Sediment Bioassays Research Articles

Biological and chemical characterization of harbour sediments from the Stockholm area

The main objective of the current study was to assess the impact of pleasure boat activities on harbour sediment quality in the Stockholm area. Sediment contamination is a growing ecological issue, and there is consequently a need to use sediment bioassays in combination with chemical analysis to determine the impact on the ecosystem. To generate sediment toxicity data relevant for the Baltic Sea, a secondary objective was to further develop and evaluate two well-established bioassays for saltwater, with the macroalga Ceramium tenuicorne and the crustacean Nitocra spinipes, to be useful also for toxicity testing of whole sediment. A major concern has been to minimize any manipulation of the sediments. A third objective was to assess whether a simple leaching procedure could be used to simulate sediment toxicity by comparing results from whole sediment and leachate tests. Surface sediments (0–2 cm) from five different types of pleasure boat harbours were collected. Chemical measurements of boat related compounds, i.e. tin organic substances (tributyltin (TBT), dibutyl tin, and monobutyl tin), polyaromatic hydrocarbons (PAHs), copper, zinc, lead, tin and irgarol were conducted. The sediments were tested for toxic effects using the established Microtox® test as well as the developed sediment tests with C. tenuicorne and N. spinipes. The endpoints are growth inhibition for the algal test and for the crustacean test mortality of larvae and rate of development expressed as the ratio between nauplia and copepodites. Two different procedures have been compared with both organisms, i.e. exposure to whole sediment and to leachate. The duration of both tests is around 1 week. All harbour locations were more or less heavily contaminated with remnants from use of anti-fouling paints. The sediment in a smaller marina (ca. 250 boats) contained the highest levels of TBT (max 1,400 µg/kg dry weight (dw)), whereas the centre of Stockholm City had the highest concentrations of all measured metals (max values Cu 252, Pb 830, Sn 25 and Zn 600 µg/kg dw) as well as high concentrations of total PAH (18 mg/kg dw). All three organisms were well suited to test the toxicity of contaminated sediments and were able to discriminate between more or less polluted sediments. The sediments in the smaller marina were most toxic along with sediments adjacent to slipways and sediments from the centre of Stockholm. No significant difference was found between the two different procedures for the algal tests. The whole sediment test was significantly more toxic to N. spinipes than the test using leachate. Our results show that in spite of prohibition for many years to use tin organic substances and copper, boat activities still contribute with high concentrations of these toxic substances from anti-fouling paints in the surface sediment and that these have effects on organisms normally living in this environment. The present study has also demonstrated an expansion of two well-established toxicity tests for the water phase to be practical also for sediment toxicity testing. This will further increase the usefulness of these test organisms and methods for hazard and risk assessment in a wide range of environments.

A retrospective analysis to explore the applicability of fish biomarkers and sediment bioassays along contaminated salinity transects

Abstract Schipper, C. A., Lahr, J., van den Brink, P. J., George, S. G., Hansen, P-D., da Silva de Assis, H. C., van der Oost, R., Thain, J. E., Livingstone, D., Mitchelmore, C., van Schooten, F-J., Ariese, F., Murk, A. J., Grinwis, G. C. M., Klamer, H., Kater, B. J., Postma, J. F., van der Werf, B., and Vethaak, A. D. 2009. A retrospective analysis to explore the applicability of fish biomarkers and sediment bioassays along contaminated salinity transects. – ICES Journal of Marine Science, 66: 2089–2105. Biological-effects monitoring in estuarine environments is complex as a result of strong gradients and fluctuations in salinity and other environmental conditions, which may influence contaminant bioavailability and the physiology and metabolism of the organisms. To select the most robust and reliable biological-effect methods for monitoring and assessment programmes, a large-scale field study was conducted in two estuarine transects in the Netherlands. The locations ranged from heavily polluted harbour areas (the ports of Rotterdam and Amsterdam) to cleaner coastal and freshwater sites. Assessment methods used included a variety of biomarkers in flounder (Platichthys flesus) and a range of in vitro (sediment extracts) and in vivo bioassays. Multivariate statistical analysis was applied to investigate correlations and relationships between various biological effects and contaminant levels in flounder liver or sediments. Several biological methods seemed to be too much affected by salinity differences for routine use in estuaries. The most discriminative biomarkers in the study were hepatic metallothionein content and biliary 1-OH pyrene in fish. Mechanism-based in vitro assays DR-CALUX and ER-CALUX applied to sediment extracts for screening of potential toxicity were much more responsive than in vivo bioassays with macro-invertebrates using survival as an endpoint.

