Predictability of copper, irgarol, and diuron combined effects on sea urchin Paracentrotus lividus

Marine biofouling and the role of biocidal coatings in balancing environmental impacts

Marine biofouling is a global problem affecting various industries, particularly the shipping industry due to long-distance voyages across various ecosystems. Therein fouled hulls cause increased fuel consumption, greenhouse gas emissions, and the spread of invasive aquatic species. To counteract these issues, biofouling management plans are employed using manual cleaning protocols and protective coatings. This review provides a comprehensive overview of adhesion strategies of marine organisms, and currently available mitigation methods. Further, recent developments and open challenges of antifouling (AF) and fouling release (FR) coatings are discussed with regards to the future regulatory environment. Finally, an overview of the environmental and economic impact of fouling is provided to point out why and when the use of biocidal solutions is beneficial in the overall perspective.

Different ecological histories of sea urchins acclimated to reduced pH influence offspring response to multiple stressors

End-of-the-century predictions on carbon dioxide (CO₂) driven ocean acidification and the continuous leakage of pesticides from inland to coastal areas are of concern for potential negative effects on marine species' early life stages which are the most vulnerable to environmental changes. Variations in seawater chemistry related to human activities may interfere with the normal development from embryo to juvenile/adult stage. However, transgenerational studies suggest that the parental generation can influence the offspring phenotype, and thus their performances, based on the environment experienced. Here we compared the transgenerational responses to a multiple stressor scenario in sea urchins (Paracentrotus lividus) that experienced different environments since their settlement: i.e., animals from a highly variable environment, such as the Venice lagoon, versus animals from a coastal area with prevailing oligotrophic conditions in the Northern Adriatic Sea. After long-term maintenance (2 and 6 months) of adult sea urchins at natural and -0.4 units reduced pH, the F1 generations were obtained. Embryos were reared under four experimental conditions: natural and -0.4 pH both in the absence and in the presence of an emerging contaminants' mixture (glyphosate and aminomethylphosphonic acid at environmentally relevant concentrations, 100 μg/L). A significant detrimental effect of both the parental and the filial pH was highlighted, affecting embryo development and growth. Nonetheless, sea urchins from both sites were able to cope with ocean acidification. The 6-months F1 response was better than that of the 2-months F1. Conversely, the F1 response of the sea urchins maintained at natural conditions did not change sensibly after more prolonged parental exposure. An additive but mild negative effect of the mixture was observed, mostly in lagoon offspring. Results suggest that long-term exposure to reduced pH leads to transgenerational acclimation but does not affect susceptibility to the tested pollutants.

Toxicity effect of Diuron on gill tissue structure and the tissue residue of blood cockles (Tegillarca granosa)

This study aimed to identify the toxicity effect of Diuron on Tegillarca granosa by determining accumulation in the soft tissues and alteration on the gill tissue structure. Wild stocks T. granosa were grouped to identify the initial Diuron concentration and 48-h exposure in different concentrations (0, 1, 2, 3, and 4 mg·L^-1). The Diuron in tissue was extracted using an established procedure and identified using High-Performance Liquid Chromatography (HPLC). Gills were analysed for histopathological study; tissue structure was classified and scored using a developed scoring system. Diuron concentration in the soft tissue of exposed T. granosa was in the range 1.27-8.09 mg·kg^-1, w/w and not proportionately increase along with the exposure concentration. The mean index values of the gill histopathology ranged from 5.25-7.67 and classified as moderate to severe. Gills characteristics and T. granosa protective behaviour potentially limit Diuron accumulation in the soft tissue.

