Using a classical weight-of-evidence approach for 4-years' monitoring of the impact of an accidental oil spill on sediment quality

Parasite communities in a marine fish indicate ecological recovery from the impacts of the Prestige oil-spill 12-13 years after the disaster

The Prestige oil-spill (2002) is one of the major marine accidents resulting in contamination of virtually all types of marine habitat along c.900 km of coastline in the North-East Atlantic. Environmental pollution affects parasite populations and communities, both directly and through effects on intermediate and definitive hosts. However, the effects of oil-spills on shelf benthic communities are poorly known. This study addressed the hypothesis of recovery of parasite communities in a marine sparid teleost, the bogue Boops boops (L.) (Teleostei: Sparidae), as indicators of environmental pollution and its effects on benthic/pelagic invertebrate communities in an impacted area off the Galician coast, Spain, 12-13 years after the Prestige oil-spill. Novel data for the metazoan parasite communities collected during 2014-2015 were analysed in association with two unique datasets, one comprising baseline data collected in 2001, one year before the Prestige oil-spill, and one comprising data collected 3-4 years post-spill (2005-2006). Using the taxonomically consistent data on parasites in a series of fish seasonal samples, we found significant differences between the two seasonal post-spill datasets taken at a 9-year time interval (3-4 years and 12-13 years post-spill) in most community metrics and infection parameters of the common species. This was in sharp contrast with the few differences between the long-term post-spill dataset of 2014-2015 and the pre-spill dataset of 2001. Multivariate community similarity analyses confirmed that these differences reflected in the substantial differentiation of parasite community composition and structure of the post-spill communities and the significant homogenisation of communities sampled 12-13 years post-spill and baseline communities. Overall, the novel analyses demonstrated a long-term directional trend in parasite community succession towards ecological recovery irrespective of the natural seasonal variability. These findings suggest longer-term oil-spill impacts on shelf benthic/pelagic invertebrate communities lasting over 10 years.

Vanadium and Cadmium in Shallow Marine Sediments: Spatial and Temporal Behavior in the Tamaulipas Continental Platform, Gulf of Mexico, Mexico

This study analyzed 27 surface sediment samples from the Tamaulipas Continental shelf to determine the spatial-temporal distribution of V and Cd (spring-summer 2016; summer 2017). Average V concentrations (99 ± 18 mg g^-1) were similar to that previously reported values for the area, while average Cd concentrations reflect uncontaminated sediments at surface level of the shelf. Inputs of V and Cd may be related to hydrocarbon and anthropogenic contributions from South and North of the Gulf of Mexico. The variability shown by both elements results from the hydrodynamics and hydrology of the area produced by local currents, eddies of the Loop Current, resuspension of fine sediments and contribution of terrigenous material. Considering that both metals showed significant differences (Shapiro-Wilk, p = 0), baseline concentrations could not be established, instead a reference interval of 79-122 µg g^-1 for V and 0.121-0.258 µg g^-1 for Cd in sediments from the Tamaulipas platform is suggested.

Groundwater Quality in the Yucatan Peninsula: Insights from Stable Isotope and Metals Analysis

High surface water-groundwater connectivity characterizes watersheds underlain by karsts, increasing contaminant transport risks. However, karsts are highly complex, making research necessary to understand the transport of contaminants from the surface, through the aquifer, to discharge areas. In Yucatan, the lack of waste water treatment raises the risk of groundwater contamination. We monitored stable isotopes (δ¹⁸ O-NO₃ and δ¹⁵ N-NO₃ ), cadmium, and lead to document waste water contamination and transport during the rainy and dry seasons, using water samples collected along the Ring of Cenotes during each season. Specific conductance and pH showed no consistent seasonality, with conductance ranging from 0.5 to 55 mS/cm and pH ranging from 6.6 to 8.6 for most samples. Nitrate concentrations in the cenotes averaged 205 ± 260 μM and no seasonal pattern was observed. Cd and Pb concentrations were 0.1 to 37.9 μg/L and 0.2 to 243.2 μg/L, respectively. Nitrate stable isotope values were 2.6 to 27.2‰ for δ¹⁸ O and 1.2 to 20.7‰ for δ¹⁵ N. The statistical relationship between δ¹⁵ N and δ¹⁸ O, in dry season samples, indicated that denitrification was occurring. A scale measure for waste water recognition showed: (1) high variability among sites probably related with dry/rainy seasons and/or diverse anthropogenic activities; and (2) specific water quality variables that contribute to contamination at each site during each season. Importantly, our analyses indicate that in the area surrounding the Ring of Cenotes, waste water exhibits spatial and temporal patterns related to complex transport and dilution processes, as is the case in karsts in general.

