The effects of oil spills on marine fish: Implications of spatial variation in natural mortality

Anthropogenic stressors and the marine environment: From sources and impacts to solutions and mitigation

Human-released contaminants are often poorly understood wholistically in marine ecosystems. This review examines the sources, pathways, impacts on marine animals, and mitigation strategies of five pollutants (plastics, per- and polyfluoroalkyl substances, bisphenol compounds, ethynylestradiol, and petroleum hydrocarbons). Both abiotic and biotic mechanisms contribute to all five contaminants' movement. These pollutants cause short- and long-term effects on many biological processes genetically, molecularly, neurologically, physiologically, reproductively, and developmentally. We explore the extension of adverse outcome pathways to ecosystem effects by considering known inter-generational and trophic relations resulting in large-scale direct and indirect impacts. In doing so, we develop an understanding of their roles as environmental stressors in marine environments for targeted mitigation and future work. Ecosystems are interconnected and so international collaboration, standards, measures preceding mass production, and citizen involvement are required to protect and conserve marine life.

Oil droplet fouling on lesser sandeel (Ammodytes marinus) eggshells does not enhance the crude oil induced developmental toxicity

The oil industry's expansion and increased operational activity at older installations, along with their demolition, contribute to rising cumulative pollution and a heightened risk of accidental oil spills. The lesser sandeel (Ammodytes marinus) is a keystone prey species in the North Sea and coastal systems. Their eggs adhere to the seabed substrate making them particularly vulnerable to oil exposure during embryonic development. We evaluated the sensitivity of sandeel embryos to crude oil in a laboratory by exposing them to dispersed oil at concentrations of 0, 15, 50, and 150 µg/L oil between 2 and 16 days post-fertilization. We assessed water and tissue concentrations of THC and tPAH, cyp1a expression, lipid distribution in the eyes, head and trunk, and morphological and functional deformities. Oil droplets accumulated on the eggshell in all oil treatment groups, to which the embryo responded by a dose-dependent rise in cyp1a expression. The oil exposure led to only minor sublethal deformities in the upper jaw and otic vesicle. The findings suggest that lesser sandeel embryos are resilient to crude oil exposure. The lowest observed effect level documented in this study was 36 µg THC/L and 3 µg tPAH/L. The inclusion of these species-specific data in risk assessment models will enhance the precision of risk evaluations for the North Atlantic ecosystems.

Persistence of fish populations to longer, more intense, and more frequent mass mortality events

Over the last decades, mass mortality events have become increasingly common across taxa with sometimes devastating effects on population biomass. In the aquatic environment, fish are sensitive to mass mortality events, particularly at the early life stages that are crucial for population dynamics. However, it has recently been shown for fish, that a single mass mortality event in early life typically does not lead to population collapse. Moreover, the frequency and intensity of extreme events that can cause mass mortality, such as marine heatwaves, are increasing. Here, we show that increasing frequency and intensity of mass mortality events may lead to population collapse. Since the drivers of mass mortality events are diverse, and often linked to climate change, it is challenging to predict the frequency and severity of future mass mortality events. As an alternative, we quantify the probability of population collapse depending on the frequency and intensity as well as the duration of mass mortality events. Based on 39 fish species, we show that the probability of collapse typically increases with increasing frequency, intensity, and duration of the mortality events. In addition, we show that the collapse depends on key traits such as natural mortality, recruitment variation, and density dependence. The presented framework provides quantitative estimates of the sensitivity of fish species to these increasingly common extreme events, which paves the way for potential mitigation actions to alleviate adverse impacts on harvested fish populations across the globe.

Transcriptome analysis of Sparidentex hasta larvae exposed to water-accommodated fraction of Kuwait crude oil

