Starnberg, Germany
Starnberg, Germany

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Hoss S.,Ecossa | Hoss S.,Bielefeld University | Heininger P.,Federal Institute of Hydrology BfG | Claus E.,Federal Institute of Hydrology BfG | And 3 more authors.
Ecological Indicators | Year: 2017

Fine, cohesive sediments provide a habitat for a very diverse fauna and considerably contribute to important ecosystem services of aquatic ecosystems. As fine sediments are often hotspots of chemical contamination, the benthic fauna has to be protected in order to maintain its ecological functioning and thereby the proper provision of important ecosystem services. However, in these habitats usually meiofaunal organisms prevail, which are, so far, neglected in biomonitoring studies, while routine benthos monitoring (e.g. according to the EU Water Framework Directive) is solely based on macroinvertebrates. The recently developed NemaSPEAR[%]-index filled this methodological gap by providing a monitoring tool using freshwater nematodes, which are one of the most abundant and species rich invertebrates in fine sediments. In the present study the NemaSPEAR[%]-index was revised and validated based on a larger data set of nematode species and physico-chemical properties in river sediments in order to increase its applicability. The larger data set led to a similar categorization of nematode species at risk (NemaSPEAR). Validation of the NemaSPEAR[%] with an independent test data set, as well as external field data published by other authors and experimental microcosm data confirmed its usefulness as a specific index detecting chemical induced changes in benthic communities, whereas the index also worked at a higher taxonomic level (genus; NemaSPEAR[%]genus). A separation of the index for metal and organic pollution (NemaSPEAR[%]metal, NemaSPEAR[%]organic) showed no benefits for assessing sediments with mixed contamination, allowing the use of only one NemaSPEAR[%] for overall pollution. Moreover, based on its variance in lowly polluted reference sediments, class boundaries were set up for categorizing samples according to their ecological status, with a NemaSPEAR[%] higher or lower 30% indicating an acceptable or not acceptable ecological status, respectively. Overall, this study confirmed the robustness and relevance of the NemaSPEAR[%]-index for assessing the quality of fine sediments and using it as a line of evidence in a weight-of-evidence framework. Thus, the index can be a valuable tool for classification and prioritization of fine sediments supporting risk managers and regulators in making sediment management decisions. © 2016 Elsevier Ltd


Hoss S.,Ecossa | Hoss S.,Institute For Biodiversitat Netzwerk Ibn | Reiff N.,Ecossa | Nguyen H.T.,Dienstleistungszentrum Landlicher Raum Rheinpfalz | And 5 more authors.
Science of the Total Environment | Year: 2014

Small-scale laboratory microcosms (30g soil in 50ml tubes) were evaluated for their suitability to assess the impact of chemicals on in situ soil nematode communities. For this purpose, appropriate conditions in the microcosms were explored to ensure stable conditions and a homogenous distribution of the nematodes. Then, the microcosms were used to assess the toxicity of insecticidal crystal proteins (Cry1A.105, Cry2Ab2, Cry3Bb1) present in genetically modified maize (MON89034×MON88017) on in situ nematode communities. Highly abundant and genus rich nematode communities could be maintained over a period of 12weeks. Due to a low variance between the replicates of the treatments, low detection limits could be achieved. Using meaningful stress indices, such as the maturity indices, the microcosm study revealed dose-dependent effects of the insecticidal Cry proteins that could be verified as toxic effects by comparing with effects of two positive controls (Cu, nematicidal Cry5B). Moreover, toxic effects could be differentiated from organic enrichment effects that were induced by the addition of plant material. With a NOECCommunity of 0.1mgkg-1 dry wt, the nematode communities reacted considerably more sensitive to the Cry proteins than a single-species nematode toxicity test (NOEC: 29mgl-1). The small-scale microcosm set-up turned out to be a suitable, low-budget tool for assessing the toxicity of chemicals on soil nematodes on community level, representing a link between single-species toxicity tests and large scale outdoor mesocosms. © 2013.


Hoss S.,Ecossa | Hoss S.,Institute For Biodiversitat Netzwerk Ibn | Menzel R.,Humboldt University of Berlin | Gessler F.,University of Gottingen | And 4 more authors.
Environmental Pollution | Year: 2013

The genetically modified maize MON89034 × MON88017 expresses different crystal (Cry) proteins with pesticidal activity against the European corn borer (Cry1.105; Cry2Ab2) and the Western corn root worm (Cry3Bb1). Non-target organisms, such as soil nematodes, might be exposed to the Cry proteins that enter the soil in course of crop growing. Therefore, the risk of those proteins for nematodes was assessed by testing their toxic effects on Caenorhabditis elegans. All three insecticidal Cry proteins showed dose-dependent inhibitory effects on C. elegans reproduction (EC50: 0.12-0.38 μmol L-1), however, at concentrations that were far above the expected soil concentrations. Moreover, a reduced toxicity was observed when Cry proteins were added jointly. A C. elegans mutant strain deficient for receptors for the nematicidal Cry5B was also resistant against Cry1.105 and Cry2Ab2, suggesting that these Cry proteins bound to the same or similar receptors as nematicidal Cry proteins and thereby affect the reproduction of C. elegans. © 2013 Elsevier Ltd. All rights reserved.


