Do microplastic particles affect Daphnia magna at the morphological, life history and molecular level?

Microplastic particles are ubiquitous not only in marine but also in freshwater ecosystems. However, the impacts of microplastics, consisting of a large variety of synthetic polymers, on freshwater organisms remains poorly understood. We examined the effects of two polymer mixtures on the morphology, life history and on the molecular level of the waterflea Daphnia magna (three different clones). Microplastic particles of similar to 40 mu m were supplied at a low concentration (1% of the food particles) leading to an average of similar to 30 particles in the digestive tract which reflects a high microplastic contamination but still resembles a natural situation. Neither increased mortality nor changes on the morphological (body length, width and tail spine length) or reproductive parameters were observed for adult Daphnia. The analyses of juvenile Daphnia revealed a variety of small and rather subtle responses of morphological traits (body length, width and tail spine length). For adult Daphnia, alterations in expression of genes related to stress responses (i.e. HSP60, HSP70 & GST) as well as of other genes involved in body function and body composition (i.e. SERCA) were observed already 48h after exposure. We anticipate that the adverse effects of microplastic might be influenced by many additional factors like size, shape, type and even age of the particles and that the rather weak effects, as detected in a laboratory, may lead to reduced fitness in a natural multi-stressor environment

Machine learning approach for flagging incomplete bid-rigging cartels

We propose a new method for flagging bid rigging, which is particularly useful for detecting incomplete bid-rigging cartels. Our approach combines screens, i.e. statistics derived from the distribution of bids in a tender, with machine learning to predict the probability of collusion. As a methodological innovation, we calculate such screens for all possible subgroups of three or four bids within a tender and use summary statistics like the mean, median, maximum, and minimum of each screen as predictors in the machine learning algorithm. This approach tackles the issue that competitive bids in incomplete cartels distort the statistical signals produced by bid rigging. We demonstrate that our algorithm outperforms previously suggested methods in applications to incomplete cartels based on empirical data from Switzerland

Moving Toward Standardized Toxicity Testing Procedures with Particulates by Dietary Exposure of Gammarids

Ecotoxicological effect assessment of particulate materials and sparingly soluble substances is an emerging field. Current standard toxicity tests of aquatic organisms are based on soluble substances which are added to the aqueous phase. Although soluble substances distribute homogeneously, particles can form aggregates, resulting in inhomogeneous distribution and unpredictable exposure. Therefore, test scenarios need to be adapted to overcome these uncertainties. We present a dietary particle exposure tool for the toxicity testing of sparingly soluble substances or particles in combination with a standardizable food source for gammarids based on decomposition and consumption tablets (DECOTABs). Four food supplements in the DEOCOTAB formulation were compared to test their influence on the energy reserves of gammarids. Although feeding rate was constant for most supplements, mortality and energy reserves revealed clear differences. Tabs supplemented with algae‐based phyll or animal protein–based trout food best met all of the requirements. Fluorescent plastic microparticles (10–65 µm) were homogenously distributed and stable in the DECOTABs. Constant feeding was observed, and the number of ingested microparticles by Gammarus roeseli was quantified in relation to the consumed food. The developed method provides a realistic and methodologically reliable uptake from the oral pathway and allows the quantification of inner exposition via feeding rate, providing a promising tool for standardized dietary exposure scenarios with particles. Environ Toxicol Chem 2021;40:1463–1476. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.Bayerische Forschungsstiftung http://dx.doi.org/10.13039/501100002745Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/50110000234

Complete qPCR run data (BL22, K34J, Max4)

This Zip Archive contains all qPCR runs analyzed in the above mentioned publication for the three Daphnia magna clones BL22, K34J and Max4. Explanations are available in the notes.docx

Data from: Do microplastic particles affect Daphnia magna at the morphological, life history and molecular level?

Microplastic particles are ubiquitous not only in marine but also in freshwater ecosystems. However, the impacts of microplastics, consisting of a large variety of synthetic polymers, on freshwater organisms remains poorly understood. We examined the effects of two polymer mixtures on the morphology, life history and on the molecular level of the waterflea Daphnia magna (three different clones). Microplastic particles of ~40 µm were supplied at a low concentration (1% of the food particles) leading to an average of ~30 particles in the digestive tract which reflects a high microplastic contamination but still resembles a natural situation. Neither increased mortality nor changes on the morphological (body length, width and tail spine length) or reproductive parameters were observed for adult Daphnia. The analyses of juvenile Daphnia revealed a variety of small and rather subtle responses of morphological traits (body length, width and tail spine length). For adult Daphnia, alterations in expression of genes related to stress responses (i.e. HSP60, HSP70 & GST) as well as of other genes involved in body function and body composition (i.e. SERCA) were observed already 48h after exposure. We anticipate that the adverse effects of microplastic might be influenced by many additional factors like size, shape, type and even age of the particles and that the rather weak effects, as detected in a laboratory, may lead to reduced fitness in a natural multi-stressor environment

Contamination des écosystèmes aquatiques continentaux par les micro-plastiques

International audienceMassive accumulation of plastic particles has been reported for marine ecosystems around the world,posing a risk to the biota. Freshwater ecosystems have received less attention despite the majority ofplastic litter being produced onshore and introduced into marine environments by rivers. Somestudies report not only the presence of microplastics in freshwater ecosystems, but show thatcontamination is as severe as in the oceans. In continental waters microplastics have been observedin both sediments (predominantly lakeshores but also riverbanks) and water samples (predominantlysurface water of lakes and rivers). This review highlights recent findings and discusses openquestions, focusing on the methodology of assessing this contaminant in freshwater ecosystems. Inthis context, method harmonization is needed in order to obtain comparable data from differentenvironmental compartments and sites. This includes sampling strategies (at spatial and temporal18 scales), sample treatment (taking into consideration high levels of organic matter and suspended19 solids) and reliable analytical methods to identify microplastics