksen, R. R., Duque, C., Christiansen, A. V. — Fri, 01 Dec 2023 13:30:24 +0100

Study region: Fensholt, Denmark. Study focus: Tile drains are commonly used in agricultural fields with loamy soils in Denmark to improve crop yield by removing excessive water. Spatial patterns of drain flows are controlled by the climate, geology, topography, and tile installation. We assessed the combined effect of topography and geology on spatial pattern of tile drain flows in 10 m resolution using numerical modelling. We developed three groundwater models using different geological models by integrating high-resolution data from geophysical methods with field estimated hydraulic conductivity. New insights: The mapping and modelling revealed small geological features of higher hydraulic conductivity in clayey-till. The results showed that the spatial patterns of drain flows to recharge ratio (drainage fraction, DF) are driven by topography; the models had a high DF in local depressions and a low DF in local hills. The DF was related to the Topographical Position Index (TPI), suggesting that the DF is controlled by small-scale topography both upstream and downstream of the study area. We found that geology amplifies the spatial patterns of tile drain flows; a higher hydraulic conductivity relative to a lower hydraulic conductivity increases the change of tile drain flow for a one-unit change in the TPI. This was attributed to a change from small-scale flow systems to field-scale flow systems. The study suggested that topography helps to delineate high and low DF while geology controls the magnitude of DF. The study emphasized the importance of mapping and modeling of geology for managing moraine agricultural areas that can be found in parts of North America and Scandinavia for agricultural water management.

Virkemidler til kystvandrådets scenarier for den centrale Limfjord

Fri, 01 Dec 2023 13:30:24 +0100

Denitrification rates measured in streams and inundated meadows

Sun, 01 Jan 2023 13:30:24 +0100

Nitrogen (N) pollution in aquatic environments is a major concern worldwide due its negative effect on water quality and biodiversity. Part of the N applied as fertilizer and manure on agricultural fields is leached to streams and further exported to the sea. To mitigate N losses from agriculture, several mitigation strategies have been implemented in Denmark including field-level measures, constructed wetlands, and restoration of wetlands.

Most of the previous research have therefore focused on investigating the retention and turnover potential of these measures. However, streams and temporarily inundated riparian area also play an important role in retaining and removing N from surface waters but the overall effect at a larger scale such as Denmark (43,100 km2) is yet poorly investigated.

To estimate the significance of N turnover in streams and temporarily flooded riparian areas, we are conducting an in situ investigation of denitrification rates spanning four seasons during 2022-2023. The denitrification rates are measured using the N isotope pairing technique in six replicate measuring chambers in 15 streams and ditches. The study will also include in situ measurements of temporarily inundated riparian areas three times a year at three locations along typical Danish streams.

The results of the present study will contribute to a new update of an existing Danish N model consisting of three sub-models (leaching model, groundwater hydrological model and several surface water sub-models; Højbjerg et al., 2020). Each sub model deals with either calculation of N-leaching from arable fields, hydrological N-transport, and N-turnover in the groundwater zone and lastly N-turnover in surface waters such as streams and temporarily inundated meadows. The model complex has been used to develop national N-retention maps for groundwater and surface waters at a scale of app. 15 km2. The new updated N-model is intended to deliver new N-retention maps on a finer scale.

Viden- og forskningsbehov for forbedret grundlag for bedriftsspecifikke opgørelser af drivhusgasudledninger i landbruget

Andersen, M. N., Adamsen, A. P. S., Andersen, T. A., et al. — Fri, 01 Dec 2023 13:30:24 +0100

Patterns and processes of methane production and oxidation in shallow lakes under different nutrient and warming treatments

Sun, 01 Jan 2023 13:30:24 +0100

Sammenhænge mellem oplandskarakteristika og tilstanden i søer uden veldefinerede afløb

Søndergaard, M., Johansson, L. S., Kjeldgaard, A. — Sun, 01 Jan 2023 13:30:24 +0100

A century of nitrogen dynamics in agricultural watersheds of Denmark

Dessirier, B., Blicher-Mathiesen, G., Andersen, H. E., et al. — Sun, 01 Oct 2023 13:30:24 +0200

Afstrømning og kvælstofkoncentrationer i jord-, dræn- og grundvand

Thorsen, M., Blicher-Mathiesen, G. — Fri, 01 Dec 2023 13:30:24 +0100

Bank erosion is as major phosphorus source in Danish catchments: how to find possible mitigation options?