Anthropogenic activities have been shown to significantly affect marine life. Water pollution and oil spills are particularly deleterious to the fish population, especially during their larval stage. In this study, Sobaity-sea bream Sparidentex hasta (Valenciennes, 1830) larvae were exposed to serial dilutions of water-accommodated fraction of Kuwait crude oil (KCO-WAF) for varying durations (3, 6, 24, 48, 72 or 96 h) in acute exposure regime. Gene expression was assessed using RNA sequencing and validated through RT-qPCR. The RNA sequencing data were aligned to the sequenced genome, and differentially expressed genes were identified in response to treatment with or without KCO-WAF at various exposure times. The highest number of differentially expressed genes was observed at the early time point of 6 h of post-exposure to KCO-WAF. The lowest number of differentially expressed genes were noticed at 96 h of treatment indicating early response of the larvae to KCO-WAF contaminant. The acquired information on the differentially expressed genes was then used for functional and pathway analysis. More than 90% of the differentially expressed genes had a significant BLAST match, with the two most common matching species being Acanthopagrus latus and Sparus aurata. Approximately 65% of the differentially expressed genes had Gene Ontology annotations, whereas > 35% of the genes had KEGG pathway annotations. The differentially expressed genes were found to be enriched for various signaling pathways (e.g., MAPK, cAMP, PI3K-Akt) and nervous system-related pathways (e.g., neurodegeneration, axon guidance, glutamatergic synapse, GABAergic synapse). Early exposure modulated the signaling pathways, while KCO-WAF exposure of larvae for a longer duration affected the neurodegenerative/nervous system-related pathways. RT-qPCR analysis confirmed the differential expression of genes at each time point. These findings provide insights into the underlying molecular mechanisms of the deleterious effects of acute exposure to oil pollution-on marine fish populations, particularly at the early larval stage of Sparidentex hasta.

Mind the gap - Relevant design for laboratory oil exposure of fish as informed by a numerical impact assessment model

Laboratory experiments provide knowledge of species-specific effects thresholds that are used to parameterize impact assessment models of oil contamination on marine ecosystems. Such experiments typically place individuals of species and life stages in tanks with different contaminant concentrations. Exposure concentrations are usually fixed, and the individuals experience a shock treatment being moved from clean water directly into contaminated water and then back to clean water. In this study, we use a coupled numerical model that simulates ocean currents and state, oil dispersal and fate, and early life stages of fish to quantify oil exposure histories, specifically addressing oil spill scenarios of high rates and long durations. By including uptake modelling we also investigate the potential of buffering transient high peaks in exposure. Our simulation results are the basis for a recommendation on the design of laboratory experiments to improve impact assessment model development and parameterization. We recommend an exposure profile with three main phases: i) a gradual increase in concentration, ii) a transient peak that is well above the subsequent level, and iii) a plateau of fixed concentration lasting ∼3 days. In addition, a fourth phase with a slow decrease may be added.

Crude oil exposure of early life stages of Atlantic haddock suggests threshold levels for developmental toxicity as low as 0.1 μg total polyaromatic hydrocarbon (TPAH)/L

Atlantic haddock (Melanogrammus aeglefinus) embryos bind dispersed crude oil droplets to the eggshell and are consequently highly susceptible to toxicity from spilled oil. We established thresholds for developmental toxicity and identified any potential long-term or latent adverse effects that could impair the growth and survival of individuals. Embryos were exposed to oil for eight days (10, 80 and 300 μg oil/L, equivalent to 0.1, 0.8 and 3.0 μg TPAH/L). Acute and delayed mortality were observed at embryonic, larval, and juvenile stages with IC₅₀ = 2.2, 0.39, and 0.27 μg TPAH/L, respectively. Exposure to 0.1 μg TPAH/L had no negative effect on growth or survival. However, yolk sac larvae showed significant reduction in the outgrowth (ballooning) of the cardiac ventricle in the absence of other extracardiac morphological defects. Due to this propensity for latent sublethal developmental toxicity, we recommend an effect threshold of 0.1 μg TPAH/L for risk assessment models.

Emerging plastic litter variants: A perspective on the latest global developments

Plastic litter is one of key reasons of environmental concern due to its adverse effect on ecosystem and health. Exposure of plastic litter to anthropogenic and ecological conditions results in a variety of emerging litter variants that fluctuate in composition, mechanical, and chemical properties. Considering the properties of these plastic litter variants, it is anticipated that the transportation of foreign species or microbial pathogens together with these litter variants is most likely to affect the marine ecosystem. Moreover the plastic litter may enter the plastic cycle or marine biota and can spread across the ocean. Very recently several emerging plastic litter variants such as anthropoquinas, plasticrust, pyroplastic, plastitar, and plastiglomerate have been reported along the coastal areas across the oceans. The purpose of this perspective is to comprehend these emerging plastic litter variants, integrate the latest developments and highlight their adverse effects on the coastal ecosystem. Further, it details the make-up, place of origin, and management strategies for these plastic litter variants.

