Research

Interests and Projects

Our research focuses on the responses of freshwater organisms and their adaptive ability to the effects of anthropogenic impacts on lentic freshwater ecosystems. It spans various levels of biological organization and complexity, includes molecular, analytical and conceptual approaches, and covers laboratory, mesocosm as well as field experiments. For more details please see research topics below.

Interested in joining us? Get in touch!

How are we, how is humanity changing life in lakes?

Ongoing Research

Phytoplankton nutritional responses

Phytoplankton are organisms that form the basis of the food web in freshwater lakes. Phytoplankton groups and species differ in their nutritional quality as a food to other organisms, such as zooplankton. But what determines their nutritional quality? And can it change? Examples of nutritious phytoplankton are diatoms and cryptophytes, because of their high lipid content and high amounts of nitrogen and phosphorus. Today in temperate regions, diatoms and cryptophytes are found in lakes during spring, when the water mixes because of the strong winds, leading to an upwell of nutrients from the lake floor. This bloom in nutritious phytoplankton creates a great start for the fresh zooplankton hatchlings after a long winter. However, with ongoing multi-facetted anthropogenic change, we’re unsure how the dynamics of phytoplankton in lakes will change and consequently also the nutrients available for consumers. Our research investigates phytoplankton responses to environmental change scenarios experimentally, both in monocultures and in mesocosm experiments. We hope that this knowledge will be the basis of future studies examining upcoming lake ecosystem challenges due to environmental change and enable us to pre-emptively create management solutions to ensure the existence of healthy lake ecosystems for the benefit of both us and nature.

CyaNoServices- Securing freshwater supporting services for biodiversity threatened by harmful cyanobacteria across ecosystems boundaries

Cyanobacterial blooms can be a threat to insect biodiversity and their services by disrupting two fundamental freshwater supporting services: (i) resource provisioning, and (ii) habitat provisioning. First, cyanobacteria can negatively affect freshwater resource provisioning by producing potent toxic compounds for terrestrial organisms in need of freshwater resources, such as pollinators. Second, cyanobacteria can affect habitat provisioning for emerging insects by direct effects from toxins, but also by indirect effects via alterations in food web interactions. This research project is part of the international project “CyaNoServices”, with collaboration partners from Sweden, Spain and Brazil. “CyaNoServices” aims to increase the security of freshwater supporting services for biodiversity threatened by harmful cyanobacteria beyond the aquatic boundary, with a focus on insect biodiversity and the multiple key ecosystem services that they provide to wildlife and human well-being. This research project will evaluate the multiple mechanisms by which harmful cyanobacterial blooms can affect the emerging insect community via changes in habitat quality.

The role of nutrition in adaptive responses of Daphnia to increased salinity

Human activities are putting significant pressure on ecosystems worldwide. In freshwater systems across the northern hemisphere, one critical stressor is the rising levels of dissolved salts, or shortly salinization. This increase stems from various sources, including agriculture, mining, and road de-icing, leading to year-round high salinity levels. Freshwater organisms are known to suffer from elevated salt levels, yet there is evidence that some can develop adaptive responses. For example, the keystone herbivore Daphnia has shown signs of salinity tolerance linked closely to diet quality. Daphnia’s tolerance to salt potentially depends on its lipid intake, particularly sterols, which play a critical role in mediating salt resilience.

In this project, we are investigating how nutrition contributes to salt tolerance adaptations. To explore this, we’re using resurrected Daphniagenotypes from a salinized lake, which show signs of genetic adaptation to elevated salinity. Our key questions include: How does nutrient availability influence Daphnia’s tolerance to salt? What are the molecular mechanisms behind its phenotypic responses to increased salinity? What are the potential costs of this adaptation, such as increased vulnerability to Cyanobacteria? To address these questions, we are conducting a range of phenotypic assays and molecular analyses in both lab and mesocosm environments. We hope that our findings will shed light on organisms’ potential to adapt to anthropogenic pressure, help refine predictions for ecosystem resilience and inform guidelines for recommended chloride levels in freshwater lakes.