Kronvang, B., Kjeldgaard, A., Larsen, S. E., Thodsen, H., Andersen, H. E. — Tue, 07 Nov 2023 13:30:24 +0100

The establishment and use of local coastal water boards is tested in Denmark to find bottom-up solutions for RBMP 2027

Tue, 07 Nov 2023 13:30:24 +0100

Megafloods in Europe can be anticipated from observations in hydrologically similar catchments

Bertola, M., Blöschl, G., Bohac, M., et al. — Wed, 01 Nov 2023 13:30:24 +0100

Megafloods that far exceed previously observed records often take citizens and experts by surprise, resulting in extremely severe damage and loss of life. Existing methods based on local and regional information rarely go beyond national borders and cannot predict these floods well because of limited data on megafloods, and because flood generation processes of extremes differ from those of smaller, more frequently observed events. Here we analyse river discharge observations from over 8,000 gauging stations across Europe and show that recent megafloods could have been anticipated from those previously observed in other places in Europe. Almost all observed megafloods (95.5%) fall within the envelope values estimated from previous floods in other similar places on the continent, implying that local surprises are not surprising at the continental scale. This holds also for older events, indicating that megafloods have not changed much in time relative to their spatial variability. The underlying concept of the study is that catchments with similar flood generation processes produce similar outliers. It is thus essential to transcend national boundaries and learn from other places across the continent to avoid surprises and save lives.

Mapping and monitoring peatland conditions from global to field scale

Minasny, B., Adetsu, D. V., Aitkenhead, M., et al. — Sun, 01 Jan 2023 13:30:24 +0100

Peatlands cover only 3–4% of the Earth’s surface, but they store nearly 30% of global soil carbon stock. This significant carbon store is under threat as peatlands continue to be degraded at alarming rates around the world. It has prompted countries worldwide to establish regulations to conserve and reduce emissions from this carbon rich ecosystem. For example, the EU has implemented new rules that mandate sustainable management of peatlands, critical to reaching the goal of carbon neutrality by 2050. However, a lack of information on the extent and condition of peatlands has hindered the development of national policies and restoration efforts. This paper reviews the current state of knowledge on mapping and monitoring peatlands from field sites to the globe and identifies areas where further research is needed. It presents an overview of the different methodologies used to map peatlands in nine countries, which vary in definition of peat soil and peatland, mapping coverage, and mapping detail. Whereas mapping peatlands across the world with only one approach is hardly possible, the paper highlights the need for more consistent approaches within regions having comparable peatland types and climates to inform their protection and urgent restoration. The review further summarises various approaches used for monitoring peatland conditions and functions. These include monitoring at the plot scale for degree of humification and stoichiometric ratio, and proximal sensing such as gamma radiometrics and electromagnetic induction at the field to landscape scale for mapping peat thickness and identifying hotspots for greenhouse gas (GHG) emissions. Remote sensing techniques with passive and active sensors at regional to national scale can help in monitoring subsidence rate, water table, peat moisture, landslides, and GHG emissions. Although the use of water table depth as a proxy for interannual GHG emissions from peatlands has been well established, there is no single remote sensing method or data product yet that has been verified beyond local or regional scales. Broader land-use change and fire monitoring at a global scale may further assist national GHG inventory reporting. Monitoring of peatland conditions to evaluate the success of individual restoration schemes still requires field work to assess local proxies combined with remote sensing and modeling. Long-term monitoring is necessary to draw valid conclusions on revegetation outcomes and associated GHG emissions in rewetted peatlands, as their dynamics are not fully understood at the site level. Monitoring vegetation development and hydrology of restored peatlands is needed as a proxy to assess the return of water and changes in nutrient cycling and biodiversity.

Three decades of regulation of agricultural nitrogen losses in Denmark

Wed, 08 Nov 2023 13:30:24 +0100

Excess nitrogen (N) losses from intensive agricultural production are a world-wide problem causing eutrophication in vulnerable aquatic ecosystems such as estuaries. Therefore, Denmark as one of the most intensively farmed countries in the world has enforced mandatory regulations on agricultural production since the late 1980s. We demonstrate the outcome of the regulations imposed on agriculture by analyzing decadal trends in nitrate (NO3-) concentrations and loads in streams using 29-32 years of detailed monitoring data and survey information on agricultural practices at field level from five intensively cultivated headwater catchments.
The analysis includes the importance of four main drivers (climate, land use, agricultural practices, and biogeophysical properties of catchments), each divided into different factors that may influence stream NO3- loads during three subperiods defined by the time of introduction of different mitigation measures: i) 1990-1998, ii) 1999-2007, and iii) 2008-2018.
Significant correlations with annual flow-weighted stream NO3- concentrations and/or loads were found for factors representing all of the four main drivers including precipitation, large scale climate fluctuations, runoff, previous year’s runoff, baseflow index, number of annual frost days, agricultural area, livestock density, field N surplus, catch crop cover, manure storage capacity, method and time of manure spreading, and time of soil tillage.
Changes in the four drivers were reflected by the load-runoff (L-Q) relationships for each of the three subperiods within each of the five headwater catchments. The five catchments experienced large but catchment-specific downward shifts in the L-Q relationship attributable to changes in land use and agricultural management within the catchments. The documented large downward shifts in NO3- loads demonstrated for the five catchments (30-52%) as a consequence of mandatory regulation over a period of nearly three decades are a unique example of how agriculture can reduce its environmental impact.

