Biochemical parameters in Tubifex tubifex as an integral part of complex sediment toxicity assessment

Background, aim, and scope

Restoration of lakes and reservoirs with extensive cyanobacterial water bloom often requires evaluation of the sediment quality. Next to the chemical analysis of known pollutants, sediment bioassays should be employed to assess toxicity of the present contaminants and to make predictions of associated risk. Brno reservoir in the Czech Republic is a typical example of water bodies with long-term problems concerning cyanobacterial water blooms. Comprehensive assessment of reservoir sediment quality was conducted since successful reservoir restoration might require sediment removal. An important part of this survey focused on an examination of the utility of Tubifex tubifex and its sublethal biochemical markers for the assessment of direct sediment toxicity.

Materials and methods

This complex study included chemical analysis of contaminants (heavy metals, organic pollutants), ecotoxicity testing of sediment elutriates (tests with Daphnia magna, Pseudomonas putida, Sinapis alba, Scenedesmus subspicatus), and other parameters. We have tested in more detail the applicability of T. tubifex as a test organism for direct evaluation of contact sediment toxicity. Survival tests after 14 days of exposure were complemented by an assessment of parameters serving as biomarkers for sublethal effects [such as total glutathione content (GSH), activities of the enzymes glutathione transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR)]. The data matrix was subjected to multivariate analysis to interpret relationships between different parameters and possible differences among locations.

Results

The multivariate statistical techniques helped to clearly identify the more contaminated upstream sites and separate them from the less contaminated and reference samples. The data document closer relationships of the detected sediment contamination with results of direct sediment exposure in the T. tubifex test regarding mortality but namely regarding the sublethal endpoints rather than the results obtained with other test organisms exposed to sediment elutriates. Aside from the reduction in T. tubifex survival, the sediments with organic pollution caused an increase in glutathione content and increased activities of glutathione S-transferase and glutathione peroxidase in the exposed T. tubifex worms.

Discussion

Results of our study confirm the suitability of T. tubifex for toxicity testing of raw waters and sediments. This longer-lasting direct contact test has proven more sensitive and appropriate to reflect a lower level of pollution than do the elutriate tests. Sensitive biochemical changes in T. tubifex, including an elevation in GSH levels and GST activities, reflect a general stimulation of detoxification metabolisms in the presence of xenobiotics. The results also suggest an important role of glutathione and related enzymes in detoxification processes and possible involvement of oxidative stress in toxicity mechanisms in benthic sediment-dwelling worms such as T. tubifex.

Conclusions

The complex assessment has identified the more contaminated samples with locally increased concentration of organic pollutants and significant ecotoxicity. The direct sediment contact test with T. tubifex and especially the biochemical parameters corresponded better to the lower level of pollution than the other tests with sediment elutriates. Despite its greater time and cost demands, the direct sediment contact test can provide a more realistic picture of exposure.

Recommendations and perspectives

Sediment bioassays should always be included as an integral part of the sediment quality assessment. The direct contact tests also take into account the more hydrophobic pollutants that are not easily available for the water elution but can still be accessible to the organisms. The T. tubifex test is a suitable option for contact sediment toxicity tests also because these animals show measurable sublethal biochemical changes that can be associated with this exposure.     

Ecotoxicological risk assessment of a quarry filling with seaport sediments using laboratory freshwater aquatic microcosms

Purpose

In France, contaminated seaport sediments cannot be discharged into the sea according to recent regulation. Hence, they must be managed on land. Among the solutions identified, that of filling terrestrial quarries located in the littoral zone is one of the most promising. However, this requires developing a methodology for ecological risk assessment; which was the aim of the SEDIGEST research program. In the present study, we report the results of toxicological impacts of three sediments on aquatic ecosystems close to a quarry. These results were used to formulate a risk assessment methodology.

Materials and methods

The ecotoxicological approach was based on laboratory microcosm assays applied to leachates obtained from the sediments. The microcosms contained synthetic water and sediment and five pelagic (micro-algae, duckweeds and daphnids) and benthic (chironomids and amphipods) freshwater species. The biota were exposed for 3 weeks to a range of leachate concentrations; metals were monitored in the water column and the effects (i.e. mortality, growth inhibition and midge emergence) were measured.

Results and discussion

The results showed an absence of acute toxicity at concentrations of <10% (v/v) but sublethal effects for concentrations between 1 and 10%. Given the complex nature of the leachates, it was difficult to determine the factors of toxicity. Metals, especially Cu, might have been responsible for some of the effects on the amphipods.

Conclusions

Future quarries filled with seaport sediments might emit pollutants to aquatic ecosystems in their vicinity, and risk assessors should ensure that predicted environmental concentrations of leachates are below the maximum leachate concentration acceptable for the whole ecosystem; for example, by multiplying the concentration safe for the microcosm organisms by a factor of 10.     

