Standardizing the methodology of sperm cell test with Paracentrotus lividus

Nanostructured cellulose sponge engineered for marine environmental remediation: Eco-safety assessment of its leachate on sea urchin reproduction (Part A)

Nanostructured cellulose sponges (CNS) have been developed as eco-friendly and sustainable engineered materials for marine environmental remediation. Despite their functionality, sensitivity, efficiency and specificity have been proved, CNS application is still limited since their environmental safety (eco-safety) has not been completely assessed. In this study, CNS were allowed to leach in natural seawater simulating the remediation process condition and the eco-safety of CNS leachate on sea urchin reproduction has been assessed by carrying out a multi-response integrated approach, combining standardized ecotoxicity tests, innovative bioassays and gamete quality assessment. Overall, the ecotoxicity data indicate that CNS leachate affects gamete quality, gamete fertilisation competence, and embryo development probably associated with the release of chemical additives used during the synthesis process. However, in the framework of the eco-design approach, consecutive leaching treatments and conditioning of CNS in seawater open the route for a new safety protocol successfully solving the ecotoxicity while maintaining CNS sorbent properties. A safe environmental application of the resulting conditioned CNS for seawater pollution remediation is envisaged.

Increased sensitivity of sea urchin larvae to metal toxicity as a consequence of the past two decades of Climate Change and Ocean Acidification in the Mediterranean Sea

The Mediterranean Sea represents a natural laboratory to infer the possible impacts of climate change and ocean acidification. In this article, we report the deteriorating ability of sea urchin larvae (Paracentrotus lividus) to cope with toxicity of a reference contaminant (Cu EC50) over the past 20 years and assessed the influence of 5 environmental factors from satellite measurements. This timeframe was divided in before and after January 2016 (46.57 μg/L vs 28.56 μg/L respectively, p < 0.001). In the second subset of data, correlation of the biological variable with CO2 and pH strengthened compared to the first part (rCO2-EC50: -0.21 vs -0.83 and rpH-EC50: 0.25 vs 0.87 respectively), with a causal link starting from one year and ending 4 months prior to EC50 measurements. Considering the continuous increase in CO2 concentrations recorded recently, this study could reveal a rapid deterioration of the health condition of this population of sea urchins in a coastal ecosystem.

Effects of Carrageenans on Biological Properties of Echinochrome

Sea urchin pigment echinochrome A (Ech), a water-insoluble compound, is the active substance in the cardioprotective and antioxidant drug Histochrome® (PIBOC FEB RAS, Moscow, Russia). It has been established that Ech dissolves in aqueous solutions of carrageenans (CRGs). Herein, we describe the effects of different types of CRGs on some properties of Ech. Our results showed that CRGs significantly decreased the spermotoxicity of Ech, against the sea urchin S. intermedius sperm. Ech, as well as its complex with CRG, did not affect the division and development of early embryos of the sea urchin. Ech reduced reactive oxygen species production (ROS) in neutrophils, caused by CRG. The obtained complexes of these substances with pro- and anti-activating ROS formation properties illustrate the possibility of modulating the ROS induction, using these compounds. The CRGs stimulate the induction of anti-inflammatory IL-10 synthesis, whereas Ech inhibits this synthesis and increases the production of the pro-inflammatory cytokines IL-6 and TNFα. The inclusion of Ech, in the complex with the CRGs, decreases Ech's ability to induce the expression of pro-inflammatory cytokines, especially TNFα, and increases the induction of anti-inflammatory cytokine IL-10. Thus, CRGs modify the action of Ech, by decreasing its pro-inflammatory effect. Whereas, the Ech's protective action towards human epithelial HT-29 cells remains to be unaltered in the complex, with κ/β-CRG, under stress conditions.

