Ecotoxicity of marine sediments: Sampling and laboratory artifacts and their impacts on risk classification.

Assessing the ecotoxicological risk of marine sediments is now a critical factor in deciding how to treat dredged material in harbor and coastal areas. Although ecotoxicological analyses are routinely required by some regulatory agencies in Europe, laboratory skills necessary to perform them are often underestimated. According to the Italian Ministerial decree No. 173/2016, ecotoxicological tests are performed on the solid phase and elutriates, and the classification of sediment quality is defined using the "Weight of Evidence" (WOE) approach. However, the decree does not provide adequate information regarding the preparation techniques and laboratory skills. As result, a wide variability among laboratories occurs. An error in the classification of ecotoxicological risk has a negative impact on the whole environmental quality and/or the economy and management of the interested area. Thus, the main aim of this study was to determine if such variability can affect the ecotoxicological outcomes of tested species and WOE associated classification, producing different options for the management of dredged sediments. Four different sediment types were selected to assess the ecotoxicological responses and their changes as a function of variability of the following factors: a) the storage time laps (STL) for both the solid phase and the elutriates; b) the methods used to prepare the elutriates (centrifugation vs. filtration), and the conservation method used for the elutriates (freshly prepared vs. freezing). Results suggest a wide variability of ecotoxicological responses among the four sediment samples here considered, differentiated according to chemical pollution, grain-size texture, and macronutrient contents. The storage time laps significantly affect the physicochemical parameters and the ecotoxicity of both the solid phase test and elutriates. For the elutriates preparation, centrifugation is preferred to filtration to preserve a better representation of sediment heterogeneity. Freezing of elutriates does not seem to show any significant effects on the toxicity. Findings allow to define a weighted schedule of the storage time of sediments and elutriates useful for laboratories to scale analytical priority and strategies related to different sediment types.

Development and validation of new analytical methods using sea urchin embryo bioassay to evaluate dredged marine sediments.

Management of dredged materials disposal is regulated by several environmental normative requirements, and it is often supported by the integration of chemical data with ecotoxicological characterization. The reliability of a bioassay to assess the potential toxicity of dredged sediments requires the selection of quality criteria that should be based on simple analytical methods and easily understandable hazard for politicians and environmental managers. The sea urchin embryo-toxicity bioassay is considered an essential component for evaluating the quality of sediments in harbour areas but its use, when based exclusively on the observation of normal vs. abnormal embryos, may alter the interpretation of the results, overestimating the risk assessment. To improve the reliability of this assay in establishing a causative relationship between quality of sediments and sea urchin embryonic development, here we developed and validated three Integrative Toxicity Indexes (ITI 2.0, ITI 3.0, ITI 4.0), modifying the already-known ITI (here ITI 1.0). Based on this aim, we used Taranto harbour as a model pilot-study to compare results to those obtained from standard criteria. Among the tested indexes, the ITI 4.0, discriminating strictly developmental delay and morphological defects from fertilized egg to gastrula stage, resulted in the most promising.

Liver histological changes and lipid peroxidation in the amphibian Ambystoma mexicanum induced by sediment elutriates from the Lake Xochimilco.