Wildlife toxicology: biomarkers of genotoxic exposures at a hazardous waste site

A large number of hazardous waste sites in the United States have undergone the initial stages of remediation or containment. At many of the remaining sites, the potential for exposure to ecological receptors is a primary concern. This manuscript reports on studies to investigate the impact on ecological receptors exposed to complex mixtures at a former creosote facility. Currently there are isolated areas on-site that were not addressed in the initial removal action that appear to be releasing polycyclic aromatic hydrocarbons (PAHs) to the surrounding environment. The U.S. EPA collected environmental samples and performed ex situ sediment bioassays to measure chronic toxicity; whereas, this study describes an in situ study to measure biomarkers of effect in two ecological receptors. Mosquitofish (Gambusia affinis) and cricket frogs (Acris crepitans) were collected from a small intermittent creek adjacent to the site, and reference stations. A weight-of-evidence ecological risk assessment was completed for the amphibian and fish communities. The ecological risk assessment was developed using analysis of media chemistry, body burden of specific PAHs, bioassay results, community surveys, and cellular genome size variation as a biomarker of genotoxicity. Flow cytometric estimates of chromosomal damage were significantly elevated for both mosquitofish and cricket frogs inhabiting the contaminated site, relative to at least one reference site. Surface water screening values for fish and amphibians exceeded screening values for PAHs by more than one order of magnitude in the on-site creek, and sediment PAH concentrations were extremely high (up to 1,549 microg/dry g). Tissue concentrations of PAHs were below screening values. Media chemistry, bioassay and genotoxicity data all support the same conclusion that on-site PAHs continue to impact aquatic receptors. The genotoxicity findings are consistent with and contribute to results of the weight-of-evidence ecological risk assessment. The results support continuing efforts to incorporate biomarkers as valuable lines of evidence within ecological risk assessment.

Agricultural Pesticides in Mississippi Delta Oxbow Lake Sediments During Autumn and Their Effects on Hyalella azteca

Agricultural pesticide contamination of sediments from five Mississippi Delta oxbow lakes and their effects and bioavailablity to Hyalella azteca were assessed during a low-application season-autumn. Three reference oxbow lakes were located in the White River National Wildlife Refuge (WRNWR), Arkansas and two impaired lakes, according to the US Environmental Agency Sect. 303 (d) Clean Water Act, were located in Mississippi. Surface sediment (top 5 cm) was collected at three sites within each lake and analyzed for 17 current and historic-use pesticides and metabolites. Chronic 28-day H. azteca sediment bioassays and pesticide body residue analyses were completed to determine the degree of biological responses and bioavailability. The greatest number of detectable pesticides in WRNWR and 303 (d) sediment samples was 9 and 12, respectively, with historic-use pesticide metabolite, p,p'-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] ubiquitous. No significant (p > 0.05) differences in animal survival were observed among sites. Animal growth was significantly (p < 0.05) less at only one site in a 303 (d)-listed lake (Macon Lake). Only six pesticides were observed in H. azteca with current-use pesticides detected at three sites; historic-use pesticides and metabolites detected at 11 sites. Animal body residues of a historic-use pesticide (dieldrin) and metabolite (p,p'-DDE) were associated with observed growth responses. Results show limited current-use pesticide contamination of sediments and H. azteca body tissues during autumn and that historic-use pesticides and metabolites are the primary contributors to observed biological responses.