Acute toxicity of zinc and arsenic to the warmwater aquatic oligochaete <Emphasis Type="Italic">Branchiura sowerbyi</Emphasis> as compared to its coldwater counterpart <Emphasis Type="Italic">Tubifex tubifex</Emphasis> (Annelida,Clitellata)

Purpose

This study aimed at evaluating the acute effects of arsenic and zinc to the warmwater aquatic oligochaete Branchiura sowerbyi. Relative sensitivity with the coldwater species Tubifex tubifex was compared. Implications for the use of B. sowerbyi in the risk assessment of sediments in the tropics are discussed.

Materials and methods

Water-only (96 h) and sediment (14 days) toxicity tests were conducted with both species evaluating a concentration series of arsenic and zinc. The tests were conducted considering the environmental conditions in the natural habitat of T. tubifex (predominantly temperate) and B. sowerbyi (predominantly tropical). Both lethal and sublethal endpoints (autotomy of the posterior body parts, abnormal behavior and appearance) were determined in the tests. The lethal (LC₁₀ and LC₅₀) and effect (EC₁₀ and EC₅₀) concentrations were also determined to assess metal sensitivity for both species.

Results and discussion

Both test species were more sensitive to Zn than As in water-only tests, which is in agreement with previous studies evaluating the toxicity of these metals to aquatic oligochaetes. Sublethal effects were generally noted at concentrations lower than those leading to mortality. The warmwater oligochaete B. sowerbyi was more sensitive to both metals tested than the coldwater species T. tubifex.

Conclusions

Study findings support the need for using indigenous tropical species in risk assessments in the tropics. In addition, sublethal effect parameters should be included in toxicity testing with aquatic oligochaetes.

     

The use of a microbial contact toxicity test for evaluating cadmium bioavailability in soil

Background, Aims and Scope

Bioavailability of toxic compounds in soil can be defined as the fraction able to come into contact with biota and to cause toxic effects. The contact toxicity tests may detect the total toxic response of all bioavailable contaminants present in a sample. The objectives of this study were to evaluate the use of microbial contact toxicity tests for cadmium bioavailability assessment and to evaluate the relationship between sorption, soil characteristics and cadmium bioavailability.

Methods

A test soil bacterium,Bacillus cereus, was put in direct contact with the solid sample. Four unpolluted soils were selected to provide solid samples with a variety of physicochemical characteristics. The toxicity and sorption behaviour of cadmium spiked to the soil samples were determined.

Results, Discussion and Conclusions

A significant correlation between contact toxicity test results and partitioning of cadmium in the soil samples (r²= 0.79, p <0.05; n = 26) was found. The results confirm that the bioavailability of cadmium in soil depends on its sorption behaviour. Cadmium sorbed to the cation exchange sites associated with fulvic acids is non-bioavailable in the toxicity test employed in this study. It is concluded that the microbial contact toxicity test is a suitable tool for detecting cadmium bioavailablity in the soils used in this study.

Outlook

The application of microbial contact toxicity tests for bioavailability assessment can be very useful for the risk identification and remediation of soil-associated contaminants.     

Integrated toxicity evaluation of a pulp deposit using organisms of different trophic levels

Purpose

In order to assess possible adverse effects originating from pulp deposits in a Swiss lake, a sediment quality triad approach was applied with chemical, ecotoxicological and ecological assessment methods.

Materials and methods

To obtain an integrative picture of the potential ecotoxicological effects on organisms of different trophic levels, four test procedures were applied. The acute effects of pulp deposit pore water on a decomposer, the amphipod Gammarus fossarum, were monitored. Chronic toxicity of the pore water was evaluated on primary producers via a growth inhibition test with unicellular green algae (Pseudokirchneriella subcapitata) and on secondary consumers in a reproduction test with the water flea Ceriodaphnia dubia. To evaluate the effects of the pulp deposit on sediment inhabitants, a whole-life-cycle test with the non-biting midge Chironomus riparius was undertaken. Chemical assessment included dissolved organic carbon, extractable organic halogenic compounds, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals. The composition of the macrozoobenthos community was analysed in order to assess the ecological effects.

Results and discussion

G. fossarum displayed increased locomotor activity at 12.5% but not at 25% sample concentration during a short-time exposure of 20 h. Chronic effects compromised the reproduction and growth of C. dubia (lowest observed effect concentration, 12.5% sample concentration) with zero population growth in 100% pulp deposit pore water. In 100% pulp deposit, C. riparius exhibited increased mortality at 10 and 17 days after oviposition. Pulp deposits of 50% and 100% concentration caused a significantly lower emergence compared with the reference treatments (lake sediment and quartz sand). Additionally, the locomotor activity of chironomids decreased significantly in 25–100% pulp deposit. No chronic effects of pulp deposit pore water on algae photosynthesis and growth could be detected. The bioassay results were in accordance with an elevated content of PAHs, PCBs and metals in the pulp deposit. Significantly more organisms known to be tolerant to organic pollution were present within the macrozoobenthos community.

