Claudia Schmitt

The chronic toxicity of ZnO nanoparticles and ZnCl2 to Daphnia magna and the use of different methods to assess nanoparticle aggregation and dissolution

Abstract In this study, the effect of ZnO nanoparticles and ZnCl2 on growth, reproduction and accumulation of zinc in Daphnia magna was determined in a 21-day chronic toxicity test. A variety of techniques were used to distinguish the free zinc ion, dissolved, nanoparticle and aggregated zinc fraction in the Daphnia test medium. The results showed similar chronic effects on growth, reproduction and accumulation for the ZnO nanoparticles (EC10, 20, 50 reproduction: 0.030, 0.049, 0.112 mg Zn/l) and the ZnCl2 (EC10, 20, 50 reproduction: 0.014, 0.027, 0.082 mg Zn/l). A large fraction of the nanoparticles rapidly dissolved after introduction in the exposure medium. Aggregation of nanoparticles was also observed but within 48 h of exposure most of these ZnO aggregates were dissolved. Based on the combined dissolution kinetics and toxicity results, it can be concluded that the toxicological effects of ZnO nanoparticles at the chronic level can be largely attributed to the dissolved fraction rather than the nanoparticles or initially formed aggregates.

Toxicity assessment of sediments from three European river basins using a sediment contact test battery

The toxicity of four polluted sediments and their corresponding reference sediments from three European river basins were investigated using a battery of six sediment contact tests representing three different trophic levels. The tests included were chronic tests with the oligochaete Lumbriculus variegatus, the nematode Caenorhabditis elegans and the mudsnail Potamopyrgus antipodarum, a sub-chronic test with the midge Chironomus riparius, an early life stage test with the zebra fish Danio rerio, and an acute test with the luminescent bacterium Vibrio fischeri. The endpoints, namely survival, growth, reproduction, embryo development and light inhibition, differed between tests. The measured effects were compared to sediment contamination translated into toxic units (TU) on the basis of acute toxicity to Daphnia magna and Pimephales promelas, and multi-substance Potentially Affected Fractions of species (msPAF) as an estimate for expected community effects. The test battery could clearly detect toxicity of the polluted sediments with test-specific responses to the different sediments. The msPAF and TU-based toxicity estimations confirmed the results of the biotests by predicting a higher toxic risk for the polluted sediments compared to the corresponding reference sediments, but partly having a different emphasis from the biotests. The results demonstrate differences in the sensitivities of species and emphasize the need for data on multiple species, when estimating the effects of sediment pollution on the benthic community.

Characterizing field sediments from three European river basins with special emphasis on endocrine effects - A recommendation for Potamopyrgus antipodarum as test organism

The assessment of endocrine disrupting potentials of field sediments has until now been mostly limited to classical chemical analysis, in vitro assays and in vivo bioassays performed with vertebrates. There is an urgent need for easy, cheap and reproducible invertebrate tests which may be applied in certain monitoring activities. Since the mudsnail Potamopyrgus antipodarum is known to be tolerant to natural stressors, but also sensitive to endocrine disrupting chemicals, it is very likely that this organism could be suitable for the assessment of endocrine effects of e.g. field sediments. Within this study the endocrine potential of sediments in three European river basins was assessed. The yeast estrogen screen (YES) and a sediment contact test with P. antipodarum were performed. Furthermore, analyses of physico-chemical properties and concentrations of heavy metals, PAHs, organotins, natural steroids and alkylphenols were done. In the sediment contact test, the reproduction of the snail was promoted by a part of the sediments. This phenomenon could not be explained by their physico-chemical properties. However, at some of those sites a high estrogenic activity was detected in the YES, leading to the assumption that endocrine disrupting compounds could be responsible for those effects. This assumption could be confirmed to some extent with partially high concentrations of xeno-estrogens (e.g. nonylphenol) at the certain sites. Our study demonstrates the applicability of the test with P. antipodarum for a variety of sediments and once again points out the need of suitable in vivo biotests for the risk assessment of field sediments.

Assessing the impact of chemical pollution on benthic invertebrates from three different European rivers using a weight-of-evidence approach.

