Antioxidant responses in estuarine invertebrates exposed to repeated oil spills: Effects of frequency and dosage in a field manipulative experiment

Morphological and transcriptional effects of crude oil and dispersant exposure on the marine sponge Cinachyrella alloclada

Marine sponges play important roles in benthic ecosystems. More than providing shelter and food to other species, they help maintain water quality by regulating nitrogen and ammonium levels in the water, and bioaccumulate heavy metals. This system, however, is particularly sensitive to sudden environmental changes including catastrophic pollution event such as oil spills. Hundreds of oil platforms are currently actively extracting oil and gas in the Gulf of Mexico. To test the vulnerability of the benthic ecosystems to oil spills, we utilized the Caribbean reef sponge, Cinachyrella alloclada, as a novel experimental indicator. We have exposed organisms to crude oil and oil dispersant for up to 24 h and measured resultant gene expression changes. Our findings indicate that 1-hour exposure to water accommodated fractions (WAF) was enough to elicit massive shifts in gene expression in sponges and host bacterial communities (8052 differentially expressed transcripts) with the up-regulation of stress related pathways, cancer related pathways, and cell integrity pathways. Genes that were upregulated included heat shock proteins, apoptosis, oncogenes (Rab/Ras, Src, CMYC), and several E3 ubiquitin ligases. 24-hour exposure of chemically enhanced WAF (CE-WAF) had the greatest impact to benthic communities, resulting in mostly downregulation of gene expression (4248 differentially expressed transcripts). Gene deregulation from 1-hour treatments follow this decreasing trend of toxicity: WAF > CE-WAF > Dispersant, while the 24-hour treatment showed a shift to CE-WAF > Dispersant > WAF in our experiments. Thus, this study supports the development of Cinachyrella alloclada as a research model organism and bioindicator species for Florida reefs and underscores the importance of developing more efficient and safer ways to remove oil in the event of a spill catastrophe.

Comparative study of immunological biomarkers in the carpet shell clams (Ruditapes decussatus) from metal-contaminated sites in the South Lagoon of Tunis (Tunisia)

The South Lagoon of Tunis (Tunisia) is a Mediterranean lagoon adversely affected by industrial contaminants, harbour activity and untreated urban sewage. In this lagoon, the clam Ruditapes decussatus has been widely used as a biomonitor of seawater pollution through measurements of parameters related to oxidative stress and neurotoxicity. However, few studies have considered parameters of the immune system of this species in the South Lagoon of Tunis. Therefore, the aim of the present work was to evaluate several immune-related parameters in the cell-free haemolymph of carpet shell clams sampled during August and February from three polluted sites in the South Lagoon of Tunis (S1, S2 and S3) and one less polluted site as a reference site (RS) in order to identify suitable biomarkers for environmental quality assessments of this ecosystem. Concerning the immune-related parameters, seasonal factors modulated phenoloxidase, lysozyme, protease and esterase activity, with lower values measured for samples collected in August than for samples collected in February. In fact, bactericidal activity against two of the pathogenic bacteria tested and the activity of most immune-related enzymes were reduced in the cell-free haemolymph of clams collected from the most sampling sites in August compared to February one. In addition, values of abiotic parameters (temperature, salinity and pH) and metal (cadmium, copper, iron, lead and zinc) concentrations in the clams' soft tissues, previously obtained and published by the authors, as well as the values of immune-related parameters were integrated using principal component analyses. Results indicated that the values of all measured immune-related parameters were negatively correlated with the temperature values and the variations most of these parameters highlighted that the chemical industrial area (S3) was the most impacted location within the South Lagoon of Tunis. The present study illustrates that the immune-related parameters measured in carpet shell clam cell-free haemolymph represent suitable biomarkers for environmental quality assessments because they provide effective seasonal and spatial discrimination.