Plastitar: A new threat for coastal environments

Oil residues have been frequently found on the coasts all over the world as a result of different accidental releases. Their partial evaporation and solidification onto the coastal rocks can produce the formation of a new solid structure forming an agglomerate with other materials, mainly microplastics (though wood, glass, sand and rocks were also found), yielding to a new plastic formation, name herein for the first time as "plastitar". These new formations have been found in several of the islands of the Canary Islands archipelago (Spain). Their study has shown that these new formations can be permanently attached to the rock, occupying even a 56% of the sampled area with an heterogeneous distribution. It was also observed that the studied plastitar was composed mainly of tar and polyethylene (90.6% of the studied particles) and polypropylene (9.4% of the studied particles) microplastics, primarily fragments (82.5%), pellets (15.7%) and lines (1.8%). The ever more frequent presence of plastics and, in particular, microplastics in coastal environments can lead to the common occurrence of these new plastic formations (probably present in other parts of the world), which long-term effects on the coasts should be further investigated.

An Emerging Cross-Species Marker for Organismal Health: Tryptophan-Kynurenine Pathway

Tryptophan (TRP) is an essential dietary amino acid that, unless otherwise committed to protein synthesis, undergoes metabolism via the Tryptophan-Kynurenine (TRP-KYN) pathway in vertebrate organisms. TRP and its metabolites have key roles in diverse physiological processes including cell growth and maintenance, immunity, disease states and the coordination of adaptive responses to environmental and dietary cues. Changes in TRP metabolism can alter the availability of TRP for protein and serotonin biosynthesis as well as alter levels of the immune-active KYN pathway metabolites. There is now considerable evidence which has shown that the TRP-KYN pathway can be influenced by various stressors including glucocorticoids (marker of chronic stress), infection, inflammation and oxidative stress, and environmental toxicants. While there is little known regarding the role of TRP metabolism following exposure to environmental contaminants, there is evidence of linkages between chemically induced metabolic perturbations and altered TRP enzymes and KYN metabolites. Moreover, the TRP-KYN pathway is conserved across vertebrate species and can be influenced by exposure to xenobiotics, therefore, understanding how this pathway is regulated may have broader implications for environmental and wildlife toxicology. The goal of this narrative review is to (1) identify key pathways affecting Trp-Kyn metabolism in vertebrates and (2) highlight consequences of altered tryptophan metabolism in mammals, birds, amphibians, and fish. We discuss current literature available across species, highlight gaps in the current state of knowledge, and further postulate that the kynurenine to tryptophan ratio can be used as a novel biomarker for assessing organismal and, more broadly, ecosystem health.

Sustainable Cross-Linkers for the Synthesis of Cellulose-Based Aerogels: Research and Application

Cellulose aerogels with polyester resin as cross-linkers have attracted much attention. This study describes the route to produce a fully bio-based aerogel with high added value from waste paper and starch, cellulose acetate and starch–cellulose acetate mixture as cross-linkers for oil adsorption, instead of the environmentally harmful polyester resin. The manufacturing process is simple, sustainable and cost-efficient, without releasing harmful by-products into the environment. The effects of different cross-linkers on the oil adsorption, dynamic oil retention, reusability and morphology of the aerogels were studied in detail. Experimental results show that these environmentally friendly recycled aerogels have a very low density, i.e., —0.0110–0.0209 g cm−3, and highly porous structures, with a porosity of 96.74–99.18%. The synthesized hydrophobic aerogels showed contact angles of ∼124–129°. The compression moduli are lower than that of an aerogel with polyester as a cross-linker, but the compression modulus of the mixture of starch and cellulose acetate especially shows a higher value than expected. The sorption capacity of the aerogels with bio-based cross-linkers was significantly increased compared to the aerogels with polyester; it is now up to 56 times their own weight. The aerogels also have good oil-retention properties.

