Jana Isanta-Navarro Group

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.

Contact: Claudia Lassen

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 Daphnia genotypes 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.

Contact: Vana Paida

CyaNoServices- Securing freshwater supporting services for biodiversity threatended by harmful cyanobacteria across ecosystem 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.

Contact: Jana Isanta-Navarro