Matthias Oetken

Bisphenol A induces superfeminization in the ramshorn snail Marisa cornuarietis(Gastropoda: Prosobranchia) at environmentally relevant concentrations.

Previous investigations have shown that bisphenol A (BPA) induces a superfeminization syndrome in the freshwater snail Marisa cornuarietis at concentrations as low as 1 μg/L. Superfemales are characterized by the formation of additional female organs, enlarged accessory sex glands, gross malformations of the pallial oviduct, and a stimulation of egg and clutch production, resulting in increased female mortality. However, these studies were challenged on the basis of incomplete experimentation. Therefore, the objective of the current approach was to bridge several gaps in knowledge by conducting additional experiments. In an initial series of experiments, study results from the reproductive phase of the snails were evaluated in the sub-micrograms per liter range. Before and after the spawning season, superfemale responses were observed [NOEC (no observed effect concentration) 7.9 ng/L, EC10 (effective concentration at 10%) 13.9 ng/L], which were absent during the spawning season. A further experiment investigated the temperature dependence of BPA responses by exposing snails at two temperatures in parallel. The adverse effect of BPA was at least partially masked at 27°C (EC10 998 ng/L) when compared with 20°C (EC10 14.8 ng/L). In M. cornuarietis, BPA acts as an estrogen receptor (ER) agonist, because effects were completely antagonized by a co-exposure to tamoxifen and Faslodex. Antiandrogenic effects of BPA, such as a significant decrease in penis length at 20°C, were also observed. Competitive receptor displacement experiments indicate the presence of androgen- and estrogen-specific binding sites. The affinity for BPA of the estrogen binding sites in M. cornuarietis is higher than that of the ER in aquatic vertebrates. The results emphasize that prosobranchs are affected by BPA at lower concentrations than are other wildlife groups, and the findings also highlight the importance of exposure conditions.

Evidence for Endocrine Disruption in Invertebrates

The issue of endocrine disruption (ED) in invertebrates has generated remarkably little interest in the past compared to research with aquatic vertebrates in this area. However, with more than 95% of all known species in the animal kingdom, invertebrates constitute a very important part of the global biodiversity with key species for the structure and function of aquatic and terrestrial ecosystems. Despite the fact that ED in invertebrates has been investigated on a smaller scale than in vertebrates, invertebrates provide some of the best documented examples for deleterious effects in wildlife populations following an exposure to endocrine-active substances. The article provides an overview of the diversity in endocrine systems of invertebrates. The principal susceptibility of invertebrates to endocrine-active compounds is demonstrated with the case studies of tributyltin effects in mollusks and of insect growth regulators, the latter as purposely synthesized endocrine disrupters. The additional evidence for ED in invertebrates from laboratory and field studies is summarized as an update and amendment of the EDIETA report from 1998. Finally, conclusions about the scale and implications of the observed effects are drawn and research needs are defined.

The Elbe flood in August 2002: Organic contaminants in sediment samples taken after the flood event

Abstract In the course of this study 37 sediment samples were analyzed. They were taken after the flooding in September 2002 along the Elbe and at the mouths of its major tributaries. The sampling program covered the entire river stretch that was affected by the floods, from Obristvi (Czech Republic) to the Elbe estuary (North Sea) on the German coast. Analyses were performed for dioxins, nonylphenols, nonylphenol ethoxylates, bisphenol A, DEHP, musk fragrances, polybrominated diphenylethers, chloroalkylphosphates, organochlorine compounds, PAH, and organotin compounds. The results show that only a few weeks after the flood, contaminant concentrations in solid matter were comparable to those prevailing beforehand. Significant sources of contaminant input proved to be the tributaries Vltava (Moldau), Bilina (both in the Czech Republic), and the Mulde (Germany), as well as industrial and municipal sewage treatment works (STW) located along the Elbe. Further point sources are to be found in still water zones such as harbors and abandoned channels. These sources are activated when erosive action stirs up older sediments. Statistical analyses of the congener distribution of the dioxins provided evidence on the sources of these contaminants and freight levels in different river sections. The chemical analyses were complemented by results of ecotoxicological investigations with two sediment organisms (Chironomus riparius and Potamopyrgus antipodarum).