Assessing the exposure risk of large pelagic fish to oil spills scenarios in the deep waters of the Gulf of Mexico

Exposure risk is assessed based on modeling suitable habitat of large pelagic fish and oil spill scenarios originating at three wells located in the western GM's deep waters. Since the fate of the oil depends on the oceanographic conditions present during the accident, as well as the magnitude and duration of the spill, which are not known a priori, the scenarios used are a statistical representation of the area in which oil spilled from the well could be found, given all possible outcomes. The ecological vulnerability assessment identified a subset of bony fish with low-medium vulnerability and elasmobranchs with medium-high vulnerability. The oiling probability and exposure risk of both bony fish and elasmobranchs hotspots vary by well analyzed. Thus, these results provide essential information for a risk management plan for the assessed species and others with economic or conservation importance distributed in the GM and worldwide.

Effects of chronic exposure to the water-soluble fraction of crude oil and in situ burn residue of oil on egg-bearing Northern shrimp (Pandalus borealis)

Oil spill clean-up measures using in situ burning can potentially result in seafloor contamination affecting benthic organisms. To mimic realistic exposure and measure effects, ovigerous Northern shrimp were continuously exposed for two weeks to the water-soluble fraction of oil coated on gravel followed by two weeks in clean seawater. North Sea crude oil (NSC) and field generated in situ burn residue (ISBR) of NSC were used (Low: 3 g/kg gravel, Medium: 6 g/kg gravel and High: 12 g/kg gravel). The concentrations of polyaromatic hydrocarbons (PAHs) in the water resulting from NSC were higher compared to ISBR. No mortality was observed in any treatment and overall moderate sublethal effects were found, mostly after exposure to NSC. Feeding was temporarily reduced at higher concentrations of NSC. PAH levels in hepatopancreas tissue were significantly elevated following exposure and still significantly higher at the end of the experiment in NSCHigh and ISBRHigh compared to control. Mild inflammatory response reactions and tissue ultrastructural alterations in gill tissue were observed in both treatments. Signs of necrosis occurred in ISBRHigh. No change in shrimp locomotory activity was noted from NSC exposure. However, ISBR exposure increased activity temporarily. Larvae exposed as pleopod-attached embryos showed significant delay in development from stage I to stage II after exposure to NSCHigh. Based on this study, oil-contaminated seafloor resulting from in situ burning clean-up actions does not appear to cause serious effects on bottom-living shrimp.

Propensity and appraisal of biochar performance in removal of oil spills: A comprehensive review

Recently, the adsorption-based environmental remediation techniques have gained a considerable attention, due to their economic viability and simplicity over other methods. Hence, detailed presentation and analysis were herein focused on describing the role of biochar in oil spill removal. Oil removal by utilizing biochar is assumed as a green-oriented concept. Biochar is a carbon-rich low-cost material with high porosity and specific surface chemistry, with a tremendous potentiality for oil removal from aqueous solutions. Oil sorption properties of biochar mainly depend on the biochar production/synthesis method, and the biomass feedstock type. In order to preserve the stability of functional groups in the structure, biochar needs to be produced/activated at low temperatures (<700 ᵒC). In general, biochar derived from biomass containing high lignin content via slow pyrolysis is more favorable for oil removal. Exceptional characteristics of biochar which intensify the oil removal capability such as hydrophobicity, oleophilicity or/and specific contaminant-surface interaction of biochar can be enhanced and be tuned by chemical and physical activation methods. Considering all the presented results, future perspectives such as the examination of biochar efficacy on oil removal efficiency in multi-element contaminated aqueous solutions to identify the best biomass feedstocks, the production protocols and large-scale field trials, are also discussed.

Influence of Dispersed Oil on the Remote Sensing Reflectance-Field Experiment in the Baltic Sea

Remote sensing techniques currently used to detect oil spills have not yet demonstrated their applicability to dispersed forms of oil. However, oil droplets dispersed in seawater are known to modify the local optical properties and, consequently, the upwelling light flux. Theoretically possible, passive remote detection of oil droplets was never tested in the offshore conditions. This study presents a field experiment which demonstrates the capability of commercially available sensors to detect significant changes in the remote sensing reflectance R_rs of seawater polluted by six types of dispersed oils (two crude oils, cylinder lubricant, biodiesel, and two marine gear lubricants). The experiment was based on the comparison of the upwelling radiance L_u measured in a transparent tank floating in full immersion in seawater in the Southern Baltic Sea. The tank was first filled with natural seawater and then polluted by dispersed oils in five consecutive concentrations of 1–15 ppm. After addition of dispersed oils, spectra of R_rs noticeably increased and the maximal increase varied from 40% to over three-fold at the highest oil droplet concentration. Moreover, the most affected R_rs band ratios and band differences were analyzed and are discussed in the context of future construction of algorithms for dispersed oil detection.