Nitrogen and phosphorus transport from drained wetlands before and after restoration

Petersen, R. J., Zak, D. H., Andersen, H. E., et al. — Wed, 20 Sep 2023 13:30:24 +0200

Riparian wetlands under undisturbed conditions fulfil important sink functions for phosphorus (P) and nitrogen (N). However, over the years, the important function of these ecotones as nutrient sinks has been significantly altered due to human intervention in many parts of the world. Today, in the face of rising global challenges like eutrophication of water bodies associated with the decline of biodiversity, increasing greenhouse gas fluxes and other societal challenges, rewetting of wetlands is proposed as a valid cost-efficient nature-based mitigation solution. The challenge is, however, that the long-term drainage and intensive agricultural use of wetlands have created significant changes in both physical and chemical soil characteristics such as significantly increased dry bulk densities and mobile P content in connection with soil carbon mineralization and land use. During the last decades, we have gained a comprehensive understanding of the processes and driving factors controlling the cycling of nutrients in wetlands. Both the hydrology and the quality of the discharging water are important determinants of the physico-chemical conditions of an individual wetland, and they control a broad range of biogeochemical processes driving the nutrient removal and thus the nutrient export to downstream systems.
In Denmark, more than 200 wetlands have been restored during the last 25 years. However, only a fraction of the restored areas are monitored for water and nutrient fluxes and none of the areas have been monitored pre-restoration. During the last couple of years, we have started monitoring several drained wetland areas. Some of these areas have recently been rewetted under continued monitoring. We will present these first results of nutrient fluxes from drained wetlands pre and post restoration and discuss the implications for future rewetting strategies.

Periphyton responses to drastic changes in nutrient concentrations under different warming scenarios in shallow lake mesocosms

Stamenković, O., Pacheco, J. P. — Wed, 01 Nov 2023 13:30:24 +0100

Periphyton plays an important role in lake ecosystem functioning and often can be key primary producer in
oligotrophic or mesotrophic shallow lakes. This community can respond rapidly to alterations in environmental
changes, which can have consequences for lake nutrient cycles and food webs. Thus, understanding how
periphyton responds to changes in key drivers, such as nutrient concentrations, is important for lake
management.
Our experiment was conducted in the climate change mesocosm facilities of Aquacosm-Aarhus University in
central Jutland, Denmark, which were designed to study the effects of eutrophication and global warming in
shallow lakes. After 20 years of operating under the same nutrient loading treatment, the nutrient loading
treatment was switched on June 1st, 2023, so high nutrient concentrations became low and vice versa. We
analysed the responses of periphyton biomass and community composition to this change in nutrient
concentrations, under three different warming scenarios: ambient, IPCC A2 scenario (2-3°C above ambient),
and A2 + 50% (4-6°C above ambient), and under two different nutrient states: high and low, in 24 shallow
lake mesocosms. For this, we used artificial plants as a substrate for periphyton development during two
experimental periods, before and after the change in nutrient concentrations. Our preliminary results showed
that periphyton biomass was lower after the change in nutrient concentrations. Community composition was
different before and after the change. Also, we fond weak but significant difference in periphyton community
composition between mesocosms with high and low nutrient concentrations. Our results should contribute to
knowledge of periphyton responses to eutrophication and oligotrophication in shallow lakes.

Impacts of plastic surface on the periphyton under different nutrient and temperature: A mesocosm experiment

Tavşanoğlu, Ü. N., Çırak, T. ., Başaran Kankılıç, G. ., et al. — Wed, 01 Nov 2023 13:30:24 +0100

The present study investigates the role of microplastics as substrates for periphyton development. Within
aquatic ecosystems. Environmental factors including nutrient availability, pH, salinity, and seasonal variations,
exert a profound influence on periphyton growth dynamics. The colonization of microplastics by periphyton
significantly impacts aquatic ecosystem structure and function due to the efficient transport capacity of
microplastics. The experiment was conducted at the Lemming Mesocosm Facility in Denmark. To assess the
flipping on the nutrient in the mesocosm system regarding the evaluation of periphyton composition, we used
different polymer types and different surface roughness. The plastic strips were positioned just beneath the
water surface in each mesocosm setup, approximately 20 cm below. Periphyton samples were carefully
harvested from the plastic surfaces and transferred to 5 ml Eppendorf tubes, preserving them with Lugol's
solution. The experiment monitored chlorophyll-a levels and sensor data to determine optimal nutrient-flipping
conditions. Upon detecting differences in nutrient levels, the microplastic strips were introduced into the
mesocosms to evaluate their influence on periphyton composition. Overall, this study elucidates the intricate
relationships between microplastics, periphyton, and aquatic ecosystems, shedding light on the potential
consequences of their interactions. Understanding these dynamics is crucial for comprehending the broader
implications of microplastic pollution in aquatic environments.

