Mandy Velthuis

Radboud University | RU · Institute for Water and Wetland Research

Global warming has been shown to affect ecosystems worldwide. Warming may, for instance,disrupt plant herbivore synchrony and bird phenology in terrestrial systems, reduce primary production inoceans, and promote toxic cyanobacterial blooms in freshwater lakes. Responses of communities will notonly depend on direct species-specific temperature effe...

Human activity is currently changing our environment rapidly, with predicted temperature increases of 1–5°C over the coming century and increased nitrogen and phosphorus inputs in aquatic ecosystems. In the shallow parts of these ecosystems, submerged aquatic plants enhance water clarity by resource competition with phytoplankton, provide habitat,...

Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater...

Benthic primary producers (BPP) in inland waters, including aquatic macrophytes and periphyton, are foundational habitats that are highly sensitive to multiple human drivers of environmental change. However, long‐term seasonal monitoring of BPP is limited, leaving us with little information on the cause, directionality, and consequences of the pote...

Peatlands store vast amounts of carbon (C). However, land-use-driven drainage causes peat oxidation, resulting in CO2 emission. There is a growing need for ground-truthing CO2 emission and its potential drivers to better quantify long-term emission trends in peatlands. This will help improve National Inventory Reporting and ultimately aid the desig...

In agricultural landscapes of North-Western Europe, the majority of water bodies do not meet the targets set by the European Water Framework Directive due to a lack of submerged macrophytes and associated biodiversity. These eutrophic waters can also be a substantial source of methane (CH4) and carbon dioxide (CO2) to the at- mosphere. Here we pres...

The presence of submerged macrophytes is a desired environmental target for coastal freshwater ecosystems. Maintaining a rich community of these species can be challenging as salinisation by sea‐level rise poses an increasing threat to ecosystem integrity. We tested the effect of salinisation on the growth and germination of freshwater macrophytes...

Greenhouse gas (GHG) emissions from small inland waters are disproportionately large. Climate warming is expected to favour dominance of algae and free-floating plants at the expense of submerged plants. Through different routes these functional plant types may have far-reaching impacts on freshwater GHG emissions in future warmer waters, which are...

Freshwater denitrification removes a considerable amount of nitrogen from inland waters, which are under pressure from eutrophication and warming. However, incomplete denitrification can lead to the formation of N2O, a potent greenhouse gas, which can amplify climatic warming. Although temperature effects on denitrification are well studied in indi...

Estimating annual CO2 budgets on drained peatlands is important in understanding the significance of CO2 emissions from peatland degradation and evaluating the effectiveness of mitigation techniques. The closed-chamber technique is widely used in combination with gap-filling of CO2 fluxes by parameter fitting empirical models of ecosystem respirati...

Phytoplankton stand at the base of the marine food‐web, and play a major role in global carbon cycling. Rising CO2 levels and temperatures are expected to enhance growth and alter carbon:nutrient stoichiometry of marine phytoplankton, with possible consequences for the functioning of marine food‐webs and the oceanic carbon pump. To date, however, t...

Een studie naar de effecten van herbivorie, bodemwoeling, saliniteit, turbiditeit en waterbodemeigenschappen op ondergedoken waterplanten op Goeree-Overflakkee

Viruses are important drivers in the cycling of carbon and nutrients in aquatic ecosystems. Since viruses are obligate parasites, their production completely depends on growth and metabolism of hosts and therefore can be affected by climate change. Here, we investigated if warming (+4°C) can change the outcome of viral infections in a natural fresh...

The abundance and stoichiometry of aquatic plants are crucial for nutrient cycling and energy transfer in aquatic ecosystems. However, the interactive effects of multiple global environmental changes, including temperature rise and eutrophication, on aquatic plant stoichiometry and palatability remain largely unknown. Here, we hypothesized that (1)...

Elevated pCO2 and warming may promote algal growth and toxin production, and thereby possibly support the proliferation and toxicity of HABs. Here, we tested whether empirical data supports this hypothesis using a meta‐analytic approach and investigated the responses of growth rate and toxin content or toxicity of numerous marine and estuarine HAB...

Global warming profoundly impacts the functioning of aquatic ecosystems. Nonetheless, the effect of warming on primary producers is poorly understood, especially periphyton production, which is affected both directly and indirectly by temperature-sensitive top-down and bottom-up controls. Here, we study the impact of warming on gross primary produc...

Methane (CH4) strongly contributes to observed global warming. As natural CH4 emissions mainly originate from wet ecosystems, it is important to unravel how climate change may affect these emissions. This is especially true for ebullition (bubble flux from sediments), a pathway that has long been underestimated but generally dominates emissions. He...

Ecological stoichiometry has proven to be invaluable for understanding consumer response to changes in resource quality. Although interactions between trophic levels occur at the community level, most studies focus on single consumer species. In contrast to individual species, communities may deal with trophic mismatch not only through elemental pl...

Climate change is expected to favour infectious diseases across ecosystems worldwide. In freshwater and marine environments, parasites play a crucial role in controlling plankton population dynamics. Infection of phytoplankton populations will cause a transfer of carbon and nutrients into parasites, which may change the type of food available for h...

The aim of the present study was to provide conclusive evidence for either genetic adaptation or phenotypic plasticity of the midge Chironomus riparius in response to metal pollution. To this purpose the genetic structure and copper sensitivity of C. riparius populations from metal-polluted and reference sites was compared. Microsatellite analysis...