Erik Jeppesen

Aarhus University | AU · Department of Bioscience

In lakes, phytoplankton sequester atmospheric carbon dioxide (CO2) and store it in the form of biomass organic carbon (OC); however, only a small fraction of the OC remains buried, while the remaining part is recycled to the atmosphere as CO2 and methane (CH4). This has the potential effect of adding CO2-equivalents (CO2-eq) to the atmosphere and p...

The growing use of sensors in fresh waters for water quality measurements generates an increasingly large amount of data that requires quality assurance (QA)/quality control (QC) before the results can be exploited. Such a process is often resource-intensive and may not be consistent across users and sensors. SentemQC (QA-QC of high temporal resolu...

Net ecosystem production (NEP) is an important indicator of lake ecosystem function and integrity. An earlier study, restricted to one geographical region, indicated that oxygen saturation levels (DO%) might be used to predict daily NEP in shallow lakes. To test the generality of the method, we used DO% data collected in a standardised pan-European...

We are delighted to invite you to the "15th International Conference on Salt Lake Research (ICSLR'24)", scheduled to be held in the scenic city of Antalya, Türkiye, from November 4-8, 2024. Since the first event, the ICSLR series has established itself as a milestone conference in saline lake research encompassing broader ecological, management an...

Biomanipulation by piscivore stocking has been widely used for restoration of temperate shallow lakes, but long-term results have been mixed. In warm (i.e., subtropical/tropical) lakes where omni-benthivorous fish prevail, the effects of piscivore stocking on small fish, plankton communities, and water quality have not been well elucidated yet. Her...

Filter-feeding bivalves have strong effects on ecosystem processes and functions. Bivalves may be used for the rehabilitation of eutrophic waters, either by being placed suspended in cages or on chains in pelagic habitats or stocked in benthic habitats. However, the effects of bivalves on the ecosystem may differ between the two habitats. A 5-week...

Harmful algal blooms (HABs) are a significant threat to freshwater ecosystems, and monitoring for changes in biomass is therefore important. Fluorescence in-situ sensors enable rapid and high frequency real-time data collection and have been widely used to determine chlorophyll- a (Chla) concentrations that are used as an indicator of the total alg...

Deep chlorophyll maximum (DCM), a chlorophyll peak in the water column, has important implications for biogeochemical cycles, energy flow and water surface algal blooms in deep lakes. However, how an observed periodically asymmetric DCM response to environmental variables remains unclear, limiting our in-depth understanding and effective eco-enviro...

Terrestrial hydrological and nutrient cycles are subjected to major disturbances by agricultural operations and urbanization that profoundly influence freshwater resources. Non‐point source pollution is one of the primary causes for water quality deterioration, and thus an emerging imperative in limnology is establishing empirical models that conne...

Shallow lakes and ponds play a crucial role in the processing of carbon and other nutrients. However, many lakes and ponds worldwide are affected by climate change and nutrient pollution. How these pressures affect the emission of the greenhouse gas nitrous oxide (N2O) is unclear. Warming and eutrophication are expected to increase the production a...

The combined impacts of anthropogenic activities and global climate changes threaten native fish communities. Such threats are particularly critical in biodiversity hot spot areas with many endemic species, as exemplified by the isolated Yun‐Gui Plateau, China. The risk of biotic homogenization is also expected to be high in such areas, but this ri...

Artificial emergency water source lakes have been built in most cities in the middle and lower reaches of the Yangtze River, China, to ensure water safety for residents. However, these new ecosystems prone to algal blooms or other degraded water quality conditions. A newly built water supply lake in the lower reaches of the Yangtze River was select...

1. The combined impacts of anthropogenic activities and global climate changes threaten native fish communities. Such threats are particularly critical in biodiversity hot spot areas with many endemic species, as exemplified by the isolated Yun-Gui Plateau, China. The risk of biotic homogenization is also expected to be high in such areas, but this...

Climate-driven changes in temperature and high nutrient inputs from anthropogenic activities significantly impact the interactions between submerged macrophytes and phytoplankton, potentially causing regime shifts in shallow freshwater lakes. Cyanobacteria, in particular, are predicted to become dominant among the phytoplankton under climate change...

The aquatic environment in lake ecosystems is greatly affected by human activities and global climate change, while studies on the cascading effects on water environments using a holistic approach are scarce. We employed generalized least squares (GLS) modeling to assess the annual trends in water quality of Lake Poyang from 1983to 2018 and found t...