Conclusions

In general, for sediment inhabitants such as chironomids, the pulp deposit has to be classified toxic. In the present test setup, the toxicity of the pulp deposit was reflected better by the chronic test systems applied than by the acute ones. The applied testing framework could be a suitable tool to assess the risk of contaminated sites, and this information will help decide whether risk mitigation measures should be taken. In addition, with a similar approach, the success of any mitigation measures taken can be assessed.     

Evaluating the necessity for thermal treatment in clay-based metal immobilization techniques as an environmentally acceptable sediment remediation process

Purpose

The objective of this research was to apply the same immobilization (stabilization/solidification) clay-based treatments to sediment contaminated with different metals (Pb, Cd, Ni, Zn, Cu, Cr) with different distributions and availabilities in sediment. We also examined the possibility of using clay as an immobilization agent without the application of thermal treatment, in order to reduce the economic cost of this expensive remediation procedure.

Materials and methods

Clay from a canal in Vojvodina, Republic of Serbia, was used as the immobilization agent in a stabilization/solidification treatment to remediate metal-contaminated sediment. Semi-dynamic and toxicity characteristic leaching tests were conducted to assess the effectiveness of the nonthermal and thermal immobilization treatments with clay, and the long-term leaching behavior of these metals was determined using the following parameters: cumulative percentage of metals leached; diffusion coefficients; leachability indices; and toxicity characteristic leaching test concentration.

Results and discussion

Based on these parameters, both clay-based treatments were effective in immobilizing metals in the contaminated sediment. Results suggest that both heating temperature and clay proportion in the sediment–clay mixture impact the degree of metal immobilization.

Conclusions

Clay-based products are potentially good immobilization materials for metal-contaminated sediments, with the distribution of metals in the original sediment not influencing the efficacy of the treatments. Even without the thermal treatment, the metals were effectively immobilized. The leaching of metals was largely inside the regulatory limits and the treated samples can be regarded as nonhazardous materials. This justifies the choice of not applying the more expensive thermal treatment during remediation, especially when treating sediments containing a mixture of pollutants.     

DanTox—a novel joint research project using zebrafish (Danio rerio) to identify specific toxicity and molecular modes of action of sediment-bound pollutants

Introduction

The European Water Framework Directive aims to achieve a good ecological and chemical status in surface water of European rivers by the year 2015. Since sediments and particulate matter act as secondary sources for pollutants, applied sediment toxicology is perceived to play a major role for obtaining new knowledge that can contribute to successful attainment of the goal. However, the existing bioassays for sediment toxicity analyses do not provide sufficient data concerning bioavailability of environmental pollutants. In this regard, there is an urgent need to combine sediment contact assays with gene expression analysis to investigate mechanism-specific sediment toxicity.

Purpose

The aim of the novel joint research project is to develop a eukaryotic test system, which can be used to investigate the ecotoxicological effects of contaminated sediments on gene expression level (DNA-array and RT-PCR). Current ecotoxicological research customarily involves a battery of bioassays to cover different toxicological endpoints (e.g., teratogenicity, genotoxicity, mutagenicity, Ah-receptor-mediated toxicity, neurotoxicity). In contrast, methods that detect alterations in gene expression offer deeper insight by elucidating how chemical exposure and/or environmental challenge affect multiple metabolic pathways leading to these particular kinds of toxic response. Gene expression profiles reflect the way cells and organisms adapt or respond to a changing environment.

Conclusion

The present project aspires to increase the fundamental molecular and physiological knowledge concerning the mode of action of environmental toxicants in zebrafish (Danio rerio). By working with partners from the academic and research institutions as well as from industry and waterway regulations, the success of this basic research-driven joint project in terms of development and implementation of novel sediment toxicity methods will be realized.     

Sublethal effects of contaminated sediment on Arenicola marina

Purpose

The highest concentrations of environmental contaminants are generally found in marine sediments, and there is a need for knowledge concerning how and whether they affect sediment-dwelling organisms. This study aimed to assess sublethal effects in Arenicola marina exposed to two sediments from a contaminated fjord and two reference locations with different sediment characteristics.

Materials and methods

Duplicate contaminated sediments were used to investigate the robustness of current protocols for sediment testing. The two reference sediments, with different grain sizes and total organic carbon, were collected from the outer Oslofjord and the two contaminated sediments from Frierfjord. Polychaetes were exposed in quadruplicate sediment microcosms and sampled after 1, 2, 4 and 8?weeks of exposure. Oxidative stress resistance (total oxyradical scavenging capacity, TOSC) and components comprising the energy budget (cellular energy allocation, CEA) were determined for individual polychaetes.