Polycyclic aromatic hydrocarbons in sediments and shellfish from Todos os Santos bay, Brazil

The present study evaluated the occurrence of 24 Polycyclic Aromatic Hydrocarbons (PAHs) in sediments and shellfish (Anomalocardia flexuosa, Crassostrea rhizophorae, and Mytella guyanensis) of Todos os Santos bay (BTS, Brazil). Total PAHs levels ranged from 89 to 921 ng g^-1 dry weight (d.w.) in sediments, and from 66 to 505 ng g^-1 d.w. in shellfish, signalizing that BTS was moderately contaminated by PAHs, mostly from pyrogenic activities. The bioaccumulation factor (BAF) of total PAHs ranged from 0.20 to 2.9 and did not show a clear trend among the studied species. BAFs of high molecular weight compounds were higher for A. flexuosa (specie found buried in fine sediment), while those of low molecular weight compounds were higher for C. rhizophorae (specie found in the roots of mangrove trees). High concentrations of PAHs, especially benzo[a]pyrene and dibenzo[a,h]anthracene, suggest that contamination compromises shellfish quality and raise concern about seafood consumption safety.

Macrozoobenthic community responses to sedimentary contaminations by anthropogenic toxic substances in the Geum River Estuary, South Korea

We investigated the sedimentary pollution by persistent toxic substances (PTSs) and their potential impacts on the macrobenthic faunal community in the Geum River Estuary, South Korea. Sediment and benthic macrofauna samples were collected from eight sites every two months during the period of February to December in 2015. Target PTSs encompassed metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn), one metalloid (As), polycyclic aromatic hydrocarbons (PAHs), and alkylphenols (APs). The significant difference to the environment of the inner and outer parts of the estuary (p < 0.05) was found with relatively high concentrations of PTSs in sediment from the inner estuary. The concentrations of Cu and Zn exceeded the sediment quality guidelines of Korea representing a potential risk to aquatic organisms. The primary source of PAHs was by-products of diesel and gasoline combustion (37%), followed by a coke oven (32%) and oil-burning (31%). The macrofaunal community was spatially distinguished between the inner and outer parts of the estuary (p < 0.05), regardless of the season. In the inner part of the estuary, the density of the macrofaunal community was high, due to the increased opportunistic species and/or some indicator species (organic polluted or enrichment), implying that the given environment was disturbed. Among the environmental parameters analyzed by the distance-based linear model (DistLM), salinity, chlorophyll-a, and nutrient concentrations were found to be key factors controlling the changes in macrofaunal community structure. Such changes in the closed estuary system would indicate that each taxonomic group had to adjust to lower salinities and alternative food sources. Overall, the distribution of PTSs and macrozoobenthic communities in the Geum River Estuary collectively reflected the environmental gradients caused by surrounding activities in the inner part of the estuary together with direct effects by the irregular inflow of freshwater.

Toxin accumulation, detoxification and oxidative stress in bivalve (Anomalocardia flexuosa) exposed to the dinoflagellate Prorocentrum lima

Prorocentrum lima is a cosmopolitan benthic dinoflagellate capable of producing the diarrhetic shellfish toxins (DSTs) okadaic acid (OA) and dinophysistoxin (DTX). These compounds may cause oxidative stress and accumulate in bivalve tissues, which become vectors of intoxication to human consumers. We investigated DST accumulation, detoxification and oxidative stress biomarkers in clams (Anomalocardia flexuosa) experimentally exposed to P. lima cells or their compounds. Experimental diets consisted of 6000 cells mL-1 of the non-toxic chlorophyte Tetraselmis sp. (C; control condition), and combinations of C with 10 P. lima cells mL-1 (T10), 100 P. lima cells mL-1 (T100), or to a toxin concentration of ∼4 μg OA L-1 and ∼0.65 μg DTX-1 L-1 (T100d). Clams were exposed to these diets for 7 days (uptake phase), followed by a 7-day depuration period. No DSTs were detected in clams exposed to treatments C (control) nor to T100d (dissolved compounds) during either uptake or detoxification phase. Conversely, clams exposed to T10 or T100 accumulated, on average, up to 2.5 and 35 μg DST kg-1 in their whole bodies at the end of the uptake phase. These concentrations are ∼64 and ∼4.5 times lower than the regulatory level of 160 μg OA kg-1, respectively. Accumulated OA quotas were 12-22 times higher in the digestive gland (DG) than in remaining tissues over the uptake phase. Quick toxin transformation was indicated by the early detection of conjugated compounds - DTX-1 and OA esters - in the DG after 6 h of exposure, with OA-ester representing the main compound (30 - 100 %) in that tissue over the experiment. During the depuration period, detoxification rates represented 0.024 h-1, 0.04 h-1 and 0.052 h-1 for OA, DTX-1 and OA-ester, respectively. The activities of catalase, glutathione S-transferase, glutathione peroxidase and the levels of oxidative stress by lipoperoxidation varied similarly in the DG of A. flexuosa individuals subjected to T100, T100d and the control condition. However, contrasting antioxidant responses were measured in those exposed to T10. These findings indicate that no oxidative stress was primarily induced by DST-producing dinoflagellates in this clam species under laboratory conditions representative of toxic bloom situations. Even though, possible interactions should be considered under multistressor scenarios.

