Scientific Results

This catalogue is obtained by conducting a systematic literature review of scientific studies and reviews related to monitoring, forecasting, and simulating the inland water cycle. The analysis maps scientific expertise across research groups and classifies findings by the type of inland water studied, application focus, and geographical scope. A gap analysis will identify missing research areas and assess their relevance to policymaking.

ID ▲ Type Year Authors Title Venue/Journal DOI Research type Water System Technical Focus Abstract Link with Projects Link with Tools Related policies ID
publications-1161 PEER REVIEWED ARTICLE 2014 Giri Kattel , Peter Gell , Marie-Elodie Perga , Erik Jeppesen , Rosie Grundell , Sandra Weller , Atun Zawadzki , Linda Barry Tracking a century of change in trophic structure and dynamics in a floodplain wetland: integrating palaeoecological and palaeoisotopic evidence 10.1111/fwb.12521 Data Management & Analytics Natural Water Bodies Summary The palaeoecological assessment, and the use of stable isotopes of carbon in subfossils of herbivores and omnivores, represents a novel approach to understand transitions in past food‐web structure and the dynamics of lake ecosystems in response to natural perturbations and human impacts. Combined with records of subfossil assemblages of cladocerans and chironomids, it may be possible to decipher whether changes are attributable to external forces or internally derived system shifts. A sediment record taken from the shallow (2.3 m depth) Kings Billabong in the River Murray floodplain (Australia) was analysed to explore changes in trophic dynamics over the past century. The palaeoecological assessment revealed that littoral assemblages of cladocerans and benthic diatoms were gradually replaced by planktonic (planktonic and facultative planktonic) assemblages after river regulation in the 1920s. The stable isotopic composition of carbon (δ13C), derived from chironomid head capsules, was relatively constant down‐core, ranging between −26.1‰ and −24.0‰, and coincided largely with the δ13C of bulk sediment samples (−25.6‰ to −22.0‰). The δ13C values of pelagic (Daphnia) and ubiquitous (Bosmina, Alona) cladocerans, however, varied markedly, with that for Daphnia between −29.8‰ (10–20 cm) and −23.2‰ (60–70 cm), and for ubiquitous cladocerans, between −29.4‰ (20–30 cm) and −24.5‰ (80–70 cm). The temporal changes in the δ13C values of cladocerans also suggest a gradual transition from a macrophyte‐dominated state to a phytoplankton‐dominated state after river regulation and further indicate changes in the horizontal migration behaviour of Daphnia depending on macrophyte abundance and predation risk. Our study demonstrates the potential of reconstructing, more precisely, the trophic dynamics of large river floodplain lakes and their ecological resilience by combining subfossil analyses with stable isotope analyses of selected subfossil groups. 603378
publications-1162 PEER REVIEWED ARTICLE 2014 Saara Olsen , Erik Jeppesen , Brian Moss , Korhan Özkan , Meryem Beklioğlu , Heidrun Feuchtmayr , María González Sagrario , Li Wei , Søren Larsen Factors influencing nitrogen processing in lakes: an experimental approach 10.1111/fwb.12511 Data Management & Analytics Natural Water Bodies Summary To help improve our understanding of the nitrogen cycle in lakes, particularly in the context of climate change, we analysed total nitrogen (TN) and nitrate (‐N) data from six mesocosm experiments (in Denmark, U.K., China and Turkey) covering different climatic regions. We assessed the effects of nitrogen (N) and phosphorus (P) loading, temperature, salinity and water level on N processing. Water column N loss (defined as the nitrogen processed in and lost from the water column in units of net amount processed per unit area and per unit of time, or in relative terms as the percentage loss of the total pool in 2 weeks) was particularly sensitive to external nutrient loading to the mesocosms. Mean water column TN loss at high N loading varied from 111 to 250 mg m−2 day−1 and increased with N loading. High P loading resulted in increased water column N loss, possibly because of increased uptake into plants and attached algae and sedimentation of the increased algal crop. High salinity generally decreased water column TN loss; on average, 10% more TN was in the water column at 12‰ salinity than at 2‰ salinity, while no significant effect of water level was found. Only weak relationships were observed between N processing and temperature, and mesocosms limited by P accumulated more nitrogen in their water columns than those with high P loadings. Our results suggest that N processing in lakes appears to be more sensitive to features of the catchment, such as hydrology and loading, than to climatic effects related to temperature, salinity and water level. 603378