Lacustrine sediments accumulate pollutants that input from the lake watershed and can be released to the water column by sediment resuspension; thus, pollutants can change their bioavailability and exert adverse effects to aquatic biota. Shallow-urban lakes are particularly susceptible to receive pollutants from urban discharges and sediment resuspension. Lake Xochimilco, in Mexico City, an urban-shallow lake, faces multiple problems: urban sprawl, overexploitation of aquifers, drying of springs, discharge of wastewater from treatment plants, and sediment resuspension. The aquatic biota living in this ecosystem is continuously exposed to the release of pollutants from the sediments. We assessed the risk that pollutants released from sediments from Lake Xochimilco, Touristic (TZ) and Agriculture zone (AZ), can exert on a native amphibian species of the lake (Ambystoma mexicanum) through exposure bioassays to sediment elutriates. We evaluate alterations in the amphibian by three approaches: biochemical (level of lipid peroxidation, LPO), cellular (ultrastructure) and the liver histology of A. mexicanum and we compare them with a batch control. Additionally, we assessed heavy metals (Pb, Cd and Hg) in elutriates. Elutriates from TZ showed the highest concentrations of the metals assessed. Organisms exposed to sediment elutriates from either study sites showed higher LPO values than control organisms (p<0.05). Organisms exposed to elutriates from the TZ showed the most conspicuous damages: hepatic vasodilation of sinusoids, capillaries with erythrocytes, leukocyte infiltration and cytoplasmic vacuolation in hepatocytes. The biological responses assessed reflected the risk that faces A. mexicanum when is exposed for prolonged periods to sediment resuspension in Lake Xochimilco.

Phytotoxicity of coal waste elutriates (Douro Coalfield, North Portugal) in Lactuca sativa.

One of the most important mining areas in the Douro Carboniferous Basin is the Pejão Coalfield. In the summer of 2017, a wildfire promoted the ignition and self-burning some of the coal waste piles in the area and caused important environmental changes, promoting a new heterogenic pedological zonation. This study aims to assess the ecotoxicological effects of 25 soil elutriates from these different soil types in seed germination and individual (emergence, growth, and morphologic alterations) and subindividual parameters in Lactuca sativa. The different evaluated endpoints were differently affected regarding the soil elutriate revealing the high heterogeneity of soil characteristics. The presence of different potentially toxic elements (e.g., Cd, Cr, Pb, Zn) in soil elutriates, even in low concentrations, caused effects on L. sativa development. Unburned coal wastes and downhill soil elutriates were able to inhibit the germination of L. sativa and affect them individually and sub-individually (decrease in size, biomass, and presence of morphological alterations). Additionally, it was observed that all soil elutriates induce a decrease in root size. The results highlight the importance of using elutriate samples in phytotoxicity studies of coal mining waste, since the tailings lixiviate may reduce plant establishment and growth, affecting the terrestrial ecosystems. The integrated use of seed germination assays with the analysis of morphological and biochemical alterations in plants proved to be sensitive parameters to evaluate the phytotoxicity of coal mining wastes.

The copepod Eurytemora affinis as a relevant species to assess estuarine sediment toxicity: Effects on gene expression and swimming behavior.

Compared to freshwater ecosystems, the health status of estuarine waters remains little studied despite their importance for many species. They represent a zone of interest for Human settlements that make them the final sink of pollution in both the water column and sediment. Once in sediments, pollutants could represent a threat to benthic as well as pelagic estuarine species through resuspension events. In the Seine estuary, the copepod Eurytemora affinis has been previously presented as a relevant species to assess resuspended sediment contamination through fitness-related effects at the individual level. The aim of the present study was to use E. affinis copepods to assess estuarine sediment-derived elutriates toxicity at environmental concentrations of particles using a molecular (i.e. transcriptomics) and a behavioral approach. Two sites along the Seine estuary were sampled. The analysis of sediments reveals that both sites have the same granulometric composition and close contamination profiles with the detection of PCBs, PAHs and pyrethroid insecticides. The transcriptomic analysis reveals that exposure to elutriates from both sites triggers the dysregulation of genes involved in biological function as defense response, immunity, ecdysone pathway or neurotoxicity with 66% and 36% of shared genes at the highest concentration for Tancarville and Fatouville. This analysis also reveals a higher count of dysregulated genes in the Fatouville site compared to the Tancarville (271 vs 148) despite their close contamination profile. These results emphasize the molecular approach sensitivity to assess environmental matrix toxicity with E. affinis. The analysis of the swimming behavior of E. affinis did not highlight significant effects after elutriate exposure. However, our strategy to assess E. affinis swimming behavior allows the discrimination of basal swimming behavior i.e. dark/light velocity changes and strong thigmotaxis behavior. Thus, it represents a promising standardized tool to assess copepods swimming behavior in ecotoxicological studies.