First ecotoxicological characterization of paraffin microparticles: a biomarker approach in a marine suspension-feeder, Mytilus sp

Microplastics are one of the main environmental pollutants in marine ecosystems, and their presence in seawater is a consequence of the widespread use of plastic materials in modern commodities. This wide usage of plastics includes the employment of microspheres in common personal care products, which end up being ultimately released into the aquatic compartment. Known ecotoxicological effects of microplastics favoured the search for technologically viable and environmentally safer alternatives, such as paraffin wax microparticles, whose ecotoxicological risks have not been entirely characterized. To address this gap, the present study exposed mussels (Mytilus sp.) for 96 h to three densities (5 mg/L, 20 mg/L and 80 mg/L) of four size ranges (100-300 μm, 300-500 μm, 400-850 μm, and 800-1200 μm) of paraffin wax particles. Toxicological endpoints were the activities of four enzymes involved in key cellular processes, including antioxidant defence (catalase (CAT), glutathione reductase (GRed) and glutathione peroxidase (GPx)) and phase II metabolism (glutathione S-transferases (GSTs)), as well as lipid content and fatty acid profiles of the digestive gland. Significant interactions between the presence/absence of food and paraffin particle density were found, as food sometimes worked as a confounding factor in the analysed biomarkers. Despite this uncertainty, some overall patterns emerged. In general, smaller paraffin wax particles (100-300 μm) caused little effects on the activity of the four enzymes tested, whereas larger particles (800-1200 μm) caused significant effects on almost all biomarkers. CAT activity was enhanced in animals exposed to larger paraffin particles, whilst GPx activity was depressed; GRed activity was not affected by the exposure to paraffin particles. The activity of GSTs was enhanced, but only in one tested condition. No effects were observed in terms of the total lipid content and fatty acids of exposed animals. Overall, data obtained in this work suggest that, at densities of paraffin wax particles comparable to the levels found in the environment for microplastic beads, no toxicity is expected to occur in the tested mussel species, by measuring the here-assessed toxicological endpoints.

Variation of Microbial Diversity in Catastrophic Oil Spill Area in Marine Ecosystem and Hydrocarbon Degradation of UCMs (Unresolved Complex Mixtures) by Marine Indigenous Bacteria

The study targeted an assessment of microbial diversity during oil spill in the marine ecosystem (Kaohsiung port, Taiwan) and screened dominant indigenous bacteria for oil degradation, as well as UCM weathering. DO was detected lower and TDS/conductivity was observed higher in oil-spilled area, compared to the control, where a significant correlation (R² = 1; P < 0.0001) was noticed between DO and TDS. The relative abundance (RA) of microbial taxa and diversities (> 90% similarity by NGS) were found higher in the boundary region of spilled-oily-water (site B) compared to the control (site C) and center of the oil spill area (site A) (B_RA/diversity > C_RA/diversity > A_RA/diversity). The isolated indigenous bacteria, such as Staphylococcus saprophyticus (CYCTW1), Staphylococcus saprophyticus (CYCTW2), and Bacillus megaterium (CYCTW3) degraded the C₁₀-C₃₀ including UCM of oil, where Bacillus sp. are exhibited more efficient, which are applicable for environmental cleanup of the oil spill area. Thus, the marine microbial diversity changes due to oil spill and the marine microbial community play an important role to biodegrade the oil, besides restoring the catastrophic disorders through changing their diversity by ecological selection and adaptation process.

