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 Sara Goncalves and Ashvini Victor have planned for the conference.

This first blog features poster contributions by Sara Goncalves and Ashvini Victor. Sara details how anthropogenic disturbances can alter microbial communities in streams, while Ashvini reveals how some pesticide co-formulants can be as toxic as the pesticides they are used with.

Stay tuned for the next two blogs this week! The presented topics are diverse, so everyone should find something interesting or relevant to their research.

Does history really matter? Aquatic microbial communities’ functioning under multiple stress

• Presenter: Sara Goncalves
• Session: Microbial community ecotoxicology under multiple stressors scenario
• Poster ID: 2.08P.6

Microbial decomposition of terrestrially-derived leaf litter, mainly driven by aquatic fungi and bacteria, is a fundamental ecosystem process making nutrients available for aquatic food webs. Due to agricultural intensification and expansion into pristine areas around the globe, these microorganisms are increasingly exposed to pesticides and fertilizers. A previous study showed that “History matters”, meaning that communities with a history of pesticide exposure are adapted to these conditions and are more tolerant relative to communities with minor disturbance history. In order to validate these insights against a larger sample size, we assessed the potential differences in the stress tolerance of aquatic microbial communities sampled from streams considered as pristine (P) or receiving either wastewater treatment plant effluents (WWTP) or run-off from vineyards (VYRO), with two streams per category. We used a fully-crossed design exposing the six distinct communities to increasing concentrations of a fungicide mixture and nutrients over 21 days (n = 5). The microbial leaf decomposition rate (k_microbial) was measured as a functional variable, along with microbial enzyme activities. k_microbial did not show a significant variation (p = .691) among the assessed communities with increasing fungicide levels, but the direction of effects was site specific. Moreover, the effects of increasing fungicide concentrations were mitigated with nutrient enrichment for all studied communities. The activity of β-glucosidase, β-xylosidase and cellobiohydrolase, enzymes responsible for the degradation of cellobiose, cellulose and hemicellulose polymers, showed a significant decrease (p < .05) in their activity with increasing fungicide concentration. On the other hand, the increase in nutrient content did not consistently lead to an increase of enzyme activity. All in all, the six studied microbial communities showed highly variable responses to the gradients of fungicide and nutrient exposure. In a next step, the interpretation of these functional variables should be supported by the study of the leaf-associated microbial community structure, which might ultimately be linked to the communities’ trait composition. Irrespective of this, the present study was not able to support the conclusions drawn from an earlier work using a similar experimental approach. Therefore, this work highlights the complexity in natural communities and their strategies to cope with stress.

Disclosure and data availability of co-formulants and their relative toxicity to active ingredients in viticultural pesticides

• Presenter: Ashvini Victor
• Session: Chemical Safety Assessment of Surfactants: Current Challenges in Regulatory Science and Future Prospects
• Poster ID: 1.15P.4

The protection goals for pesticides in regulatory frameworks and guidelines in the European Union have focused on the active ingredients (a.i.). In academia, however, the lack of openly available information on co-formulants of pesticides hampers the research progress that could be made in terms of toxicity to non-target communities. In view of the various compounds listed in the many pesticide patent applications, it is understood that the undisclosed co-formulants are mixtures of compounds that could potentially be more harmful than concluded in an amendable regulatory framework. This research was done to further contribute to the awareness of co-formulants toxicity to non-target communities of organisms.

Being in a wine region of Germany, we were curious about the co-formulants found in the products used in vineyards. The Julius-Kuhn Institute reports almost yearly, a list of a.i. applied by winegrowers in Germany. We found 70 different compounds in 69 out of 132 pesticide formulations that had disclosed additional compounds in the product safety data sheets (SDS), of the top four most applied fungicides, herbicides and insecticides. The disclosure of co-formulants in SDS varies among countries as there was a challenge identifying the products just by the name because often there is no common identification or patent code. Approximately 75% of the co-formulants found were at least corrosive, a health hazard or a hazard to the environment, many are poorly tested compounds and there are those not considered for registration under REACH unless they are used for non-pesticide uses as well (ECHA, 2017). The EC50 data that was available for only 31 of them, indicated that several of them are relatively more toxic to Daphnia magna than the a.i. of the examined formulation. Moreover, 17 of these more toxic compounds did indeed coincide with similar EC50 values of the pesticide formulation. The investigation on pesticides as a whole was pursued for a shift away from limiting the risk assessment to mainly a.i. and metabolites. Among other findings are patterns such as the mysteriously consistent undisclosure of the formulations containing MCPA, dicamba, mecoprop-P and 2,4-D and substances found such as unapproved a.i and biocide a.i. The goal was also to emphasize the importance of combined ecotoxicity of not just multiple a.i. in a product, but of the complex mixtures of co-formulants from the point of manufacturing the compounds, to production and application of the pesticides.