Our research at University of Koblenz-Landau is going virtual at SETAC SciCon! In this three-part blog series, we highlight several poster and platform presentations of our researchers: Today, find out what Ralf. B. Schäfer, Alexander Feckler, and Eric Bollinger have planned for the conference.

This third blog features platform contributions by Ralf. B. Schäfer, Alexander Feckler, and Eric Bollinger. Ralf talks about the problems of linking pesticide exposures to macroinvertebrate biodiversity losses in streams and elaborates on the underlying processes. Alexander presents his latest research on the adverse effects of nanoparticles on both emergence and energy reserves of aquatic insects, which may adversely affect trophic transfers. Eric shares his research on leaf litter decomposition in streams and how this essential process may be structurally and functionally altered by fungicide exposures.

Responses of invertebrates in streams to pesticides: review of field studies and conclusions for risk assessment

• Presenter: Ralf B. Schäfer
• Session: Embedding Ecological Concepts in Ecotoxicology: Processes, Populations and Communities
• Talk ID: 2.05.1

Pesticides encompass a variety of chemicals that are deliberately released into the environment to control agricultural pests. Before pesticides are placed on the market, they undergo a complex authorisation procedure that aims to prevent unacceptable effects on ecosystems. The authorisation largely relies on data from laboratory and semi-field studies. In the first part of my presentation, I review field studies on the effects of pesticides on macroinvertebrates in freshwater ecosystems. Field studies were the key in establishing evidence that despite a complex pesticide authorisation procedure, effects of agricultural pesticide use (mainly insecticides and fungicides) on macroinvertebrates are widespread. Of 13 field studies in different regions of the world in the last 15 years, nine found a clear or likely relationship between pesticide toxicity or concentrations and biotic responses such as community composition or different indices. I discuss the problem of establishing causality based on field studies and governmental monitoring data. In the second part, I provide an overview of ecological processes that moderate the action of pesticides in (linked) ecosystems that need consideration if the aim is to prevent biodiversity loss in these systems.

Cross-boundary transport of nanoparticles via merolimnic insects compromises aquatic subsidy quality

• Presenter: Alexander Feckler
• Session: Impact and trophic transfer of chemical pollutants in food webs within and across ecosystem boundaries
• Talk ID: 2.07.3

Knowledge on how and to which extent contaminants are transported from the aquatic environment to terrestrial ecosystems is still scarce. The emergence of merolimnic aquatic insects may constitute one potential pathway for contaminants directly into terrestrial food webs. At the same time, contaminants may cause adverse effects on the temporal emergence pattern and nutritional quality of aquatic insects. Consequently, both the trophic transfer of contaminants by and shifts in the availability and quality of aquatic subsidies can be of serious concern for the well-being of terrestrial predators. To address this issue, we exposed caddisfly larvae (Chaetopteryx villosa)towards nanoparticles (NPs; 4 and 400 µg nTiO₂/L; 6.5 µg nAu/L) as model contaminants for 140 d using a laboratory flow-through stream microcosm system. In addition, the photocatalytic effects of NPs on the response of Chaetopteryx were assessed by additional exposure to ultraviolet irradiation at ambient intensities. Consumption of leaf material, survival, emergence rate and its temporal pattern, energy reserves (=lipids), and concentration of NPs in adult (emerged) organisms were monitored.

NPs delayed Chaetopteryx emergence by ≤30 days and reduced lipid reserves by ≤40%. Furthermore, emerging Chaetopteryx carried substantial concentrations of nTiO₂ (up to 2.68 ng/mg) and nAu (1.51 ng/mg). These results underline the potential for contaminant transfer from the aquatic to the terrestrial ecosystem via the emergence of merolimnic aquatic insects. Assuming that median internal NP concentrations measured here are comparable among merolimnic insect species and that the total annual biomass of emerging merolimnic insects from streams measured elsewhere, NP-fluxes from the aquatic to the terrestrial environment can potentially be as high as 2.4-56.5 mg nTiO₂/m² and 1.4-31.8 mg nAu/m². These data raise concern about the implications for higher trophic levels in riparian systems associated with the transfer of contaminants from the aquatic environment into the terrestrial food web. However, even though recent studies on the transport of contaminants (e.g., microplastics, metals, NPs, and pharmaceuticals) suggest effects on the aquatic-terrestrial subsidy, this area of research is still in its infancy and requires further scrutiny.

Looking beneath the surface: are fungicide effects in sediments comparable to those in the benthic zone?

• Presenter: Eric Bollinger
• Session: Microbial Community Ecotoxicology under Multiple Stressors Scenarios
• Talk ID: 2.08.3

Leaf litter decomposition is a microbially driven ecosystem process, that is crucial for energy and nutrient fluxes in streams and can be negatively affected by fungicides. Although most of the organic matter is stored in sediments, information about fungicide effects in the hyporheic zone is missing. In a full-factorial laboratory experiment (n=7), the effects of a fungicide mixture on the structure (fungal biomass and sporulation as well as phospholipid fatty acid fingerprint) and functioning (leaf decomposition) of leaf-associated microbial communities in the hyporheic and benthic zone was studied. Substrate-dependence of fungicide effects was tested by using two grain sizes. In the hyporheic zone leaf decomposition, fungal biomass, fungal sporulation and general microbial abundance were lower than in the benthic zone, while the importance of microbes other than fungi increased. This effect is most likely triggered by differences in oxygen conditions or hydraulic conductivity. In line with previous studies targeting fungicide effects, benthic fungal biomass and fungal community composition were affected. However, in the fine-grained hyporheic zone fungicide effects on leaf decomposition showed a two-fold greater effect size relative to the benthic zone. This might be caused by a lower hydraulic conductivity of the fine sediment, which influences the dispersal of microorganisms as well as oxygen and nutrient fluxes across the sediment-water-interface and within the sediment. Functional effects, especially in the hyporheic zone, were not fully explicable by the analyzed structural endpoints. We can nevertheless conclude, that fungicide effects can be even more severe in the hyporheic zone, requiring further assessments to improve risk analyses.