Oxidative Stress and Damage Biomarkers in Clam Ruditapes decussatus Exposed to a Polluted Site: The Reliable Biomonitoring Tools in Hot and Cold Seasons

In the present study, a multi-biomarker approach was used to assess the biological effects of metal pollution in the southern lagoon of Tunis, on clam Ruditapes decussatus both in "hot" (in summer) and "cold" (in winter) seasons. Clams were collected in August 2015 and February 2016 from three sites of the lagoon and from Louza considered a reference site. The concentrations of five trace metals (cadmium, copper, iron, lead, and zinc) in the soft tissues of R. decussatus were evaluated at the sampling sites. A core of biomarkers indicative of (a) neurotoxicity (acetylcholinesterase, AChE); (b) biotransformation (glutathione S-transferase, GST); (c) oxidative stress (catalase, CAT; total glutathione peroxidase, T-GPx; total glutathione peroxidase, T-GPx; selenium-dependent glutathione peroxidase, Se-GPx; glutathione reductase, GR; superoxide dismutase, SOD) (d) lipid peroxidation (malondialdhyde, MDA level), and (e) apoptotic process (caspase 3-like, CSP3) was selected for measurements of environmental effects on the populations of clams collected from the different sampling sites. The results of metal bioaccumulation in soft tissues of Ruditapes decussatus revealed a high pollution in the South Lagoon of Tunis with spatial variation and relatively high levels at the navigation channel. Anthropogenic pollutants in the lagoon led to the activation of antioxidant defense and biotransformation enzymes to oxidative damage of the membrane and activation of apoptosis, and revealed neurotoxicity. Among this core of biomarkers, the antioxidants enzymes (CAT, SOD, GR, and GPx) were very sensitive, allowing the discrimination among sites and pointing to the navigation channel as the most impacted site in the southern lagoon of Tunis. Moreover, a significant effect of season was recorded on biomarkers responses (e.g., CAT, GR, SOD, AChE, and CSP3 activities and MDA levels) with higher levels in winter than in summer, probably influenced by the reproductive stage and food availability. Finally, the measurement of the selected core of biomarkers in the whole soft tissues of clams was considered as an integrated indicator of environmental stress. Moreover, R. decussatus proved to be a remarkable sentinel species capable to establish a reliable diagnosis of the health status of the marine environment in different areas of the southern lagoon of Tunis, both in "hot" and "cold" seasons.

Concentration and distribution of polycyclic aromatic hydrocarbons in oysters from Todos os Santos Bay (Bahia, Brazil)

The aim of the present study was to evaluate the presence of polycyclic aromatic hydrocarbons (PAHs) in oysters (Crassostrea rhizophorae) collected from Todos os Santos Bay (Bahia, Brazil). The total PAH concentration was highest in Madre de Deus (36.3 to 37.8 ng g^-1 in dry weight, dw), which is located near a petrochemical complex, oil refinery, and commercial port. In the Paraguaçu river estuary, PAH concentrations varied between 23.2 and 25.7 ng g^-1 dw. The lowest concentrations (1.55 ng g^-1 dw) were found in the Jaguaribe river estuary, which can be considered a relatively preserved area. The main source of PAHs in the study areas was observed to be pyrogenic. Values of benzo[a]pyrene toxic equivalent ranged from 0.28 to 4.20. The concentrations of PAHs in oysters from the Paraguaçu river estuary and in Madre de Deus indicate the possible lifetime risk of developing cancer in humans who feed on it.