Assessing the acute and chronic toxicity of exposure to naturally occurring oil sands deposits to aquatic organisms using Daphnia magna.

In the Athabasca region, the oil sands are located at or near the surface making open-pit mining viable. In addition, the Athabasca River and its tributaries flow through these oil sands deposits, thereby receiving bitumen-associated contaminants through natural fluvial erosional and weathering processes. A key knowledge gap has been related to understanding both the magnitude and significance of the toxicological and ecological effects on aquatic organisms exposed to naturally occurring bitumen entering fluvial systems. Using the Daphnia magna model system, this study assessed the ecotoxicological effects of exposure to bitumen-elutriate treatments that simulated the early stages of fluvial/erosional exposure conditions. No significant among-site differences were observed in the survival of D. magna after 48 h exposure to elutriates produced from a 24 h extraction cycle, and chemical analysis indicated low concentration of a complex mixture of hydrocarbon and metal contaminants. In contrast, the same elutriates impaired reproduction and growth after a 21-day chronic exposure. F1 neonates from the chronic tests were tested for sensitivity to the reference substance potassium dichromate, revealing a decrease in their sensitivity. Inter-generational effects were also observed, with a significant decrease in subsequent neonate production, when daphnids were moved to a clean medium. Supplemental acute toxicity assays using 48 and 72 h bitumen extraction cycles progressively increased daphnid mortality after a 48-h exposure to the respective elutriates. This indicates that bitumen-associated contaminants are being liberated after initial input and fluvial washing (24 h), highlighting the need for future work to assess toxicity responses and associated elutriate water chemistry of a longer fluvial exposure time-series. This work contributes to our understanding of the possible effects of natural bitumen exposure on riverine aquatic ecosystems, providing new information to inform the delineation of baseline conditions to assess environmental change and the design of future regional effects-based monitoring programs.

Effects of elutriates from contaminated coastal sediments on different life cycle phases of planktonic diatoms.

We assessed the effects of elutriates from sediments collected at three stations in the polluted Bay of Bagnoli-Coroglio along the Campania coast (Tyrrhenian Sea, Italy) using three planktonic diatoms regularly occurring in the area, Pseudo-nitzschia multistriata, P. arenysensis and Chaetoceros socialis. Specifically, we tested the production of sexual stages in the heterothallic Pseudo-nitzschia species with the hypothesis that pollutants could impair sexual reproduction. We also tested the seeding capacity of spores of C. socialis after up to six months of storage in elutriates, assuming that pollutants could affect the capability of resting stages to germinate. Elutriate from station 56, with the highest concentrations of pollutants, impaired growth, sexual reproduction and spore germination. Elutriates from stations 25 and 84 caused moderate enhancement of growth and sexual reproduction in Pseudo-nitzschia as compared with control conditions, and also had intermediate effect on spore seeding capacity.

What is the best endpoint for assessing environmental risk associated with acidification caused by CO2 enrichment using mussels?

Carbon capture and storage is a technology that has been widely determined to be one of the best choices for the short-term reduction of atmospheric CO2 emissions. The aim of this study was to analyze the effects of CO2 enrichment in the ocean on the mussel species Mytilus galloprovincialis using three different endpoints: mortality, embryo-larval development, and neutral red retention time assays (NRRT). Acute effects were found to be associated with a pH values of 6.0 while citotoxity effects and embryo-larval development were associated with a pH value of 7.0. The NRRT assay and embryo-larval development can be recommended as good endpoints for assessing the environmental risk associated with acidification by CO2 enrichment because they provide sensitive responses on the effects of changes in seawater pH on mussels in a short period of time. Moreover, this study may support policymakers in finding appropriate solutions for the conservation of marine ecosystems.