Medium-term dynamics of element concentrations in a sparid fish and its isopod parasite after the Prestige oil-spill: Shifting baselines?

Historically, the European Atlantic is probably the most important oil-spill hotspot worldwide. One of the most recent accidents occurred in 2002 when the oil-tanker Prestige sank over the Galician Bank causing two major oil-spills followed by several small leaks until March 2003. This resulted in contamination of virtually all types of marine habitat. Considering that parasites have proved to be good effect and accumulation bioindicators, the present study addresses the medium-term changes in trace element content after the Prestige oil-spill in a model host-parasite system, the bogue, Boops boops (Sparidae) and the isopod Ceratothoa oestroides. To our knowledge, this study is the first to address trace element concentrations in natural fish and parasite populations associated with the effects of an oil-spill. We observed that both test organisms examined, the host and the parasite, indicate a detectable change in the relative composition of trace element concentrations before and after the Prestige oil-spill. Multivariate analyses also indicated a differential response of the different tissues to the temporal sampling sequence. However, analyses of both host and parasite tissues supported the pattern of a gradual temporal transition to a state of relative trace element content distinctly departing from the pre-spill situation. Moreover, the parasite-host element accumulation ratios better depicted this temporal pattern. Additionally, changes in V concentrations in fish liver tissues and Ni concentrations in the parasite tissues suggest that this host-parasite system may be a useful tool to assess these two element contaminations linked to heavy fuel oil-spill.

In situ microbial remediation of crude oil-soaked marine sediments using zeolite carrier with a polymer coating

Marine oil spill pollution is an important environmental problem in the world, especially crude oil-soaked marine sediments, because they are difficult to be remediated. In this study, in situ bioremediation of oil-soaked sediment was performed in the middle of the Bohai Sea. Oil-degrading bacteria were adsorbed on powdery zeolite (PZ)/granular zeolites (GZ) surfaces and then wrapped with poly-γ glutamic acid (γ-PGA). Settling column and wave flume experiments were conducted to model marine conditions and to select appropriate biological reagents. The optimal conditions were as follows: the average diameter of GZ 3 mm, mass ratio of GZ/PZ 2:1, and concentration of γ-PGA 7%. After bioremediation, over 50% of most oil-spilled pollutants n-alkanes (C₁₂ to C₂₇) and polycyclic aromatic hydrocarbons were degraded in 70 days. This work resulted in a successful trial of in situ bioremediation of oil-soaked marine sediments.

Bioaugmentation strategy employing a microbial consortium immobilized in chitosan beads for oil degradation in mesocosm scale

A bacterial consortium composed by four metagenomic clones and Bacillus subtilis strain CBMAI 707, all derived from petroleum reservoirs, was entrapped in chitosan beads and evaluated regarding hydrocarbon degradation capability. Experiments were carried out in mesocosm scale (3000L) with seawater artificially polluted with crude oil. At different time intervals, mesocosms were sampled and subjected to GC-FID and microbiological analyses, as total and heterotrophic culturable bacterial abundance (DAPI and CFU count), biological oxygen demand (BOD) and taxonomic diversity (massive sequencing of 16S rRNA genes). The results obtained showed that degradation of n-alkane hydrocarbons was similar between both treatments. However, aromatic compound degradation was more efficient in bioaugmentation treatment, with biodegradation percentages reaching up to 99% in 30days. Community dynamics was different between treatments and the consortium used in the bioaugmentation treatment contributed to a significant increase in aromatic hydrocarbon degradation.

Prioritization of in silico models and molecular descriptors for the assessment of ready biodegradability

Ready biodegradability is a key property for evaluating the long-term effects of chemicals on the environment and human health. As such, it is used as a screening test for the assessment of persistent, bioaccumulative and toxic substances. Regulators encourage the use of non-testing methods, such as in silico models, to save money and time. A dataset of 757 chemicals was collected to assess the performance of four freely available in silico models that predict ready biodegradability. They were applied to develop a new consensus method that prioritizes the use of each individual model according to its performance on chemical subsets driven by the presence or absence of different molecular descriptors. This consensus method was capable of almost eliminating unpredictable chemicals, while the performance of combined models was substantially improved with respect to that of the individual models.

