Pharmaceuticals contribute greatly to human and animal health. Given their specific biological targets, pharmaceuticals pose a significant environmental risk by affecting organisms and ecosystem processes, including leaf-litter decomposition. Although litter decomposition is a central process in forest streams, the consequences of exposure to pharmaceuticals remain poorly known. The present study assessed the impact of antibiotics as an important class of pharmaceuticals on the growth of the leaf-shredding amphipod Gammarus fossarum over 24 days. Exposure scenarios involved an antibiotic mixture (i.e. sulfamethoxazole, trimethoprim, erythromycin-H2O, roxithromycin, clarithromycin) at 0, 2 and 200 µg/L to assess impacts resulting from exposure to both water and food. The antibiotics had no effect on either leaf-associated fungal biomass or bacterial abundance. However, modification of leaf quality (e.g. through shifts in leaf-associated microbial communities) may have triggered faster growth of gammarids (assessed in terms of body mass gain) at the low antibiotic concentration relative to the control. At 200 µg/L, however, gammarid growth was not stimulated. This outcome might be due to a modified ability of the gut microflora to assimilate nutrients and carbon. Furthermore, the observed lack of increases in the diameter of the gammarids’ peduncles, despite an increase in gammarid mass, suggests antibiotic-induced effects in the moulting cycle. Although the processes responsible for the observed effects have not yet been identified, these results suggest a potential role of food-quality, gammarid gut microflora and alteration in the moulting cycle in mediating impacts of antibiotics on these detritivores and the leaf decomposition process in streams.

Due to the high use of antibiotics and antiparasitics for the treatment of livestock, there is concern about the potential impacts of the release of these compounds into freshwater ecosystems. In this context, the present study quantified the acute toxicity of two antibiotics (sulfadiazine and sulfadimidine), and three antiparasitic agents (flubendazole, fenbendazole, ivermectin) for nine freshwater invertebrate species. These experiments revealed a low degree of toxicity for the sulfonamide antibiotics, with limited implications in the survival of all test species at the highest test concentrations (50 and 100 mg/L). In contrast, all three antiparasitic agents indicated on the basis of their acute toxicity risks for the aquatic environment. Moreover, chronic toxicity data from the literature for antiparasitics, including effects on reproduction in daphnids, support the concern about the integrity of aquatic ecosystems posed by releases of these compounds. Thus, these pharmaceuticals warrant further careful consideration by environmental risk managers.

Recent evidence indicates that a variety of antibiotic residues may affect the integrity of streams located downstream from wastewater treatment plants. Aquatic communities comprising bacterial and fungal decomposers and invertebrate detritivores (shredders) play an important role in the decomposition of allochthonous leaf litter, which acts as a primary energy source for small running waters. The aim of the present study was to assess whether an antibiotic mixture consisting of sulfamethoxazole, trimethoprim, erythromycin‐H 2 O, roxithromycin, and clarithromycin has an effect on such a decomposer–detritivore system. Leaf discs were exposed to these antibiotics (total concentration of 2 or 200 μg/L) for approximately 20 d before offering these discs and corresponding control discs to an amphipod shredder, Gammarus fossarum , in a food choice experiment. Gammarus preferred the leaf discs conditioned in the presence of the antibiotic mixture at 200 μg/L over the control discs (pair‐wise t test; p = 0.006). A similar tendency, while not significant, was observed for leaves conditioned with antibiotics at a concentration of 2 μg/L. The number of bacteria associated with leaves did not differ between treatments at either antibiotic concentration ( t test; p = 0.57). In contrast, fungal biomass (measured as ergosterol) was significantly higher in the 200 μg/L treatment ( t test; p = 0.038), suggesting that the preference of Gammarus may be related to a shift in fungal communities. Overall these results indicate that mixtures of antibiotics may disrupt important ecosystem processes such as organic matter flow in stream ecosystems, although effects are likely to be weak at antibiotic concentrations typical of streams receiving wastewater treatment plant effluents.