Periphyton in a changing world: unravelling the effects of global change stressors on freshwater periphyton in shallow lake mesocosms

Pacheco, J. P., Aznarez, C., Cao, Y., et al. — Wed, 01 Nov 2023 13:30:24 +0100

Benthic algae and cyanobacteria play crucial roles in the structure and functioning of freshwater ecosystems,
particularly in shallow lakes. Multiple stressors associated with global change can impact freshwater
periphyton, consequently influencing ecological responses at the ecosystem level, including nutrient dynamics,
primary production, and food webs. In this study, we investigate the impact of various global change stressors
on the biomass and composition of freshwater periphyton using different experimental approaches in shallow
lake mesocosms under various climatic conditions. These experiments included the effects of warming,
nutrient enrichment, nutrient depletion, salinisation and changes in food webs (increased omnivory by fish).
Our results suggest that global change stressors may induce contrasting effects on the biomass and composition
of periphyton. Warming scenarios alone do not induce changes in periphyton biomass or composition, but they
influence the responses to other stressors such as salinisation, changes in nutrients and responses to omnivory
by fish. Low nutrient concentrations tend to favour periphyton over phytoplankton, while this response is
regulated by top-down effects. Extreme environmental conditions, such as a drastic decrease in nutrient
concentrations, or high salinity, induce compositional oversimplifications in periphyton composition, with
dominance of a few dominant species, either of large-sized filamentous green algae in the case of low nutrients
or low salinity or increased dominance of cyanobacteria at high salinity levels. We further discuss the diverse
interactions between these stressors and their potential impacts on freshwater ecosystems within projected
scenarios of global change.

Effects of Climate Change on the Habitat Suitability and Distribution of Endemic Freshwater Fish Species in Semi-Arid Central Anatolian Ecoregion in Türkiye

Korkmaz, M., Mangıt, F., Dumlupınar, İ., et al. — Sat, 01 Apr 2023 13:30:24 +0200

Climate change is affecting freshwater ecosystems globally, particularly those in semi-arid and arid regions. The Central Anatolian Ecoregion (CAE) in Türkiye has a semi-arid climate and is home to numerous endemic fish species. We used species distribution modelling to elucidate the distribution of sixteen endemic fish species in CAE and predicted their potential distributions for 2041–2060 and 2081–2100 based on the CMIP6 climate model. Half of the species are predicted to experience a significant loss of climatically suitable areas. Anatolichthys fontinalis, Gobio gymnostethus, Gobio hettitorum, and Pseudophoxinus burduricus will face a complete loss of suitable areas by 2081–2100 under a high emissions climate scenario, whereas Cobitis bilseli, Egirdira nigra, Gobio intermedius, and Squalius anatolicus will experience a significant loss. The other eight species can potentially benefit from climate warming if all other stressors remain equal. Anthropogenic stressors, such as water abstraction for irrigation, pollution, invasive species introductions, and dam construction, are already putting endemic fish populations in CAE under extreme pressure. Climate change is expected to exacerbate these threats. Regular monitoring of freshwater ecosystems and fish fauna in the CAE and protecting the region from key anthropogenic stressors are recommended to successfully conserve these endemic freshwater fishes under climate change.

European river typologies fail to capture diatom, fish, and macrophyte community composition

Jupke, J. F., Birk, S., Apostolou, A., et al. — Sun, 01 Oct 2023 13:30:24 +0200

Typology systems are frequently used in applied and fundamental ecology and are relevant for environmental monitoring and conservation. They aggregate ecosystems into discrete types based on biotic and abiotic variables, assuming that ecosystems of the same type are more alike than ecosystems of different types with regard to a specific property of interest. We evaluated whether this assumption is met by the Broad River Types (BRT), a recently proposed European river typology system, that classifies river segments based on abiotic variables, when it is used to group biological communities. We compiled data on the community composition of diatoms, fishes, and aquatic macrophytes throughout Europe and evaluated whether the composition is more similar in site groups with the same river type than in site groups of different river types using analysis of similarities, classification strength, typical species analysis, and the area under zeta diversity decline curves. We compared the performance of the BRT with those of four region-based typology systems, namely, Illies Freshwater Ecoregions, the Biogeographic Regions, the Freshwater Ecoregions of the World, and the Environmental Zones, as well as spatial autocorrelation (SA) classifications. All typology systems received low scores from most evaluation methods, relative to predefined thresholds and the SA classifications. The BRT often scored lowest of all typology systems. Within each typology system, community composition overlapped considerably between site groups defined by the types of the systems. The overlap tended to be the lowest for fishes and between Illies Freshwater Ecoregions. In conclusion, we found that existing broad-scale river typology systems fail to delineate site groups with distinct and compositionally homogeneous communities of diatoms, fishes, and macrophytes. A way to improve the fit between typology systems and biological communities might be to combine segment-based and region-based typology systems to simultaneously account for local environmental variation and historical distribution patterns, thus potentially improving the utility of broad-scale typology systems for freshwater biota.