Equilibrium partitioning theory to predict the sediment toxicity of the anionic surfactant C 12-2-LAS to Corophium volutator

The study of the effect of the sorption of linear alkylbenzene sulfonates (LAS) on the bioavailability to marine benthic organisms is essential to refine the environmental risk assessment of these compounds. According to the equilibrium partitioning theory (EqP), the effect concentration in water-only exposure will be similar to the effect concentration in the sediment pore water. In this work, sorption and desorption experiments with two marine sediments were carried out using the compound C 12-2-LAS. The effect of the sediment sorption on the toxicity of benthic organisms was studied in water-only and in sediment bioassays with the marine mud shrimp Corophium volutator. In addition, three common spiking methods were tested for its application in the toxicity tests, as well as the stability of the surfactant during the water-only and sediment–water test duration. LC50 values obtained from water-only exposure showed a good correspondence with the pore water concentrations calculated from the sorption and desorption isotherms in the spiked sediments.

Acute toxicity of some treatments commonly used by the salmonid aquaculture industry to Corophium volutator and Hediste diversicolor: Whole sediment bioassay tests

The commercial farming of Atlantic salmon, Salmo salar, typically requires the periodic application of copper-based anti-foulants and chemotherapeutic treatments, including Slice ®, Excis ®, Salmosan ® and Aquatet ®/Tetraplex ® to reduce the effects of biological pests. Information on the environmental safety of any chemical agent released into the aquatic environment must be obtained before a product can be licensed for use, but such information typically exists only in confidential technical reports which can be difficult to obtain. Furthermore, different test organisms, experimental protocols and reporting procedures make comparison of the various compounds/studies difficult. Here we present a series of 10-day, whole sediment bioassay tests that determined the concentrations of emamectin benzoate (EB), cypermethrin (CP), azamethiphos (AZ) and oxytetracycline hydrochloride (OTC), the active ingredients of the aforementioned chemotherapeutants, and copper, that caused 50% mortality (LC 50) in the non-target benthic crustacean, Corophium volutator. Additional whole sediment bioassays of identical design were conducted with the non-target polychaete worm, Hediste diversicolor exposed to copper and EB. C. volutator demonstrated similar sensitivity to EB and AZ, with LC 50s of 153 (95% confidence intervals, CI = 119–198) and 182 (95% CI = 152–217) µg active ingredient [kg wet sediment] − 1 respectively. OTC caused 50% mortality of C. volutator at a concentration of 414 (95% CI = 233–734) µg OTC [kg wet sediment] − 1 . The LC 50 for H. diversicolor exposed to EB was 1368 (95% CI = 744–2516) µg EB [kg wet sediment] − 1 , an order of magnitude greater than that for C. volutator. Conversely, C. volutator was able to tolerate much higher concentrations of copper than H. diversicolor, with LC 50s of 193,326 (95% CI = 171,034–218,523) and 74,988 (95% CI = 61,192–91,895) µg Cu [kg wet sediment] − 1 respectively. CP was the most toxic to C. volutator of all compounds investigated, causing 50% mortality at a concentration of 5 (95% CI = 4–6) µg CP [kg wet sediment] − 1 . These data allow direct inter-comparison of the toxicities of some of the commonly applied treatments used by the global salmonid aquaculture industry.

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.

Passaic river sediment interstitial water phase I toxicity identification evaluation

A suite of tests was conducted to evaluate and identify the cause or causes of toxicity in Passaic River sediments. Sediment toxicity was measured with three types of bioassays: a whole sediment bioassay with the marine amphipod, Ampelisca abdita, and interstitial water bioassays with A. abdita and the bioluminescent bacterium Vibrio fisheri (Microtox ®). In addition, a Phase I Toxicity Identification Evaluation (TIE) was conducted to elucidate the cause of observed toxicity. Analytical concentrations of selected residues in whole sediment and interstitial water from the five sampling stations were considered in conjunction with the conclusions drawn from the toxicity tests and Phase I TIE results. Finally, a toxic units approach was used to evaluate the predicted toxicity of measured interstitial water residue concentrations. There was a lack of toxic response in the short-term interstitial water bioassays, indicating that oxidants, soluble forms of metals, and dissolved phase neutral organics were not likely toxicants. However, there was significant toxicity indicated by the whole sediment A. abidita bioassays. After 10 days, there was complete or near complete mortality in amphipods exposed to all of the sediment samples tested. Removal of interstitial water toxicity by filtration was common to all four stations that exhibited measurable initial toxicity. The observed toxicity characteristics are consistent with particle associated neutral organics. This conclusion is supported by toxicity removal via filtration, lack of toxicity in the Microtox ® assays, and the fact that whole sediments were more toxic than was interstitial water.