Growth and metabolism of adult polar cod (Boreogadus saida) in response to dietary crude oil

The increasing human presence in the Arctic shelf seas, with the expansion of oil and gas industries and maritime shipping, poses a risk for Arctic marine organisms such as the key species polar cod (Boreogadus saida). The impact of dietary crude oil on growth and metabolism of polar cod was investigated in the early spring (March-April) when individuals are expected to be in a vulnerable physiological state with poor energy stores. Adult polar cod were exposed dietarily to three doses of Kobbe crude oil during an eight weeks period and followed by two weeks of depuration. Significant dose-responses in exposure biomarkers (hepatic ethoxyresorufine-O-deethylase [EROD] activity and 1-OH phenanthrene metabolites in bile) indicated that polycyclic aromatic hydrocarbons (PAHs) were bioavailable. Condition indices (i.e. Fulton's condition factor, hepatosomatic index), growth, whole body respiration, and total lipid content in the liver were monitored over the course of the experiment. The majority of females were immature, while a few had spawned during the season and showed low hepatic lipid content during the experiment. In contrast, males were all, except for one immature individual, in a post-spawning stage and had larger hepatic energy stores than females. Most specimens, independent of sex, showed a loss in weight, that was exacerbated by exposure to crude oil and low hepatic liver lipids. Furthermore, females exposed to crude oil showed a significant elevation of oxygen consumption compared to controls, although not dose-dependent. This study highlights the importance of the energy status of individuals for their response to a crude oil exposure.

Differential detoxifying responses to crude oil water-accommodated fraction in Hyallela curvispina individuals from unpolluted and contaminated sites

Sublethal effects of water-accommodated fraction (WAF) from crude oil of Neuquén basin, Northern Patagonia-Argentina, were examined on both antioxidant and detoxification system of Hyalella curvispina adults collected in Los Barreales (LB) lake and in an oil-polluted stream (DS). The effects of WAF exposure during 6, 24 and 48 h were evaluated in the glutathione content (GSH) and glutathione S-transferase (GST), catalase (CAT) and cytochrome P450 (CYP450) activities. Populations from DS and LB showed not only different basal GSH content and enzyme activities but also different behavior to WAF exposure. LB population exposed to WAF showed a significant increase in GSH content, CAT and CYP450 activities, compared to control group. DS population presented high basal levels in CAT and CYP activity compared with LB population, but their response to WAF exposure was minor. Amphipods from DS, chronically exposed to hydrocarbons, were adapted to their environment.

Exploring inter-species sensitivity to a model hydrocarbon, 2-Methylnaphtalene, using a process-based model

We compared inter-species sensitivity to a model narcotic compound, 2-Methylnaphthalene, to test if taxonomical relatedness, feeding guilds, and trophic level govern species sensitivities on species distributed in different regions. We fitted a toxicokinetic-toxicodynamic model to survival patterns over time for 26 species using new and raw data from the literature. Species sensitivity distributions provided little insight into understanding patterns in inter-species sensitivity. The range of no-effect concentrations (NEC) obtained for 26 species showed little variation (mean 0.0081 mM; SD 0.009). Results suggest that the NEC alone does not explain the complexity of the species tolerances. The dominant rate constant and the derived time to observe an effect (t₀), a function of concentration, might provide the means for depicting patterns in sensitivity and better ecotoxicological testing. When comparing the t₀ functions, we observed that Arctic species have shorter time frames to start showing effects. Mollusks and second trophic level species took longer to build up a lethal body burden than the rest. Coupling our results with fate and transport models would allow forecasting narcotic compounds toxicity in time and thus improve risk assessment.

Enhanced removal of sediment-associated total petroleum hydrocarbons under bioturbation by polychaete perinereis aibuhitensis

Bioturbation processes could influence the physical, chemical and biological properties of aquatic sediments and improve the mineralization of organic matter in sediment. The influence of bioturbation by polychaete Perinereis aibuhitensis on the removal of sediment-associated total petroleum hydrocarbon (TPH) was evaluated through laboratory experiment with P. aibuhitensis cultured in crude oil contaminated coastal sediment. After 60 days, the TPH concentrations in the sediments were significantly decreased compared to the initial concentrations, in which the TPH concentrations in bioturbation experiments (with worms) were significantly lower than those in control experiments (without worms) for both low (1.48 ± 0.19g/kg dry wt) and high (2.67 ± 0.33 g/kg dry wt) TPH-contaminated groups, indicating bioturbation enhanced the removal of TPH in sediment. The TPH removal rates in high TPH group were significantly lower than those in low TPH group, suggested that petroleum pollution inhibited the degradation of petroleum hydrocarbons in sediment. However, the stimulation efficiency was higher in high TPH group than that in low TPH group, which may be the result of enhanced hydrocarbon's bioavailability by digestive fluid during gut transit.