Uddybning af faktorer, der kan påvirke effekten eller strømningsvejen i et åbent minivådområde

Pugliese, L., Iversen, B. V., Hoffmann, C. C., Børgesen, C. D. — Sun, 01 Oct 2023 13:30:24 +0200

Benthic diatom index for water quality biomonitoring of Danish running waters

Pacheco, J. P., Larsen, S. E., Baattrup-Pedersen, A. — Mon, 11 Sep 2023 13:30:24 +0200

Afsluttende rapport: Fire pilotprojekter for multifunktionel jordfordeling 2015-2022

Thu, 01 Dec 2022 13:30:24 +0100

Representation of Hydrological Components under a Changing Climate—A Case Study of the Uruguay River Basin Using the New Version of the Soil and Water Assessment Tool Model (SWAT+)

Sat, 01 Jul 2023 13:30:24 +0200

SWAT+ is a revised version of the SWAT model that has the capability to route flow across landscape units in the catchment, which is expected to improve the spatial representation of processes in watersheds. We applied the SWAT+ model in the Uruguay River Basin, an international river basin in South America with a total surface area of 370,000 km², in order to (1) assess the water balance components, (2) represent their spatial distribution, and (3) examine their changes over time. The catchment was divided into uplands and floodplains and a decision table rule was developed based on streamflow data. The SPOTPY Python library was linked to SWAT+ and used as a tool to perform sensitivity analyses and calibration. The model represented the fluctuations of discharge well, although there was a general tendency to underestimate peak flows. Blue (precipitation and runoff) and green (evapotranspiration and soil water content) hydrological components were spatially plotted. Overall, SWAT+ simulated a realistic spatial distribution of the water cycle components. A seasonal Mann–Kendall test suggests a positive increasing trend in the average temperature (p-value = 0.007; Sen’s slope = 0.09), the soil water content (p-value = 0.02; Sen’s slope = 1.29), and evapotranspiration (p-value: 0.03; Sen’s slope = 1.97), indicating that the ecosystem experienced a changing climate during the simulation period. The findings presented in this study are of significant value for the impacts of sustainable management and the evaluation of climate change on water resources in the Uruguay River Basin.

Videreudvikling af model for metaller i vandløbsvand

Sørensen, P. B., Damgaard, C., Bjerg, P. L., et al. — Wed, 01 Mar 2023 13:30:24 +0100

Denne rapport indgår i et større arbejde med udvikling af statistiske modeller til estimering af koncentrationer af miljøfarlige forurenende stoffer i overfladevand for Miljøstyrelsen ved at videreudvikle på en pilotudgave af en statistisk model (MetalStat) for forekomsten af 5 metaller som opløst koncentration i vandløbsvand. Rapporten tager således udgangspunkt i afrapportering af MetalStats principper givet i Sørensen et al., 2022. Modellen er sat op, så metalkoncentrationen i vandløbet regnes for at være bestemt af det ID15 opland, som målestationen er placeret i, hvor et ID15 opland har en varierende udstrækning på typisk 10-15 km2. Opgaven for 2022 er at få pilotudgaven af MetalStat valideret og modnet, så den kan indgå i Miljøstyrelsens forvaltning.

Root development is faster in common species of Potamogeton compared to declining species of Potamogeton in Danish lowland streams

Wed, 01 Nov 2023 13:30:24 +0100

The decline in biodiversity in freshwater ecosystems occurs at an alarming rate throughout the world. In Denmark, we know from historical records that several species within the plant genus Potamogeton, that were previously widespread in Danish freshwater ecosystems, are now under severe decline. In this study, we explore root development in two common and three declining Potamogeton species applying an experimental approach. Specifically, we examined if root development characteristics can contribute to explain the contrasting success of these species in the contemporary stream vegetation in Denmark. In accordance with our hypothesis, our results showed that common species of Potamogeton produced roots faster, had longer roots and produced more roots per growth node than declining Potamogeton species. This was particularly clear for P. crispus. Overall, our results expose a mechanism that is likely to affect the ability of these species to maintain populations in highly disturbed lowland streams in Denmark and therefore contribute to explain the contrasting success of these species.

EUSEDcollab

Matthews, F., Verstraeten, G., Borrelli, P., et al. — Fri, 01 Dec 2023 13:30:24 +0100

As a network of researchers we release an open-access database (EUSEDcollab) of water discharge and suspended sediment yield time series records collected in small to medium sized catchments in Europe. EUSEDcollab is compiled to overcome the scarcity of open-access data at relevant spatial scales for studies on runoff, soil loss by water erosion and sediment delivery. Multi-source measurement data from numerous researchers and institutions were harmonised into a common time series and metadata structure. Data reuse is facilitated through accompanying metadata descriptors providing background technical information for each monitoring station setup. Across ten European countries, EUSEDcollab covers over 1600 catchment years of data from 245 catchments at event (11 catchments), daily (22 catchments) and monthly (212 catchments) temporal resolution, and is unique in its focus on small to medium catchment drainage areas (median = 43 km², min = 0.04 km², max = 817 km²) with applicability for soil erosion research. We release this database with the aim of uniting people, knowledge and data through the European Union Soil Observatory (EUSO).