Hoss S.,Ecossa | Claus E.,Federal Institute of Hydrology BfG | Von der Ohe P.C.,Helmholtz Center for Environmental Research | Brinke M.,Bielefeld University | And 3 more authors.
Environment International | Year: 2011

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 (NemaSPEnotAR). 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. © 2011 Elsevier Ltd.


Traunspurger W.,Bielefeld University | Hoss S.,Ecossa | Witthoft-Muhlmann A.,Institute for Lake Research | Wessels M.,Institute for Lake Research | Gude H.,Bielefeld University
Fundamental and Applied Limnology | Year: 2012

Between February and April 2004, 48 sites in Lake Constance (Germany) were investigated to determine the distribution of the meiobenthic community, including 16 sites from the sub-littoral (13 - 30 m water depth), 16 sites from the profundal (31- 99 m) and 16 sites from the deep profundal (100 - 250 m). Lake-wide analysis showed no simple distribution pattern, but rather a heterogenic meiobenthic community composition, with nematodes representing the dominant group (48.7 %), followed by rotifers (27.7 %), harpacticoids (7.7 %), copepods (5.0 %), oligochaetes (3.7 %), ostracods (3.1 %), nauplii (1.9 %) and tardigrades (1.2 %). The relative abundances of all other investigated meiobenthic groups (cladocerans, chironomids, arachnids, gastrotrichs) were below 1 %. The densities of meiobenthic organisms varied greatly between sites, with nematodes reaching up to 3,336,676 and rotifers up to 6,357,008 individuals per m2. The abundances of most organisms varied significantly between the different water zones. Nematodes, copepods, nauplii and cladocerans, however, were equally distributed between sub-littoral and the profundal zones. Organisms showed their highest levels of abundance in the sub-littoral zone, with the exception of harpacticoids and ostracods, which were most abundant in the profundal and deep profundal respectively. A multivariate statistical analysis revealed that besides Chl-a explaining 47 % of the variance degenerated algae, water depth, mean grain size, organic carbon, C/N ratio and total phosphorus were significantly correlated with lake-wide community structure. In the sub-littoral, mean grain size was the most important parameter explaining 25.4 % of the variance, while in the profundal Chl-a (29.4 %) and in the deep profundal algae pigments (38.6 %) were the most important parameters for meiofaunal distribution and environmental variables. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.


Hagerbaumer A.,Bielefeld University | Hoss S.,Ecossa | Heininger P.,German Federal Institute of Hydrology | Traunspurger W.,Bielefeld University
Journal of Nematology | Year: 2015

With respect to their high abundances, their role as intermediaries between microorganisms and higher trophic levels, and their ubiquitous occurrence in all habitats, nematodes are of strong potential interest as environmental indicators. Ecotoxicological methods to evaluate the risk of anthropogenic pollutants on ecosystems require both in vitro and in vivo toxicity tests to investigate either mechanisms or pathways of toxicity and to set accurate toxicity thresholds. For this, the interest in nematodes as model organisms in ecotoxicology increased over the past few decades and existing appropriate experimental methods are reviewed in this manuscript. An overview of the various existing ecotoxicological tools for nematodes, ranging from molecular laboratory methods to experimental model ecosystem approaches, and their role as indicator organisms is given. The reviewed studies, approaches that range from species-based to community-based methods, reveal exciting possibilities for the future use of nematodes in ecotoxicological studies. Suitable ecotoxicological tools and ecological indices for nematodes should be integrated in weight-of-evidence approaches for assessing the ecological risk of contamination. © The Society of Nematologists 2015.


Hoss S.,Ecossa | Schlottmann K.,Bielefeld University | Traunspurger W.,Bielefeld University
Environmental Science and Technology | Year: 2011

Benthic organisms ingest dissolved and particle-bound contaminants together with their food, whereas it is not clear which fraction of the ingested suspension causes the toxic effects. In the standard toxicity test using the nematode Caenorhabditis elegans, the organisms are fed with bacteria that bind contaminants, thus influencing the bioavailability of the contaminants for the organisms. To unravel the role of food bacteria in the toxicity of contaminants in C. elegans, suspensions with varying densities of bacteria were spiked with the toxic metal cadmium (Cd), either via the water or via the bacteria. The toxicity of Cd to C. elegans was clearly related to the uptake of bacteria in the nematode's gut. An increase in the bacterial density resulted in a significant decrease in the toxicity of Cd such that toxic effects better correlated with the aqueous than with the bacterial-bound or total Cd concentrations. The results suggested that the aqueous Cd that was ingested together with the food was the best available fraction and thereby mainly caused the observed toxicity on the reproduction of C. elegans. © 2011 American Chemical Society.