Elevated toxicity of resuspended mine tailings over time

Resuspension of disposed mine tailings is an important secondary source of heavy metal pollution in affected regions. UK copper mine tailings were continuously resuspended in seawater over 14 days to understand potential metal dissolution and associated ecotoxicological impacts. Aqueous concentrations of arsenic increased 859%, nickel 85%, manganese and cadmium over 40%, and vanadium and zinc over 20%. Green sea urchin (Psammechinus miliaris) gametes were exposed to 18-h (18hr) and 14-day (14d) resuspension elutriates. Fertilisation success dropped from 72% (18hr) to 21.06% (14d). Toxicity Index (TI) values (reduced fertilisation membrane quality and fertilisation success) increased from 1.6 (18hr) to 2.8 (14d). Embryo polyspermy frequencies increased from 17.58% (18hr) to 21.13% (14d). Higher TI values and polyspermy rates indicate impacts may go beyond standard bioassay endpoints. Current predictions of mine tailing impacts may be underestimated. This is important for ecosystem resilience when considering other anthropogenic stressors such as climate change. CAPSULE: Disturbance of metal contaminated sediments over prolonged periods results in ever increasing dissolution concentrations, and elevated toxicity of the water medium to biological receptors.

An environmentally realistic pesticide and copper mixture impacts embryonic development and DNA integrity of the Pacific oyster, Crassostrea gigas

Frequent occurrences of pesticides in the environment have raised concerns that combined exposure to these chemicals may result in enhanced toxicity through additive or synergistic interaction between compounds. Spermatozoa and embryos of the Pacific oyster, Crassostrea gigas, were exposed to different concentrations of a pesticide mixture with and without copper, mimicking the cocktail of pollutants occurring in the oyster culture area of Arcachon Bay. For the 1× exposure condition, measured concentration corresponds to a total concentration of 1.083 μg L^-1 for the mixture of 14 pesticides and to 6.330 μg L^-1 for copper (Cu). Several endpoints including larval abnormalities, DNA damage to spermatozoa and embryo and gene expression in D-larvae were investigated. Results demonstrated that pesticide mixtures in combination with or without copper induced a dose-dependent increase in embryotoxic and genotoxic effects on D-larvae from the lowest tested dose of 0.1×. Transcription of genes involved in anti-oxidative stress (cat), respiratory chain (coxI), metal detoxification (mt1 and mt2), and cell cycle arrest and apoptosis (p53) was found to be significantly downregulated while the xenobiotic biotransformation gene gst was significantly upregulated in embryos exposed to pesticide mixture with and without Cu. These findings raise the question of the possible impacts of mixtures of pesticides and metals on wild or farmed oyster populations from polluted coastal marine areas.

First molecular evidence of the toxicogenetic effects of copper on sea urchin Paracentrotus lividus embryo development

Bioassays with sea urchin embryos are widely used to define the environmental quality of marine waters. Anomalies during embryogenesis are generally considered as end-points, whereas a toxigenomic approach, despite it is wide use in other species, is yet in its infancy. In the present study we evaluated toxigenic effects induced by copper on the sea urchin Paracentrotus lividus embryo, combining morphological observations with gene expression analysis. Many anthropogenic activities release copper in the marine environment, with harmful effects on aquatic organisms. In the present study P. lidivus embryos were exposed to different concentrations of copper (24, 36, 48 μg/L) and the activation of fifty specific marker genes, involved in different biological processes (stress, skeletogenesis, development/differentiation, detoxification) was investigated at early blastula, late gastrula and pluteus stage. At blastula stage no morphological anomalies were found, with early down-regulation of genes involved in development/differentiation and a moderate up-regulation of some detoxification genes. At gastrula stage a slight increase in developmental anomalies (up to 19% of malformed embryos) was followed by an increased number of targeted genes belonging to the same two classes, relative to the blastula stage. At pluteus stage morphological anomalies increased in a dose dependent manner. All the analyzed genes were strongly up-regulated, stress and skeletogenic genes showing a "late response" and almost all genes were targeted by copper at all the concentrations tested. The present study represents the first molecular report on the potential negative effect of copper on P. lividus embryos in the environment. Gene expression analysis should be considered as a promising tool for future environmental biomonitoring programs.