publications-1163 PEER REVIEWED ARTICLE 2017 Joachim Audet , Érika M. Neif , Yu Cao , Carl C. Hoffmann , Torben L. Lauridsen , Søren E. Larsen , Martin Søndergaard , Erik Jeppesen , Thomas A. Heat-wave effects on greenhouse gas emissions from shallow lake mesocosms 10.1111/fwb.12930 Uncategorized Natural Water Bodies Abstract Shallow lakes are a key component of the global carbon cycle. It is, therefore, important to know how shallow lake ecosystems will respond to the current climate change. Global warming affects not only average temperatures, but also the frequency of heat waves (HW). The impact of extreme events on ecosystems processes, particularly greenhouse gas (GHG) emissions, is uncertain. Using the world's longest‐running shallow lake experiment, we studied the effects of a simulated summer HW on the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The experimental mesocosms had been exposed to different temperature treatments and nutrient loading for 11 years prior to the artificial HW. In general, there was an increase in total GHG emissions during the 1‐month artificial HW, with a significant increase in CO2, CH4 and N2O being observed in the shallow lake mesocosms. No significant effect of the HW on CO2 emissions could be traced, though, in the mesocosms with high nutrient levels. Furthermore, the data suggested that in addition to the direct effect of increased temperature on metabolic processes during the HW, biotic interactions exerted a significant control of GHG emissions. For example, at low nutrient levels, increased CO2 emissions were associated with low macrophyte abundance, whereas at high nutrient levels, decreased phytoplankton abundance was linked to increased emissions of CO2 and CH4. In contrast to the observable heat‐wave effect, no clear general effect of the long‐term temperature treatments could be discerned over the summer, likely because the potential effects of the moderate temperature increase, applied as a press disturbance, were overridden by biotic interactions. This study demonstrates that the role of biotic interactions needs to be considered within the context of global warming on ecosystem processes. 603378
publications-1164 PEER REVIEWED ARTICLE 2016 Péter Borza , Thomas Huber , Patrick Leitner , Nadine Remund , Wolfram Graf Current velocity shapes co-existence patterns among invasive Dikerogammarus species 10.1111/fwb.12869 Data Management & Analytics Natural Water Bodies Summary Facilitative interactions among co‐evolved representatives of the endemic Ponto‐Caspian fauna are regarded as a major factor of their invasion success. Nevertheless, the most renowned examples represent interactions between different trophic levels or functional groups, while ecologically similar species can be expected to show competition‐based niche partitioning. Here, we test for differences in the realized niche of three invasive Dikerogammarus species (Crustacea: Gammaridae) in their co‐occurring range. We sampled multiple habitats within sites distributed along the River Danube to test whether some environmental variables could reveal spatial niche differentiation among the three species of Dikerogammarus, and if so, to test a predictive model outside the zone of co‐occurrence. Spatial niche differentiation was present among the species, primarily determined by current velocity (and associated substrate preference), likely reflecting a stress tolerance–competitive ability trade‐off. Suspended matter concentration was also relevant, suggesting food resources (through filter feeding) might represent another important niche axis, somewhat loosening the terms of co‐existence between D. haemobaphes and the other two species. Environmental variables could effectively explain the absence of D. bispinosus in the Lower Danube, implying that the co‐existence of the three species is possible only along a sufficiently wide current velocity gradient, and the observed turnovers are the result of niche expansion in the absence of the stronger competitor. Hence, differences in invasion success may be attributed to a stress tolerance–competitive ability trade‐off. Our results suggest the advantage of D. villosus is attributable to its competitive dominance, allowing it to monopolize lentic and/or structured habitats, which represents a fortunate pre‐adaptation to anthropogenic alterations of aquatic ecosystems. The presence of D. villosus does not greatly affect the expansion of D. haemobaphes; however, the exclusion of D. bispinosus from lentic habitats by D. villosus probably strongly limits its potential to spread by active dispersal. 603378