Long‐term sediment bioassay of lead toxicity in two generations of the marine amphipod Elasmopus laevis, S.I. Smith, 1873

Sediments are evaluated for toxicity by measuring mortality in a single cohort of amphipods in either acute (10-d) or chronic (28-d) bioassays. This investigation differed from conventional bioassays in four ways: Sublethal effects (fecundity) were estimated; the testing period was 60+ d; two successive generations were examined; and Elasmopus laevis Smith, 1873, amphipods were employed. Four test sediments were created between 58 and 424 microg/g of lead using the 30-microg/g whole-sediment as the control. Bioaccumulated lead at 60 d varied as a linear function of lead concentration in the sediments. Fecundity, as estimated by offspring-per-chamber and/or percent reproductive success, was reduced as sediment lead concentrations increased and reproduction was delayed compared with the control. The reduction in offspring production per test chamber varied significantly as an inverse function of lead sediment concentration, best described by a curvilinear exponential equation. It was concluded that E. laevis exposed to 118 microg/g and higher could not maintain a population as large as that in the control. Although the current sediment quality guideline for lead stipulates that adverse biological effects likely will occur above 218 microg/g, this study revealed a statistically significant negative reproductive response at 118 microg/g lead, and suggests that the current regulatory guideline for lead, based on lethality, should be reconsidered.

Toxicity Assessment of Diazinon in a Constructed Wetland Using Hyalella azteca

The goal of this study was to examine the use of a constructed wetland to mitigate the ecological impacts of simulated diazinon runoff from agricultural fields into receiving waters, via 48 h aqueous and sediment bioassays using Hyalella azteca. Aqueous animal 48 h survival varied temporally and spatially in conjunction with measured diazinon concentrations. Sediment H. azteca survival varied temporally and spatially in conjunction with measured diazinon concentrations, but less than aqueous exposures, confirming that sediment bound diazinon was less bioavailable than aqueous diazinon.

Responses of Hyalella azteca to a Pyrethroid Mixture in a Constructed Wetland

Constructed wetlands used to mitigate pesticide runoff from agricultural fields into receiving systems (e.g., lakes, rivers, streams) have been successful in reducing concentrations of non-point source pollutants such as agricultural insecticides (Moore et al., 2002; Leistra et al., 2003; Bouldin et al., 2005). Such wetlands also have important functions in enhancing the water quality and ecological values (Moore et al., 2002), and different phases (i.e., aqueous, sediment and detritus) have separate roles, as either sinks or sources, in determining effectiveness of wetlands in mitigating pesticide toxicity. For these reasons, the importance of elucidating potential effectiveness of wetlands in reducing pesticide toxicity to aquatic biota exposed to these different phases needs to be addressed. The pyrethroid insecticides, k-cyhalothrin and cyfluthrin, were used as model contaminants in a constructed wetland located in Leflore County, Mississippi, USA, designed to mitigate runoff from an agricultural field. Pyrethroids are used on a variety of agricultural crops in Mississippi, however most applications are primarily with cotton (Gossypium sp.) (USDA, 2004). Approximately 3,150 kg of k-cyhalothrin and 10,350 kg of cyfluthrin were applied in Mississippi in 2003 and, as a result, may contribute to non-point source contamination of aquatic environments (USDA, 2004). This study examined the use of a constructed wetland to mitigate ecological impacts of a simulated pyrethriod mixture (k-cyhalothrin and cyfluthrin) in runoff from agricultural fields to receiving aquatic systems by using 48 h aqueous, detrital and sediment bioassays with the freshwater test organism, Hyalella azteca.