Toxicity profiling of marine surface sediments: A case study using rapid screening bioassays of exhaustive total extracts, elutriates and passive sampler extracts.

This study was carried out in the framework of the ICON project (Integrated Assessment of Contaminant Impacts on the North Sea) (Hylland et al., 2015) and aimed (1) to evaluate the toxicity of marine sediments using a battery of rapid toxicity bioassays, and; (2) to explore the applicability and data interpretation of in vitro toxicity profiling of sediment extracts obtained from ex situ passive sampling. Sediment samples were collected at 12 selected (estuarine, coastal, offshore) sites in the North Sea, Icelandic waters (as reference sites), south-western Baltic Sea and western Mediterranean during autumn 2008. Organic extracts using a mild non-destructive clean-up procedure were prepared from total sediment and silicone passive samplers and tested with five in vitro bioassays: DR-Luc bioassay, ER-Luc bioassay, AR-EcoScreen bioassay, transthyretin (TTR) binding assay, and Vibrio fischeri bioluminescence bioassay. In vitro toxicity profiling of total sediment and silicone passive sampler extracts showed the presence of multiple organic contaminations by arylhydrocarbon receptor agonists (e.g. polycyclic aromatic hydrocarbons) and endocrine-active compounds, as well as non-specific toxicity caused by organic contaminants, at virtually all sampling sites. In vitro responses to total sediment extracts from coastal/estuarine sites were significantly different from those in offshore sites (p < 0.05). Several bioassays of passive sampler extracts showed highest activity in some offshore sediment samples. Impact on embryogenesis success and larval growth in undiluted sediment elutriates was shown at some sites using the in vivo sea urchin embryo test. The observed toxicity profiles could only partially be explained by the chemical target analysis, indicating the presence of unknown or unanalysed biologically-active compounds in the sediments. In vitro bioassay testing with silicone passive sampler extracts of sediments is a promising tool to assess the toxic potency of the bioavailable fraction of hydrophobic sediment contaminants, but further work will be needed before it can be routinely applied for sediment quality assessment.

Phosphogypsum as a soil fertilizer: Ecotoxicity of amended soil and elutriates to bacteria, invertebrates, algae and plants.

Phosphogypsum (PG) is a metal and radionuclide rich-waste produced by the phosphate ore industry, which has been used as soil fertilizer in many parts of the world for several decades. The positive effects of PG in ameliorating some soil properties and increasing crop yields are well documented. More recently concerns are emerging related with the increase of metal/radionuclide residues on soils and crops. However, few studies have focused on the impact of PG applications on soil biota, as well as the contribution to soils with elements in mobile fractions of PG which may affect freshwater species as well. In this context the main aim of this study was to assess the ecotoxicity of soils amended with different percentages of Tunisian phosphogypsum (0.0, 4.9, 7.4, 11.1, 16.6 and 25%) and of elutriates obtained from PG - amended soil (0.0, 6.25, 12.5 and 25% of PG) to a battery of terrestrial (Eisenia andrei, Enchytraeus crypticus, Folsomia candida, Hypoaspis aculeifer, Zea mays, Lactuca sativa) and aquatic species (Vibrio fischeri, Daphnia magna, Raphidocelis subcapitata, Lemna minor). Both for amended soils and elutriates, invertebrates (especially D. magna and E. andrei) were the most sensitive species, displaying acute (immobilization) and chronic (reproduction inhibition) effects, respectively. Despite the presence of some concerning metals in PG and elutriates (e.g., zinc and cadmium), the extremely high levels of calcium found in both test mediums, suggest that this element was the mainly responsible for the ecotoxicological effects observed. Terrestrial and aquatic plants were the most tolerant species, which is in line with studies supporting the application of PG to increase crop yields. Nevertheless, no stimulatory effects on growth were observed for any of the species tested despite the high levels of phosphorus added to soils by PG. Given the importance of soil invertebrates for several soil functions and services, this study gives rise to new serious concerns about the consequences of PG applications on agricultural soils.