A review on physical remediation techniques for treatment of marine oil spills

There is a huge risk of contamination of water bodies due to the various oil exploration, transport, and industrial operational activities that are taking place across the world. Physical remediation techniques are considered extremely important for tackling the problems of marine oil spills. This paper provides a unique, specific review on the physical remediation of marine oil spills with special emphasis on types of available physical remediation techniques and their working principles. It also describes the chief latest improvements in the physical remediation techniques that have taken place with time. The paper discusses the various ways by which oil and its derivatives contaminate, and the subsequent effects these contaminants have on the marine ecosystem. The article discusses salient features that make physical remediation an effective marine oil spill counter-measure capable of recovering appreciable amounts of oil while causing minimal or no damage to the marine ecosystem and the workers carrying out the cleanup. Regarding the physical remediation methods, future research may focus on the development of hybrid booms, improved performance of skimmers for different oil types, and further applications involving novel materials like nanoparticles, zeolites for sorbents.

Environmental effects of offshore produced water discharges: A review focused on the Norwegian continental shelf

Produced water (PW), a large byproduct of offshore oil and gas extraction, is reinjected to formations or discharged to the sea after treatment. The discharges contain dispersed crude oil, polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), metals, and many other constituents of environmental relevance. Risk-based regulation, greener offshore chemicals and improved cleaning systems have reduced environmental risks of PW discharges, but PW is still the largest operational source of oil pollution to the sea from the offshore petroleum industry. Monitoring surveys find detectable exposures in caged mussel and fish several km downstream from PW outfalls, but biomarkers indicate only mild acute effects in these sentinels. On the other hand, increased concentrations of DNA adducts are found repeatedly in benthic fish populations, especially in haddock. It is uncertain whether increased adducts could be a long-term effect of sediment contamination due to ongoing PW discharges, or earlier discharges of oil-containing drilling waste. Another concern is uncertainty regarding the possible effect of PW discharges in the sub-Arctic Southern Barents Sea. So far, research suggests that sub-arctic species are largely comparable to temperate species in their sensitivity to PW exposure. Larval deformities and cardiac toxicity in fish early life stages are among the biomarkers and adverse outcome pathways that currently receive much attention in PW effect research. Herein, we summarize the accumulated ecotoxicological knowledge of offshore PW discharges and highlight some key remaining knowledge needs.

Effects of Exposure to Low Concentrations of Oil on the Expression of Cytochrome P4501a and Routine Swimming Speed of Atlantic Haddock (Melanogrammus aeglefinus) Larvae In Situ

Exposure to environmentally relevant concentrations of oil could impact survival of fish larvae in situ through subtle effects on larval behavior. During the larval period, Atlantic haddock (Melanogrammus aeglefinus) are transported toward nursery grounds by ocean currents and active swimming, which can modify their drift route. Haddock larvae are sensitive to dispersed oil; however, whether exposure to oil during development impacts the ability of haddock larvae to swim in situ is unknown. Here, we exposed Atlantic haddock embryos to 10 and 80 μg oil/L (0.1 and 0.8 μg ∑PAH/L) of crude oil for 8 days and used a novel approach to measure its effect on the larval swimming behavior in situ. We assessed the swimming behavior of 138 haddock larvae in situ, in the North Sea, using a transparent drifting chamber. Expression of cytochrome P4501a (cyp1a) was also measured. Exposure to 10 and 80 μg oil/L significantly reduced the average in situ routine swimming speed by 30-40% compared to the controls. Expression of cyp1a was significantly higher in both exposed groups. This study reports key information for improving oil spill risk assessment models and presents a novel approach to study sublethal effects of pollutants on fish larvae in situ.