Previous Research

Phenotypic Plasticity and Evolvability

Predicting if and how quickly organisms can adapt to anthropogenic change is one of the greatest challenges of our times. Unfortunately, prediction is notoriously challenging in practice because the rate and direction of adaptive evolutionary change depends on the phenotypic variation that is available to selection. This, in turn, depends on the relationship between genetic and phenotypic variation (GP map), something that is very difficult and laborious to quantify. As a result, biologists have generally been rather pessimistic about the possibility to predict evolution over more than a few generations, even when selective pressures are known. Recent theory suggests a way out of this dilemma. The basic idea is that the responses to genetic (e.g., mutation) and environmental perturbation are linked through development. Here we set out to answer the question: Why are organisms so good at adapting, and can they get even better? Utilizing environmental perturbations as selective pressures, we are studying the relationship between plasticity and evolvability in green algae. Stay tuned for the first results.

Road Salt

Salinization of freshwater ecosystems is a growing hazard for organisms and ecosystem functioning worldwide. In northern latitudes, road salt that is being transported into water bodies can cause year-round increases in lake salinity levels. Exploring the environmental factors driving the susceptibility of freshwater zooplankton to road salt is crucial for assessing the impact of salinization on food web processes. We found that the susceptibility of freshwater zooplankton to salinization strongly depends on the dietary lipid supply and thus the phytoplankton community composition. Hence, trophic state related differences in the phytoplankton community composition need to be considered when assessing the consequences of salinization for freshwater ecosystem functioning. However, in nature it is seldom only a single stressor but rather a variety of stressors affecting eco- system functioning and organismal interactions. We could show that road salt and the tire rubber antiozonant, 6PPD, have synergistic negative effects on the population growth on rotifers, common freshwater herbivores.

We were involved in a global study, assessing how salt tolerance of Daphnia is related to the prevailing environmental conditions of site of origin. During the summer of 2023, we also participated in an Aquacosm experiment, investigating different modes of salinization on plankton communities. Stay tuned for the first results on both projects.

Ecological Stoichiometry

A key component of the theory of ecological stoichiometry is the Growth Rate Hypothesis (GRH). The GRH states that variation in organismal stoichiometry (in particular, C:P and N:P ratios) is driven by growth-dependent allocation to P-rich ribosomal RNA that leads to differential increases in biomass P content. The GRH was originally formulated to help explain observed differences in C:N:P ratios of different species of zooplankton and has since been applied across a wide range of organisms. The GRH has found broad but not uniform support in studies across diverse biota and habitats. In this project we investigated if there are fundamental rules that link the biochemical properties of cells to dynamical processes in eco- systems. We evaluated the GRH with intensive physiological, evolutionary, and ecological work on three model organisms that represent key ecological functional groups: Pseudomonas putida (chemoheterotrophic decomposer), the green alga Chlamydomonas reinhardtii (photoautotroph), and the crustacean Daphnia pulex (primary consumer / herbivore).

In a first publication we show that in Chlamydomonas reinhardtii, the different components of the GRH differed in their robustness. The most reliable component is that %P of organismal biomass increases with faster growth. Furthermore, we could show that the GRH is most robust under high N:P environmental conditions and performs worst under low light conditions, helping to clarify the domain of conditions under which the GRH holds or fails to hold. More publications on the empirical work have been submitted- stay tuned.

Evolution of grazer resistance

Lake ecosystems around the globe are suffering from nutrient pollution and the associated proliferation of harmful cyanobacteria. In past decades, eutrophication has been reversed in many lake ecosystems through extensive restoration measures. Making use of resurrection ecology, we showed how trophic state-related changes in the relative abundance of cyanobacteria resulted in the evolution and the subsequent loss of grazer resistance to cyanobacteria. We demonstrated that this evolution of grazer resistance involved changes in dietary sterol requirements, challenging the common assumption that changes in the ability to cope with cyanobacteria are exclusively mediated through an adaptation to cyanobacterial toxins.