Tom Shatwell

• Dr. rer nat
• Professor at Ostwestfalen-Lippe University of Applied Sciences and Arts

Winter phytoplankton blooms have been documented in several temperate lakes, yet the mechanisms triggering them remain poorly understood. Understanding the ecology of these blooms is key for predicting succession patterns, especially given the impact of climate change on winter conditions. To elucidate the relationships between exponential algal gr...

Trophic interactions determine food web structure and influence biodiversity, community structure, ecosystem functioning, and food web responses to global change. These interactions are highly flexible, changing on temporal scales from diurnal to evolutionary times due to phenotypic plasticity, rapid evolution and species sorting. Small-scale exper...

Lake Bosumtwi in tropical Ghana has been known for its recurrent fish kills, but they have recently been reported to happen less frequently. The lake formed in a meteorite impact crater in Ghana, West Africa. It plays an important role for the local inhabitants for recreation and for fisheries. The lake is deep, and recent observations indicate tha...

Artificial light propagating towards the night sky can be scattered back to Earth and reach ecosystems tens of kilometres away from the original light source. This phenomenon is known as artificial skyglow. Its consequences on freshwaters are largely unknown. In a large-scale lake enclosure experiment, we found that skyglow at levels of 0.06 and 6...

The restoration of the North Aral was an unprecedented effort to save a large water basin by construction of a dam that separates it from the rest of the desiccating Aral Sea area. As a result, the lake volume has stabilized at 27.5 km3, the area has increased from 2800 km2 (2006) to 3400 km2 (2020), and the salinity has dropped from 18 to 10 g kg-...

Lentic waters integrate atmosphere and catchment processes, and thus ultimately capture climate signals. However, studies of climate warming effects on lentic waters usually do not sufficiently account for a change in heat flux from the catchment through altered inflow temperature and discharge under climate change. This is particularly relevant fo...

Lakes represent a vital source of freshwater, accounting for 87% of the Earth’s accessible surface freshwater resources and providing a range of ecosystem services, including water for human consumption. As climate change continues to unfold, understanding the potential evaporative water losses from lakes becomes crucial for effective water managem...

Global warming is shifting the thermal dynamics of lakes, with resulting climatic variability heavily affecting their mixing dynamics. We present a dual ensemble workflow coupling climate models with lake models. We used a large set of simulations across multiple domains, multi‐scenario, and multi GCM‐ RCM combinations from CORDEX data. We forced a...

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...

Water quality and hypoxia in lakes and reservoirs are strongly associated with water renewal. Yet vertical water exchange is still not fully understood and challenging to evaluate in highly dynamic systems. Here, we applied a scaling approach using the vertical timescale, vertical water age (VWA), defined as time since a water parcel last touched t...

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...

A precise understanding of the mechanisms causing phytoplankton blooms in reservoirs is still lacking, especially in large riverine reservoirs. To better understand these blooms, the role of the complex hydrodynamics caused by dam operation must be quantified. Here we examine how synergistic hydrodynamic processes, rather than individual metrics, t...

Artificial light at night (ALAN) affects many areas of the world and is increasing globally. To date, there has been limited and inconsistent evidence regarding the consequences of ALAN for plant communities, as well as for the fitness of their constituent species. ALAN could be beneficial for plants as they need light as energy source, but they al...

Artificial light at night (ALAN) is predicted to have far-reaching consequences for natural ecosystems given its influence on organismal physiology and behaviour, species interactions and community composition. Movement and predation are fundamental ecological processes that are of critical importance to ecosystem functioning. The natural movements...

We coupled 21st century climate projections with a well-established water quality model to depict future ecological changes of Rappbode Reservoir, Germany. Our results document a chain of climate-driven effects propagating through the aquatic ecosystem and interfering with drinking water supply: intense climate warming (RCP8.5 scenario) will firstl...

Die Anpassung von Wasserinfrastrukturen an den Klimawandel ist notwendig, dies gilt auch für Talsperren. Obwohl zahlreiche Klimaprognosen vorliegen, ist es aber oft schwierig, konkrete Handlungsanweisungen für deren Management bzw. notwendige Investitionen abzuleiten.