Insights into the CuO nanoparticle ecotoxicity with suitable marine model species

Metal oxide nanoparticles, among them copper oxide nanoparticles (CuO NPs), are widely used in different applications (e.g. batteries, gas sensors, superconductors, plastics and metallic coatings), increasing their potential release in the environment. In aquatic matrix, the behavior of CuO NPs may strongly change, depending on their surface charge and some physical-chemical characteristics of the medium (e.g. ionic strength, salinity, pH and natural organic matter content). Ecotoxicity of CuO NPs to aquatic organisms was mainly studied on freshwater species, few tests being performed on marine biota. The aim of this study was to assess the toxicity of CuO NPs on suitable indicator species, belonging to the ecologically relevant level of consumers. The selected bioassays use reference protocols to identify Effect/Lethal Concentrations (E(L)C), by assessing lethal and sub-lethal endpoints. Mortality tests were performed on rotifer (Brachionus plicatilis), shrimp (Artemia franciscana) and copepod (Tigriopus fulvus). While moult release failure and fertilization rate were studied, as sub-lethal endpoints, on T. fulvus and sea urchin (Paracentrotus lividus), respectively. The size distribution and sedimentation rates of CuO NPs, together with the copper dissolution, were also analyzed in the exposure media. The CuO NP ecotoxicity assessment showed a concentration-dependent response for all species, indicating similar mortality for B. plicatilis (48hLC₅₀ = 16.94 ± 2.68mg/l) and T. fulvus (96hLC₅₀ = 12.35 ± 0.48mg/l), followed by A. franciscana (48hLC₅₀ = 64.55 ± 3.54mg/l). Comparable EC₅₀ values were also obtained for the sub-lethal endpoints in P. lividus (EC₅₀ = 2.28 ± 0.06mg/l) and T. fulvus (EC₅₀ = 2.38 ± 0.20mg/l). Copper salts showed higher toxicity than CuO NPs for all species, with common sensitivity trend as follows: P. lividus ≥ T. fulvus (sublethal endpoint) ≥ B. plicatilis >T. fulvus (lethal endpoint) >A. franciscana. CuO NP micrometric aggregates and high sedimentation rates were observed in the exposure media, with different particle size distributions depending on the medium. The copper dissolution was about 0.16% of the initial concentration, comparable to literature values. The integrated ecotoxicological-physicochemical approach was used to better describe CuO NP toxicity and behavior. In particular, the successful application of ecotoxicological reference protocols allowed to produce reliable L(E)C data useful to identify thresholds and assess potential environmental hazard due to NPs.

Are environmental risk estimations linked to the actual environmental impact? Application to an oil handling facility (NE Spain)

The environmental risk analysis of aquatic systems includes the evaluation of the likelihood that adverse ecological effects may occur as a result of exposure to one or more stressors. In harbor areas, pollution is provided by a complex mixture of substances with different levels of toxicity, persistence and bioaccumulation, which complicates the hazards characterization and their multiple effects. A study of the relationship between the environmental impact and the environmental risk assessment at a specific isolated oil handling facility was undertaken. The environmental risk of the oil handling facility, considering the consequences of specific pollutants, was estimated and the associated environmental impact was quantified based on a 'weights of evidence' approach. The contamination quantified at the potentially affected area around the monobuoy of Tarragona has proved to be related with environmental risk estimations but the lines of evidence obtained do not allow us to assert that the activity developed at this facility has an associated environmental impact.

Potential toxicity of improperly discarded exhausted photovoltaic cells

Low tech photovoltaic panels (PVPs) installed in the early '80s are now coming to the end of their life cycle and this raises the problem of their proper disposal. As panels contain potentially toxic elements, unconventional, complex and costly procedures are required to avoid environmental health risks and in countries where environmental awareness and economic resources are limited this may be especially problematic. This work was designed to investigate potential risks from improper disposal of these panels. To accomplish this aim an exhausted panel was broken into pieces and these were placed in water for 30 days. The resulting leached solution was analyzed to determine chemical release or used in toto, to determine its potential toxicity in established tests. The end points were seed germination (on Cucumis sativus and Lens culinaris) and effects on early development in three larval models: two crustaceans, Daphnia magna and Artemia salina, and the sea urchin Paracentrotus lividus. Our results show that the panels release small amounts of electrolytes (Na, Ca and Mg) into solution, along with antimony and manganese, with a concentration under the accepted maximum contaminant level, and nickel at a potentially toxic concentration. Developmental defects are seen in the plant and animal test organisms after experimental exposure to the whole solution leached from the broken panel. The toxic effects revealed in in vitro tests are sufficient to attract attention considering that they are exerted on both plants and aquatic animals and that the number of old PVPs in disposal sites will be very high.

