Stable isotope analysis (δ13C and δ15N from liver and muscle) was used to assess trophic relationships between Atlantic bluefin tuna (ABFT) (Thunnus thynnus) and striped dolphin (SC) (Stenella ...coeruleoalba) in the Strait of Gibraltar (SoG). δ15N values from ABFT muscle and liver tissues were significantly different from those of dolphin samples, but no for δ13C values. Diet estimation by MixSIAR models from muscle and liver revealed that ABFT fed mainly on squids (Todaropsis eblanae and Illex coindetii). The shrimp Pasiphaea sp. was estimated to be the most important prey-species in the diet of SC. Trophic positions estimated from muscle and liver isotopic data suggested that ABFT occupy a higher trophic level than SC. Estimations of isotopic niche, as measured by the standard ellipse area, indicated that ABFT show a broader trophic niche than SC; furthermore, SEAc did not show trophic overlap between both predators. The results of this study suggest that resource partitioning occurs between ABFT and SC in the SoG ecosystem.
•Trophic relationships between bluefin tuna and striped dolphin were assessed by SIA.•MixSIAR mixing model estimated that ABFT fed mainly on squids.•Decapod shrimp was estimated to be the main dietary component for SC.•TP estimations suggested that ABFT occupy higher trophic levels than SC.•Resource partitioning occurs between ABFT and SC.
Background
Bioaccumulation of hydrophobic organic compounds (HOCs) along freshwater food chains is a major environmental concern as top predators in food webs are relevant for human consumption. To ...characterize and manage the associated risks, considerable numbers of organisms are sampled regularly for monitoring purposes. However, ethical and financial issues call for an alternative, more generic and more robust approach for assessing the internal exposure of fish that circumvents large variability in biota sampling due to interindividual differences. Passive sampling devices (PSDs) offer a fugacity-based approach for pollutant enrichment from different abiotic environmental compartments with a subsequent estimation of bioaccumulation in fish which we explored and compared to HOC concentrations in fish as determined using traditional approaches.
Results
In this study, concentrations in silicone-based PSDs applied to the water phase and suspended particulate matter (SPM) of a river polluted with HOCs were used to estimate the concentration in model lipids at thermodynamic equilibrium with either environmental compartment. For comparison, muscle tissue of seven fish species (trophic level 1.8 to 2.8) was extracted using traditional exhaustive solvent extraction, and the lipid-normalized concentrations of HOCs were determined. The PSD-based data from SPM proved to be a more conservative estimator for HOCs accumulated in fish than those from water. Body length of the fish was found to be more suitable to describe increasing accumulation of HOCs than their trophic level as derived from stable isotope analysis and might offer a suitable alternative for future studies.
Conclusions
By combining fugacity-based sampling in the abiotic environment, translation into corresponding concentrations in model lipids and body length as an indicator for increasing bioaccumulation in fish, we present a suggestion for a robust approach that may be a meaningful addition to conventional monitoring methods. This approach potentially increases the efficiency of existing monitoring programs without the need to regularly sacrifice vertebrate species.
Graphical Abstract
In soils and sediments contaminated by Hydrophobic Organic Compounds (HOCs), the total concentrations are less indicative of potential exposure and distribution than the associated freely dissolved ...concentrations (
C
free
) or chemical activity. Therefore, these two parameters are increasingly used to assess sediment contamination with regard to their (1) partitioning into the water column, (2) bioaccumulation and (3) baseline toxic potential. In this work, sediments from a chronically polluted coastal area, with similar total PAH concentrations, were studied using PDMS coated glass jars (obtaining
C
free(SW)
and chemical activity) to predict baseline toxicity and potential bioaccumulation from these sediments. The results indicate that, on the one hand, the chemical activity of the sediments differed by up to one order of magnitude and was below the level at which lethal baseline toxicity is expected, but is still a cause for concern due to the presence of other pollutants and different mechanisms of action. On the other hand, the combination of
C
free
measurements and Biota to Sediment Accumulation Factors (BSAFs) allowed concentrations in different target organs of benthic flatfish, hypothetically exposed to these chronically polluted sediments, to be estimated. This new approach allows us to predict the concentration in biological tissues under the study of
C
free(SW)
in sediments, as a useful tool in risk assessment.