PubMed | German Federal Institute of Hydrology BfG, Ecossa and Justus Liebig University
Type: Journal Article | Journal: Environmental science & technology | Year: 2016

In chronic toxicity tests with Caenorhabditis elegans, it is necessary to feed the nematode with bacteria, which reduces the freely dissolved concentration (Cfree) of hydrophobic organic chemicals (HOCs), leading to poorly defined exposure with conventional dosing procedures. We examined the efficacy of passive dosing of polycyclic aromatic hydrocarbons (PAHs) using silicone O-rings to control exposure during C. elegans toxicity testing and compared the results to those obtained with solvent spiking. Solid-phase microextraction and liquid-liquid extraction were used to measure Cfree and the chemicals taken up via ingestion. During toxicity testing, Cfree decreased by up to 89% after solvent spiking but remained constant with passive dosing. This led to a higher apparent toxicity on C. elegans exposed by passive dosing than by solvent spiking. With increasing bacterial cell densities, Cfree of solvent-spiked PAHs decreased while being maintained constant with passive dosing. This resulted in lower apparent toxicity under solvent spiking but an increased apparent toxicity with passive dosing, probably as a result of the higher chemical uptake rate via food (CUfood). Our results demonstrate the utility of passive dosing to control Cfree in routine chronic toxicity testing of HOCs. Moreover, both chemical uptake from water or via food ingestion can be controlled, thus enabling the discrimination of different uptake routes in chronic toxicity studies.


PubMed | Ecossa, Helmholtz Center Munich and Bielefeld University
Type: Journal Article | Journal: Environmental toxicology and chemistry | Year: 2015

The use of colloidal iron oxide (FeOx) in the bioremediation of groundwater contamination implies its increasing release into the environment and requires an assessment of its ecotoxicological risk. Therefore, microcosm experiments were carried out to investigate the impact of ferrihydrite colloids on the bacterial and meiofaunal communities of pristine freshwater sediments. The effects of ferrihydrite colloids were compared with those of ferrihydrite macroaggregates to discriminate between colloid-specific and general FeOx impacts. The influence of ferrihydrite colloids on the toxicity of sediment-bound fluoranthene was also considered. At high concentrations (496 mg Fe kg(-1) sediment dry wt), ferrihydrite colloids had a significant, but transient impact on bacterial and meiofaunal communities. Although bacterial community composition specifically responded to ferrihydrite colloids, a more general FeOx effect was observed for meiofauna. Bacterial activity responded most sensitively (already at 55 mg Fe kg(-1) dry wt) without the potential of recovery. Ferrihydrite colloids did not influence the toxicity of sediment-bound fluoranthene. Significant correlations between bacterial activity and meiofaunal abundances were indicative of trophic interactions between bacteria and meiofauna and therefore of the contribution of indirect food web effects to the observed impacts. The results suggest that the application of ferrihydrite colloids for remediation purposes in the field poses no risk for benthic communities, given that, with the exception of generic bacterial activity, any negative effects on communities were reversible.


PubMed | Ecossa, Bielefeld University and German Federal Institute of Hydrology
Type: Journal Article | Journal: Journal of nematology | Year: 2015

With respect to their high abundances, their role as intermediaries between microorganisms and higher trophic levels, and their ubiquitous occurrence in all habitats, nematodes are of strong potential interest as environmental indicators. Ecotoxicological methods to evaluate the risk of anthropogenic pollutants on ecosystems require both in vitro and in vivo toxicity tests to investigate either mechanisms or pathways of toxicity and to set accurate toxicity thresholds. For this, the interest in nematodes as model organisms in ecotoxicology increased over the past few decades and existing appropriate experimental methods are reviewed in this manuscript. An overview of the various existing ecotoxicological tools for nematodes, ranging from molecular laboratory methods to experimental model ecosystem approaches, and their role as indicator organisms is given. The reviewed studies, approaches that range from species-based to community-based methods, reveal exciting possibilities for the future use of nematodes in ecotoxicological studies. Suitable ecotoxicological tools and ecological indices for nematodes should be integrated in weight-of-evidence approaches for assessing the ecological risk of contamination.

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