Results and discussion

Arenicola maintained and increased body weights over the initial 4?weeks of exposure in all groups, except in one reference sediment (Elle). There were no differences between treatments in the scavenging capacity (TOSC). The most striking difference in how polychaetes partitioned energy resources was a difference in lipid and carbohydrate allocations for Arenicola held in the contaminated sediments over the initial weeks. Cellular respiration appeared to increase in polychaetes held in the Elle sediment and decreased for polychaetes held in the two Frierfjord sediments by weeks?4 and 8. In the overall CEA, this was offset by increased energy per weight stored in the Elle group, which resulted in an overall positive CEA for polychaetes held in that sediment, whereas polychaetes in the other treatments were close to neutral. Although CEA would thus indicate that Elle polychaetes had good health status, their body weight also decreased significantly over the experimental period compared to other treatments, indicating an overall negative effect.

Conclusions

This study has shown the importance of sediment characteristics when evaluating toxicity and how resource allocation can differ dramatically over a short time span in polychaetes held in similarly contaminated sediments. There were no clear effects of sediment contamination on CEA or TOSC in the polychaete A. marina. The findings are relevant for the design of both short- and long-term sediment studies.     

Application of a plant bioassay for the evaluation of ecotoxicological risks of heavy metals in sediments affected by mining activities

Purpose

The objective of this work was to evaluate the effectiveness of a plant bioassay (Phytotoxkit®) for screening ecotoxicological risks in sediments affected by mining activities.

Materials and methods

A total of 42 sediment samples affected by mining activities were studied, including 39 sediment samples from the Sierra Minera, Spain, an area affected by old extraction procedures, and three sediments from an area affected by opencast mining. These three samples were then mixed with limestone filler at 10, 20 and 30 %, providing nine stabilised samples. The total and soluble metal(loid) content (As, Cd, Cu, Fe, Pb and Zn) was determined in all samples, and the Phytotoxkit® bioassay was applied to determine the ecotoxicological effect of this procedure.

Results and discussion

The stabilised material had a neutral pH and low soluble metal(loid) concentration, similar to that of samples in which a natural attenuation process had taken place because of mixing with surrounding carbonate-rich materials. An ecotoxicological survey identified the low toxicity levels of the stabilised samples.

Conclusions

The applied bioassay is a good tool for screening metal(loid) contamination in areas affected by mining activities, since it provides information on both natural and simulated attenuation processes. The mixing of sediments with limestone filler could be applied to the remediation of zones affected by mining activities, because the toxicological effect on the tested organisms in the stabilised sediments was reduced significantly and the metal(loid) content was diminished.     

Toxicity survey of Canadian Arctic marine sediments

Purpose

This paper reports a toxicity survey of Canadian Arctic marine sediments. During the Amundsen scientific cruise, eight sites distributed across the Canadian Arctic and sub-Arctic regions were selected to highlight sensitive areas affected by either atmospheric deposition, ocean current, river drainage, or anthropogenic activities. As part of the Canadian-led ArcticNet research program, this study aims to monitor and to better understand potential changes likely to impact the Arctic.

Materials and methods

Surface sediments were investigated with bioanalytical tests to assess sediment toxicity. Testing of sediment elutriates was undertaken with the ARTOXKIT M, Microtox liquid phase (MLPA), and ROTOXKIT M toxicity assays, while whole sediment testing was carried out with the Microtox solid phase assay (MSPA) toxicity test procedure. Sediment mercury (Hg) content was also determined in each sample since Hg transport and toxicity is specifically an important issue in the Arctic and is generally a key indicator of the pollution status in many aquatic ecosystems.

Results and discussion

Based on bioassay results and sediment granulometric criteria, these Arctic sediments must be considered nontoxic. However, based on MSPA half maximal inhibitory concentrations (IC50s) and/or MLPA threshold effect concentration (TEC) values, some degree of toxicity may be measureable particularly in the sediments located in southern and northeast Hudson Bay. The Hudson Bay watershed drains 30% of Canadian rivers and extends to northern USA. Despite the large Hg concern in the Arctic, the input of local or long-range Hg sources does not appear to be a contributing factor to sediment toxicity.

Conclusions

These initial results are valuable in that they set baseline quality levels for these sediments as of 2005. As such, future comparisons can be made to assess temporal and spatial trends. Human activity and climate change is expected to impact these regions in the future, resulting in further reduction of sea ice extent, access to new Arctic seaways, and drilling associated with the exploitation of natural resources.     

Comparison of approaches towards ecotoxicity evaluation for the application of dredged sediment on soil

Purpose

The toxicity of 36 dredged sediments from the Czech Republic was investigated using a large battery of bioassays. The aim of this study was to investigate the feasibility of ecotoxicity testing in general and of individual bioassays more specific and to investigate how the results of bioassays are determined by the physicochemical properties of sediment samples and/or sediment contamination.

