Walter Traunspurger

Effects of dissolved organic matter (DOM) on the bioconcentration of organic chemicals in aquatic organisms — a review —

Current knowledge on the effects of dissolved organic matter (DOM) on the bioconcentration of organic chemicals in aquatic animals (water fleas, mussels, amphipods and fish) is summarized. A graphical representation of the available data gives an overview of the magnitude of the observed effects. Most of the studies have shown decreases in bioconcentration in the presence of DOM (2 to 98% relative to DOM-free controls). However, at low DOM levels, up to 10 mg/L, also enhancements of bioconcentration due to DOM, ranging from 2 to 303% have been reported. Generally, the change in BCFW (Bioconcentration factor on a wet weight basis) per mg/L DOC was most pronounced at low levels of DOC. The data also show that DOM from different sources with different characteristics and quality can lead to substantial variations in the bioconcentration of organic compounds at comparable levels of DOC. While decreases in bioconcentration have generally been attributed to a lack of bioavailability of DOM-bound chemical, no mechanisms have been proposed to explain increased uptake of xenobiotics caused by DOM.

The effects of nematodes on bacterial activity and abundance in a freshwater sediment

Abstract The effects of natural nematode communities on bacterial activity and abundance were investigated in a microcosm study. Nematodes were added at different densities to a freshwater sediment and bacterial parameters were measured after 1, 5, 9, and 17 days. Significant effects of nematode density on bacterial activity were noted on day 5. No long-term changes in bacterial activity were recorded. Bacterial abundance displayed an overall decrease in both treatments and controls. In a second experiment, the effect of nematode feeding-type on bacterial activity was studied. Microcosms were incubated with 100 individuals of a fungus-feeding (Aphelenchus avenae) or a bacteria-feeding nematode species (Caenorhabditis elegans) respectively, and bacterial activity was determined after 0, 1, 2, 4, and 7 days. Significant time and feeding-type effects were found, with consistently higher bacterial activity estimates in treatments with bacteria-feeding nematodes. These results suggest that grazing affects bacterial activity, and indicate that grazing by nematodes may be more important in stimulating bacterial activity than bioturbation or excretion. Combining these results, we conclude that natural nematode communities may have an impact on bacterial activity, and that the magnitude of this impact depends on the proportion of actively feeding bactivores within the community.

Toxicity analysis of freshwater and marine sediments with meio- and macrobenthic organisms: a review

Benthic metazoans play a key role as test organisms in toxicity analyses of aquatic ecosystems. This report gives an overview of the species of benthic metazoans used for the assessment of toxicity in freshwater and marine sediments, as well as of the criteria relevant to the choice between test species and procedures. The main applications of these organisms are mono-species bioassays, test-batteries, analyses of benthic communities and bioaccumulation studies. Sediment toxicity assays, including acute and chronic exposures, have been developed for nematodes, insects, oligochaetes, polychaetes, crustaceans, molluscs and echinoderms. At least 30 species of freshwater and 71 species of marine and estuarine benthic metazoans have thus far been used in sediment toxicity bioassays. Although aquatic pollution is a world-wide problem, most sediment toxicity bioassays have been developed for organisms native to Europe and North America. The most common bioassay endpoints are mortality, development, growth and behavioural responses. The value of genetic, biochemical, physiological and pathological responses as toxicity endpoints is currently being investigated. The quest for additional test species and protocols is still a worthwhile endeavour in sediment ecotoxicology.

Ecotox-evaluation strategy for soil bioremediation exemplified for a PAH-contaminated site

During a bioremediation of a PAH-contaminated site chemical and biological analyses were carried out. The biological investigations included ecotoxicological analyses in the aqueous extract, (Pseudomonas putida, Photobacterium phosphoreum, daphnids, algae, fish) and analyses in the soil with introduced organisms (plants, earthworms) and natural soil organisms (nematodes, microorganisms). In all test systems a correspondence between decreasing toxicity and degradation of the easily biodegradable PAHs was found. From investigations with aqueous extracts therefore not only conclusions on potential risks for groundwater can be drawn, but these tests also seem to allow risk assessments for soil inhabitants. Furthermore with these tests comprising dilution series the extent of toxicity for soil organisms can be quantified more precisely than with terrestrial investigations. Of all aquatic test systems a constant remaining toxicity was found only in the Microtox text. The test with Daphnia magna indicated the intermediate formation of organism specific toxic metabolites. Therefore useful information may be obtained with biological analyses which complement chemical analyses. For an extensive assessment of a contaminated site a test battery is advisable.