The aim of this study was to combine different lines of evidence on the impact of chemical pollution on benthic invertebrate communities in three European river basins (Elbe, Scheldt, and Llobregat). The study integrates chemical analyses, a battery of different sediment toxicity tests, and field data from soft-sediment meio- and macrobenthic fauna within a sediment-quality triad in which chironomids, oligochaetes, and nematodes are identified on the species level. The use of TU (toxic units) and msPAF (multi-substance potentially affected fraction) in an approach assessing the chemical impact as well as the integration of sediment toxicity tests with bacteria (Vibrio fischeri), benthic invertebrates (Caenorhabditis elegans, Potamopyrgus antipodarum, Lumbriculus variegatus, Chironomus riparius), and fish embryos (Danio rerio), together with univariate and non-parametric multivariate statistical analyses of the biological data revealed significant differences between unpolluted and polluted sites in all three river basins. To combine the different results obtained in the sediment-quality triad, a scoring system was successfully developed based on a simple algorithm. This system provides an easily understandable scheme for non-experts among decision makers and water managers.

Effect directed analysis of riverine sediments—The usefulness of Potamopyrgus antipodarum for in vivo effect confirmation of endocrine disruption

In vivo tests are not commonly used in effect directed analysis (EDA) approaches. In the present study, a novel methodology was developed whereby Potamopyrgus antipodarum, which is known to be sensitive to endocrine disrupting compounds, was used as test organism. Field sediments from a polluted site in the north of Belgium were extracted and fractionated using three coupled and automatically switched normal-phase HPLC columns. Part of the fractions were spiked to artificial sediments and tested in a sediment contact test with P. antipodarum. The other part was used for an in vitro effect confirmation with the ER-LUC and anti-AR CALUX assays. Two of the six tested fractions stimulated the reproduction of the snails, while two others inhibited the reproduction. The fractions that caused an increase in reproduction also showed an increased estrogenic potency in the ER-LUC assay. Chemical analysis revealed that one of the most prominent compounds in those fractions was bisphenol-A, which has already been reported to have a stimulating effect on the reproduction of P. antipodarum by other authors. Due to the fact that previous studies have shown that this snail is also present in the field at this certain site, it was possible to directly link the results with effects that were observed in the field. This study indicates that effect directed analyses, supported by in vivo biotests, are very useful tools in order to identify the compounds that cause adverse effects on organisms or even population level.

In situ cage experiments with Potamopyrgus antipodarum - a novel tool for real life exposure assessment in freshwater ecosystems.

In situ experiments are an important tool within ecotoxicological research but there is a lack of suitable methodologies especially for freshwater invertebrate species. Within this study, a novel in situ methodology with Potamopyrgus antipodarum was developed. Snails were inserted into cages, made of Plexiglas measuring 7 × 9 × 7 cm(3) and fixed with stainless steel pins into the sediment at the relevant sampling sites. During the experiment physico-chemical properties of the water and concentrations of metals, PAHs and PCBs were measured in the sediment. The growth and survival of the snails was not affected, but the reproduction increased significantly at one of the most polluted sites. The increase in reproduction was neither correlated with physico-chemical parameters, nor with the concentrations of the different compounds, but maybe related to certain groups of estrogenic compounds. The study demonstrates the excellent applicability of this novel in situ test.