Unexpectedly, the 10-year fishing ban in the Yangtze River has quickly expanded to almost all of the adjacent isolated lakes, where fish resources have been already abundant due to high primary productivity and intensive artificial stocking. Things have worsened in most of these lakes due to an overcrowding of fish. The dense population of fish, es...

The state transition theory suggests that the decline of submerged macrophytes in shallow lakes is closely associated with reduced stoichiometric homeostasis, particularly phosphorus homeostasis (HP). The degradation typically progresses from deeper to shallower regions, indicating a potential positive correlation between the deepwater adaptabil...

Understanding how the causal feedback between phytoplankton and environmental drivers controlling the chlorophyll a (Chl a, as a proxy of phytoplankton biomass)–nutrient relationships are modulated under different ecosystem conditions is a major challenge in aquatic ecology. Using an empirical dynamic model (convergent cross mapping) on a 20‐yr dat...

Phytoplankton has been used as a paradigm for studies of coexistence of species since the publication of the “paradox of the plankton.” Although there are a wealth of studies about phytoplankton assemblages of lakes, reservoirs and rivers, our knowledge about phytoplankton biodiversity and its underlying mechanisms in mountain headwater stream ecos...

We investigated the individual and combined impacts of manipulation of submerged macrophytes, large-bodied cladocerans, and nutrients on plankton communities in a tropical hypereutrophic shallow reservoir. We tested how the addition of the macrophyte Ceratophyllum demersum, the cladoceran Sarsilatona serricauda, and nutrients affected phytoplankton...

Sediment properties have a crucial effect on the growth and recovery of aquatic plants in lakes. Addition of various chemical substances has been proposed to reinforce the recovery of plants after a nutrient loading reduction. However, the effects of such sediment amendments on plant growth, especially those from rhizosphere microorganisms, is limi...

Sustainable development depends on the integration of the economy, society, and environment. Yet, escalating environmental challenges pose threats to both society and the economy. Despite progress in addressing environmental issues to promote sustainability, knowledge gaps in scientific research, technological advancement, engineering practice, and...

Biological invasions are among the most serious threats to ecosystems. The golden apple snail Pomacea canaliculata (Lamarck, 1822) is considered one of the top 100 worst invasive alien species in the world. These snails consume benthic primary producers, including submerged macrophytes, which may lead to an increase in nutrient concentration in the...

Submerged macrophytes are crucial for the restoration of shallow eutrophic lake but they are diminished in coverage or lost with eutrophication. Their recovery after nutrient loading reduction depends on water and sediment nutrient levels. We studied the combined impacts of sediment fertility (low/high nitrogen and phosphorus content) and water nut...

Phytoplankton communities are crucial components of aquatic ecosystems, and since they are highly interactive, they always form complex networks. Yet, our understanding of how interactive phytoplankton networks vary through time under changing environmental conditions is limited. Using a 29-year (339 months) long-term dataset on Lake Taihu, China,...

Cultural eutrophication is the main cause of the decline of submerged plants in freshwater ecosystems. While many studies have focused on the nutrient uptake by the roots of these plants, less attention has been given to the effects of eutrophication on root structure. We designed a mesocosm experiment with Eurasian watermilfoil (Myriophyllum spica...

Because of the first observations in the 1900s of the oligotrophic and eutrophic states of lakes, researchers have been interested in the process that makes lakes become turbid because of high phytoplankton biomass. Definitions of eutrophication have multiplied and diversified since the mid‐20th century, more than for any other ecological process....

Because of the first observations in the 1900s of the oligotrophic and eutrophic states of lakes, researchers have been interested in the process that makes lakes become turbid because of high phytoplankton biomass. Definitions of eutrophication have multiplied and diversified since the mid-20th century, more than for any other ecological process....

Shallow lakes are often rich in submerged macrophytes that play an important role in functioning of shallow lake ecosystems. Omnivorous fish can intensify eutrophication by enhancing the growth of phytoplankton, leading to higher water turbidity and light attenuation with negative effect on the growth of submerged macrophytes. However, the effects...

The global wastewater surge demands constructed wetlands (CWs) to achieve the UN’s Sustainable Development Goals (SDG); yet the pollutant removal interactions and global sustainability of small CWs are unclear. This study synthesizes small CW data from 364 sites worldwide. The removal efficiency of organic matter and nutrient pollutants of small CW...

Climate change is one of the most significant challenges worldwide in the Anthropocene, and it is predicted to importantly affect biological diversity, especially in freshwaters. Freshwater fishes are facing considerable global threats, particularly in eco-sensitive semi-arid to arid areas such as the Arabian Peninsula, which is considered a highly...