Artificial light at night significantly alters the predictability of the natural light cycles that most animals use as an essential Zeitgeber for daily activity. Direct light has well-documented local impacts on activity patterns of diurnal and nocturnal organisms. However, artificial light at night also contributes to an indirect illumination of t...

Aquatic ecosystems are threatened by eutrophication from nutrient pollution1. In lakes, eutrophication causes a plethora of deleterious effects, such as harmful algal blooms, fish kills2 and increased methane emissions3. However, lake-specific responses to nutrient changes are highly variable, complicating eutrophication management4. These lake-spe...

Water-level reduction frequently occurs in deep reservoirs, but its effect on dissolved oxygen concentration is not well understood. In this study we used a well-established water quality model to illustrate effects of water level dynamics on oxygen concentration in Rappbode Reservoir, Germany. We then systematically elucidated the potential of sel...

Phytoplankton blooms in late winter or spring occur regularly in temperate lakes and transport significant amounts of nutrients to the sediment when they sink. However, information on the transfer of nutrients between the two seasons remains scarce. Here we studied the phytoplankton community composition and how it affects vertical nutrient fluxes...

Lake evaporation plays an important role in the water budget of lakes. Predicting lake evaporation responses to climate change is thus of paramount importance for the planning of mitigation and adaption strategies. However, most studies that have simulated climate change impacts on lake evaporation have typically utilised a single mechanistic model...

Background Aggregations of cyanobacteria in lakes and reservoirs are commonly associated with surface blooms, but may also occur in the metalimnion as subsurface or deep chlorophyll maxima. Metalimnetic cyanobacteria blooms are of great concern when potentially toxic species, such as Planktothrix rubescens, are involved. Metalimnetic blooms of P. r...

Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a...

Deforestation is currently a widespread phenomenon and a growing environmental concern in the era of rapid climate change. In temperate regions, it is challenging to quantify the impacts of deforestation on the catchment dynamics and downstream aquatic ecosystems such as reservoirs and disentangle these from direct climate change impacts, let alone...

Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a...

Light pollution is an environmental stressor of global extent that is growing exponentially in area and intensity. Artificial skyglow, a form of light pollution with large range, is hypothesized to have environmental impact at ecosystem level. However, testing the impact of skyglow at large scales and in a controlled fashion under in situ condition...

Lake Sevan is the largest freshwater body in the Caucasus region, situated at an altitude of 1,900 m asl. While it is a major water resource in the whole region, Lake Sevan has received little attention in international limnological literature. Although recent studies pointed to algal blooms and negative impacts of climate change and eutrophication...

Light pollution is an environmental stressor of global extent that is growing exponentially in area and intensity. Artificial skyglow, a form of light pollution with large range, is hypothesized to have environmental impact at ecosystem level. However, testing the impact of skyglow at large scales and in a controlled fashion under in situ condition...

We investigate the "macronutrient-access hypothesis", which states that the balance between stoichiometric macronutrient demand and accessible macronutrients controls nutrient assimilation by aquatic heterotrophs. Within this hypothesis, we consider bioavailable dissolved organic carbon (bDOC), reactive nitrogen (N) and reactive phosphorus (P) to b...

Plain Language Summary The Qinghai‐Tibet Plateau possesses the largest alpine lake system, which plays a crucial role in the land‐atmosphere interaction. Data on thermal properties of Tibetan lakes during the ice‐covered season are extremely scarce. The first observations on the thermal and radiation regime under ice of the largest freshwater lake...

Model ensembles have several benefits compared to single-model applications but are not frequently used within the lake modelling community. Setting up and running multiple lake models can be challenging and time consuming, despite the many similarities between the existing models (forcing data, hypsograph, etc.). Here we present an R package, Lake...

One of the most important physical characteristics driving lifecycle events in lakes is stratification. Already subtle variations in the timing of stratification onset and break-up (phenology) are known to have major ecological effects, mainly by determining the availability of light, nutrients, carbon and oxygen to organisms. Despite its ecologica...