Comparative Toxicity Assessment of Nanosilver on Three Daphnia Species in Acute, Chronic and Multi-Generation Experiments

The antibacterial properties of nanosilver have led to a versatile application spectrum including medical purposes and personal care products. However, the increasing use of nanosilver has raised concerns about its environmental impacts. Long-term exposure studies with aquatic invertebrates are essential to assess possible adverse effects on aquatic ecosystems. In the present study, acute (48 h), chronic (21 d) and long-term effects of nanosilver (primary size 15 nm) on five successive generations of three Daphnia species (D. magna, D. pulex, and D. galeata) were investigated. Acute EC50 values of nanosilver were 121 µg Ag L−1 for D. magna being the least sensitive species and 8.95 and 13.9 µg Ag L−1 for D. pulex and D. galeata, respectively. Chronic exposure provided EC10 values of 0.92 µg Ag L−1 for D. magna showing the most sensitive chronic reaction and 2.25 and 3.45 µg Ag L−1 for D. pulex and D. galeata, respectively. Comparative exposure to AgNO3 revealed a generally higher toxicity of the soluble form of silver. The multi-generation experiments resulted in effects on the population level for all tested species. Exposure of D. magna indicated an increased toxicity of nanosilver in the fifth generation of animals exposed to 10 µg Ag L−1. Neonates from pre-exposed parental daphnids did not completely recover when transferred into clean water. Exposure of D. pulex and D. galeata revealed not only increasing toxicity in some generations, but also greater tolerance to nanosilver. This study contributes to the assessment of the risk potential of nanosilver on aquatic ecosystems. It shows that effects of nanosilver vary within one genus and change with exposure duration. Therefore, long-term studies considering different aquatic species are needed to better understand the possible effects of nanosilver on aquatic ecosystems.

Effects of cadmium and tributyltin on development and reproduction of the non-biting midge Chironomus riparius (Diptera)—baseline experiments for future multi-generation studies

In this study the effects of tributyltin (TBT) and cadmium (Cd) were tested on the freshwater arthropod Chironomus riparius (Diptera) in life-cycle experiments. To this end, the OECD guideline 218 was extended with reproduction relevant parameters (e.g. number of fertile egg masses per female). Based on these reproduction data the number of larvae for next generation and the population growth rate were calculated. Experiments were performed using environmentally relevant concentrations of the test substances in the sediment (nominal ranges: 50–200 μ g Sn/kg and 0.2–2.1 mg Cd/kg, on a dry weight basis). Quartz sand was used as sediment in order to develop a test system for a following research project, focusing on the effects of TBT and Cd as model stressors on C. riparius populations in multi-generation studies. Both model stressors caused significant effects on development and reproduction of C. riparius. Larval mortality proved to be a sensitive parameter and a clear concentration-response relationship was observed with a significant increase (P < 0.001) at the highest TBT concentration and at a Cd concentration of 1.17 mg Cd/kg dw (P < 0.05). The two highest TBT concentrations emergence was significantly (P < 0.05) delayed compared to the solvent control. For Cd a clear prolonged average main emergence interval was observed, but not for TBT. TBT and Cd inhibited also oviposition. These effects resulted in a concentration-depended reduction of the population growth rate.

The Biological Effects and Possible Modes of Action of Nanosilver

Novel physicochemical and biological properties have led to a versatile spectrum of applications for nanosized silver particles. Silver nanoparticles are applied primarily for their antimicrobial effects, and may variety of commercially available products have emerged. To better predict and prevent possible environmental impacts from silver nanoparticles that are derived from increasing production volumes and environmental release, more data on the biological effects are needed on appropriate model organisms. We examined the literature that addressed the adverse effects of silver nanoparticles on different levels of biological integration, including in vitro and in vivo test systems. Results of in vitro studies indicate a dose-dependent programmed cell death included by oxidative stress as main possible pathway of toxicity. Furthermore, silver nanoparticles may affect cellular enzymes by interference with free thiol groups and mimicry of endogenous ions. Similar mechanisms may apply for antibacterial effects produced by nonasilver. These effects are primary from the interference nanosilver has with bacterial cell membranes. Few in vivo studies have been performed to evaluated the toxic mode of action of nanosilver or to provide evidence for oxidative stress as an important mechanism of nanosilver toxicity. Organisms that are most acutely sensitive to nanosilver toxicity are the freshwater filter-freeding organisms. Both in vitro and in vivo studies have demonstrated tha silver ions released from nanoparticle surface contribute to the toxicity, and, indeed, some findings indicated a unique nanoparticles effect. For an adequate evaluation of the environmental impact of nanosilver, greater emphasis should be placed on combining mechanistic investigations that are performed in vitro, with results obtained in in vivo test systems. Future in vivo test system studies should emphasize long-term exposure scenarios. Moreover, the dietary uptake of silver nanoparticles and the potential to bioaccumulate through the food web should be examined in detail.