publications-1165 PEER REVIEWED ARTICLE 2017 Sandra Brucet , Ülkü Nihan Tavşanoğlu , Arda Özen , Eti Ester Levi , Gizem Bezirci , Ayşe İdil Çakıroğlu , Erik Jeppesen , Jens-Christian Sv Size-based interactions across trophic levels in food webs of shallow Mediterranean lakes 10.1111/fwb.12997 AI & Machine Learning Natural Water Bodies Abstract Body size is a key trait of an organism which determines the dynamics of predator–prey interactions. Most empirical studies on the individual size distribution of the aquatic community have focused on the variations in body size of a single trophic level as a response to certain environmental variables or biotic factors. Few studies, however, have evaluated how individual size structure is altered simultaneously across interacting trophic levels and locations. Such comparative examinations of the size distribution in predator and prey communities may bring insight into the strength of the interactions between adjacent trophic levels. We assessed the potential predation effect of size‐structured predators (i.e. predation by individuals of different sizes) on prey size structure using data from 30 shallow Turkish lakes spanning over five latitudinal degrees. We correlated size diversity and size evenness of predator and prey assemblages across the planktonic food web after accounting for the confounding effects of temperature and resource availability which may also affect size structure. We expected to find a negative relationship between size diversity of predators and prey due to the enhanced strength of top‐down control with increasing predator size diversity. We also hypothesised that competitive interactions for resources in less productive systems would promote a higher size diversity. We further expected a shift towards reduced size diversity and evenness at high temperatures. In contrast to our hypothesis, we found a positive correlation between size structures of two interacting trophic levels of the planktonic food web; thus, highly size‐diverse fish assemblages were associated with highly size‐diverse zooplankton assemblages. The size evenness of fish and phytoplankton assemblages was negatively and positively related to temperature, respectively. Phytoplankton size diversity was only weakly predicted by the resource availability. Our results suggest that size structure within a trophic group may be controlled by the size structure at adjacent trophic levels, as well as by temperature and resource availability. The positive relationship between the size diversity of fish and zooplankton suggests that higher diversity of the resources drives a higher size diversity of consumers or vice versa, and these effects are beyond those mediated by taxonomic diversity. In contrast, the size diversity and size evenness of phytoplankton are mainly influenced by physical factors in this region and perhaps in warm shallow lakes in general. 603378
publications-1166 PEER REVIEWED ARTICLE 2017 Ersoy, Z., Jeppesen, E., Sgarzi, S., Arranz, I., Cañedo-Argüelles, M., Quintana, X, D., Landkildehus, F., Lauridsen, T. L., Bartrons, M., Brucet, S. Size-based interactions and trophic transfer efficiency are modified by fish predation and cyanobacteria blooms in Lake Mývatn, Iceland 10.1111/fwb.13039 Data Management & Analytics River Basins Abstract Trophic cascade studies have so far mostly focused on changes in the abundance, biomass, or average size of prey and predators. In contrast, individual size‐based interactions, playing a key role in the trophic structure and functioning of aquatic ecosystems, have been less explored. We conducted a 3‐month in situ experiment in Lake Mývatn, Iceland, with two fish treatments (with and without fish, Gasterosteus aculeatus). After the first month of the experiment, Anabaena blooms appeared in the lake. We studied the effects of fish predation and occurrence of cyanobacteria blooms on the individual size structure (i.e. the distribution of the number of organisms over a size range) of zooplankton and phytoplankton. We also assessed the potential consequences for trophic transfer efficiency (TTE) (measured as the predator to prey biomass ratio) in the planktonic food web. Our results showed that fish predation and cyanobacteria bloom had a negative relationship with size diversity of zooplankton, which became dominated by small‐sized individuals in both cases. The phytoplankton size diversity changed over time particularly due to the blooming of large‐sized Anabaena, and its increase was apparently mainly driven by changes in resources. Low zooplankton size diversity related to fish predation reduced TTE, particularly in the enclosures with fish. This may be because low zooplankton size diversity represents a lower partition of resources among consumers, thereby decreasing the trophic energy transfer. With the occurrence of Anabaena bloom, high phytoplankton size diversity coincided with a lower energy transfer in all enclosures likely due to reduced zooplankton grazing when large‐sized colony‐forming Anabaena dominated. In conclusion, our results indicate that both top‐down and bottom‐up forces significantly influence the size structure of planktonic communities. The changes in size structure were related to shifts in the energy transfer efficiency of the Lake Mývatn food web. Thus, our study underpins the importance of taking into account size‐based interactions in the study of trophic cascades, particularly in a warming climate where strong planktivorous fish predation and frequent cyanobacteria blooms may occur. 603378