This article summarises the results of long-term research and monitoring on 17 lakes and reservoirs in Germany. Following nutrient reduction, water quality improved in most water bodies since the early 1990s, but most are unlikely to meet the requirements of the Water Framework Directive of the European Union (EU-WFD) by 2015 and cyanobacteria stil...

In temperate lakes, it is generally assumed that light rather than temperature constrains phytoplankton growth in winter. Rapid winter warming and increasing observations of winter blooms warrant more investigation of these controls. We investigated the mechanisms regulating a massive winter diatom bloom in a temperate lake. High frequency data and...

Lake ecosystems, and the organisms that live within them, are vulnerable to temperature change1–5, including the increased occurrence of thermal extremes⁶. However, very little is known about lake heatwaves—periods of extreme warm lake surface water temperature—and how they may change under global warming. Here we use satellite observations and a n...

Model ensembles have several benefits compared to single-model applications but are not frequently used within the lake modelling community. Setting up and running multiple lake models can be challenging and time consuming, despite the many similarities between the existing models (forcing data, hypsograph, etc.). Here we present an R package, Lake...

The thermal structure in reservoirs affects the development of aquatic ecosystems, and can be substantially influenced by climate change and management strategies. We applied a two-dimensional hydrodynamic model to explore the response of the thermal structure in Germany's largest drinking water reservoir, Rappbode Reservoir, to future climate proj...

Metalimnetic oxygen minima are observed in many lakes and reservoirs, but the mechanisms behind this phenomena are not well understood. Thus, we simulated the metalimnetic oxygen minimum (MOM) in the Rappbode Reservoir with a well-established two-dimensional water quality model (CE-QUAL-W2) to systematically quantify the chain of events leading to...

The physical response of lakes to climate warming is regionally variable and highly dependent on individual lake characteristics, making generalizations about their development difficult. To qualify the role of individual lake characteristics in their response to regionally homogeneous warming, we simulated temperature, ice cover, and mixing in fou...

The physical response of lakes to climate warming is regionally variable and highly dependent on individual lake characteristics, making generalisations about their development difficult. To qualify the role of individual lake characteristics in their response to regionally homogeneous warming, we simulated temperature, ice cover and mixing in four...

The effectiveness of controlling nitrogen (N) to manage lake eutrophication is debated. Long‐term, whole‐lake case studies are required to determine whether diazotrophic cyanobacteria can fix sufficient N to offset a reduction of N‐inputs. We document the recovery of shallow, productive Lake Müggelsee (Germany) over 37 yr (sampling interval 1–2 wee...

The modelling community has identified challenges for the integration and assessment of lake models due to the diversity of modelling approaches and lakes. In this study, we develop and assess a one-dimensional lake model and apply it to 32 lakes from a global observatory network. The data set included lakes over broad ranges in latitude, climatic...

Climate forecasts project a global increase in extreme weather events, but information on the consequences for ecosystems is scarce. Of particular significance for lakes are severe storms that can influence biogeochemical processes and biological communities by disrupting the vertical thermal structure during periods of stratification. An exception...

Phytoplankton growth depends not only on mean intensity but also on the dynamics of the light supply. In surface mixed layers, phytoplankton may rapidly move between strong light and almost darkness. The nonlinear light-dependency of growth may differ between constant and fluctuating light because of the different frequency distribution of light an...

The hydrology of the lake-rich Tibetan Plateau is important for the global climate, yet little is known about the thermal regime of Tibetan lakes due to scant data. We (i) investigated the characteristic seasonal temperature patterns and recent trends in the thermal and stratification regimes of lakes on the Tibetan Plateau and (ii) tested the perf...

Summary D5.1-1 Part 1: Multi-stressors on surface water and effects on ecological statusHumans have increased the discharge of pollution, altered water flow regime and modified the morphology of rivers. All these actions have resulted in multiple pressures on freshwater ecosystems, undermining their biodiversity and ecological functioning. The Euro...

The hydrology of the lake-rich Tibetan Plateau is important for the global climate yet little is known about the thermal regime of Tibetan lakes due to scant data. We (i) investigated the characteristic seasonal temperature patterns and recent trends in thermal and stratification regime of lakes on the Tibetan Plateau and (ii) tested theperformance...