The impact of global warming on plant abundance has been widely discussed, but it remains unclear how warming affects plant physiological traits, and how these traits contribute to the abundance of aquatic plants. We explored the adjustments in physiological traits of two common aquatic plant species (Potamogeton crispus L. an Elodea canadensis Mic...

The impact of global warming on plant abundance has been widely discussed, but it remains unclear how warming affects plant physiological traits, and how these traits contribute to the abundance of aquatic plants. We explored the adjustments in physiological traits of two common aquatic plant species (Potamogeton crispus L. an Elodea canadensis Mic...

Aquatic plants play a key role in the structuring and functioning of shallow lake ecosystems. However, eutrophication often triggers shifts in plant communities and species diversity, especially in the early stages when the water is still clear. Additionally, water depth is an important factor regulating aquatic plant communities. We conducted a 50...

Lakes are hotspots for the biogeochemical processing of carbon, including dissolved organic matter (DOM). A less degradable fraction of DOM, preserved for a long time, can be categorized as recalcitrant DOM (RDOM). Lake RDOM is an important but neglected carbon sink, and its characteristics and transformation processes remain largely unknown. Highl...

We used biological and physical responses at 71 shallow waterbodies with contrasting nutrient levels undergoing recovery from eutrophication to predict potential changes in waterbird species abundance, an important component of lake ecosystems. These general predictions were tested using 28 years of breeding waterbird data from three Danish shallow...

The alarming increase in the frequency of blooms of Microcystis in freshwater lakes and reservoirs occurs worldwide, with major implications for their ecosystem functioning and water quality. The dominance of Microcystis is tightly related to colonial formation by Microcystis. However, studies of the colonial development of Microcystis morphospecie...

Invasion of zebra mussels (Dreissena polymorpha) can have profound effects on lake ecosystems. We investigated the overall ecological effects after invasion and fast expansion of zebra mussels in eight lakes in Denmark belonging to the same watercourse systems but with different morphological and eutrophication characteristics. A few years after th...

Harmful algal blooms (HABs) are a significant threat to freshwater ecosystems, and monitoring for changes in biomass is therefore important. Fluorescence in-situ sensors enable rapid and high frequency real-time data collection and have been widely used to determine chlorophyll- a (Chla) concentrations that are used as an indicator of the total alg...

Ecological resilience is critical for ecosystems to persist in the face of perturbations without shifting to a different state. Global biodiversity loss in multiple ecosystems is considered to be associated with decreasing ecological resilience and increasing the risk of ecosystem collapse. However, how temporal changes in biodiversity affect ecolo...

Using data on 23 Danish lakes, we conducted mass balances to develop total nitrogen (TN) models for predicting annual mean TN in lakes based on external TN loading and found high predictability when including lake hydraulic retention time and mean depth in the model. We further used a unique 30-year mass balance data series from 10 Danish lakes wit...

The Water Framework Directive (WFD) requires actions from European Union Member States to reduce external nutrient loading in lakes of moderate/poor/bad ecological status and restore their good ecological status. Several poor-quality Danish lakes have been exempted from WFD criteria (and more proposed), due to suspected major imported nutrient cont...

Changes in salinity have a profound influence on ecological services and functions of inland freshwater ecosystems, as well as on the shaping of microbial communities. Bacterioplankton, generally classified into free-living (FL) and particle-attached (PA) forms, are main components of freshwater ecosystems and play key functional roles for biogeoch...

Phytoplankton taxa are strongly interconnected as a network, which could show temporal dynamics and non-linear responses to changes in drivers at both seasonal and long-term scale. Using a high quality dataset of 20 Danish lakes (1989-2008), we applied extended Local Similarity Analysis to construct temporal network of phytoplankton communities for...

Classic biogeography provides the context for understanding why largescale patterns of biodiversity occur where they do. However, over the past half century, human activities have greatly changed biogeographic patterns and caused accelerating loss of biodiversity on the earth. In spite of the Launch of Conservation Biogeography a couple of decades...

Protected areas are critical for providing ecosystem services. However, studies on the effect of protected areas on ecosystem service enhancement remain lacking, which restricts efficient protected area management. In this study, a statistical matching approach was used to analyze the role of 637 protected areas in China in enhancing ecosystem serv...

Primary producers form the base of lake ecosystems and, due to their often short lifecycles, respond rapidly to changing conditions. As the Arctic is warming nearly four times faster than the global average, we see major shifts in environmental conditions, which impacts lake ecosystem functioning. Previous studies have found a general increase in p...