Material and methods

In 2008 and 2010, 36 sediment samples were collected from rivers and ponds and from sediment heaps in different parts of the Czech Republic. Both their physicochemical properties and their levels of contamination with POPs and heavy metals were analyzed. The ecotoxicities of the sediments were evaluated using the four bioassays from the new Czech directive 257/2009 Coll. concerning the application of dredged sediments on agricultural land (Enchytraeus crypticus reproduction, Folsomia candida reproduction, Lactuca sativa root elongation, and potential ammonium oxidation). The results of the four directive bioassays were compared with the results of other soil bioassays (Caenorhabditis elegans mortality, Eisenia fetida avoidance and reproduction) and eluate bioassays (Daphnia magna immobilization, Pseudokirchneriella subcapitata growth inhibition test, and Vibrio fischeri luminescence).

Results and discussion

We demonstrate that the battery suggested in Czech directive 257/2009 Coll. is highly effective in identifying toxic samples; these bioassays clearly revealing different types of toxicity and different exposure routes. Shorter alternative bioassays may be added especially when fast toxicity identification is needed. Eluate bioassays identified samples potentially hazardous to aquatic ecosystems. Their inclusion into the assessment scheme should be considered if the goal of assessment is also the protection of aquatic ecosystems. The results of our multivariate analysis show that specific physicochemical properties and contamination may affect bioassay responses. C. elegans was the most sensitive bioassay to physicochemical properties and also to organic contamination, while eluate bioassays were sensitive to heavy metal pollution.

Conclusions

Most effects detected by the bioassays could not be explained by the levels of toxicants measured or by the natural characteristics of sediments. Our results show that bioassays are irreplaceable in dredged sediment risk assessment because they complement information provided by chemical analyses.     

Combined effects of technical grade fenitrothion, humic acids and particulate matter on cholinesterase activity in freshwater invertebrates

Purpose

The relative sensitivity of two freshwater invertebrate organisms to the organophosphorus insecticide fenitrothion was assessed by measuring cholinesterase (ChE) activity, a well-known biomarker of both exposure and effect to organophosphorus pesticides. The influence of different concentrations of humic acids (HAs) and particulate matter on fenitrothion bioavailability was assessed in the more sensitive species.

Materials and methods

The selected invertebrates were the dwelling feeding oligochaete Lumbriculus variegatus and the pulmonate gastropod Biomphalaria glabrata. Acute 48-h bioassays were performed exposing organisms to different fenitrothion concentrations. The concentrations that induced 50 % inhibition of enzyme activity (EC₅₀) were calculated. Fenitrothion bioavailability was investigated using different concentrations of commercial HA or particulate matter. Sand and a diverse selection of chromatographic resins that have been proposed as analogues of natural sediments were selected. For these experiments, animals were exposed to a fenitrothion value similar to the EC₅₀.

Results and discussion

The 48-h EC₅₀ values were 12?±?2 and 23?±?3 μg?l^?1 for L. variegatus and B. glabrata, respectively. Depending on HA concentration and the characteristics of particles, ChE activity was similar or higher than the value recorded for animals exposed only to the pesticide in aqueous solution.

Conclusion

The results indicated that L. variegatus was the more sensitive species of the two. In this species, fenitrothion bioavailability did not increase due to the presence of either different HA concentrations or particulate matter. The experimental approach may constitute a useful tool to predict the influence of dissolved organic matter and sediment particles on fenitrothion bioavailability and toxicity to non-target aquatic invertebrates.     

Ecotoxic impact of suspended solids collected from polluted surface waters

Scope and background

Earlier studies showed that artificially contaminated particulate matter could be responsible for acute effects in water fleas and fish. Physical/chemical measurements on suspended solids and river water collected in the field showed that these samples were often contaminated with mixtures of toxic molecules.

Objectives

The present pilot study was started to investigate the possible ecotoxic impact of suspended solids collected in situ.

Methods

Suspended solids and river waters were collected from 22 locations of polluted rivers in the Flanders. An extensive list of chemical components and physical parameters were measured in these matrices. Partition coefficients for water column and suspended solids were calculated. Toxicity of suspensions of solid materials was investigated in 3 test organisms of different trophic levels: Bacteria (BIOMET®), filter feeder (Daphnia magna) and fish (rainbow trout (Oncor-hynchus mykiss) or zebrafish (Danio rerio)). The acute toxicity was measured in a worst-case scenario using high concentrations of solids resuspended in standard medium and at standard conditions.

Results and discussion

The partition coefficients were highly variable, showing that this parameter is not simply related to the octanol/water partition coefficient or to the total organic carbon content of the solids in field conditions, as is often assumed in exposure models. The field material of some locations was toxic. Bacteria were the most sensitive test organisms, showing EC20 values at field relevant concentrations. For some samples, acute toxic effects were seen in fish and water fleas. The chemical content of the samples was very complex and could not simply be related to toxicity. Some samples were highly contaminated with toxic chemicals and yet caused no toxic effects, while other samples did not show extremely high concentrations, but were toxic to the test organisms.