Hutchinson and Löffler's (1956) classification of lakes based on the seasonal thermal mixing regime has become a cornerstone of any analysis of lakes as elements of the earth surface. Until now however the lake classification has lacked a physically sound quantitative criterion distinguishing between two fundamental lake types: thermally stratified...

Water transparency affects the thermal structure of lakes, and within certain lake depth ranges, it can determine whether a lake mixes regularly (polymictic regime) or stratifies continuously (dimictic regime) from spring through summer. Phytoplankton biomass can influence transparency but the effect of its seasonal pattern on stratification is unk...

Stickstofflimitation in Binnengewässern - Ist Stickstoffreduktion ökologisch sinnvoll und wirtschaftlich vertretbar? Abschlussbericht NITROLIMIT Phase II

Rewetting of long-term drained fens often results in the formation of eutrophic shallow lakes with an average water depth of less than 1 m. This is accompanied by a fast vegetation shift from cultivated grasses via submerged hydrophytes to helophytes. As a result of rapid plant dying and decomposition, these systems are highly dynamic wetlands char...

Rewetting of long-term drained fens often results in the formation of eutrophic shallow lakes with an average water depth of less than 1 m. This is accompanied by a fast vegetation shift from cultivated grasses via submerged hydrophytes to helophytes. As a result of rapid plant dying and decomposition, these systems are highly-dynamic wetlands char...

In lakes, trophic change and climate change shift the relationship between nutrients and physical factors, like temperature and photoperiod, and interactions between these factors should affect the growth of phytoplankton species differently. We therefore determined the relationship between P-limited specific growth rates and P-quota (biovolume bas...

tWhen severely degraded fens are rewetted, they often become shallow lakes with an average water depthof less than 1 m. The additional high nutrient availability in highly decomposed peat soils of these newlyformed ecosystems favours the fast establishment of a small number of helophytes while the return of losttarget species like low sedges and br...

Phytoplanktonarten unterscheiden sich in ihren Ansprüchen hinsichtlich Ressourcen wie Nährstoffe, Licht und andere physikalische Faktoren. Wechselwirkungen zwischen Nährstoffen und physikalischen Faktoren beeinflussen daher die Artenzusammensetzung einer Phytoplanktongemeinschaft. In der vorliegenden Arbeit wurde der Einfluss von Temperatur und Pho...

We investigated the combined effects of thermal pollution from a nuclear power plant (NPP) and regional climate warming on the thermal regime of a lake. For this purpose, we used the lake model FLake and analyzed 50 years of temperature data from Lake Stechlin, Germany, which served as the cooling water reservoir for the Rheinsberg NPP from 1966 un...

Diatoms often dominate temperate lakes and rivers in spring, when increasing temperature and daylength coincide with decreasing silicate concentrations. Since interactions between these factors may be important, we cultivated Stephanodiscus minutulus and Nitzschia acicularis (freshwater diatoms) under silicon limitation at different temperatures an...

We measured specific growth rates of Stephanodiscus minutulus, Nitzschia acicularis (diatoms), and Limnothrix redekei (cyanobacterium) under fluctuating and constant light in semi-continuous culture at 10°C, 15°C, and 20°C and under photoperiods of 6 h d−1 and 12 h d−1. Fluctuating light regimes simulated regular vertical mixing in lakes with a rat...

The effects of the recent warming trend in many northern temperate lakes on the species composition of spring phytoplankton remain poorly understood, especially because a recent change in nutrients has complicated efforts, and previous studies have defined spring according to the calendar. We analysed data from 1979 to 2004 from Lake Müggelsee (Ber...

Global climate change alters the relationship between temperature and light in aquatic ecosystems, which is expected to affect the success of different phytoplankton species. To examine this, the interactions between temperature, photoperiod and light exposure (LE) (integral daily light supply) on specific growth rates were analysed for Limnothrix...

A pond in Sydney's Centennial Park is fed by stormwater from a 120 ha catchment that has predominantly residential land use. Over a period of several months the pond inflow and outflow were monitored to observe flow rate, suspended solids and total phosphorus concentration. In all runoff events, the inflows were characterized by rapid increases in...