Aquatic ecosystems are threatened by eutrophication from nutrient pollution. In lakes, eutrophication causes a plethora of deleterious effects, such as harmful algal blooms, fish kills and increased methane emissions. However, lake-specific responses to nutrient changes are highly variable, complicating eutrophication management. These lake-specifi...

Terrestrial inputs and subsequent degradation of dissolved organic matter (DOM) in lake ecosystems can result in rapid depletion of dissolved oxygen (DO). Inputs of terrestrial DOM including organic acids can also lead to decreases in pH. However, to date, few studies have investigated the linkages between terrestrial DOM inputs, DO and pH levels i...

Shallow lake ecosystems are particularly prone to disturbances such as pulsed dissolved organic matter (allochthonous-DOM; hereafter allo-DOM) loadings from catchments. However, the effects of allo-DOM with contrasting quality (in addition to quantity) on the planktonic communities of microbial loop are poorly understood. To determine the impact of...

Due to the large spatiotemporal variability in the processes controlling carbon emissions from lakes, estimates of global lake carbon emission remain uncertain. Identifying the most reliable predictors of CO2 and CH4 concentrations across different hydrological features can enhance the accuracy of carbon emission estimates locally and globally. Her...

The combination of chemical phosphorus (P) inactivation and submerged macrophyte transplantation has been widely used in lake restoration as it yields stronger effects than when applying either method alone. However, the dose effect of chemical materials on P inactivation when used in combination with submerged macrophytes and the influences of the...

When restoring shallow lakes, the recovery of submerged macrophytes is of vital importance to obtain clear water conditions. However, post-restoration recovery of small omnivorous fish can increase water nutrient concentrations through excretion. The impact of these recycled nutrients on submerged macrophytes is not well-studied, and it may depend...

In this chapter we first give an overview of the systematics, morphology, and anatomy of fish followed by a general overview of fish communities in lakes and streams. We then discuss size-efficiency and size-selectivity of fish feeding as well as the importance of visibility for fish predation. Next, we deal with top-down and bottom-up regulations...

With increasing anthropogenic activities, freshwater ecosystems around the world are becoming increasingly affected by various pressures, including eutrophication, overfishing, and irrational stocking, which may have a negative impact on the food web structure. Despite the extensive research and proposed management measures for eutrophic lakes, the...

Understanding how phytoplankton interacts with local and regional drivers as well as their feedbacks is a great challenge, and quantitative analyses of the regulating role of human activities and climate changes on these feedback loops are also limited. By using monthly monitoring dataset (2000–2017) from Lake Taihu and empirical dynamic modelling...

The invasive red swamp crayfish Pro-cambarus clarkii (Girard, 1852) can affect freshwater ecosystems, their macrophyte communities in various ways. To examine the effects of red swamp crayfish on clearwater macrophyte-dominated lakes, we performed a 28-day mesocosm experiment, without and with presence of red swamp crayfish, with or without access...

Saline lakes are rapidly drying out across the globe, particularly in Central Asia, due to climate change and anthropogenic activities. We present the results of a long-read next generation sequencing analysis of the 16S rRNA-based taxonomic structure of bacteriomes of the Tengiz-Korgalzhyn lakes system. We found that the shallow endorheic, mostly...

Freshwater fishes are at the center of the freshwater biodiversity crisis, which is unfortunate as they significantly contribute to global diversity, accounting for 40% of all fish species and 25% of vertebrates worldwide. Global pressures such as land and water use changes, pollution, invasive species, and climate change pose significant threats t...

Rivers receive, transport, and are reactors of terrestrial dissolved organic matter (DOM) and are highly influenced by changes in hydrological conditions and anthropogenic disturbances, but the effect of DOM composition on the dynamics of the bacterial community in rivers is poorly understood. We conducted a seasonal field sampling campaign at two...

Freshwaters are considered to be the most vulnerable ecosystems facing biological invasions, and the red swamp crayfish (Procambarus clarkii) is one of the most widespread aquatic invasive species in the world. P. clarkii has negative impacts on water quality in the lakes that it invades by, for instance, increasing their turbidity and nutrient con...

For shallow lakes, the most dramatic ecosystem shift is that from a clear-water, macrophyte-dominated regime to a turbid, phytoplankton-dominated regime. Whereas many studies have focused on the factors that trigger such shifts, it is still unclear how these changes shape fish diversity. In the present study, we characterised the fish communities t...