Swimming speed alteration in the early developmental stages of Paracentrotus lividus sea urchin as ecotoxicological endpoint

Behavioral endpoints have been used for decades to assess chemical impacts at concentrations unlikely to cause mortality. With recently developed techniques, it is possible to investigate the swimming behavior of several organisms under laboratory conditions. The aims of this study were: i) assessing for the first time the feasibility of swimming speed analysis of the early developmental stage sea urchin Paracentrotus lividus by an automatic recording system ii) investigating any Swimming Speed Alteration (SSA) on P. lividus early stages exposed to a chemical reference; iii) identifying the most suitable stage for SSA test. Results show that the swimming speed of all the developmental stages was easily recorded. The swimming speed was inhibited as a function of toxicant concentration. Pluteus were the most appropriate stage for evaluating SSA in P. lividus as ecotoxicological endpoint. Finally, swimming of sea urchin early stages represents a sensitive endpoint to be considered in ecotoxicological investigations.

Application of different enzyme assays and biomarkers for pollution monitoring of the marine environment

New phosphatase and DNase inhibition tests for assessing the total pollution of a natural marine ecosystem were applied. The seawater samples with different pollution degrees were collected in the Troitsa Bay of the Peter the Great Bay (the Sea of Japan). The sensitivity of the alkaline phosphatase test to integrated pollution was in accordance with the sensitivity of the standard sea urchin sperm cell toxicity test. The increased seawater pollution level was shown to result in an up to fourfold increase in specific activities of acid and alkaline phosphatases from the mussel Crenomytilus grayanus. It was demonstrated that a complex methodological approach can be used to assess marine water areas, as well as to assess the biological conditions of invertebrates adapting to different environmental and anthropogenic effects.

Assessment of sediment toxicity in the Lagoon of Venice (Italy) using a multi-species set of bioassays

Within the framework of a Weight of Evidence (WoE) approach, a set of four toxicity bioassays involving the amphipod Corophium volutator (10 d lethality test on whole sediment), the sea urchin Paracentrotus lividus (fertilization and embryo toxicity tests on elutriate) and the pacific oyster Crassostrea gigas (embryo toxicity test on elutriate) was applied to sediments from 10 sampling sites of the Venice Lagoon (Italy). Sediments were collected during three campaigns carried out in May 2004 (spring campaign), October 2004 (autumn campaign) and February 2005 (winter campaign). Toxicity tests were performed on all sediment samples. Sediment grain-size and chemistry were measured during spring and autumn campaigns. This research investigated (i) the ability of toxicity tests in discriminating among sites with different contamination level, (ii) the occurrence of a gradient of effect among sampling sites, (iii) the possible correlation among toxicity tests, sediment chemistry, grain size and organic carbon, and (iv) the possible occurrence of toxicity seasonal variability. Sediment contamination levels were from low to moderate. No acute toxicity toward amphipods was observed, while sea urchin fertilization was affected only in few sites in just a single campaign. Short-term effects on larval development of sea urchin and oyster evidenced a clear spatial trend among sites, with increasing effects along the axis connecting the sea-inlets with the industrial area. The set of bioassays allowed the identification of a spatial gradient of effect, with decreasing toxicity from the industrial area toward the sea-inlets. Multivariate data analysis showed that the malformations of oyster embryos were significantly correlated to the industrial contamination (metals, polynuclear aromatic hydrocarbons, hexachlorobenzene and polychlorinated biphenyls), while sea urchin development to sediment concentrations of As, Cr and organic carbon. Both embryo toxicity tests were significantly affected by high ammonia concentrations found in the elutriates extracted from some mudflat and industrial sediments. No significant temporal variation of the toxicity was observed within the experimental period. Amendments to the set of bioassays, with inclusion of chronic tests, can certainly provide more reliability and consistency to the characterization of the (possible) toxic effects.