A sediment bioassay to assess the effects of aquaculture waste on growth, reproduction, and survival of Sphaerium simile (Say) (Bivalvia: Sphaeriidae)

Increasing concerns regarding the environmental sustainability of freshwater cage aquaculture have encouraged new research on the potential impacts of this industry. A trout aquaculture facility was operated in Lake 375 at the Experimental Lakes Area (ELA) in northwestern Ontario, Canada, in 2003 and 2004. As part of this experiment, the spatial extent and magnitude of the potential impacts of aquaculture waste on the benthic community were assessed in 2004 through a novel sediment bioassay using the fingernail clam Sphaerium simile (Say) (Bivalvia: Sphaeriidae). Survival, growth, reproduction, and metal body burdens were evaluated for individual clams exposed for 6 weeks to sediment collected from directly below the fish cage, and from 1, 3, 5, 8, and 50 m away. The clams exposed to sediment from directly under the cage experienced 100% mortality, and this was attributed to the lower bulk density of the sediment (0.09 g cm − 3 dw) that was heavily influenced by the sedimentation of farm waste, as compared with sites further from the cage (0.11–0.12 g cm − 3 dw). In addition, copper and zinc concentrations were 5 and 7 times greater in the sediment from directly under the cage at mean concentrations of 109 and 1054 μg g − 1 dw, respectively, compared to all other sites at 14–22 and 116–152 μg g − 1 dw, respectively, and may have also contributed to the mortality of these clams. Clams in all other sediment treatments experienced no mortality and had low tissue concentrations of copper (3.9–5.4 μg g − 1 dw) and zinc (23.9–32.3 μg g − 1 dw), consistent with the low concentrations of copper and zinc observed in all of these sediments. Clams exposed to sediment from 1 m from the cage had significantly greater growth than clams exposed to sediments collected 3, 5, and 8 m from the cage. There were no significant differences in average embryo size, but the number of embryos per adult was significantly greater in the clams exposed to the 1 m sediment than those exposed to the 50 m sediment. No significant differences were detected in sediment nutritional quality as measured by C:N ratios and organic content, which were both similar between the 1, 3, 5, 8, and 50 m sites. Results from this study suggest that the effects of rainbow trout ( Oncorhynchus mykiss Walbaum) aquaculture on fingernail clams would mainly occur directly under or within a close radius of the cage. This sediment bioassay was an effective method for testing the impacts of cage culture on the growth, reproduction and survival of benthic invertebrates such as the fingernail clam.

Ammonium Toxicity at High pH in a Marine Bioassay Using Corophium volutator

Two forms of ammonium exist in water: un-ionized ammonia NH3 and ionized ammonium NH4+. The toxicity to many aquatic organisms is primarily attributed to the NH3 (un-ionized) species, with the NH4+ ion (ionized) species being relatively less toxic. The pH level influences the degree of ionization. It is therefore very important that quality criteria be derived for total ammonium levels at several pH values in order to allow correct interpretation of the sediment bioassay with Corophium volutator. The responses of Corophium to total ammonium were studied in a series of pH-controlled experiments. The LC50 of total ammonium showed a significant decrease with increasing pH, in both water-only and sediment experiments. The results indicated a combined NH4+ and NH3 toxicity at pH levels less than 8.3. The results can be used to set pH-dependent water quality criteria for total ammonium in overlying water in a 10-day sediment bioassay with Corophium volutator.

Translating bioassay results to field population responses using a Leslie-matrix model for the marine amphipod Corophium volutator