Development of the sea urchin Heliocidaris crassispina from Hong Kong is robust to ocean acidification and copper contamination

Metallic pollution is of particular concern in coastal cities. In the Asian megacity of Hong Kong, despite water qualities have improved over the past decade, some local zones are still particularly affected and could represent sinks for remobilization of labile toxic species such as copper. Ocean acidification is expected to increase the fraction of the most toxic form of copper (Cu²⁺) by 2.3-folds by 2100 (pH ≈7.7), increasing its bioavailability to marine organisms. Additionally, multiple stressors are likely to exert concomitant effects (additive, synergic or antagonist) on the organisms living in the sea. Here, we tested the hypothesis that copper-contaminated waters are more toxic to sea urchin larvae under future pH conditions. We exposed sea urchin embryos and larvae to two low-pH and two copper treatments (0.1 and 1.0 μM) in three separate experiments. Over the short time typically used for toxicity tests (up to 4-arm plutei, i.e. 3 days), larvae of the sea urchin Heliocidaris crassispina were robust and survived the copper levels present in Hong Kong waters today (≤0.19 μM) as well as the average pH projected for 2100. We, however, observed significant mortality with lowering pH in the longer, single-stressor experiment (Expt A: 8-arm plutei, i.e. 9 days). Abnormality and arm asymmetry were significantly increased by pH or/and by copper presence (depending on the experiment and copper level). Body size (d3; but not body growth rates in Expt A) was significantly reduced by both lowered pH and added copper. Larval respiration (Expt A) was doubled by a decrease at pH_T from 8.0 to 7.3 on d6. In Expt B1.0 and B0.1, larval morphology (relative arm lengths and stomach volume) were affected by at least one of the two investigated factors. Although the larvae appeared robust, these sub-lethal effects may have indirect consequences on feeding, swimming and ultimately survival. The complex relationship between pH and metal speciation/uptake is not well-characterized and further investigations are urgently needed to detangle the mechanisms involved and to identify possible caveats in routinely used toxicity tests.

Copper release rate needed to inhibit fouling on the west coast of Sweden and control of copper release using zinc oxide

How zinc oxide influences copper release has been tested and the lowest release rate of copper from various combinations of copper and zinc in a paint matrix evaluated, whilst still deterring macrofouling, including barnacles and bryozoans. Copper (I) oxide was added to a generic AF paint in 0, 8.5, 11.7 or 16.3 wt% copper oxide in combination with 0, 10 or 20 wt% zinc oxide and applied on PMMA panels. The results show that zinc influences the release rate of copper. When 10 and 20 wt% zinc was added, the total amount of copper released significantly increased by on average 32 and 47% respectively. All treatments that included copper were successful in deterring macrofouling, including the treatment with the lowest average Cu release rate, ie 4.68 μg cm^-2 day^-1.

Risk assessment of selected priority pollutants coming from boating activities

In this work, we evaluated the risk posed to aquatic organisms in the coastal waters of Albania and Apulia (Italy) by two priority pollutants (PPs), Irgarol 1051 and Diuron, used as biocides in antifouling paints on boat hulls. With this aim, we carried out an extensive 3-year monitoring in ports and marinas along the coasts of both countries, which showed a widespread occurrence of both PPs, with Irgarol 1051 concentrations usually being lower than the Diuron ones. The measured concentrations were compared with regulatory Environmental Quality Standards (EQS) (Directive 2008/105/EC) and used to perform a probabilistic Ecological Risk Assessment (ERA), for a thorough evaluation of the potential adverse effects upon marine ecosystem. Irgarol 1051 amounts above the Annual Average Concentration (AA-EQS, 2.5 ng/L) were often detected in Apulia and, less frequently, in Albania. Moreover, in Apulia, sometimes the Maximum Allowable Concentrations (MAC-EQS, 16 ng/L) was exceeded. In Apulia, where levels exceeded MAC/AA-EQS, ERA found not negligible probabilities of exceeding the toxicity level (6-18 %). A less critical situation was observed for Diuron whose levels were always below the MAC-EQS (1800 ng/L) in both countries and, in Albania, also below the AA-EQS (200 ng/L). On the other hand, in Apulia, this limit was exceeded in some locations. Correspondingly, ERA determined a not negligible risk in these sites (probability of exceedance 4-7 %).