The project VALIMAR (Validation of biomarkers for the assessment of small stream pollution): objectives, experimental design, summary of results, and recommendations for the application of biomarkers in risk assessment

Between 1995 and 1999, active and passivebiomonitoring experiments in two small streams,and tests with pollutant mixtures in thelaboratory were performed with brown trout(Salmo trutta f. fario) and stone loach(Barbatula barbatula) in order toevaluate the suitability of biomarkersrepresenting different levels of biologicalorganization for the assessment of pollution insmall streams. The following groups ofbiomarker responses were measured in bothspecies: (1) induction of stress proteins(hsp70) in fish liver, (2) alterations in theactivities of 13 metabolic enzymes and ofacetylcholine esterase in liver or brain in vivo as well as in cultured fish cells, (3)changes in phase I and II biotransformationenzyme activities in liver, (4) responses ofblood parameters, (5) histopathologicalalterations in liver, kidney, gills, andspleen, and (6) ultrastructural effects in theliver, gills, and kidney of individuals, aswell as in fish cell cultures. To supplementthese biomarker studies, (7) behavioral changesof fish and (8) impacts on embryo developmentwere also investigated. In parallel, the teststreams were characterized morphometrically,limnologically and analytically for five years.Furthermore, during the second-half of thisproject, ecological studies characterizingbrown trout and stone loach populationdemography and the fish, macro- andmeiozoobenthos communities in the two teststreams were also included. The present papersummarizes the aims and scopes and the generalresults of this project and provides a detaileddescription of the experimental designs whichare the basis of all related studies reportedin this issue. Recommendations are alsoprovided for the application of biomarkers inrisk assessment of small stream pollution.

Nematode species at risk--a metric to assess pollution in soft sediments of freshwaters.

Soft sediments are often highly polluted as many of the toxic chemicals introduced into surface waters bind to settling particles. The resulting accumulation of pollutants in the sediments poses a risk for benthic communities. However, pollution induced changes in benthic communities have been difficult to determine when using macro-invertebrates as bioindicators, as these organisms are often absent in soft sediment. The present study therefore examined the ability of meiofaunal organisms, specifically, nematodes, to assess the ecological status of soft sediments. Over a 9-year period, nematode communities present in sediments collected from large rivers and lake Constance in Germany were studied. These sediments showed a large range of physico-chemical properties and anthropogenic contamination. After the degree of metal and organic contamination was translated into ecotoxicologically more relevant toxic units (TUs), multivariate methods were used to classify nematode taxa in species at risk (NemaSPEAR) or not at risk (NemaSPE(not)AR). This approach clearly distinguished the influence of sediment texture from that of the toxic potential of the samples and thus allowed classification of the nematode species according to their sensitivity to or tolerance of toxic stress. Two indices, expressing the proportion of species at risk within a sample (NemaSPEAR[%](metal), NemaSPEAR[%](organic)), were calculated from independent data sets obtained in field and experimental studies and showed good correlations with the toxic potential (field data) or chemical concentrations (microcosm data). NemaSPEAR[%] indices for metal and organic pollution were therefore judged to be suitable for assessing the impact of chemical contamination of freshwater soft sediments.

Environmental risk assessment of ivermectin: A case study.

The veterinary parasiticide ivermectin was selected as a case study compound within the project ERAPharm (Environmental Risk Assessment of Pharmaceuticals). Based on experimental data generated within ERAPharm and additional literature data, an environmental risk assessment (ERA) was performed mainly according to international and European guidelines. For the environmental compartments surface water, sediment, and dung, a risk was indicated at all levels of the tiered assessment approach. Only for soil was no risk indicated after the lower tier assessment. However, the use of effects data from additional 2-species and multispecies studies resulted in a risk indication for collembolans. Although previously performed ERAs for ivermectin revealed no concern for the aquatic compartment, and transient effects on dung-insect populations were not considered as relevant, the present ERA clearly demonstrates unacceptable risks for all investigated environmental compartments and hence suggests the necessity of reassessing ivermectin-containing products. Based on this case study, several gaps in the existing guidelines for ERA of pharmaceuticals were shown and improvements have been suggested. The action limit at the start of the ERA, for example, is not protective for substances such as ivermectin when used on intensively reared animals. Furthermore, initial predicted environmental concentrations (PECs) of ivermectin in soil were estimated to be lower than refined PECs, indicating that the currently used tiered approach for exposure assessment is not appropriate for substances with potential for accumulation in soil. In addition, guidance is lacking for the assessment of effects at higher tiers of the ERA, e.g., for field studies or a tiered effects assessment in the dung compartment.