Bioassays can be used for the assessment of sediment contamination. The response is classified based on a statistical scale indicating a certain effect percentage being significantly different from the controls (e.g. mortality classes of 0–10%, 10–20% etc.). The ecological relevance of this statistical scale is low. Extrapolating the observed mortality to population success could facilitate the development of a more ecological relevant scale. By incorporating the results of bioassays in population models, the consequences of the presence of contaminants can be studied at the population level. Based on a Leslie matrix combined with mathematical modelling of important biological processes, a population model is developed for Corophium volutator, a marine amphipod used in sediment bioassays. A literature review is carried out to specify reproduction, growth, mortality and predation and the way these factors depend on temperature and food availability. This resulted in a model describing the population development (population growth rate) of C. volutator. Field data of the C. volutator population in the Oesterput, a location in the Dutch Eastern Scheldt estuary, are applied to study the capability of the model to describe a field population. For populations tested in bioassays, without food limitation and predation, increasing population sizes (population growth rate ( λ) >1) are predicted between +6.5 °C and +30.0 °C. Mortality observed in bioassays will reduce λ. Using a realistic temperature profile, a maximum allowable bioassay response of 30.5% reducing λ to a value of 1 was determined. However, also external factors like predation and food limitation will reduce the value of λ. This hampers the definition of a generic threshold based on population effects. The developed model forms a useful intermediate in the translation of bioassay effects to population effects for C. volutator. Not only does the model provide new information about the sensitivity of test organisms and thus contributes to reducing uncertainty in test results, but it provides a means to increase the ecological relevance of bioassays responses. These latter capabilities are valuable to the regulation authorities.

Exposure to Cadmium-Phenanthrene Mixtures Elicits Complex Toxic Responses in the Freshwater Tubificid Oligochaete, Ilyodrilus templetoni

The joint toxicity of metal-hydrocarbon mixtures in sediments was investigated using cadmium (Cd) and phenanthrene (Phen) as model contaminants. Sediment bioassays were utilized to quantify effects of individual and combined contaminants in the bulk-deposit feeding oligochaete Ilyodrilus templetoni. Combined contaminants elicited antagonistic lethal effects and independent responses for feeding rate (measured as sediment ingestion). The 10-d LC(50) for Cd alone was 1375 mg kg(-1) (95% C.I. 1340-1412), whereas Phen elicited no mortality even when loaded to sediment saturation. The presence of Phen decreased Cd lethality, increasing the LC(50) of Cd by as much as 40%. Regression analyses indicated that Phen was nearly 10 times more potent than Cd in eliciting feeding rate reductions. Exposure to Cd-Phen mixtures resulted in feeding rate reductions equivalent to those caused by Phen alone. The marked reduction in sediment ingestion induced by the co-pollutant Phen reduced exposure to Cd via ingestion. We suggest that this Phen-induced reduction in Cd exposure decreased Cd bioaccumulation and subsequent lethality. More generally, we suggest that even if the toxicological effects among dissimilarly acting chemicals (including metals and hydrocarbons) are independent, contaminant mixtures may elicit unexpected interactive effects facilitated by modifying exposure.

A biological effects monitoring survey of Cardigan Bay using flatfish histopathology, cellular biomarkers and sediment bioassays: Findings of the Prince Madog Prize 2003

Cardigan Bay on the western coast of the UK is considered a pristine location with much of its coastal and marine habitats protected under various national and EC Directives. Despite this, populations of the flatfish dab (Limanda limanda) captured from Cardigan Bay display elevated levels of liver tumours relative to the background prevalence of the disease. This study describes the findings of a research cruise that took place during November 2003 to assess the prevalence of tumours in dab from selected sites in and around Cardigan Bay. In addition, potential causative mechanisms were investigated via measurement of a range of end points (including composition and abundance of benthic and phytoplankton communities, sediment toxicity and cellular biomarkers of genotoxicity) from sediment, water and biota samples. Fish captured from South Cardigan Bay displayed a relatively higher prevalence of liver tumours compared to those captured from Red Wharf Bay. Hepatocellular adenoma (8% and 2%, respectively) and hepatocellular foci of cell alteration (18% and 6%, respectively) were most prevalent in South Cardigan Bay. Analysis of the sediment failed to distinguish any differences in toxicity between the two sampling sites. However, DNA strand breaks in red blood cells of dab were significantly higher (p < 0.05) in fish collected from Red Warf Bay compared with those sampled at Cardigan Bay. The alignment of biological effects measures via such integrated cruise programs are discussed. This work was partly funded under the auspices of the 2003 Prince Madog Prize.