Acute and chronic toxicity of four frequently used UV filter substances for Desmodesmus subspicatus and Daphnia magna

As a consequence of growing public concern about UV radiation effects on human health chemical and physical UV filters are increasingly used in personal care and other products. The release of these lipophilic and often persistent compounds into surface waters may pose a risk for aquatic organisms. The aim of the study was to determine effects of four frequently used UV filters on primary aquatic producers and consumers, the green alga Desmodesmus subspicatus and the crustacean Daphnia magna. Exposure to benzophenone 3 (BP3), ethylhexyl methoxycinnamate (EHMC), 3-benzylidene camphor (3-BC) and 3-(4′-methylbenzylidene)-camphor (4-MBC) resulted in growth inhibition of D. subspicatus with 72 h IC10 values of 0.56 mg/L (BP 3), 0.24 mg/L (EHMC), 0.27 mg/L (3-BC) and 0.21 mg/L (4-MBC). EC50 concentrations in the acute test with D. magna were 1.67, 0.57, 3.61 and 0.80 mg/L for BP3, EHMC, 3-BC and 4-MBC, respectively. Chronic exposure of D. magna resulted in NOECs of 0.04 mg/L (EHMC) and 0.1 mg/L (3-BC and 4-MBC). BP 3 showed no effects on neonate production or the length of adults. Rapid dissipation of these substances from the water phase was observed indicating the need for more frequent test medium renewal in chronic tests or the use of flow-through test systems.

Rapid genetic erosion in pollutant-exposed experimental chironomid populations.

Few studies have evaluated how effectively environmental contamination may reduce genetic diversity of a population. Here, we chose a laboratory approach in order to test if tributyltin (TBT) exposure at environmentally relevant concentrations leads to reduced genetic variation in the midge Chironomus riparius. Two TBT-exposed and two unexposed experimental populations were reared simultaneously in the laboratory for 12 generations. We recorded several life-history traits in each generation and monitored genetic variation over time using five variable microsatellite markers. TBT-exposed strains showed increased larval mortality (treatments: 43.8%; controls: 27.8%), slightly reduced reproductive output, and delayed larval development. Reduction of genetic variation was strongest and only significant in the TBT-exposed strains (treatments: -45.9%, controls: -24.4% of initial heterozygosity) after 12 generations. Our findings document that chemical pollution may lead to a rapid decrease in genetic diversity, which has important implications for conservation strategies and ecological management in polluted environments.

Effects of Ethinyloestradiol and Methyltestosterone in Prosobranch Snails

Recent reports have shown that a number of pharmaceuticals do occur not only in raw sewage but also in effluents of sewage treatment works, sewage sludge and receiving surface waters (Daughton and Ternes 1999; Kummerer 2001). The list of pharmaceuticals detected in aquatic ecosystems is steadily increasing while almost nothing is known regarding their potential effects on aquatic wildlife. Although concentrations of pharmaceuticals in the aquatic environment are generally in the lower ng l−1 and μg l−1 range, it has to be considered that these compounds were developed to exhibit a high biological activity, often associated with a high stability so that they are not readily biodegradable. Therefore, concerns have been raised regarding the potential impact from such compounds on aquatic wildlife even at the low reported environmental concentrations because of unknown safety factors and because accumulating compounds may attain much higher concentrations in organisms than in the water phase.

Long-term effects of nanoscaled titanium dioxide on the cladoceran Daphnia magna over six generations

We investigated the impact of nanoscaled titanium dioxide (nTiO2) on Daphnia magna populations in a multi-generational study over six generations (F0-F5). Each generation was exposed for 21 days to nTiO2 (AEROXIDE(®) TiO2 P25, primary particle size 21 nm) while mortality, individual growth, reproduction and population growth rates (PGR) were assessed as endpoints. The size distribution of nTiO2 in the single test media was analysed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). nTiO2 concentrations were measured using ICP-MS. Mortality and individual growth of D. magna were significantly affected with increasing exposure duration and concentration. Daphnids demonstrated decreasing reproduction over generations in all treatment groups (1.19-6 mg/L) but not in the control. At concentration levels of 1.78 mg/L chronic exposure resulted in a population collapse after five generations. This study indicates that multi-generational studies are suitable for evaluating long-term effects of nanoparticles since they reflect potential effects more accurately than single generation tests.