Udredning af næringsstoftilførslen til Vandplankystvandet Rødsand og Bredningen imellem forskellige NOVANA-opgørelser

Thodsen, H., Tornbjerg, H. — Mon, 17 Apr 2023 13:30:24 +0200

Socioeconomic and historical factors shape nature in cities

Aznarez, C., Pacheco, J. P. — Wed, 16 Aug 2023 13:30:24 +0200

This study investigates how socio-economic and historical factors shape urban nature, highlighting the 'luxury' and 'legacy' effects on biodiversity, vegetation and ecosystem services. The results emphasize the need for equitable access to these benefits and strategies to enhance urban nature.

The nutrient uptake bioassay (NUB): A method to estimate the nutrient uptake capacity of biofilms for the functional assessment of river ecosystems

Sun, 01 Oct 2023 13:30:24 +0200

River ecosystems host a large biodiversity and provide essential ecosystem services but are threatened by multiple anthropogenic activities that degrade their structure and functioning. Although both structure and functioning are key components of ecological status, river monitoring programmes rely almost exclusively on structural indicators, such as community structure, or water quality, neglecting functional attributes. Scientists have pointed towards some promising functions, such as organic matter decomposition, as potential indicators of river functional status. However, it may not be the best indicator to assess the ecosystem functioning of river ecosystem subjected to certain impacts, such as nutrient inputs. Additionally, managers have seldom used functional indicators, probably because of the lack of simple, routine protocols. Here we present the nutrient uptake bioassay (NUB), a simple and straightforward method to measure nutrient uptake by river biofilm that could be developed as a functional indicator of river ecological status. The NUB consists in deploying biofilm carriers in the river for a specific period, allowing biofilm colonization. Biofilm carriers are then incubated in the field in a nutrient-enriched standard solution for one hour and finally the remaining nutrient concentration in the standard medium is measured. Nutrient uptake is calculated from the difference between the initial and final nutrient concentrations. Chlorophyll in the biofilm carriers can also be measured to calculate biofilm accrual rates. The NUB has been developed based on a mesocosm and a field experiments, which showed that the NUB provides additional, non-redundant information to current biomonitoring techniques. Overall, the NUB is a cheap, robust and reliable method that can be applied by most river monitoring practitioners and can be adapted to most river types and situations. As nutrient uptake is linked to the self-purification capacity of rivers, the NUB results provide information about an important ecosystem service. Therefore, we suggest that the NUB can be developed as part of the monitoring toolbox available for managers to improve the assessment of river ecological status and to diagnose the causes of ecosystem impairment.

Luxury and legacy effects on urban biodiversity, vegetation cover and ecosystem services

Tue, 01 Aug 2023 13:30:24 +0200

Socio-economic and historical drivers shape urban nature distribution and characteristics, as luxury (wealth-related) and legacy (historical management) effects. Using remote sensing and census data on biodiversity and socio-economic indicators, we examined these effects on urban biodiversity and vegetation cover in Vitoria-Gasteiz (Basque Country). We also tested the luxury and legacy hypotheses on regulating ecosystem services (ES) and explored predictor interactions. Higher educational attainment positively correlated with urban biodiversity, confirming the luxury effect, but had no effect on vegetation cover or ES. Older areas had higher vegetation cover and ES evidencing a legacy effect with an inverse response on biodiversity, attributable to more recent management strategies promoting biodiversity in green spaces. Habitat quality amplified the luxury effect, while population density strengthened the legacy effect. Our results suggest that urban biodiversity is mainly driven by socio-economic factors, while vegetation cover and ES are influenced by management legacies in interaction with population density.

Alkalinity and its influence on benthic diatom assessments in Danish running waters

Pacheco Esnal, J. P., Larsen, S. E., Baattrup-Pedersen, A. — Wed, 01 Feb 2023 13:30:24 +0100

Alkalinity and PO4 co-varies in Danish running waters, and this affects the applicability of the diatom-based indicator of eutrophication SID_TID. Through the analysis of physicochemical and diatom databases, we evaluated the influence of alkalinity on the ability to meet ecological targets and sought to disentangle the effect of alkalinity by the abundance of target diatom species as indicator of high alkalinity and low PO4. Alkalinity was correlated to trophic status indicators (PO4 and BI5), confirming that it is an important interfering factor influencing the SID_TID, and we thus discuss potential causes of the association between these factors. We found no relationship of alkalinity with the abundance of target diatom species. We then developed a probability model, which indicated that at alkalinity values greater than 2,6 mEq/L the probability of meeting ecological targets based on the SID_TID declines drastically and, therefore, the convenience of this index at higher alkalinities should be evaluated.