publications-1167 PEER REVIEWED ARTICLE 2016 Emma Göthe , Annette Baattrup-Pedersen , Peter Wiberg-Larsen , Daniel Graeber , Esben A. Kristensen , Nikolai Friberg Environmental and spatial controls of taxonomic versus trait composition of stream biota 10.1111/fwb.12875 Uncategorized River Basins Summary The spatial organisation of biotic communities derives from factors operating at a wide range of spatial and temporal scales. Despite strong scientific evidence of prevalent spatial control of community composition in freshwater ecosystems, local environmental factors are often considered as the main drivers of community change. Furthermore, taxonomic approaches are most frequently used, and few studies have compared the relative importance of local and regional control of trait versus the taxonomic composition in stream ecosystems. Using a spatially dense data set covering all stream sizes in a lowland European region of c. 42 000 km2 and three organism groups (macrophytes, macroinvertebrates and fishes), we compared the relative importance of spatial and environmental determinants of species and trait composition in the study streams, classified into headwaters (stream order 1–2) and downstream sites (stream order >2). We hypothesised that (i) there is a higher correspondence between environmental conditions and trait composition than with species composition, (ii) dispersal limitation (pure spatial structuring) is greater in headwaters than in downstream sites and (iii) dispersal limitation (pure spatial structuring) is weakest for macroinvertebrates, intermediate for macrophytes and strongest for fishes. The most consistent pattern across organisms and stream order groups was a higher correspondence between environmental variation and trait composition as well as a higher number of environmental variables significantly related to trait composition than with species composition (hypothesis 1). Spatial structuring peaked in headwater macrophyte communities and downstream fish communities (hypotheses 2 & 3) – a pattern that was amplified when separate analyses of traits describing species dispersal potential were undertaken. Our study highlights the potential of traits to capture multiple environmental changes in stream ecosystems and illustrates how organism‐specific and highly context‐dependent patterns in community organisation can emerge as a consequence of interactions between habitat connectivity (i.e. top versus lower parts of the stream network) and organism dispersal potential. 603378
publications-1168 PEER REVIEWED ARTICLE 2017 Beibei Hao , Haoping Wu , Yu Cao , Wei Xing , Erik Jeppesen , Wei Li Comparison of periphyton communities on natural and artificial macrophytes with contrasting morphological structures 10.1111/fwb.12991 Data Management & Analytics River Basins Abstract It remains an open question whether or not artificial macrophytes are good alternatives to natural macrophytes in studies of periphyton abundance and composition in lakes. Here, a mesocosm experiment was conducted in winter (when plant growth is low) to compare simultaneously the periphyton community on three submerged macrophytes (Potamogeton lucens, Vallisneria sp. and Cabomba caroliniana) with contrasting leaf structural complexities (leaf fractal dimension = 1.12, 1.17 and 1.37, respectively) and on three types of artificial macrophytes with similar morphologies as the natural plants. We also compared intertreatment differences in phytoplankton sampled from mesocosms. Both for natural and artificial macrophytes, the periphyton chlorophyll a (Chl‐a) was positively associated with leaf fractal dimension. Although the morphological structure of natural and artificial plants and the physicochemical characteristics of the water were similar, the periphyton community differed between natural and artificial macrophytes, with the difference being dependent on the leaf structural complexity of the macrophytes. For leaves with a simple structural complexity, the abundance and composition of periphyton on natural and artificial plants were not statistically different. In addition, periphyton Chl‐a, density and biovolume were higher on the adaxial side than on the abaxial side of natural P. lucens leaves, but no differences were found between sides of the artificial leaves. For leaves with a medium structural complexity, the abundance of periphyton was lower on the natural than artificial plants, and the proportion of diatoms to the total community differed. For leaves with a high structural complexity, periphyton Chl‐a of the artificial plants was notably higher than on the natural plants, while no significant differences were found for periphyton density, biovolume, and the proportion of diatoms and green algae. Permutational multivariate analysis of periphyton genus composition confirmed that periphyton composition on the artificial plants (medium and high leaf structural complexities) was different overall from that on the natural plants. Phytoplankton Chl‐a, density, biovolume, and diversity did not show any pronounced differences among treatments. Our results suggest that artificial macrophytes cannot fully substitute for natural plants even when they are morphologically similar. Artificial macrophytes should therefore be used with caution when investigating the periphyton community on macrophytes. 603378