Fabrication of Magnetically Inorganic/Organic Superhydrophobic Fabrics and Their Applications

In order to solve the problem caused by oil spills and organic solvent contamination, novel magnetically inorganic/organic superhydrophobic fabrics are fabricated via a facile method. Cotton fabrics are immersed in a mixture of functionalized Co_0.2Mg_0.8Fe₂O₄ (FCMFO) nanoparticles, vinyl-terminated polydimethylsiloxane (VPDMS), trimethylolpropane triacrylate, and 2-hydroxy-2-methylpropiophenone before UV irradiation for 100 s to obtain the multifunctional superhydrophobic fabrics with magnetic property. The coated fabrics show excellent superhydrophobicity, and the water contact angle is 157.1° when the mass ratio of FCMFO nanoparticles to VPDMS is 0.3. These superhydrophobic fabrics have high oil/water separation efficiency (98.7% for dichloromethane/water) and high oil flux (71,506 L·m^-2·h^-1 for dichloromethane/water). Even after 20 separation cycles, oil/water separation efficiency and oil flux maintain 96.4% and 64,012 L·m^-2·h^-1, respectively. Furthermore, the magnetic property of these superhydrophobic fabrics could be used in the separation of oil from water. Moreover, the superhydrophobic fabrics possess exceptional self-cleaning performance, mechanical durability, chemical stability, and flame retardancy. These multifunctional superhydrophobic fabrics are potential for wide applications.

Sources, presence and potential effects of contaminants of emerging concern in the marine environments of the Great Barrier Reef and Torres Strait, Australia

Current policy and management for marine water quality in the Great Barrier Reef (GBR) in north-eastern Australia primarily focusses on sediment, nutrients and pesticides derived from diffuse source pollution related to agricultural land uses. In addition, contaminants of emerging concern (CECs) are known to be present in the marine environments of the GBR and the adjacent Torres Strait (TS). Current and projected agricultural, urban and industrial developments are likely to increase the sources and diversity of CECs being released into these marine ecosystems. In this review, we evaluate the sources, presence and potential effects of six different categories of CECs known to be present, or likely to be present, in the GBR and TS marine ecosystems. Specifically, we summarize available monitoring, source and effect information for antifouling paints; coal dust and particles; heavy/trace metals and metalloids; marine debris and microplastics; pharmaceuticals and personal care products (PPCPs); and petroleum hydrocarbons. Our study highlights the lack of (available) monitoring data for most of these CECs, and recommends: (i) the inclusion of all relevant environmental data into integrated databases for building marine baselines for the GBR and TS regions, and (ii) the implementation of local, targeted monitoring programs informed by predictive methods for risk prioritization. Further, our spatial representation of the known and likely sources of these CECs will contribute to future ecological risk assessments of CECs to the GBR and TS marine environments, including risks relative to those identified for sediment, nutrients and pesticides.

Nonlethal Biomarkers of Oxidative Stress in Oiled Sediment Exposed Southern Flounder (Paralichthys lethostigma): Utility for Field-Base Monitoring Exposure and Potential Recovery

The Deepwater Horizon (DWH) blowout resulted in the deposition of toxic polycyclic aromatic hydrocarbons (PAHs), in the coastal sediments of the Gulf of Mexico. The immediate effects on an ecosystem from an oil spill are clearly recognizable, however the long-term chronic effects and recovery after a spill are still not well understood. Current methodologies for biomonitoring wild populations are invasive and mostly lethal. Here, two potential nonlethal biomonitoring tools for the assessment of PAH toxicity and induced biological alterations in the field, were identified using laboratory-validated methods. In this study, subadult southern flounder (Paralichthys lethostigma) were chronically exposed to DWH surrogate oiled sediments for 35 days; a subset of these exposed flounder were then provided a clean nonexposure period to ascertain the utility of selected biomarkers to monitor recovery post exposure. After chronic exposure, there was an increase in gene expression of cytochrome P450 1A but not glutathione S-transferase. There was also a notable imbalance of oxidants to antioxidants, measured as reduced glutathione, oxidized glutathione, and their ratio in the blood. Evidence of subsequent oxidative damage due to chronic exposure was found through lipid peroxidation and DNA damage assessments of liver, gill, and blood.