Mesocosm Design and Implementation of Two Synchronized Case Study Experiments to Determine the Impacts of Salinization and Climate Change on the Structure and Functioning of Shallow Lakes

Özkan, K., Korkmaz, M., Amorim, C. A., et al. — Sat, 01 Jul 2023 13:30:24 +0200

Salinization of freshwater ecosystems is one of the major challenges imposed largely by climate change and excessive water abstraction for irrigated crop farming. Understanding how aquatic ecosystems respond to salinization is essential for mitigation and adaptation to the changing climate, especially in arid landscapes. Field observations provide invaluable data for this purpose, but they rarely include sufficient spatial and temporal domains; however, experimental approaches are the key to elucidating complex ecosystem responses to salinization. We established similar experimental mesocosm facilities in two different climate zones in Turkey, specifically designed to simulate the effects of salinization and climate change on shallow lake ecosystems. These facilities were used for two case-study experiments: (1) a salinity gradient experiment consisting of 16 salinity levels (range: 0–50 g/L); and (2) a heatwave experiment where two different temperature regimes (no heatwave and +6 °C for two weeks) were crossed with two salinity levels (4 and 40 g/L) with four replicates in each treatment. The experiments lasted 8 and 2 months, respectively, and the experimental mesocosms were monitored frequently. Both experiments demonstrated a significant role of salinization modulated by climate on the structure and function of lake ecosystems. Here, we present the design of the mesocosm facilities, show the basic results for both experiments and provide recommendations for the best practices for mesocosm experiments conducted under saline/hypersaline conditions.

Macrophyte removal affects nutrient uptake and metabolism in lowland streams

Wed, 01 Nov 2023 13:30:24 +0100

Macrophytes provide essential ecosystem services in lowland streams, including nutrient uptake that can reduce downstream transport to vulnerable coastal areas. Despite that, to ensure water conveyance and effective run off from agricultural fields, aquatic plant biomass is removed regularly in many European streams (i.e. weed cutting practices). However, the impacts of weed cutting on stream ecosystem processes are not yet well documented. Here, we studied the effect of weed cutting on nutrient retention and ecosystem metabolism in three lowland streams with contrasting dominant vegetation communities (submergent and emergent plants) during summer in Denmark. Our results showed a decrease in nutrient retention; uptake velocity of ammonium decreased 34–77 % and of phosphate decreased 50–77 %. Ecosystem metabolic rates also decreased after weed cutting, both in gross primary production (9 %, 60 % and 85 %) and respiration (47 %, 69 % and 76 %). The effects of weed cutting on these ecosystem processes prevailed three weeks after the cutting occurred. Understanding the effects of weed cutting on stream ecosystem functioning can improve nature-based management strategies to control eutrophication of downstream coastal areas.

Omkostningseffektiv placering af fosforvirkemidler i forhold til søer

Hasler, B., Filippelli, R., Levin, G., et al. — Thu, 01 Jun 2023 13:30:24 +0200

Rapporten præsenterer datagrundlag og funktionalitet i TargetEconN_P-modellen, som er udviklet til omkostningseffektive valg af virkemidler for at opfylde fosfor- og kvælstofindsatskrav for sø- og kystvandoplande i hele Danmark. Rapporten omfatter også eksempler på resultater for scenarier, dels for omkostningseffektiv opfyldelse af fosforindsatskrav, og dels et scenarie hvor sideeffekterne for fosfor opgøres som følge af virkemidler til reduktion af kvælstoftab til kystvandene

Field scale SWAT+ modeling of corn and soybean yields for the contiguous United States