Cytotoxicity and enzymatic biomarkers as early indicators of benthic responses to the soluble-fraction of diesel oil

Xenobiotics from oil tanker leaks and industrial discharges are amongst the main human impacts to confined coastal areas. We assessed the genotoxic responses to the water-soluble fraction of diesel oil in the polychaete Laeonereis culveri and the bivalve Anomalocardia flexuosa, two widespread benthic species in subtropical estuaries from the Southwestern Atlantic. We hypothesized that the highest responsiveness would be expressed by significantly different biomarkers responses between control and oil-impacted treatments. Responsiveness to diesel oil was investigated using an experimental design with two fixed factors (contaminant percentages and times of exposure). After exposure, we monitored the responses of the oxidative stress enzymes and performed micronuclei tests. Results were congruent for both species. Antioxidant defense of glutathione S-transferase and the induction of micronuclei and nuclear buds, the latter just for the bivalve, were significantly affected by polycyclic aromatic hydrocarbons, with significant increases on the seventh day of exposure and in the higher concentrations, compared to controls groups. We assessed the benefits and drawbacks of using each biomarker in laboratory experiments. Both species are indicators of early, and rapid responses to genotoxic contaminants in subtropical estuarine habitats. We suggest that the micronuclei frequency in A. flexuosa is a simple, fast and cheap test for genotoxicity in oil-impacted areas. Such early biomarkers are needed to develop better protocols for impact assessment and monitoring under real field conditions.

Biomonitoring role of some cellular markers during heat stress-induced changes in highly representative fresh water mollusc, Bellamya bengalensis: Implication in climate change and biological adaptation

Owing to increasing concern of global climate-change, temperature rise is of great interest which can be primarily evaluated from the seasonal variations in some organisms. Aquatic environment can be extremely stressful to its inhabitants because most of them are poikilothermous. In the present study, attempt was made to evaluate the biological effects of oxidative-stress and adaptive/antioxidant capacities during temperature variations (36-40 °C for 24hrs to 72hrs) in Bellamya bengalensis both in environmental and laboratory conditions by testing some biomarkers like HSP70, catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH) and glutathione reductase (GR). The biomarker potency of the molecules and the anti-oxidative metabolic-network was postulated and extrapolated to find its resemblance to the climate-change associated organismal variations. In a natural and eco-restored environment in the Eastern part of India, 10-20 fold increases in CAT, SOD and HSP70 protein expressions (Western blot results) were noticed in Bellamya paralleling to their increased enzymatic activities (gel zymogram studies) due to the seasonal (summer versus winter) temperature variation. It is evident from the consecutive three years' study that this variation resulted in the unfavorable physico-chemical changes of water quality parameters like dissolved oxygen, biochemical oxygen demand, alkalinity and consequently decreased the animal density in summer. And that was revived due to their higher reproduction-rate in post rainy/winter season when temperature normalizes resulting in a restoration of favorable environment. In laboratory condition, the reduced GR and increased GPx indicated the oxidative damage as evident by higher tissue MDA level following to higher mortality. Changes in SOD and CAT activities suggest activation of physiological mechanism to scavenge the ROS produced during heat stress. However, when mortality increased at different time points (36 °C - 72 h and 38 °C - 72 h), these enzyme activities also decreased as they failed to save the tissues from ROS. The results suggest that temperature variation does alter the active oxygen metabolism by modulating antioxidant enzyme activities, which can be used as biomarker to detect sub-lethal effects of climate change-associated pollution. The parity in environmental and laboratory experimental results may justify this laboratory experiment as model heat-stress experiment and indicate temperature as a universal stressor which alone or in combination with other water parameters initiates a consistent adapting behavior. The Bellamya bengalensis being the highest faunal representative in its habitat may serve as a good bioindicator species.