Integrated Environmental Assessment and ManagementVolume 5, Issue 1 p. 175-177 Special Series Reducing uncertainty in environmental risk assessment (era): clearly defining acute and chronic toxicity tests Torsten Hahn, Torsten Hahn Fraunhofer ITEM, Hannover, GermanySearch for more papers by this authorJenny Stauber, Corresponding Author Jenny Stauber [email protected] Centre for Environmental Contaminants Research, CSIRO Land and Water, Sydney, AustraliaCentre for Environmental Contaminants Research, CSIRO Land and Water, Sydney, AustraliaSearch for more papers by this authorStuart Dobson, Stuart Dobson Centre for Ecology and Hydrology, Monks Wood, United Kingdom, USASearch for more papers by this authorPaul Howe, Paul Howe Centre for Ecology and Hydrology, Monks Wood, United Kingdom, USASearch for more papers by this authorJanet Kielhorn, Janet Kielhorn Fraunhofer ITEM, Hannover, GermanySearch for more papers by this authorGustav Koennecker, Gustav Koennecker Fraunhofer ITEM, Hannover, GermanySearch for more papers by this authorJerry Diamond, Jerry Diamond Tetra Tech, Owings Mills, MD, USASearch for more papers by this authorChris Lee-Steere, Chris Lee-Steere Australian Environment Agency, Deakin, ACT, AustraliaSearch for more papers by this authorUwe Schneider, Uwe Schneider National Standards and Guidelines Office, Environment Canada, Gatineau, QC, CanadaSearch for more papers by this authorYoshio Sugaya, Yoshio Sugaya National Institute for Environmental Studies, Ibaraki, JapanSearch for more papers by this authorKen Taylor, Ken Taylor Existing Substances Division, Environment Canada, Gatineau, QC, CanadaSearch for more papers by this authorRick Van Dam, Rick Van Dam Environmental Research Institute of the Supervising Scientist, Darwin, AustraliaSearch for more papers by this authorInge Mangelsdorf, Inge Mangelsdorf Fraunhofer ITEM, Hannover, GermanySearch for more papers by this author Torsten Hahn, Torsten Hahn Fraunhofer ITEM, Hannover, GermanySearch for more papers by this authorJenny Stauber, Corresponding Author Jenny Stauber [email protected] Centre for Environmental Contaminants Research, CSIRO Land and Water, Sydney, AustraliaCentre for Environmental Contaminants Research, CSIRO Land and Water, Sydney, AustraliaSearch for more papers by this authorStuart Dobson, Stuart Dobson Centre for Ecology and Hydrology, Monks Wood, United Kingdom, USASearch for more papers by this authorPaul Howe, Paul Howe Centre for Ecology and Hydrology, Monks Wood, United Kingdom, USASearch for more papers by this authorJanet Kielhorn, Janet Kielhorn Fraunhofer ITEM, Hannover, GermanySearch for more papers by this authorGustav Koennecker, Gustav Koennecker Fraunhofer ITEM, Hannover, GermanySearch for more papers by this authorJerry Diamond, Jerry Diamond Tetra Tech, Owings Mills, MD, USASearch for more papers by this authorChris Lee-Steere, Chris Lee-Steere Australian Environment Agency, Deakin, ACT, AustraliaSearch for more papers by this authorUwe Schneider, Uwe Schneider National Standards and Guidelines Office, Environment Canada, Gatineau, QC, CanadaSearch for more papers by this authorYoshio Sugaya, Yoshio Sugaya National Institute for Environmental Studies, Ibaraki, JapanSearch for more papers by this authorKen Taylor, Ken Taylor Existing Substances Division, Environment Canada, Gatineau, QC, CanadaSearch for more papers by this authorRick Van Dam, Rick Van Dam Environmental Research Institute of the Supervising Scientist, Darwin, AustraliaSearch for more papers by this authorInge Mangelsdorf, Inge Mangelsdorf Fraunhofer ITEM, Hannover, GermanySearch for more papers by this author First published: 05 November 2009 https://doi.org/10.1897/1551-3793-5.1.175Citations: 3Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume5, Issue1January 2009Pages 175-177 RelatedInformation

This study tested the hypothesis: “does adaptation to fluctuating salinities lead to enhanced survival of the harpacticoid copepod M. parva when exposed to a combination of particle associated chlorpyrifos (CPF) exposure and hypoosmotic stress during a 96h sediment toxicity test?” The CPF exposure concentrations of 5.89–5.38μg/kg and the salinity decrease from 15 to 3ppt were based on conditions observed in the temporarily open Lourens River estuary, South Africa, in order to simulate changes during a runoff event. Results of the three-factorial ANOVA showed that pre-adaptation to varying salinities (p=0.02; p=0.001), salinity decrease (p=0.035; p<0.001), and CPF exposure (p<0.001; p<0.001), all had a significant negative impact on the survival rate of female and male M. parva, with a higher sensitivity of males specimens. The significant two-way interaction of salinity×adaptation for females and males (p=0.021; p<0.001), indicate that adaptation to fluctuating salinities was beneficial for male and female copepods, but the hypothesis of a three-way interaction was not supported. However, a trend indicated a lower survival rate of non-adapted females and males exposed to CPF and hypoosomotic stress (38±17%; 0±0%), compared to pre-adapted organisms (59±6.6%; 8.9±10%), which requires further elucidation. This study has important implications for the management of temporarily open estuaries in South Africa regarding regulation of freshwater abstraction from rivers.