Čerkasova, N., White, M., Arnold, J., et al. — Tue, 01 Aug 2023 13:30:24 +0200

CONTEXT: Despite a steady increase in staple crop yields over the past ten years, current agricultural production must escalate even more to keep pace with the expected world population growth, which in turn will require improved agricultural methods that are adapted to many environmental pressures. Comprehensive models that can simulate crop production systems and the impact of management and conservation practices on natural resources and the environment, including water quality at large scale present important contributions to this challenge. OBJECTIVE: To this end we developed the National Agroecosystem Model (NAM): a comprehensive model that uses the updated Soil and Water Assessment Tool (SWAT+) to accurately simulate staple crop yields across the contiguous United States (CONUS), with an initial focus on Corn (Zea mays L.) and Soybean (Glycine max L. Merr.) yields. METHODS: Available open-access data was used to setup this high-resolution modeling system, where every 8-digit hydrologic unit (HUC8) is represented as an individual SWAT+ simulation. A total of 2201 HUC8 simulations across the CONUS were interconnected from upstream to downstream to make the NAM. Field boundary data was used to setup the NAM in such a way that every identified cultivated field is modeled as a unique Hydrologic Response Unit (HRU). Simulated corn and soybean yield from over 2.5 million field-type HRUs were compared to reported average annual corn and soybean yields for the respective area for the 2015–2020 period. RESULTS AND CONCLUSIONS: Results show a good agreement between simulated and reported yields (R² = 0.90 for corn and R² = 0.70 for soybeans), with a very good model performance in the high corn and soybean production region of the US Corn Belt (Relative Error < ±5%). SIGNIFICANCE: Apart from assessing the capability of the updated SWAT+ model, we also demonstrate the new crop yield calibration module embedded in SWAT+, highlight changes to the plant growth module, and model parameterization. Results of an analysis of possible crop production differences for corn and soybeans in irrigated, tiled, and non-irrigated-non-tiled fields are also discussed. The versatility of the NAM provides the possibility to analyze information on impacts of changing conservation practices and enables identification of conservation gains and remaining conservation needs at the national scale.

Cost effectiveness, nitrogen, and phosphorus removal in field-based woodchip bioreactors treating agricultural drainage water

Plauborg, F., Skjødt, M. H., Audet, J., Hoffmann, C. C., Jacobsen, B. H. — Sat, 01 Jul 2023 13:30:24 +0200

Nitrogen (N) and phosphorus (P) losses to surface and coastal waters are still critically high across Europe and globally. Measures to mitigate and reduce these losses are being implemented both at the cultivated land surface and at the edge-of-fields. Woodchip bioreactors represent a new alternative in Denmark for treating agricultural drainage water, and the present study—based on two years of data from five Danish field-based bioreactors—determined N removal rates varying from 1.49 to 5.37 g N m⁻³ d⁻¹ and a mean across all bioreactors and years of 2.90 g N m⁻³ d⁻¹. The loss of phosphorus was relatively high the first year after bioreactor establishment with rates varying from 298.4 to 890.8 mg P m⁻³ d⁻¹, but in the second year, the rates ranged from 12.2 to 77.2 mg P m⁻³ d⁻¹. The investments and the costs of the bioreactors were larger than expected based on Danish standard investments. The cost efficiency analysis found the key issues to be the need for larger investments in the bioreactor itself combined with higher advisory costs. For the four woodchip bioreactors considered in the cost efficiency analysis, the N removal cost was around DKK 350 per kg N ($50 per kg N), which is ca. 50% higher than the standard costs defined by the Danish authorities. Based on the estimated costs of the four bioreactor facilities included in this analysis, a bioreactor is one of the most expensive nitrogen reduction measures compared to other mitigation tools.

Nitrogen and phosphorus losses in Nordic and Baltic agricultural monitoring catchments – Spatial and temporal variations in relation to natural conditions and mitigation programmes

Kyllmar, K., Bechmann, M., Blicher-Mathiesen, G., et al. — Fri, 01 Sep 2023 13:30:24 +0200

Nitrogen (N) and phosphorus (P) losses via agricultural drainage water have negative impacts on receiving water bodies and large-scale programmes to reduce nutrient losses have been established in the Nordic and Baltic countries, together with agricultural catchment monitoring programmes. This study evaluated time series (9–40 years) of data from 34 selected Nordic-Baltic catchments for spatial and temporal variations in area-specific water discharge (mm) and in concentrations and transport of total nitrogen (TN) and total phosphorus (TP). Water discharge from the catchments varied from 125 mm (Denmark) to > 1000 mm (Norway). Catchments with low TN concentrations (≤3 mg L^-1) were dominated by clay or grass leys or were undrained with reduction of nitrate (NO₃) in shallow groundwater. Catchments with high TN concentrations (≥10 mg L^-1) had loams and cereal crops. TP concentrations were highest (≥0.45 mg L^-1) in catchments with erosive soils, relatively high water discharge and cereal crops, and lowest (≤0.07 mg L^-1) in catchments with permeable soils. Generalised additive mixed model (GAMM) analysis of time series of transport and flow-weighted concentrations of TN and TP for temporal patterns revealed decreases in TN concentrations in seven catchments and increases in eight, while four had periods with opposing trends. TN concentrations decreased in Denmark and Sweden in 1990–2010, following introduction of mitigation programmes. TP concentrations decreased in eight catchments and increased in six, while one showed opposing trends. Decreases in TP coincided with improved P balance in catchments with sand and loam. To further reduce N and P losses, a tailored set of mitigation measures is needed for each combination of soil, climate, geohydrology and agricultural production. Intensive monitoring of small catchments can reveal how N and P losses relate to natural conditions and to changes in agricultural production.

Minivådområder tilbageholder tungmetaller

Nilsson, I. F., Hoffmann, C. C., Kristiansen, S. M. — Mon, 01 May 2023 13:30:24 +0200