The effect of hypoxia and hydrocarbons on the anti-predator performance of European sea bass (Dicentrarchus labrax)

Hydrocarbons contamination and hypoxia are two stressors that can coexist in coastal ecosystems. At present, few studies evaluated the combined impact of these stressors on fish physiology and behavior. Here, we tested the effect of the combination of hypoxia and petrogenic hydrocarbons on the anti-predator locomotor performance of fish. Specifically, two groups of European sea bass (Dicentrarchus labrax) were exposed to clean water (Ctrl) or oil-contaminated water (Oil). Subsequently, fish of both groups were placed in normoxic (norx) or hypoxic (hyp) experimental tanks (i.e. four groups of fish were formed: Ctrl norx, Ctrl hyp, Oil norx, Oil hyp). In these tanks, escape response was elicited by a mechano-acoustic stimulus and recorded with a high speed camera. Several variables were analyzed: escape response duration, responsiveness (percentage of fish responding to the stimulation), latency (time taken by the fish to initiate a response), directionality (defined as away or toward the stimulus), distance-time variables (such as speed and acceleration), maneuverability variables (such as turning rate), escape trajectory (angle of flight) and distancing of the fish from the stimulus. Results revealed (i) effects of stressors (Ctrl hyp, Oil norx and Oil hyp) on the directionality; (ii) effects of Oil norx and Oil hyp on maneuverability and (iii) effects of Oil hyp on distancing. These results suggest that individual stressors could alter the escape response of fish and that their combination could strengthen these effects. Such an impact could decrease the probability of prey escape success. By investigating the effects of hydrocarbons (and the interaction with hypoxia) on the anti-predator behavior of fish, this work increases our understanding of the biological impact of oil spill. Additionally, the results of this study are of interest for oil spill impact evaluation and also for developing new ecotoxicological tools of ecological significance.

Diesel uptake by an indigenous microbial consortium isolated from sediments of the Southern Gulf of Mexico: Emulsion characterisation

In this study a microbial consortium, dominated by members of the genera Marinobacter and Alcanivorax (Gammaproteobacteria) isolated from marine sediments of Southern Gulf of Mexico, was assessed to grow in a bubble column bioreactor using 13 g L^-1 of diesel (aliphatic and aromatic hydrocarbons mix including nonane and hexadecane) as the sole carbon source. The consortium was able to produce 3.3 g L^-1 of biomass, measured as suspended solids. Microbial growth was detectable, even substrate depletion, after 8 days of cultivation. The emulsifier activity and its influence on the droplet size were also evaluated: it was observed that droplet diameter decreases as emulsifier activity increases. The bubble column bioreactor system proposed in this research could be used as a biotechnological process for the remediation of a contaminated body in important petrochemical regions, for example, Veracruz, México, where some points of sea and fresh-water bodies were analysed to find nonane and hexadecane in all sample water. It is important due to a lack of information, regarding hydrocarbon pollution in this port area, is filled.

A state-of-the-art model for spatial and stochastic oil spill risk assessment: A case study of oil spill from a shipwreck

Oil spills are serious environmental issues that potentially can cause adverse effects on marine ecosystems. In some marine areas, like the Baltic Sea, there is a large number of wrecks from the first half of the 20th century, and recent monitoring and field work have revealed release of oil from some of these wrecks. The risk posed by a wreck is governed by its condition, hazardous substances contained in the wreck and the state of the surrounding environment. Therefore, there is a need for a common standard method for estimating the risks associated with different wrecks. In this work a state-of-the-art model is presented for spatial and stochastic risk assessment of oil spills from wrecks, enabling a structured approach to include the complex factors affecting the risk values. A unique feature of this model is its specific focus on uncertainty, facilitating probabilistic calculation of the total risk as the integral expected sum of many possible consequences. A case study is performed in Kattegat at the entrance region to the Baltic Sea to map the risk from a wreck near Sweden. The developed model can be used for oil spill risk assessment in the marine environment all over the world.