Effects of hydrocarbon pollution in the structure of macrobenthic assemblages from two large estuaries in Brazil

Changes in the structure of benthic macrofauna and its relationship with hydrocarbon contamination were determined at different spatial scales in sublittoral sediments of two large estuaries in Brazil. Guanabara Bay (GB) is a heavily polluted estuary due to the presence of a large industrial complex and high demographic density. Laranjeiras Bay (LB) lies in an Environmental Protection Area and can still be considered as preserved from human activities. Despite some spatial differences within each bay, the PAHs concentrations were significantly and consistently higher in GB, with values generally above the threshold effect levels. No signs of hydrocarbon contamination were observed in LB. Macrofauna abundance, diversity and overall assemblage structure were largely different between bays. Canonical analysis of principal coordinates (CAP), used to model the relationship between macrofauna and PAHs levels, indicated that this class of hydrocarbons is the main structuring factor of soft-bottom assemblages in both bays.

Effects of an in situ diesel oil spill on oxidative stress in the clam Anomalocardia flexuosa

Intensive exploitation and transport of oil and derivatives are increasing the risk of coastal contamination by either dramatic disasters or diffuse sources. Tools for monitoring diffuse contamination, such as diesel oil that leaks from marine vessels are much needed. We experimentally tested the efficiency of antioxidant biomarkers as indicators of chronic exposure to diesel oil in a mudflat from the subtropical Bay of Paranaguá, in southern Brazil. We examined the effects of three successive diesel oil spills, with two weeks of recovery time between exposures, on the edible clam Anomalocardia flexuosa. Previous studies have highlighted its potential as a bioindicator species for diesel oil contamination in subtropical and tropical ecosystems. Endpoints measured in gill and digestive gland homogenates included the activity of antioxidant enzymes SOD, GPx, GST and levels of lipid peroxides. PAHs concentration in sediments and soft tissue were also quantified. GST and SOD were the most responsive biomarkers to the exposure. There were significant but non-cumulative departures from control levels in organisms from treated samples, which were, in all cases, more common 48 h after each experimental spill. Biomarker responses were more evident in the digestive gland than in gills. This work validated the short-term responsiveness of biomarkers as measures of repeated pulsed in situ exposure to low concentrations of diesel oil. For their routine implementation into monitoring programs for tropical estuaries our general recommendations are 1) to include several reference sites, 2) to analyze biomarker data using a logarithmic-scale and 3) to interpret deviations from "normal" activity as multiplicative interval differences.

Green technological approach to synthesis hydrophobic stable crystalline calcite particles with one-pot synthesis for oil-water separation during oil spill cleanup

The process of separating oil and water from oil/water mixtures is an attractive strategy to answer the menace caused by industrial oil spills and oily wastewater. In addition, water coproduced during hydrocarbon exploitation, which can be an economic burden and risk for freshwater resources, can become an important freshwater source after suitable water-oil separation. For oil-water separation purposes, considerable attention has been paid to the preparation of hydrophobic-oleophilic materials with modified surface roughness. However, due to issues of thermodynamic instability, costly and complex methods as well as lack of ecofriendly compounds, most of hydrophobic surface modified particles are of limited practical application. The study presents a facile procedure, to synthesize crystalline particles of calcite, which is the most stable polymorph of CaCO₃ from industrial CaCO₃ using oleic acid as an additive in a one-pot synthesis method. The XRD results show that the synthesized particles were a well-crystallized form of calcite. The FTIR results reflect the appearance of the alkyl groups from the oleic acid in synthesized particles which promotes the production of calcite with 'rice shape' (1.64 μm) (aggregated by spherical nanoparticle of 19.56 nm) morphology with concomitant changes in its surface wettability from hydrophilic to hydrophobic. The synthesized particles exhibited near to super hydrophobicity with ∼99% active ratio and a contact angle of 143.8°. The synthesized hydrophobic calcite particles had an oleophilic nature where waste diesel oil adsorption capacity of synthesized calcium carbonate (HCF) showed a very high (>99%) and fast (7 s) oil removal from oil-water mixture. The functional group of long alkyl chain including of CO bounds may play critical roles for adsorption of diesel oils. Moreover, the thermodynamically stable crystalline polymorph calcite (compared to vaterite) exhibited excellent recyclability. The isothermal study reflects the comparatively high value of correlation coefficient (R² = 0.94) for the Langmuir isotherm compared to those of the Freundlich isotherm (R² = 0.82) showed that the adsorption of diesel oil onto the hydrophobic CaCO₃ adsorbent was much better described by the Langmuir isotherm. The kinetics study of second-order rate expression (R² = 0.99) more fitted with the experimental data compare to first-order model (R² = 0.92). The synthesized calcite exhibited a significant dual oleophilic and hydrophobic nature that can be applicable for oil adsorption/or removal purpose in oil contaminated areas in environment and/or industrial oily wastewater for green, simple, and inexpensive environmental cleanup.