Quantitative consensus of bioaccumulation models for integrated testing strategies

A quantitative consensus model based on bioconcentration factor (BCF) predictions obtained from five quantitative structure-activity relationship models was developed for bioaccumulation assessment as an integrated testing approach for waiving. Three categories were considered: non-bioaccumulative, bioaccumulative and very bioaccumulative. Five in silico BCF models were selected and included into a quantitative consensus model by means of the continuous formulation of Bayes' theorem. The discrete likelihoods commonly used in the qualitative Bayesian model were substituted by probability density functions to reduce the loss of information that occurred when continuous BCF values were distributed across the three bioaccumulation categories. Results showed that the continuous Bayesian model yielded the best classification predictions compared not only to the discrete Bayesian model, but also to the individual BCF models. The proposed quantitative consensus model proved to be a suitable approach for integrated testing strategies for continuous endpoints of environmental interest.

Seabird feathers as monitors of the levels and persistence of heavy metal pollution after the Prestige oil spill

We measured heavy metal concentrations in yellow-legged gulls (n = 196) and European shags (n = 189) in order to assess the temporal pattern of contaminant exposure following the Prestige oil spill in November 2002. We analysed Pb, Cu, Zn, Cr, Ni and V levels in chick feathers sampled at four colonies during seven post-spill years (2003-2009), and compared results with pre-spill levels obtained from feathers of juvenile shag corpses (grown in spring/summer 2002). Following the Prestige wreck, Cu (4.3-10 μg g(-1)) and Pb concentrations (1.0-1.4 μg g(-1)) were, respectively, between two and five times higher than pre-spill levels (1.5-3.6 and 0.1-0.4 μg g(-1)), but returned to previous background concentrations after three years. Our study highlights the suitability of chick feathers of seabirds for assessing the impact of oil spills on heavy metal contamination, and provides the best evidence to date on the persistence of oil pollution after the Prestige incident.

Assessing sediment hazard through a weight of evidence approach with bioindicator organisms: a practical model to elaborate data from sediment chemistry, bioavailability, biomarkers and ecotoxicological bioassays

Quality assessments are crucial to all activities related to removal and management of sediments. Following a multidisciplinary, weight of evidence approach, a new model is presented here for comprehensive assessment of hazards associated to polluted sediments. The lines of evidence considered were sediment chemistry, assessment of bioavailability, sub-lethal effects on biomarkers, and ecotoxicological bioassays. A conceptual and software-assisted model was developed with logical flow-charts elaborating results from each line of evidence on the basis of several chemical and biological parameters, normative guidelines or scientific evidence; the data are thus summarized into four specific synthetic indices, before their integration into an overall sediment hazard evaluation. This model was validated using European eels (Anguilla anguilla) as the bioindicator species, exposed under laboratory conditions to sediments from an industrial site, and caged under field conditions in two harbour areas. The concentrations of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons and trace metals were much higher in the industrial compared to harbour sediments, and accordingly the bioaccumulation in liver and gills of exposed eels showed marked differences between conditions seen. Among biomarkers, significant variations were observed for cytochrome P450-related responses, oxidative stress biomarkers, lysosomal stability and genotoxic effects; the overall elaboration of these data, as those of standard ecotoxicological bioassays with bacteria, algae and copepods, confirmed a higher level of biological hazard for industrial sediments. Based on comparisons with expert judgment, the model presented efficiently discriminates between the various conditions, both as individual modules and as an integrated final evaluation, and it appears to be a powerful tool to support more complex processes of environmental risk assessment.

An integrated approach to determine sediment quality in areas above CO2 injection and storage in agreement with the requirements of the international conventions on the protection of the marine environment

The urgent need to reduce the greenhouse emissions to the atmosphere has leaded to study new systems to capture and store carbon dioxide (CO(2)). The sequestration of CO(2) in marine geological formations is one of these systems proposed at the international level to effectively reduce the concentration of atmospheric CO(2). Although permanent containment is expected, it is necessary to determine the risk of leakage to the marine environment. The integrated model for the evaluation of the environmental quality of the marine environment will contribute to determine the potential environmental pathways and effects that are relevant to the consideration of the potential consequences of the leakage of CO(2) and incidental associated substances from the geological formations to the marine environment. In addition, this model will satisfy the requirements for a safe CO(2) storage in sub-seabed geological formations set in the international conventions on the protection of the marine environment (1992 OSPAR Convention and 1996 London Protocol). The objective of this paper is to show how to adapt classical methodologies based on a weight-of-evidence approach to establish the impact of CO(2) leaks in the sediment quality. It is described how the classical methods should modify their application when acidification occurs related to CO(2) leaks being the main potential impact in these areas.