Multidisciplinary screening of toxicity induced by silica nanoparticles during sea urchin development

The aim of this study was to investigate the potential toxicity of Silica nanoparticles (SiO2 NPs) in seawater by using the sea urchin Paracentrotus lividus as biological model. SiO2 NPs exposure effects were identified on the sperm of the sea urchin through a multidisciplinary approach, combining developmental biology, ecotoxicology, biochemistry, and microscopy analyses. The following responses were measured: (i) percentage of eggs fertilized by exposed sperm; (ii) percentage of anomalies and undeveloped embryos and larvae; (iii) enzyme activity alterations (acetylcholinesterase, AChE) in the early developmental stages, namely gastrula and pluteus. Sperms were exposed to seawater containing SiO2 NPs suspensions ranging from 0.0001mg/L to 50mg/L. Fertilization ability was not affected at any concentration, whereas a significant percentage of anomalies in the offspring were observed and quantified by means of EC50 at gastrula stage, including undeveloped and anomalous embryos (EC50=0.06mg/L), and at pluteus stage, including skeletal anomalies and delayed larvae (EC50=0.27mg/L). Moreover, morphological anomalies were observed in larvae at pluteus stage, by immunolocalizing molecules involved in larval development and neurotoxicity effects - such as acetylated tubulin and choline acetyltransferase (ChAT) - and measuring AChE activity. Exposure of sea urchins to SiO2 NPs caused neurotoxic damage and a decrease of AChE expression in a non-dose-dependent manner. In conclusion, through the multidisciplinary approach used in this study SiO2 NPs toxicity in sea urchin offspring could be assessed. Therefore, the measured responses are suitable for detecting embryo- and larval- toxicity induced by these NPs.

Sperm exposure to carbon-based nanomaterials causes abnormalities in early development of purple sea urchin (Paracentrotus lividus)

We examined egg fertilisation in purple sea urchin (Paracentrotus lividus) after sperm exposure to carbon-based nanomaterials, carbon black (CB) and graphene oxide (GO), from 0.0001 mg/L to 1.0mg/L. Gastrula stage embryos were investigated for acetylcholinesterase and propionylcholinesterase activities, and their morphological characteristics. Plutei were analysed for morphological abnormalities, with emphasis on skeletal rod formation. Egg fertilisation was significantly affected by CB, at all concentrations tested. Loss of cell adhesion at the gastrula surface was observed in eggs fertilised with sperm treated with CB. However, concentration-dependent morphological anomalies were observed in the gastrulae and plutei formed after sperm exposure to either CB or GO. The activities of both cholinesterases decreased in the gastrulae, although not in a concentration-dependent manner. These effects appear to arise from physical interactions between these carbon-based nanomaterials and the sperm, whereby nanomaterials attached to the sperm surface interfere with fertilisation, which leads to disturbances in the signalling pathways of early embryonic development. Reduced cholinesterase activity in gastrulae from eggs fertilised with nanomaterial-treated sperm confirms involvement of the cholinergic system in early sea urchin development, including skeletogenesis.

Application of a toxicity test battery integrated index for a first screening of the ecotoxicological threat posed by ports and harbors in the southern Adriatic Sea (Italy)