publications-1169 PEER REVIEWED ARTICLE 2017 Érika M. Neif , Daniel Graeber , Liliana Rodrigues , Simon Rosenhøj-Leth , Tinna M. Jensen , Peter Wiberg-Larsen , Frank Landkildehus , Tenna Riis , Responses of benthic algal communities and their traits to experimental changes in fine sediments, nutrients and flow 10.1111/fwb.12965 Uncategorized River Basins Summary Lowland stream ecosystems are subjected to multiple anthropogenic stressors, usually nutrient enrichment in combination with sedimentation of fine particles and low flow periods in summer. Here, we investigated the temporal development of the benthic algae community in response to these three stressors and linkages to the trait characteristics of the community to explore the mechanisms responsible for stress‐induced community changes. We investigated the response of benthic algae species composition, traits (life forms, cell size categories), biovolume and chlorophyll a (Chl‐a) concentration to low flow in combination with nutrient enrichment and fine sedimentation in twelve large outdoor stream flumes (12 m long) resembling small streams in size and habitat characteristics. The experiment consisted of two phases: a normal‐flow phase followed by a low‐flow phase (90% current velocity reduction), each spanning 4 weeks. We applied a eutrophication scenario (mean increases of 1.14–5.48 mg N/L and 0.01–0.06 mg P/L in the flumes for dissolved inorganic nitrogen and phosphate respectively) throughout the experiment. Under low flow, we supplemented this with a fine sedimentation scenario (>90% stream bed cover). We took samples once in the normal‐flow phase and every week during the low‐flow phase. We observed strong responses in the benthic algae community to sudden changes in low flow and fine sedimentation, mediating rapid species turnover with a decreased algal biovolume and increased abundance of large, motile species. However, we did not observe any pronounced responses to nutrient enrichment. In contrast to the observations for other variables, we found a continuous increase in Chl‐a concentration during low flow. This was likely due to continuous fine sedimentation during this phase, reducing light availability which probably resulted in an increase of cell‐level Chl‐a concentration in response to light limitation and lower rates of light‐induced Chl‐a degradation. The rapid response of the benthic algal community to the applied stressors suggests that even short periods of major stressor exposure may significantly affect benthic algae in lowland systems. We suggest that short‐term stress events may have cascading effects on several important ecosystem processes given the importance of benthic algae for the productivity of these systems. 603378
publications-1170 PEER REVIEWED ARTICLE 2017 Saara Olsen , Yu Cao , María Florencia Gutierrez , Sandra Brucet , Frank Landkildehus , Torben L. Lauridsen , Thomas A. Davidson , Martin Søndergaar Effect of a nitrogen pulse on ecosystem N processing at different temperatures: A mesocosm experiment with 15 NO 3 − addition 10.1111/fwb.12940 Data Management & Analytics River Basins Abstract Shallow lakes may play an important role for the nitrogen (N) balance in drainage basins by processing, transferring and retaining N inputs. An increase in the frequency of storm‐induced short‐term N pulses and increased water temperatures are both likely outcomes of climate change, potentially affecting the N processing in lakes. An experiment with a K15NO3− pulse addition (increase in NO3− concentration from c. 0.1 to 2 mg/L) was carried out in 12 mesocosms with relatively low (applies to Danish lakes) total N (TN) and total phosphorus (TP) concentrations (c. 0.3 mg N L−1 and 0.04 mg P L−1) to assess the effects of an N pulse on N processing and storage in shallow lake ecosystems. The mesocosms have a hydraulic retention time of approximately two and a half months, and at the time of the experiment, they had been adapted to contrasting temperatures for a period of 10 years: ambient, T3 (heating according to the Intergovernmental Panel on Climate Change 2007 A2 scenario, +3.7–4.5°C, depending on season) and T5 (heating with A2 + 50%, +4.9–6.6°C). Macrophytes and filamentous algae retained up to 40% and 30% of the added 15N, respectively, reflecting their high biomass in the mesocosms. Macrophytes and filamentous algae constituted between 70% and 80% of the biomass of all primary producers during the experiment in the T3 and ambient treatments and between 20% and 40% in T5. By comparison, less than 1% of the added 15N diffused to the sediment and less than 5% was lost to the atmosphere as N2 gas. Snails represented the long‐term storage of 15N, retaining up to 6% of the tracer and with detectable enrichment 100 days after tracer addition. We found no significant differences among the temperature treatments in the 15N turnover after pulse dosing. However, a larger percentage of 15N was stored in macrophytes in the ambient and T3 mesocosms, reflecting higher biomasses than in T5 where filamentous algae were more abundant. Macrophytes and filamentous algae rather than temperature were therefore key controllers of N processing during the summer N pulse in these shallow, relatively low TP lakes. 603378