Characterization of Laguncularia racemosa transcriptome and molecular response to oil pollution

Mangroves are ecosystems of economic and ecological importance. Laguncularia racemosa (Combretaceae), popularly known as white mangrove, is a species that greatly contributes to the community structure of neotropical and West African mangrove forests. Despite the significance of these ecosystems, they have been destroyed by oil spills that can cause yellowing of leaves, increased sensitivity to other stresses and death of trees. However, the molecular response of plants to oil stress is poorly known. In this work, Illumina reads were de novo assembled into 46,944 transcripts of L. racemosa roots and leaves, including putative isoform variants. In addition to improving the genomic information available for mangroves, the L. racemosa assembled transcriptome allowed us to identify reference genes to normalize quantitative real-time PCR (qPCR) expression data from oil-stressed mangrove plants, which were used in RNASeq validation. The analysis of expression changes induced by the oil exposure revealed 310 and 286 responsive transcripts of leaves and roots, respectively, mainly up-regulated. Enriched GO categories related to chloroplasts and photosynthesis were found among both leaf and root oil-responsive transcripts, while "response to heat" and "response to hypoxia" were exclusively enriched in leaves and roots, respectively. The comparison of L. racemosa 12-h-oil-stressed leaf expression profile to previous Arabidopsis heat-stress studies and co-expression evidence also pointed to similarities between the heat and oil responses, in which the HSP-coding genes seem to play a key role. A subset of the L. racemosa oil-responsive root genes exhibited similar up-regulation profiles to their Arabidopsis homologs involved in hypoxia responses, including the HRA1 and LBD41 TF-coding genes. Genes linked to the ethylene pathway such as those coding for ERF TFs were also modulated during the L. racemosa root response to oil stress. Taken together, these results show that oil contamination affects photosynthesis, protein metabolism, hypoxia response and the ethylene pathway in L. racemosa 12-h-oil-exposed leaves and roots.

Effects of oil spills on fish production in the Niger Delta

The Niger Delta region is the oil producing area of Nigeria, which consists of highly diverse ecosystems that are supportive of numerous species of terrestrial and aquatic fauna and flora. Crude oil spills endanger fish hatcheries in coastal water and also contaminate valuable fish. This study examines the effects of oil spills on fish production in the Niger Delta of Nigeria from 1981–2015 using an estimable Cobb Douglas production function. The findings suggest that oil production and spills negatively affect fish production, while farm labour has a positive effect on fish production. On the other hand, fishery loan exerts a negative effect on fish production and this could be ascribed to the bottlenecks in accessing these loans. This study corroborates the findings in literature on the negative concomitance of oil spills and fish production and suggests a cautious approach to oil exploration activities for a sustainable development in the region.

Applying spatiotemporal models to monitoring data to quantify fish population responses to the Deepwater Horizon oil spill in the Gulf of Mexico

Quantifying the impacts of disturbances such as oil spills on marine species can be challenging. Natural environmental variability, human responses to the disturbance (e.g., fisheries closures), the complex life histories of the species being monitored, and limited pre-spill data can make detection of effects of oil spills difficult. Using long-term monitoring data from the state of Louisiana (USA), we applied novel spatiotemporal approaches to identify anomalies in species occurrence and catch rates. We included covariates (salinity, temperature, turbidity) to help isolate unusual events. While some species showed evidence of unlikely temporal anomalies in occurrence or catch rates, we found that the majority of the observed anomalies were also before the Deepwater Horizon event. Several species-gear combinations suggested upticks in the spatial variability immediately following the spill, but most species indicated no trend. Across species-gear combinations, there was no clear evidence for synchronous or asynchronous responses in occurrence or catch rates across sites following the spill. Our results are in general agreement to other analyses of monitoring data that detected small impacts, but in contrast to recent results from ecological modeling that showed much larger effects of the oil spill on fish and shellfish.

Combined effects of fishing and oil spills on marine fish: Role of stock demographic structure for offspring overlap with oil

It has been proposed that the multiple pressures of fishing and petroleum activities impact fish stocks in synergy, as fishing-induced demographic changes in a stock may lead to increased sensitivity to detrimental effects of acute oil spills. High fishing pressure may erode the demographic structure of fish stocks, lead to less diverse spawning strategies, and more concentrated distributions of offspring in space and time. Hence an oil spill may potentially hit a larger fraction of a year-class of offspring. Such a link between demographic structure and egg distribution was recently demonstrated for the Northeast Arctic stock of Atlantic cod for years 1959-1993. We here estimate that this variation translates into a two-fold variation in the maximal proportion of cod eggs potentially exposed to a large oil spill. With this information it is possible to quantitatively account for demographic structure in prospective studies of population effects of possible oil spills.