Heavy metal contamination in sandy beach macrofauna communities from the Rio de Janeiro coast, Southeastern Brazil

We evaluated concentrations of eight heavy metals Cr, Zn, Pb, Ni, Cu, Cd, Co and V, in tissues of representative macrofauna species from 68 sandy beaches from the coast of Rio de Janeiro state. The links between contamination levels and community descriptors such as diversity, evenness, density and biomass, were also investigated. Metal concentrations from macrofaunal tissues were compared to maximum permissible limits for human ingestion stipulated by the Brazilian regulatory agency (ANVISA). Generalized linear models (GLM's) were used to investigate the variability in macrofauna density, richness, eveness and biomass in the seven different regions. A non-metric multidimensional scaling analysis (n-MDS) was used to investigate the spatial pattern of heavy metal concentrations along the seven regions of Rio de Janeiro coast. Variation partitioning was applied to evaluate the variance in the community assemblage explained by the environmental variables and the heavy metal concentrations. Our data suggested high spatial variation in the concentration of heavy metals in macrofauna species from the beaches of Rio de Janeiro. This result highlighted a diffuse source of contamination along the coast. Most of the metals concentrations were under the limits established by ANVISA. The variability in community descriptors was related to morphodynamic variables, but not with metal contamination values, indicating the lack of direct relationships at the community level. Concentration levels of eight heavy metals in macrofauna species from 68 sandy beaches on Rio de Janeiro coast (Brazil) were spatially correlated with anthropogenic activities such as industrialization and urbanization.

Baseline levels of oxidative stress biomarkers in species from a subtropical estuarine system (Paranaguá Bay, southern Brazil)

Offshore petroleum exploration has increased the risks of oil spills in coastal tropical and subtropical habitats. Monitoring tools are needed to assess and protect environmental health. We determined baseline values of antioxidant biomarkers (CAT, SOD, GPx, GST, MDA) for five ecologically relevant species in a subtropical system in southern Brazil. Regional baseline levels are compared with literature data as a basis to eventually test their efficacy as post-spill monitoring tools. Differences in the antioxidant response among species, contamination, and seasons were tested using univariate and multivariate analyses. The bivalves Anomalocardia flexuosa and Crassostrea rhizophorae and the catfish Genidens genidens emerge as suitable sentinel species. Seasonality is the main factor accounting for biomarkers variability, and not background contamination level. However, interactions between season and contamination level are also significant, indicating that biomarkers respond to complex environmental settings, a fact that needs to be fully understood for designing proper monitoring programs.

Oxidative stress in two tropical species after exposure to diesel oil

Recent offshore petroleum exploration has increased the risks of oil spills worldwide. We investigated biomarker responses to diesel oil exposure in two tropical and subtropical species, the clam Anomalocardia flexuosa and the polychaete Laeonereis culveri. Animals were exposed to oil-spiked sediment at two different concentrations (0.5 L and 1.0 L m^-2). Activities of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx); glutathione transferase (GST); and lipid peroxides (LPO) were assessed in bivalve digestive glands and polychaete whole-body homogenates at 36 and 60 h of exposure. Significant variation in enzymatic antioxidant activity depended on the sampling time after exposure. No similar response patterns, either increases or decreases, were detected for the two target species, and biomarker responses were species-specific. L. culveri showed clearer patterns in its antioxidant response and should be prioritized over other species in biomonitoring studies involving oil exposure. Understanding the temporal variability of these biomarkers is a necessary action before implementing them as indicators measures in oil contamination biomonitoring programs. Our results provide a better understanding of biomarker responses in subtropical species, evidencing their potential use as sentinels of oil contamination.