Aquatic acute species sensitivity distributions of ZnO and CuO nanoparticles

Metal oxide nanoparticles are increasingly being produced and will inevitably end up in the aquatic environment. Up till now, most papers have studied individual nanoparticle effects. However, the implementation of these data into a risk assessment tool, needed to characterise their risk to the aquatic environment, is still largely lacking. Therefore, aquatic species sensitivity distributions (SSDs) were constructed for ZnO and CuO nanoparticles and 5% hazard concentrations (HC5) were calculated in this study. The effect of individual nanoparticles on these SSDs was estimated by comparison with bulk SSDs. Additionally, the effect of nanoparticle dynamics (aggregation and dissolution) was considered by evaluating the effect of aggregate size on the toxicity, by estimation of the dissolved fraction and comparison with SSDs for ZnCl2 and CuCl2 inorganic salt. Bacteria, protozoa, yeast, rotifera, algae, nematoda, crustacea, hexapoda, fish and amphibia species were included in the analysis. The results show that algae (Zn) and crustacea (Zn, Cu) are the most sensitive species when exposed to the chemicals. Similar acute sensitivity distributions were obtained for ZnO nanoparticles (HC5: 0.06 with 90% confidence interval: 0.03-0.15 mg Zn/l; 43 data points), bulk ZnO (HC5: 0.06 with CI: 0.03-0.20 mg Zn/l; 23 dps) and ZnCl2 (HC5: 0.03 with CI: 0.02-0.05 mg Zn/l; 261 dps). CuO nanoparticles (HC5: 0.15 with CI: 0.05-0.47 mg Cu/l; 43 dps) are more toxic than the bulk materials (HC5: 6.19 with CI: 2.15-38.11 mg Cu/l; 12 dps) but less toxic than CuCl2 (HC5: 0.009 with CI: 0.007-0.012 mg Cu/l; 594 dps) to aquatic species. However, the combined dissolution and SSD results indicate that the toxicity of these nanoparticles is mainly caused by dissolved metal ions. Based on the available information, no current risk of these nanoparticles to the aquatic environment is expected.

Include or exclude? A review on the role and suitability of aquatic invertebrate neozoa as indicators in biological assessment with special respect to fresh and brackish European waters

This paper reviews published knowledge on how to deal with invasive species during biological quality assessments in European river systems for water management and assessments of ecological quality required, for example, by the European Water Frame Work Directive. The papers studied included international papers and some standards for water assessment. An overview of the current state of neozoa research showed that many different topics are treated, comprising biogeography and fauna records, species replacements and effectiveness of colonisation, life cycles, competition between native and invasive species, habitat quality and pathways of migration. Additionally, some papers have been published recently on the integration of neozoa in index-based assessment systems. Although the decline or increase of alien species populations and the corresponding impacts on indigenous populations were frequently observed, the mechanisms behind the invasions often remain hypothetical. In the reviewed papers, issues such as possible reasons for coexistence, tolerances, quality of habitat or water, life history traits and introduction of diseases were rarely covered. Few neozoa are sufficiently investigated to be categorised as indicators. After discussing the advantages and disadvantages of inclusion or exclusion, inclusion of invaders in assessments of both biodiversity (all species) and human impact (only species classified in their specific tolerance) is suggested. Further research is required to (1) update and assign ecological profiles of the non-indigenous species currently and (2) assess the effects of new invaders on native communities.

Effects of inbreeding on mouthpart deformities of Chironomus riparius under sublethal pesticide exposure

Mouthpart deformities in chironomids have been reported to indicate adverse effects of environmental pollutants. The authors assessed rates of mouthpart deformities in tributyltin-exposed, inbred, and outcrossed Chironomus riparius larvae over multiple generations. The authors found that the occurrence of mouthpart deformities was significantly correlated with inbreeding, whereas no correlation was found with the tributyltin exposure. The present study confirms the strong effect of high inbreeding rates on developmental deformities in chironomids.

In vivo effect confirmation of anti-androgenic compounds in sediment contact tests with Potamopyrgus antipodarum

In order to investigate the sensitivity of Potamopyrgus antipodarum to anti-androgenic compounds, three spiked sediment tests were performed. The substances benzanthrone (7H-benz[de]anthracen-7-one), traseolide (ATII) and androstenone (5α-Androst-16-en-3-one) were previously identified in an effect-directed analysis study of the river Schijn in the north of Belgium. Although, in previous studies, all of the three compounds exhibited anti-androgenic activities in vitro, only the oxy-PAH benzanthrone had significant stimulating effects on the snails’ reproduction. The reproduction of P. antipodarum was significantly stimulated, following a sigmoidal dose response curve, whereby an EC50 of 10 ng/g dry sediment was calculated. Mortality was significantly increased at the highest concentration (69 ng/g dry sediment). The results indicate different relative potencies for the in vivo test with P. antipodarum and the in vitro anti-AR-CALUX assay, performed in a previous study. This highlights the importance of combined in vitro and in vivo assays for the effect assessment of field sediments.