Conclusions

Results show that biotests are needed, next to chemical measurements, to estimate the toxic impact of complex environmental matrices. A better understanding of the adsorption/desorption behaviour of toxic molecules in the water compartment and in living organisms will contribute to a better environmental risk assessment.

Recommendations and outlook

The results indicate that the ecotoxic impact of suspended solids in the field should be further investigated in realistic (non-worst-case) conditions, i.e. for chronic effects at field relevant concentrations. And more extensive scientific research is needed to understand the adsorption/desorption behaviour of toxic molecules in different physicochemical matrices.     

Bioassay-directed Fractionation of Organic Extracts of Marine Surface Sediments from the North and Baltic Sea - Part II: Results of the biotest battery and development of a biotest index (8 pp)

-

Part I: Determination and identification of organic pollutants Part II: Results of the biotest battery and development of a biotest index

-

Preamble. This series of two papers presents the results of an interdisciplinary research project (ISIS) dealing with bioassay-directed fractionation of marine sediment extracts. Part I presents the extraction and fractionation procedure as well as the results of chemical analysis, including non-target analysis of sediments. Part II describes the results of the biotest battery in relation to chemicals possibly causing parts of the observed effects. A biotest index is used to compare the toxicities of the samples.

-

AUTHORS / AFFILIATIONS Ninja Reineke (3), Werner Wosniok (4), Dirk Danischewski (1), Heinrich Hühnerfuss (3), Angelika Kinder (5), Arne Sierts-Herrmann (5), Norbert Theobald (2), Hans-Heinrich Vahl (6), Michael Vobach (1), Johannes Westendorf (6) and Hans Steinhart (5).

-

(1) Federal Research Centre for Fisheries, Institute for Fishery Ecology, Palmaille 9, 22767 Hamburg, Germany (2) Federal Maritime and Hydrographic Agency, Bernhard-Nochtstr. 78, 20359 Hamburg, Germany (3) University of Hamburg, Institute for Organic Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany (4) University of Bremen, Institute of Statistics, Bibliothekstr. 1, 28334 Bremen, Germany (5) University of Hamburg, Institute for Food Chemistry, Grindelallee 117, 20146 Hamburg, Germany (6) University of Hamburg, University Hospital Hamburg-Eppendorf, Department for Toxicology, Vogt-Kölln-Str. 30, 22527 Hamburg, Germany (7) Eurofins Wiertz-Eggert-Jörissen, Stenzelring 14b, 21107 Hamburg, Germany

Goal, Scope and Background

The ecological relevance of contaminants in mixtures is difficult to assess, because of possible interactions and due to lacking toxicity data for many substances present in environmental samples. Marine sediment extracts, which contain a mixture of environmental contaminants in low concentrations, were the object of this study. The extracts were investigated with a set of different biotests in order to identify the compound or the substance class responsible for the toxicity. For this goal, a combination of biotests, biotest-directed fractionation and chemical analysis has been applied. Further on, a strategy for the development of a biotest index to describe the toxicity of the fractions without a prior ranking of the test results is proposed. This article (Part II) focuses on the biological results of the approach.

Methods

The toxicological potential of organic extracts of sediments from the North Sea and the Baltic Sea was analyzed in a bioassay-directed fractionation procedure with a set of biotests: luciferase reporter gene assays on hormone receptor and Ah receptor, arabinose resistance test, fish embryo test (Danio rerio), comet assay, acetylcholinesterase inhibition test, heat-shock protein 70 induction, oxidative stress and luminescence inhibition test (Vibrio fischeri). The test results provided the basis for the calculation of a biotest index by factor analysis to compare the toxicity of the samples and fractions.

Results and Discussion

Results of 11 biotests on different fractionation levels of the samples were described and discussed with regard to the occurrence of contaminants and their toxic potentials. Polychlorinated biphenyls, polycyclic aromatic hydrocarbons, quinones, brominated indoles and brominated phenols were in the focus of interest. A biotest index was constructed to compare the toxic responses in the samples and to group the biotest results.

Conclusion

The procedure presented in this study is well suited for bioassay-directed fractionation of marine sediment extracts. However, in relatively low contaminated samples, high enrichment factors and sufficient fractionation is necessary to allow identification of low concentrations of contaminants which is required to link effects and possible causes. In the present case, the relation between substances and effects was difficult to uncover due to relatively low concentrations of pollutants compared to the biogenic matrix and to the remaining complexity of the fractions. The results, with respect to the brominated phenols and indoles in the samples, highlight the successful use of bioassay directed fractionation in the case of high concentrations and high toxicity.