Life cycle and population growth rate of Caenorhabditis elegans studied by a new method

BackgroundThe free-living nematode Caenorhabditis elegans is the predominant model organism in biological research, being used by a huge number of laboratories worldwide. Many researchers have evaluated life-history traits of C. elegans in investigations covering quite different aspects such as ecotoxicology, inbreeding depression and heterosis, dietary restriction/supplement, mutations, and ageing. Such traits include juvenile growth rates, age at sexual maturity, adult body size, age-specific fecundity/mortality, total reproduction, mean and maximum lifespan, and intrinsic population growth rates. However, we found that in life-cycle experiments care is needed regarding protocol design. Here, we test a recently developed method that overcomes some problems associated with traditional cultivation techniques. In this fast and yet precise approach, single individuals are maintained within hanging drops of semi-fluid culture medium, allowing the simultaneous investigation of various life-history traits at any desired degree of accuracy. Here, the life cycles of wild-type C. elegans strains N2 (Bristol, UK) and MY6 (Münster, Germany) were compared at 20°C with 5 × 109Escherichia coli ml-1 as food source.ResultsHigh-resolution life tables and fecundity schedules of the two strains are presented. Though isolated 700 km and 60 years apart from each other, the two strains barely differed in life-cycle parameters. For strain N2 (n = 69), the intrinsic rate of natural increase (rmd-1), calculated according to the Lotka equation, was 1.375, the net reproductive rate (R0) 291, the mean generation time (T) 90 h, and the minimum generation time (Tmin) 73.0 h. The corresponding values for strain MY6 (n = 72) were rm = 1.460, R0 = 289, T = 84 h, and Tmin = 67.3 h. Peak egg-laying rates in both strains exceeded 140 eggs d-1. Juvenile and early adulthood mortality was negligible. Strain N2 lived, on average, for 16.7 d, while strain MY6 died 2 days earlier; however, differences in survivorship curves were statistically non-significant.ConclusionWe found no evidence that adaptation to the laboratory altered the life history traits of C. elegans strain N2. Our results, discussed in the light of earlier studies on C. elegans, demonstrate certain advantages of the hanging drop method in investigations of nematode life cycles. Assuming that its reproducibility is validated in further studies, the method will reduce the inter-laboratory variability of life-history estimates and may ultimately prove to be more convenient than the current standard methods used by C. elegans researchers.

Invertebrate colonization of granular activated carbon filters

Results of biological sampling of granular activated carbon (GAC) filtrate taken between May 1994 and August 1995 at three different treatment plants along the river Rhine indicate that GAC filters are colonized by invertebrates. Dominating organism groups were rotifers and nematodes. Depending on operational characteristics, mainly regeneration intervals and backwashing procedures, the filter colonization can lead to an output of organisms in high numbers with the filtrate. Examples are given for the development of filter colonization and for the influence of different backwashing procedures to reduce numbers of invertebrates in GAC filters. These findings underline the establishment of a complex food web in a GAC filter, the consequences of which still remain to be investigated in detail.

A three year study of seasonal dynamics of a zoobenthos community in a eutrophic lake

The meiofauna community in the eutrophic Lake Obersee was investigated, with special emphasis on nematodes, from March 2001 to December 2003. Meiobenthos showed a stable annual and seasonal pattern with oligochaetes contributing most to benthic biomass and nematodes to benthic abundance. With 152 nematode species, Lake Obersee is the most nematode species-rich lentic habitat described so far. The nematode community was dominated by the family Monhysteridae. Bacterial feeders were the most abundant feeding type; omnivorous nematodes contributed most to total nematode biomass. Reproduction occurred throughout the year, with most species reproducing parthenogenetically. No seasonal pattern in reproductive strategies was found.