Integrated biomonitoring assessment of the Lesina Lagoon (Southern Adriatic Coast, Italy): preliminary results

An integrated biomonitoring program for marine and coastal ecosystems quality assessment combines the chemical characterization of a site with the evaluation of the possible structure alterations of its living communities. This can be considered an useful tool for better identifying the summarized effects of all the components interacting with the biota. Such an integrated procedure was carried out for the assessment of the quality of the Lesina Lagoon (Southern Adriatic Coast, Italy). The water parameters levels showed a high primary production (2–6 μg l−1); the sediment and pore water toxicity bioassays recorded a low or moderate diffused toxicity. Besides, the benthic meiofauna community structure was characterized by prevalent Nematoda taxa with a homogeneous spatial distribution. On these basis, the Lesina Lagoon seems to be characterized by a prevalent organic pollution mainly related to agricultural and zootechnical activities which, due to the lagoon’s conformation, presents a homogeneous spatial distribution.

Toxicity of atrazine to the juvenile hard clam, Mercenaria mercenaria

The herbicide atrazine is one of the most heavily used pesticides in the United States. The effects of atrazine on the clam Mercenaria mercenaria were evaluated in aqueous and sediment laboratory assays. Juvenile clams of approximately 1 mm in size were used for all experiments. An acute aqueous bio-assay was used to determine the 96-h LC 50 for the juvenile clams. A chronic aqueous bioassay was conducted at lower atrazine concentrations over a 10-day exposure period to examine both lethal and sublethal (dry mass, shell size, and condition index) endpoints. A chronic sediment bioassay examined mortality and sublethal endpoints in a 10-day exposure. The acute 96-h LC 50 was 5608 μg/L with 95% confidence intervals ranging from 5003 to 6287 μg/L. Results of the chronic aqueous assay indicated both lethal and sublethal (reduced shell size) effects at high atrazine concentrations. In the 10-day chronic aqueous assay, the no observable effect concentration was 500 μg/L, the lowest observable effect concentration was 1000 μg/L, and the maximum allowable toxicant concentration (MATC) was 707 μg/L. There were no significant effects of atrazine in the chronic sediment exposure. Safe concentrations for the aqueous experiments were estimated by applying an uncertainty factor of 10 to the calculated MATC values. While there were adverse effects of atrazine at high concentrations, these results suggest that atrazine is not directly toxic to M. mercenaria at environmentally relevant concentrations.

Contaminated sediments and bioassay responses of three macroinvertebrates, the midge larva Chironomus riparius, the water louse Asellus aquaticus and the mayfly nymph Ephoron virgo

Bioassays are widely used to estimate ecological risks of contaminated sediments. We compared the results of three whole sediment bioassays, using the midge larva Chironomus riparius, the water louse Asellus aquaticus, and the mayfly nymph Ephoron virgo. We used sediments from sixteen locations in the Dutch Rhine-Meuse Delta that differed in level of contamination. Previously developed protocols for each bioassay were followed, which differed in sediment pretreatment, replication, and food availability. The Chironomus bioassay was conducted in situ, whereas the other two were conducted in the laboratory. The measured endpoints, survival and growth, were related to contaminant levels in the sediment and to food quantity in water and sediment. Only the response of A. aquaticus in the bioassay was correlated with sediment contamination. Food availability in overlying water was much more important for C. riparius and E. virgo, thereby masking potential sediment contaminant effects. We conclude that growth of A. aquaticus was depressed by sediment contamination, whereas growth of E. virgo and C. riparius was stimulated by seston food quantity. We discuss that the trophic state of the ecosystem largely affects the ecological risks of contaminated sediments.

Reproduction of the estuarine and marine amphipod Corophium volutator (Pallas) in laboratory for toxicity testing

The acute whole sediment bioassay with the estuarine and marine amphipod Corophium volutator (Pallas) is broadly used within Europe. Hitherto, the test is carried out with field-collected animals. In order to provide a more standardized and continuously available test organism reproduction and growth experiments were performed for a period of one year in laboratory under simulated summer conditions (light/dark 16:8 at 15, 19, and 23 °C). C. volutator was the first time reproduced successfully in laboratory for several generations and independent from its natural life cycle also in winter. The females produced two to three broods with a mean number of 96 offspring. A mean growth rate of 0.07 mm per day was determined at 15 °C. The reproduction and growth experiments provide consequently the essential base for the development of a chronic toxicity test with C. volutator.