Recommendation and Outlook

In general, it has been shown that a marine risk assessment requires focusing on the input of diffuse sources and taking into account the fact of mixture toxicity. Effects resulting from biogenic substances will make the assessment of the influence of anthropogenic substances even more difficult.     

Assessing the risk of a 50-year-old dump site in the Baltic Sea by combining chemical analysis, bioaccumulation, and ecotoxicity

Purpose

During the late 1950s and early 1960s, industrial waste material highly enriched with various contaminants (e.g., heavy metals, polycyclic aromatic hydrocarbons (PAHs)) was dumped in the inner Bay of Mecklenburg, western Baltic Sea. Between 2002 and 2004, a research program was initiated using chemical analysis in combination with bioanalytical techniques to assess the extent and variability in contamination at this dump site (DS). The data were compared to a reference area (RS) with similar environmental conditions, which is representative of the western Baltic Sea.

Materials and methods

Twelve PAHs were investigated to assess their ecological hazard, as they were identified as major pollutants in the dumped material. In addition to analyzing the actual PAH contamination status in the sediments, PAHs measured in the soft tissue of Arctica islandica were also used as an indicator of contaminant bioaccumulation. A biotest battery was applied to determine the toxic effects of contaminants in the sediment.

Results and discussion

Significantly elevated PAH concentrations (sum of 12 PAHs) of ～3,000 ng g^?1 dw and higher bioaccumulation factors (BAFs) were determined in the soft body tissue of A. islandica collected at DS (t test, p?=?0.025). The results also showed that the sediment PAH contamination was significantly higher at DS (1,952–5,466 ng g^?1 dw) than at RS (1,384–2,315 ng g^?1 dw). The results revealed a major heterogeneity in the PAH concentration at DS due to an attempt to cover the toxic material with clean clay. This resulted in a more heterogeneous distribution of the dump material rather than covering it up completely. However, not all relevant contaminants were included in this study, not only because it is too costly to determine them all but also because unidentified contaminants present at concentrations below the limit of detection cannot be measured. Bioassays were used to fill this gap in the hazard assessment in a cost-effective way by investigating the possible effects of sediment contamination on benthic organisms. The results showed a high variability and magnitude of growth and luminescence inhibition. Bacterial contact tests with marine organisms showed a high toxicity response (>80 % inhibition) from DS sediments. In contrast, the luminescent bacteria test (Vibrio fischeri) showed equivalent effects of sediments from both DS and RS.

Conclusions

The spatial distribution of toxicity in DS, the bioaccumulation in mussels and the analytical evidence of PAH pollution clearly show that the dumped material still represents a potential risk even after 60 years.     

Suspended sediment dynamics during flushing flows in a large impounded river (the lower River Ebro)

Purpose

The aim of this work was to improve the understanding of the spatial and temporal dynamics of suspended sediment transport during flushing flows in a large regulated river, the lower River Ebro (NE Spain).

Materials and methods

Relationships between sediment and discharge (i.e. discharge (Q)–suspended sediment concentrations (SSC)) were examined during six flushing flows using continuous discharge and turbidity records obtained at six monitoring sections distributed along the lower Ebro River for the 2008–2011 period.

Results and discussion

Analyses revealed marked spatial and temporal patterns. At the spatial scale, the Q–SSC relationships were mostly influenced by the different routing velocity of discharge and sediment waves. At the upstream sections, the sediment peak usually preceded peak discharge (i.e. clockwise loop); however, flow routing through the 85-km channel length tends to increase the lag between them, modifying the hysteresis towards counter-clockwise patterns in the downstream direction. At the temporal scale, the season when the artificial releases were performed strongly influenced the sediment availability, with similar-magnitude flushing flows generating higher sediment peaks in autumn than in spring.

Conclusions

These results are of great interest in order to reinforce the flushing flows programme in the lower Ebro River, so as to help achieve the sustainability of the riverine and deltaic ecosystems.     

Applying a GLM-based approach to model the influence of soil properties on the toxicity of phenmedipham to Folsomia candida

Purpose

Soil properties are the main explanation to the different toxicities obtained in different soils due to their influence on chemical bioavailability and the test species performance itself. However, most prediction studies are centred on a few soil properties influencing bioavailability, while their direct effects on test species performance are usually neglected. In our study, we develop prediction models for the toxicity values obtained in a set of soils taking into account both the chemical concentration and their soil properties.

Materials and methods

The effects on the avoidance behaviour and on reproduction of the herbicide phenmedipham to the collembolan Folsomia candida is assessed in 12 natural soils and the Organisation for Economic Co-operation and Development (OECD) artificial soil. The toxicity outcomes in different soils are compared and explanatory models are constructed by generalised linear models (GLMs) using phenmedipham concentrations and soil properties.

Results and discussion

At identical phenmedipham concentrations, the effects on reproduction and the avoidance response observed in OECD soil were similar to those observed in natural soils, while effects on survival were clearly lower in this soil. The organic matter and silt content explained differences in the avoidance behaviour in different soils; for reproduction, there was a more complex pattern involving several soil properties.