Ports and harbors may represent a threat for coastal ecosystems due to pollutant inputs, especially those derived from maritime activities. In this study, we report a first assessment of the ecotoxicological threat posed by six ports and harbors of opposite coastal regions, Apulia and Albania, in the southern Adriatic Sea (Italy). A bioassay battery consisting of four different species representing different trophic levels, algae Dunaliella tertiolecta, bacteria Vibrio fischeri, crustacean Artemia salina, and echinoids Paracentrotus lividus, has been used to assess sediment elutriates, pore waters, and sediment suspensions. Two different approaches of toxicity data integration, worst case and integrated index, have been used to determine the most appropriate procedure for the investigated sites. All sites with the worst case approach showed high toxicity levels. The chronic test with algae was the most sensitive identifying the highest effects in the battery. This effect can be attributable to contaminants derived from antifouling paints. The sediments, evaluated with V. fischeri test, often showed toxicity not found in the aqueous matrices of the same sites and that can be mainly linked to organic compounds. The test battery used in this study allowed us to perform a preliminary screening of the ecotoxicological risk of the studied area. In fact, the species utilized for toxicity tests responded differently to the investigated samples, showing different sensitivity. The test battery integrated index did not allow highlighting the differences among the sites and showed a general high ecotoxicological risk. A larger number of tests with higher sensitivity together with a tailored attribution of weights to endpoints and matrices will improve the final site evaluation.

Current and emerging environmentally-friendly systems for fouling control in the marine environment

Following the ban in 2003 on the use of tributyl-tin compounds in antifouling coatings, the search for an environmentally-friendly alternative has accelerated. Biocidal TBT alternatives, such as diuron and Irgarol 1051®, have proved to be environmentally damaging to marine organisms. The issue regarding the use of biocides is that concerning the half-life of the compounds which allow a perpetuation of the toxic effects into the marine food chain, and initiate changes in the early stages of the organisms' life-cycle. In addition, the break-down of biocides can result in metabolites with greater toxicity and longevity than the parent compound. Functionalized coatings have been designed to repel the settlement and permanent attachment of fouling organisms via modification of either or both surface topography and surface chemistry, or by interfering with the natural mechanisms via which fouling organisms settle upon and adhere to surfaces. A large number of technologies are being developed towards producing new coatings that will be able to resist biofouling over a period of years and thus truly replace biocides as antifouling systems. In addition urgent research is directed towards the exploitation of mechanisms used by living organisms designed to repel the settlement of fouling organisms. These biomimetic strategies include the production of antifouling enzymes and novel surface topography that are incompatible with permanent attachment, for example, by mimicking the microstructure of shark skin. Other research seeks to exploit chemical signals and antimicrobial agents produced by diverse living organisms in the environment to prevent settlement and growth of fouling organisms on vulnerable surfaces. Novel polymer-based technologies may prevent fouling by means of unfavourable surface chemical and physical properties or by concentrating antifouling compounds around surfaces.

Embryotoxicity and spermiotoxicity of nanosized ZnO for Mediterranean sea urchin Paracentrotus lividus

The effect of nano ZnO (nZnO) upon the fertilization and early development of embryos of the Mediterranean sea urchin Paracentrotus lividus is reported herein for the first time. Zn ion (ZnCl2) and bulk ZnO (bZnO) toxicity were assessed for comparison. The embryotoxicity tests showed a 100% effect already at 1 μM of nZnO (expressed as [Zn]) while bZnO and ZnCl2 showed EC50s of 0.98 [0.88-1.19] μM [Zn] and 2.02 [1.97-2.09] μM [Zn], respectively. Noteworthy, the frequency of developmental defects for the three compounds was dissimilar and a specific trend for larval skeletal abnormality produced by nZnO was observed. The sperm fertilization capability was only slightly affected by the tested chemicals while the effects were dramatic on the offspring quality of sperms exposed to ZnO compounds resulting in an early block of the regular larval development. ZnO toxicity seems related not only to Zinc ions but also to some surface interactions of particle/aggregates with target organisms and/or with the seawater.

In vitro reactive oxygen species production by mitochondria from the rabbitfish Siganus fuscessens livers and the effects of Irgarol-1051

In this study, the mitochondria from the livers of Siganus fuscessens were exposed to the Irgarol-1051with or without respiratory chain inhibitors using succinate or malate as the substrate, and the effects on mitochondrial ROS production were tested. The mitochondrial ROS production was significantly enhanced by antimycin A with an increase of more than three folds but not by rotenone and NaN3, and this may suggest complex III is the major ROS-producing site. Irgarol-1051 treatments gave a somewhat contradictory result: this chemical can inhibit the mitochondrial ROS production but the inhibition decreased with the increase of doses. These contradictory data about Irgarol-1051 may be explained by the balance between the effects of inhibition through the opening of small-size pores and stimulation through blocking electron transfer, but the mechanism laid behind needs more evidence to support. As Irgarol-1051 was continuously used in antifouling and its bio-concentration factor is up to 160 in fish, the toxic effect of Irgarol-1051 on aquatic animals should be paid more attention to.