Oversimplification and overstandardization in biological methods: sperm bioassays in ecotoxicology as a case of study and a proposal for their reformulation

An interesting toxicological bioassay (fertilization inhibition in sea urchin) uses as assessment criterion a variable (fertilization ratio) whose variation with time creates two types of difficulties. First, it fails to distinguish between the toxic effect and the spontaneous decline in the sperm activity, causing some inconsistencies. Second, the sensitivity of the fertilization ratio to many other variables of the system requires a complex standardization, constraining the achievement of the method without solving its main problem. Our proposal consists of using a parameter (sperm half-life) as the response of the assay, and describing explicitly the behavior of the system as a simultaneous function of dose and time. This new focus is able to solve the problematic character of the results based on the fertilization ratio and by using the same data set which is required by the conventional approach; it simplifies the protocol, economizes experimental effort, provides unambiguous and robust results, and contributes to the detection of an artefactual temperature effect, which is not very evident under the usual perspective. Potential application of this new approach to the improvement of other formally similar bioassays is finally suggested.

NOEC and LOEC as merely concessive expedients: two unambiguous alternatives and some criteria to maximize the efficiency of dose-response experimental designs

NOEC and LOEC (no and lowest observed effect concentrations, respectively) are toxicological concepts derived from analysis of variance (ANOVA), a not very sensitive method that produces ambiguous results and does not provide confidence intervals (CI) of its estimates. For a long time, despite the abundant criticism that such concepts have raised, the field of the ecotoxicology is reticent to abandon them (two possible reasons will be discussed), adducing the difficulty of clear alternatives. However, this work proves that a debugged dose-response (DR) modeling, through explicit algebraic equations, enables two simple options to accurately calculate the CI of substantially lower doses than NOEC. Both ANOVA and DR analyses are affected by the experimental error, response profile, number of observations and experimental design. The study of these effects--analytically complex and experimentally unfeasible--was carried out using systematic simulations with realistic data, including different error levels. Results revealed the weakness of NOEC and LOEC notions, confirmed the feasibility of the proposed alternatives and allowed to discuss the--often violated--conditions that minimize the CI of the parametric estimates from DR assays. In addition, a table was developed providing the experimental design that minimizes the parametric CI for a given set of working conditions. This makes possible to reduce the experimental effort and to avoid the inconclusive results that are frequently obtained from intuitive experimental plans.

Assessing the toxicity of chemical compounds associated with land-based marine fish farms: the sea urchin embryo bioassay with Paracentrotus lividus and Arbacia lixula

In aquaculture, disinfection of facilities, prevention of fish diseases, and stimulation of fish growth are priority goals and the most important sources of toxic substances to the environment, together with excretory products from fish. In the present study, embryos of two species of sea urchin (Paracentrotus lividus and Arbacia lixula) were exposed to serial dilutions of six antibiotics (amoxicillin (AMOX), ampicillin, flumequine (FLU), oxytetracycline (OTC), streptomycin (ST), and sulfadiazine [SFD]) and two disinfectants (sodium hypochlorite (NaClO) and formaldehyde [CH(2)O]). Alterations in larval development were studied, and the effective concentrations (ECs) were calculated to evaluate the toxicity of the substances. Both species showed similar sensitivities to all substances tested. Disinfectants (EC(50) = 1.78 and 1.79 mg/l for CH(2)O; EC(50) = 10.15 and 11.1 mg/l for NaClO) were found to be more toxic than antibiotics. AMOX, OTC, and ST caused <20 % of alterations, even at the highest concentrations tested. FLU was the most toxic to P. lividus (EC(50) = 31.0 mg/l) and SFD to A. lixula (EC(50) = 12.7 mg/l). The sea urchin bioassay should be considered within toxicity assessment-monitoring plans because of the sensitivity of larvae to disinfectants.

A standardization of Amphibalanus (Balanus) amphitrite (Crustacea, Cirripedia) larval bioassay for ecotoxicological studies

A series of 10 intra-laboratory bioassays and an inter-laboratory assay involving nine laboratories, were performed to validate the use of Amphibalanus amphitrite larvae as test organisms for ecotoxicological studies. The standardization protocol utilized Cadmium Nitrate as a reference toxicant and larval immobilization (after 24 and 48 h) as the end-point. The statistical data analysis showed high homogeneity in intra-laboratory EC(50) values among bioassay repetitions (coefficient of variation (CV)=15.8% after 24 h and 16.9% after 48 h); also CV values obtained in inter laboratory comparison exercise were not higher than the 50%, variation coefficient mentioned in the ISO standards for the precision of inter-laboratory assays. The results demonstrated that the protocol implemented for the balanus larval bioassay comply with the international standards both for intra- and inter-laboratory precision.