Integrated sediment quality assessment in Paranaguá Estuarine System, Southern Brazil

Sediment quality from Paranaguá Estuarine System (PES), a highly important port and ecological zone, was evaluated by assessing three lines of evidence: (1) sediment physical-chemical characteristics; (2) sediment toxicity (elutriates, sediment-water interface, and whole sediment); and (3) benthic community structure. Results revealed a gradient of increasing degradation of sediments (i.e. higher concentrations of trace metals, higher toxicity, and impoverishment of benthic community structure) towards inner PES. Data integration by principal component analysis (PCA) showed positive correlation between some contaminants (mainly As, Cr, Ni, and Pb) and toxicity in samples collected from stations located in upper estuary and one station placed away from contamination sources. Benthic community structure seems to be affected by both pollution and natural fine characteristics of the sediments, which reinforces the importance of a weight-of-evidence approach to evaluate sediments of PES.

A multibiomarker approach using the polychaete Arenicola marina to assess oil-contaminated sediments

BACKGROUND, AIM AND SCOPE

Marine and coastal sediments can accumulate substantial concentrations of metals and hydrocarbons, yet the consequences of this contamination for exposed biota in situ can be difficult to establish. Here, we examine the hypothesis that exposure to contaminated sediments can lead to detrimental effects in sediment-dwelling species. The combination of chemical and biological assessment allows the identification of the impact of chemical contamination, and their use as assessment tools is becoming increasingly important.

MATERIALS AND METHODS

The study was applied to marine sediments from the Bay of Algeciras (S Spain) impacted by multiple, low-level contaminant inputs, and the Galician Coast (NW Spain), historically impacted by an oil spill (Prestige 2002), with two reference sites selected in UK and Spain. The common lugworm Arenicola marina was exposed in the laboratory for 14 days to the marine sediments, and a suite of biomarkers of sublethal toxicity was combined with analytical chemistry to test for relationships between sediment contamination and effect.

RESULTS

Moderate to strong correlations between organics, metals, and biological responses were observed, with DNA damage as measured using the Comet assay forming the largest contribution toward the observed differences (p < 0.05). The responses of worms from sites experiencing different contamination loads were clearly distinguishable.

DISCUSSION

We show how a combination of multibiomarkers with analytical chemistry can be used to investigate the toxicity of marine sediments, enabling the differentiation of sites showing different types of contamination. There are clear relationships in sublethal assays that can be related to the putative mode of toxicity of the contaminants.

CONCLUSIONS

The use of A. marina in this way provides a sensitive, holistic approach to sediment toxicity assessment, enabling comparisons between oil-polluted sites to be quantified.

RECOMMENDATIONS AND PERSPECTIVES

These tools provide a relatively simple, rapid, and economic way to test the environmental status of oil-contaminated sediment.

A weight of evidence approach for quality assessment of sediments impacted by an oil spill: the role of a set of biomarkers as a line of evidence

In an attempt to incorporate both line of evidence (LOE) and classical weight of evidence (WOE) approaches for the assessment of sediment quality, a set of biomarkers were analyzed in target tissues of two invertebrate species after 28 days of exposure to sediments impacted by oil (derived from the tanker Prestige (2002)). The integration of biomarkers with sediment contamination, acute toxicity and benthic alteration parameters provides an "early warning" tool which not only indicates the environmental quality of an area, but also constitutes an advisory tool for potential ecological risks. The selected biomarkers provide information about the first biological responses due to the presence of contaminants in the environment providing predictable reports about further effects to the ecosystem. The present study demonstrates that the use of a set of biomarkers as part of a WOE approach designed to assess contaminated sediments contributes added value to the classical LOE and allows characterization of the environmental status of the studied area in a more precise and accurate way.

Sediment contamination, bioavailability and toxicity of sediments affected by an acute oil spill: Four years after the sinking of the tanker Prestige (2002)

Sediment contamination and three bioassays were used to determine the sediment quality four years after an oil spill (Prestige, 2002): the Microtox test, a 10-day bioassay using the amphipod Ampelisca brevicornis, and a polychaete 10-day toxicity test with the lugworm Arenicola marina. In addition, bioaccumulation of PAHs was examined in the polychaete after 10 days of exposure. The results obtained from the toxicity tests and bioaccumulation analyses were statistically compared to the sediment chemical data, in order to assess the bioavailability of the contaminants, their effects, and their relationship with the oil spill. The sediments studied were from two areas of the Galician Coast (NW Spain): the Bay of Corme-Laxe and the Cíes Island, located in the Atlantic Island National Park. The results point to a decrease in contamination with respect to previous studies and to the disappearance of the acute toxicity four years after the oil spill. However an important bioaccumulation of PAHs was detected in the organisms exposed to sediments from Corme-Laxe, suggesting that despite the recovery of the environmental quality of the area, effects in the biota might be occurring.