Embryotoxic and genotoxic effects of heavy metals and pesticides on early life stages of Pacific oyster (Crassostrea gigas)

This study evaluated embryotoxicity and genotoxicity of two dissolved metals copper and cadmium (Cu and Cd) and two pesticides (metolachlor and irgarol) occurring in Arcachon Bay (SW France) in Pacific oyster (Crassostrea gigas) larvae and investigated the relationship between those two endpoints. Embryotoxicity was measured by calculating the percentage of abnormal D-shaped larvae and genotoxicity was evaluated with DNA strand breaks using the comet assay. After 24h exposure, significant increases of the percentage of abnormal D-larvae and the DNA strand breaks were observed from 0.1 μg L⁻¹ for Cu, 10 μg L⁻¹ for Cd and 0.01 μg L⁻¹ for both irgarol and metolachlor in comparison with the controls. A strong positive relationship between embryotoxicity and genotoxicity was recorded for Cu, Cd and metolachlor. The current study suggests that copper, irgarol and metolachlor can induce larval abnormalities and DNA damage in a population of exposed oysters at environmentally relevant concentrations.

Physiological and biochemical responses of Synechococcus sp. PCC7942 to Irgarol 1051 and diuron

Cyanobacteria are prokaryotic algae found in oceans and freshwaters worldwide. These organisms are important primary producers in aquatic ecosystems because they can provide essential food for grazers and herbivores. In this study, the physiological and biochemical responses of the freshwater cyanobacterium Synechococcus sp. PCC7942 to two organic booster biocides Irgarol 1051 and diuron were compared and evaluated using 96 h growth tests in a batch-culture system. The 96 h median effective concentrations (EC(50)) were 0.019 and 0.097 μmol L(-1) for Irgarol 1051 and diuron, respectively, which indicate that Irgarol 1051 is about 5 times more toxic than diuron to cyanobacteria. Moreover, remarkable physiological and biochemical responses occurred in the Irgarol 1051 and diuron treatments. Irgarol 1051 and diuron stimulated cyanobacterial growth, increased the soluble protein content, and enhanced the catalase (CAT) activity at low concentrations, but inhibited them at high concentrations. However, the malondialdehyde (MDA) and polysaccharide content of the cyanobacteria were only significantly affected by Irgarol 1051. These observations suggest that Irgarol 1051 and diuron are toxic to Synechococcus sp. PCC7942, and their use should be restricted in maritime industries.

Toxic effects of pentachlorophenol, azinphos-methyl and chlorpyrifos on the development of Paracentrotus lividus embryos

The application of many current-use pesticides has increased after the disuse of persistent, bioaccumulative or toxic ones as DDT or chlordane. Many of the used pesticides are considered less dangerous towards the environment for their physico-chemical properties. This study investigated the toxic effects of three current-use pesticides, pentachlorophenol (PCP), azinphos-methyl (AZM), and chlorpyrifos, on Mediterranean sea urchin Paracentrotus lividus early development and offspring quality. The experimental results showed that the most toxic pesticides were PCP and AZM at EC50 level. Nevertheless at low concentration PCP resulted the less toxic compound and showed EC1 value more protective than NOEC. PCP at high concentration seemed to modify cytoskeleton assembly, while at low concentrations, it could alter the deposition of the larval skeleton. OPs at low concentrations until 300 μg/l showed a similar toxicological behaviour with a trend corresponding to the pesticide concentrations. At high concentration (500 μg/l) the effect mainly observed was the embryos pre-larval arrest. This investigation highlighted the relevance to evaluate, in coastal seawaters, the levels of the used pesticides to understand the real impact on benthic populations mainly in sites characterized by intensive agriculture or floriculture activities, such as the coastal areas of the Mediterranean Sea.