Conclusions

Our results highlight the need for approaches taking into account all the soil properties as a whole, as a necessary step to improve the prediction of the toxicity of particular chemicals to any particular soil.     

Assessment of cytotoxicity and AhR-mediated toxicity of sediments from water level fluctuation zone in the Three Gorges Reservoir,China

Purpose

The Three Gorges Dam project is one of the biggest projects in the world. The water level fluctuation zone (WLFZ) was created with impoundment. The purpose of the current study is to investigate the ecotoxicological potential of the sediment extracts from the WLFZ and propose future WLFZ monitoring for early detection of environmental changes brought about by pollution.

Materials and methods

The investigation was performed by using cell-based in vitro bioassays to determine acute cytotoxicity (neutral red retention assay) and mechanism-specific aryl hydrocarbon receptor (AhR)-mediated activity (7-ethoxyresorufin-O-deethylase (EROD) induction assay) of sediment extracts with rainbow trout (Oncorhynchus mykiss) liver cells (RTL-W1).

Results and discussion

Results showed that the cytotoxicity and AhR-mediated toxicity potential of the sediment extracts from the WLFZ in the Three Gorges Reservoir (TGR) were moderate of level compared with the ecotoxicity of sediments from other river systems. However, according to a sediment classification system in Germany, sediments from some individual sites in the WLFZ showed strong toxicity. Compared to the results from the Yangtze River in our previous study, more attention should be paid to the aryl hydrocarbon receptor inducers in the WLFZ in TGR.

Conclusions

The in vitro bioassays used in this study may serve as a valuable tool to predict the potential ecological hazards of the organic pollutants in the WLFZ to the aquatic organisms in some extent.

     

Dominant discharges for suspended sediment transport in a highly active Pyrenean river

Purpose

Dominant discharges and associated sediment dynamics of the River Isábena, a 445-km² catchment in the central Pyrenees of Spain that is punctuated by badlands, are analysed.

Materials and methods

Calculations of suspended sediment loads are based on continuous records of discharge and turbidity obtained at the basin outlet for the period 2005–2010.

Results and discussion

Dominant discharges for sediment load (i.e. effective discharge) present a bimodal distribution, with one peak falling in the range of low flows and the other associated to less frequent but higher magnitude floods (i.e. bankfull). The highly suspended sediment availability in the badlands, together with the high connectivity between the badlands and the stream network and the important in-channel fine sediment storage, causes both large and small events to remobilize fines. Baseflows, despite their low competence, generate resuspension and massive sediment loads. Thus, effective discharge (i.e. the discharge which transports most of the sediment) is not solely associated with bankfull (i.e. the discharge that dominates channel form), but to a wider range of discharges. Consequently, this river channel is not specifically adjusted to convey most of the sediment load during high floods, as in many other rivers, but instead large volumes of sediment are transferred downstream at an almost constant rate.

Conclusions

Results suggest that dominant discharge may play a lesser role in terms of (suspended) sediment load in non-supply-limited fluvial systems and/or in rivers that permanently work close to, or at, full transport capacity, as is the case of the Isábena.     

Connectivity of sediment transport in a semiarid environment: a synthesis for the Upper Jaguaribe Basin,Brazil

Purpose

Hydrosedimentological studies conducted in the semiarid Upper Jaguaribe Basin, Brazil, enabled the identification of the key processes controlling sediment connectivity at different spatial scales (10⁰–10⁴ km²).

Materials and methods

Water and sediment fluxes were assessed from discharge, sediment concentrations and reservoir siltation measurements. Additionally, mathematical modelling (WASA-SED model) was used to quantify water and sediment transfer within the watershed.

Results and discussion

Rainfall erosivity in the study area was moderate (4600 MJ mm ha^?1 h^?1 year^?1), whereas runoff depths (16–60 mm year^?1), and therefore the sediment transport capacity, were low. Consequently, ～60 % of the eroded sediment was deposited along the landscape, regardless of the spatial scale. The existing high-density reservoir network (contributing area of 6 km² per reservoir) also limits sediment propagation, retaining up to 47 % of the sediment at the large basin scale. The sediment delivery ratio (SDR) decreased with the spatial scale; on average, 41 % of the eroded sediment was yielded from the hillslopes, while for the whole 24,600-km² basin, the SDR was reduced to 1 % downstream of a large reservoir (1940-hm³ capacity).

Conclusions

Hydrological behaviour in the Upper Jaguaribe Basin represents a constraint on sediment propagation; low runoff depth is the main feature breaking sediment connectivity, which limits sediment transference from the hillslopes to the drainage system. Surface reservoirs are also important barriers, but their relative importance to sediment retention increases with scale, since larger contributing areas are more suitable for the construction of dams due to higher hydrological potential.