Global change ecotoxicology: Identification of early life history bottlenecks in marine invertebrates, variable species responses and variable experimental approaches

Climate change is a threat to marine biota because increased atmospheric CO₂ is causing ocean warming, acidification, hypercapnia and decreased carbonate saturation. These stressors have toxic effects on invertebrate development. The persistence and success of populations requires all ontogenetic stages be completed successfully and, due to their sensitivity to environmental stressors, developmental stages may be a population bottleneck in a changing ocean. Global change ecotoxicology is being used to identify the marine invertebrate developmental stages vulnerable to climate change. This overview of research, and the methodologies used, shows that most studies focus on acidification, with few studies on ocean warming, despite a long history of research on developmental thermotolerance. The interactive effects of stressors are poorly studied. Experimental approaches differ among studies. Fertilization in many species exhibits a broad tolerance to warming and/or acidification, although different methodologies confound inter-study comparisons. Early development is susceptible to warming and most calcifying larvae are sensitive to acidification/increased pCO₂. In multistressor studies moderate warming diminishes the negative impact of acidification on calcification in some species. Development of non-calcifying larvae appears resilient to near-future ocean change. Although differences in species sensitivities to ocean change stressors undoubtedly reflect different tolerance levels, inconsistent handling of gametes, embryos and larvae probably influences different research outcomes. Due to the integrative 'developmental domino effect', life history responses will be influenced by the ontogenetic stage at which experimental incubations are initiated. Exposure to climate change stressors from early development (fertilization where possible) in multistressor experiments is needed to identify ontogenetic sensitivities and this will be facilitated by more consistent methodologies.

Influence of salinity on fertilization and larval development toxicity tests with two species of sea urchin

Sea urchin embryo-larval development (ELD) and fertilization tests have been widely used in ecotoxicity studies and are included in regulatory frameworks. Biological processes occur naturally within a range of salinity that depends on the species considered. In an attempt to determine the optimum range of salinity, ELD and fertilization bioassays were performed at different salinities (15-40.5‰) with two species of Atlantic sea urchin: Arbacia lixula and Paracentrotus lividus. In the ELD assay, the optimum range of salinity was wider for A. lixula (29-35.5‰) than for P. lividus (29-33‰). In the fertilization assay with P. lividus as a bioindicator species, the highest percentage of fertilization (90%) was obtained at salinities of between 29 and 33‰. More research on A. lixula is required, since the fertilization success was below 60%. The results of the present study demonstrate that salinity may be a confounding factor in interpreting ELD test results.

Acrosome reaction of sperm in the mud crab Scylla serrata as a sensitive toxicity test for metal exposures

In order to test the sensitivity of the sperm cell of the mud crab Scylla serrata to heavy metals, the toxic effects of Ag+, Cd2+, Cu2+, and Zn2+ on the acrosome reaction (AR) were studied by artificially inducing the AR of sperm exposed to heavy metals, counting the AR rates by light microscopy, and observing structural changes in sperm by transmission electron microscopy. The AR in S. serrata occurs at two stages. The first stage (ARI) is the eversion of the subacrosomal material. The second stage (ARII) is the ejection of the acrosomal filament. The results showed the EC50 values of the AR based on (ARI + ARII)% for Ag+, Cd2+, Cu2+, and Zn2+ were 10.02, 2.14, 13.69, and 2.21 microg/L, and the EC50 values based on ARII % of Ag+, Cd2+, Cu2+, and Zn2+ were 1.96, 0.20, 1.46, and 0.34 microg/L. The order of toxicity is Cd2+ > Zn2+ > Cu2+ > Ag+ based on the percentage of reacted sperm at the second stage. Sperm cells exposed to heavy metals showed an increased rate of swelling, shape irregularities, and the acrosomal filament of some sperm cells was, crooked, ruptured, and even dissolved. The AR of the sperm cell from S. serrata is more sensitive to the tested heavy metals compared to sea urchin sperm cell toxicity tests.