Organotin contamination in South American coastal areas

Organotin compounds (OTs) were used in antifouling paints for more than four decades. However, due to their widespread intensive use and high toxicity, undesirable effects in non-target marine organisms have been detected since the early 1980s. Consequently, the International Maritime Organization banned new maritime applications of these products on January 1, 2003 and their presence on ship hulls from January 1, 2008. Although extensively studied in Europe, North America, Oceania, and Asia, environmental levels and effects of organotin contamination are still poorly known for South America. Thus, the current review aimed to present the actual status of this problem in South America by summarizing and comparing the available data in the literature. An overview of the OTs concentrations in sediment and biota and their effects, mainly imposex in marine gastropods, are presented. This work showed that in Atlantic coastal areas of South America there are "hot spots" of OTs contamination, similar to that observed in industrialized countries of Northern Hemisphere. On the other hand, the number of accomplished studies in the Pacific coast is extremely low. Despite the limitation on studies about OTs environmental levels and their related effects, the available data pointed out for a widespread TBT contamination along the South American coastal areas. Therefore, the establishment of baselines of organotin contamination in the Pacific coast and the implementation of temporal trend studies in the South American coastal areas is crucial to verify the effectiveness of local regulations and OTs global ban, and to map the most sensitive areas related to present and future antifouling impacts.

Antifouling strategies: history and regulation, ecological impacts and mitigation

Biofouling increases drag on marine vessels resulting in higher fuel consumption and can also facilitate the transport of harmful non-indigenous species (NIS). Antifouling technologies incorporating biocides (e.g., copper and tributyltin) have been developed to prevent settlement of organisms on vessels, but their widespread use has introduced high levels of contamination into the environment and raised concerns about their toxic effects on marine communities. The recent global ban on tributyltin (1 January 2008) and increasing regulation of copper have prompted research and development of non-toxic paints. This review synthesises existing information regarding the ecological impact of biocides in a wide range of organisms and highlights directions for the management of antifouling paints. We focus particularly on representatives of the recent past (copper and tributyltin) and present (copper and 'booster') biocides. We identify knowledge gaps in antifouling research and provide recommendations relating to the regulation and phasing-out of copper.

Cadmium, lead and their mixtures with copper: Paracentrotus lividus embryotoxicity assessment, prediction, and offspring quality evaluation

The aim of this research was to assess the combined effects of three heavy metals (copper, lead, cadmium) on the fertilization and offspring quality of the sea urchin Paracentrotus lividus at EC50, NOEL, and EC1 concentrations. The observed data were compared with the predictions derived from approaches of Concentration Addition (CA) and Independent Action (IA) in order to evaluate the proper prediction of the observed mixture toxic effect. The P. lividus embryotoxicity of trace metals decreases as follows: Cu > Pb > Cd at all toxicity concentration tested. EC50 mixture revealed less toxic only than Cu; EC50 was 0.80 (± 0.07) mg/l, the offspring malformations were mainly P1 type (skeletal alterations) up to 20% mixture concentration, and P2 type from 70% concentration. The NOEL and EC1 mixtures evidenced that all compounds contribute to the overall toxicity, even if present at low concentrations: the former EC50 was 0.532 (± 0.058) mg/l and the latter was 1.081 (± 0.240) mg/l. The developmental defects observed were mainly P1 type in both mixtures. Both CA and IA models did not accurately predict mixture toxicity for EC50 and NOEL mixtures. Instead, EC1 mixture effects seemed well represented by the IA model. The protective action of the CA model, although quite accurate when applied to simple biological systems like algae and bacteria, but failed to represent the worst-case in this study with more complex organisms. It would be useful to introduce in the models one or more factors that take into account the complexity of these biological systems.