With regard to possible detrimental effects of human and veterinary antibiotics in the aquatic environment, most research in this field assesses direct impacts of pharmaceuticals on vertebrate or invertebrate test organisms. Another related area of concern is the possible development of antibiotic-resistant bacteria by introducing antimicrobials into the aquatic compartment. However, indirect effects of antibacterials on the trophic cascade have rarely been investigated. This study contributes with an example of how indirect effects of antibiotics on leaf litter decay can be measured and to what extent shredder organisms might be affected. Results from food-selection experiments using Gammarus pulex (Amphipoda) demonstrated clear preferences for leaves conditioned in the absence versus those conditioned in the presence of two antibiotics, oxytetracycline and sulfadiazine. Although this result suggested that microbial and fungal colonisation during leaf litter conditioning might be adversely affected in the antibiotic-treated groups, analyses of total carbon and nitrogen content of conditioned leaf discs did not reveal differences among the treatments.

Spraydrift and edge-of-field runoff are important routes of pesticide entry into streams. Pesticide contamination originating from spraydrift usually resides in the water phase, while pesticides in contaminated runoff are to a large extent associated with suspended particles (SPs). The effects of two organophosphorous insecticides (OPs), chloropyrifos (CPF) and azinphos-methyl (AZP), on acetylcholinesterase (AChE) activity in rainbow trout were compared between two exposure scenarios, simulating spraydrift- and runoff-borne contamination events in the Lourens River (LR), Western Cape, South Africa. NOECs of brain AChE inhibition, determined after 1h of exposure followed by 24h of recovery, were 0.33μgl−1 for aqueous CPF, 200mgkg−1 for SP-associated CPF and 20mgkg−1 for SP-associated AZP (at 0.5gl−1 SP). The highest aqueous AZP concentration tested (3.3μgl−1) was without significant effects. Previously reported peak levels of aqueous CPF in the LR (∼0.2μgl−1) are close to its NOEC (this study), suggesting a significant toxicological risk to fish in the LR. By contrast, reported levels of SP-associated OPs in the LR are 20–200-fold lower than their NOECs (this study). In a comparative in situ study, trout were exposed for seven days at agricultural (LR2, LR3) and upstream reference (LR1) sites. No runoff occurred during the study. Brain AChE was significantly inhibited at LR3. However, OP levels at LR3 (CPF 0.01μgl−1; AZP 0.14μgl−1) were minor compared to concentrations having effects in the laboratory (see above). Additionally, muscle AChE activity was significantly higher in caged trout from LR1 than in animals maintained in laboratory tanks.

W ith its first appearance in 1986, Ulrich Beck’s work on risk society opened a new way of describing contemporary society.1 Industrial society in its specific modernity is shown as a sociological form of the past, which has already been replaced by what is called risk society. According to this suggestion, the society we live in can no longer be understood by observing politics, for it is marked by different subpolitics operating beyond democratic legitimation. Nevertheless, these subpolitics radically change the society we live in day by day: “Sub-political innovation institutionalized as ‘progress’ remains under the jurisdiction of business, science and technology, for whom democratic procedures are invalid. This becomes problematic in the continuity of reflexive modernization processes where in the face of increased or hazardous productive forces the sub-politics has taken over the leading role from politics in shaping society. . . .”2 The notion of subpolitics addresses a third form, beyond the opposition of the political and the nonpolitical:

The aerobic metabolic rate of the freshwater prosobranch Bithynia tentaculata (L.) was measured as the rate of oxygen consumption by groups of snails acclimated to temperatures of 12 degrees C, 18 degrees C and 24 degrees C. Responses to acute temperature alteration were also monitored. The results revealed that metabolic rate is essentially independent of ambient temperature: no differences were found among the respiration rates of the three differently acclimated groups. Metabolic effects of acutely elevated temperature were usually compensated in a highly efficient manner, resulting in low Q(10) values between 1.08 and 2.24. However, the 12 degrees C-acclimated snails remained inactive at temperatures above 18 degrees C, which is a typical stress response in B. tentaculata. The same behaviour occurred in 24 degrees C-acclimated snails at experimental temperatures below 24 degrees C. In both cases no active respiration rates could be determined. When the 18 degrees C-acclimated group was exposed to an experimental temperature of 12 degrees C, their oxygen consumption rate declined with a Q(10) of 5.53. In relation to previous findings on life-cycle strategy, as well as nutritional and reproductive physiology in B. tentaculata, the present results are discussed in the context of a seasonally controlled metabolism, reflecting the seasonally varying physiological needs of this species.

Acute effects of the endocrine disruptor bis(tri-n-butyltin) oxide (TBTO) on molting-hormone biosynthesis and imaginal-disc development were investigated in larvae of the midge Chironomus riparius (Meigen). Ecdysteroid synthesis was measured by 24-h incubation of molting-hormone-synthesizing tissues (prothoracic glands) in vitro with or without the addition of TBTO. The amount of ecdysteroids produced was analyzed by radioimmunoassay. Developmental effects in vivo were investigated by determining the developmental phase of the genital imaginal discs before and after a 48-h exposure to TBTO in water. Sex-specific effects were found with both endpoints. Ecdysteroid synthesis was significantly reduced (analysis of variance [ANOVA], p < or = 0.005) in female larvae at all concentrations (TBTO-Sn at 50, 500, and 5,000 ng/L), whereas a significant elevation of the biosynthesis rate occurred in male larvae in the 500-ng/L treatment (ANOVA, p < or = 0.05). In vivo experiments with development of the genital imaginal disc within a 48-h exposure period revealed a significantly slower development in female larvae and a significantly faster development in male larvae (contingency tables, p < or = 0.001) at all concentrations tested (TBTO-Sn at 10, 50, 200, and 1,000 ng/L). These results partly coincided with the in vitro effects on molting-hormone synthesis. The 48-h median lethal concentration (LC50) was 25 microg/L (20-30 microg/L 95% confidence intervals). The combination of in vitro and in vivo methods has proven to be a useful approach for the detection of endocrine effects of TBTO in C. riparius at levels 2,000-fold below the LC50 value. High sensitivity and short test duration suggest that chironomids may have potential as freshwater sentinel organisms for endocrine-disrupting chemicals.

The use of vitellogenesis as a marker for possible effects of endocrine disrupting agents on insects was tested in the aquatic midge Chironomus riparius. As test substances the synthetic ecdysoid tebufenozide, and the endocrine disruptors bisphenol a and 4-n-nonylphenol were applied in a semi-static manner. The yolk protein contents of freshly emerged (24 h) male and female midges were determined by an ELISA procedure. In males, where always low amounts of immunoreactivity were apparent, yolk concentrations were lowered by 10% after a 80 microg/l tebufenozide treatment, and by 20-25% after exposition to bisphenol a at concentrations of 1, 100, and 3,000 microg/l. 4-n-nonylphenol contamination caused an inverted dose-response curve. At low test concentrations (1.9-30 microg/l) reduced yolk immunoreactivity occurred, while at medium concentrations (120 and 500 microg/l) no significant effects were observable. In the most highly contaminated group (2,000 microg/l) yolk protein immunoreactivity was elevated to 107% of the control. Female yolk protein contents were affected only in the 3,000 microg bisphenol a/l contaminated group, where yolk immunoreactivity was reduced by ca. 10% compared to the control.

The effects of the molting-hormone agonistic insecticide tebufenozide on larvae of the midge Chironomus riparius Meigen were tested in two different exposure setups. After static contamination of first-instar larvae the NOEC, LOEC, and LC50 values were 13.2, 17.4, and 21.14 microg/L, respectively. Semistatic exposure of fourth-instar larvae revealed a lower susceptibility of elder larvae (NOEC 30 microg/L, LOEC 60 microg/L, and LC50 81.94 microg/L). In both cases mortality was not immediate; the effects were postponed and almost exclusively linked to the processes of pupation and emergence. Pupal mortality in the semistatic exposure scheme was twice as high in males as in females during a 100 microg/L treatment. This sex-specific effect probably resulted from the endocrine activity of tebufenozide. Its detection underlines the suitability of C. riparius as a model organism for investigating effects of endocrine-disrupting chemicals in aquatic insects.