A new effect residual ratio (ERR) method for the validation of the concentration addition and independent action models

BACKGROUND, AIM, AND SCOPE

Glutaraldehyde (GA) often acts as an effective sterilant, disinfectant, and preservative in chemical products. It was found that GA had clearly acute toxicity to aquatic organisms. Furthermore, GA in natural environment could not exist as single species but as complex mixtures. To explore the toxicity interaction between GA and the other environmental pollutant, it is necessary to determine the mixture toxicities of various binary mixtures including GA. Two reference models, concentration addition (CA) and independent action (IA), are often employed to evaluate the mixture toxicity, which can be finished by comparing the concentration-response curves (CRCs) predicted by the reference models with the experimental CRC of the mixture. However, the CRC-based method cannot effectively denote the degree of the deviations from the reference models, especially at very low effect levels. Though the model deviation ratio (MDR) can be used to quantitatively evaluate the deviation of a mixture at EC50 level from the reference model, it is difficult to evaluate the deviations at the lower effect levels. Therefore, the primary aim of this study was to develop a new effect residual ratio (ERR) method to validate the deviations from the reference models at various effect levels.

MATERIALS AND METHODS

Four chemicals having possible dissimilar mode of actions with GA, acetonitrile (ACN), dodine (DOD), simetryn (SIM), and metham sodium (MET), were selected as another component in the binary mixtures including GA, which constructed four binary mixtures, GA-ACN, GA-DOD, GA-SIM, and GA-MET ones. For each binary mixture, two equipotent mixture rays where the concentration ratios of GA to another mixture component are respectively EC50 and EC5 ones were designed and their toxicities (expressed as a percent inhibition to Photobacterium phosphoreum) were determined by microplate toxicity analysis. The observed concentration-response curve (CRC) of a ray was compared with that predicted by CA or IA model to qualitatively assess the toxicity interaction of the mixture ray. To quantitatively and effectively examine the deviations at various effect levels from the reference models, a new concept, ERR at an effect, was defined, and the ERR was employed to evaluate the deviation at various effects with confidence intervals.

RESULTS

For three binary mixtures, GA-ACN, GA-DOD, and GA-SIM, the CRCs predicted by IA models were almost located in the 95% confidence intervals of the experimental CRCs for both equipotent mixture rays, which indicated the independent actions between binary mixture components. However, two rays of GA-MET binary mixture displayed a little synergistic action because both CRCs predicted by CA and IA were lower than the experimental CRC. ERR showed the same results as MDR, but ERR results at low effect area were clearer than MDR ones.

DISCUSSION

In CRC comparison, the deviation of CA (for GA-ACN, GA-DOD, and GA-SIM combinations) or IA (for GA-MET) model from the experimental values could be obviously observed at medium area of the CRC. However, at very low effect levels, both deviations of CA and IA and difference between CA and IA model predictions were not very apparent. Thus, it was difficult to confirm which model, CA or IA, had better predicted power at very low effect levels. MDR in many literatures often refers to a ratio at EC50 level. It was also difficult to reflect not only the deviation fact at the other ECx but also the deviation uncertainty. After we extended the definition of MDR to all ECx and examined the 95% confidence intervals based on observation, the plot of the redefined MDRs at many effect levels could better explain the deviations of CA or IA model from the observation. However, MDRs at very low effect levels did not still reflect the high uncertainty there. The ERRs defined in our paper could explicitly explain the degree of deviation from the reference models and especially reflect the high uncertainty at very low effects. It could be said that the ERR is a better indicator than MDR.

CONCLUSIONS

The new ERR validation method developed in our laboratory could provide us with the information about the toxicity interaction between the mixture components and quantitatively assess the accuracy of the reference models (CA or IA) at whole effect levels. The ERR method conquered the invalidation of the classical CRC comparison method on the deviation decision at low effect levels and also got the advantage over the MDR methods.

RECOMMENDATIONS AND PERSPECTIVES

It holds promise to become an effective method of hazard and risk assessments of chemical mixtures by well characterizing the uncertainty at very low effect levels.