Using
C
free
and specific BSAFs, the concentrations in target organs of benthic fish, hypothetically exposed to sediments under specific environmental real conditions, can be estimated.
In soils and sediments contaminated by Hydrophobic Organic Compounds (HOCs), the total concentrations are less indicative of potential exposure and distribution than the associated freely dissolved ...concentrations (Cfree) or chemical activity. Therefore, these two parameters are increasingly used to assess sediment contamination with regard to their (1) partitioning into the water column, (2) bioaccumulation and (3) baseline toxic potential. In this work, sediments from a chronically polluted coastal area, with similar total PAH concentrations, were studied using PDMS coated glass jars (obtaining Cfree(SW) and chemical activity) to predict baseline toxicity and potential bioaccumulation from these sediments. The results indicate that, on the one hand, the chemical activity of the sediments differed by up to one order of magnitude and was below the level at which lethal baseline toxicity is expected, but is still a cause for concern due to the presence of other pollutants and different mechanisms of action. On the other hand, the combination of Cfree measurements and Biota to Sediment Accumulation Factors (BSAFs) allowed concentrations in different target organs of benthic flatfish, hypothetically exposed to these chronically polluted sediments, to be estimated. This new approach allows us to predict the concentration in biological tissues under the study of Cfree(SW) in sediments, as a useful tool in risk assessment.
This paper describes a study of the occurrence, levels and temporal evolution of PAHs in a bay characterized by persistent chronic impacts. A total of 40 samples, 20 of sediment and 20 of water, were ...taken at each of five different stations, in four sampling campaigns. Analyses of pollutants have been made using GC-MS. Results indicate that in a coastal environment subjected to chronic pollution by pyrolytic PAHs, episodes of petrogenic pollution, like oil-spills, can be identified by the combination of different source ratios. Results also indicate that, in the study area, PAHs are transported from superficial water to sediment. This conclusion is based on the degree of coincidence found in the presence/absence of individual PAHs in both compartments and in their petrogenic/pyrolytic nature, the positive sedimentation rate in the study area, together with the performance of the analyses of unfiltered water and the distribution of sources of PAHs found.
A new analytical approach has been developed to extract and quantify HDPE microparticles from marine sediments. This is the first method that has been proposed using routine laboratory equipment that ...incorporates slow mixing and air flux for floatation in order to collect the supernatant by overflow, using NaCl saturated solutions. The technique developed in this study comprised the preparation of an HDPE standard of different sizes and calibration curves for artificial enrichment of sediments. Two different techniques were used and compared regarding quantification: (a) stereoscopic microscopy and visual sorting and (b) confocal microscopy and image-processing counting. Microplastics of different sizes were extracted and quantified in sediments with several total concentrations of particles, and different groups of sizes were identified ranging from 0.850 to 0.100 mm. Recoveries exceeding 90% for sediments with higher concentrations of microplastics and above 80% for those with lower concentrations emphasise the potential of this methodology. This is even more remarkable if it is taken into account that different sizes were also used in these experiments. The use of this technique will result not only in a more complete assessment of microplastic concentrations but also in higher repeatability in inter-laboratory comparisons. In addition, this methodology is also suitable for applying the extraction of different polymers of microplastics using other salt solutions such as NaI or ZnCl
2
.
A new analytical approach has been developed to extract and quantify microplastics from sediments, using routine laboratory equipment and NaCl solutions.
A new analytical approach has been developed to extract and quantify HDPE microparticles from marine sediments. This is the first method that has been proposed using routine laboratory equipment that ...incorporates slow mixing and air flux for floatation in order to collect the supernatant by overflow, using NaCl saturated solutions. The technique developed in this study comprised the preparation of an HDPE standard of different sizes and calibration curves for artificial enrichment of sediments. Two different techniques were used and compared regarding quantification: (a) stereoscopic microscopy and visual sorting and (b) confocal microscopy and image-processing counting. Microplastics of different sizes were extracted and quantified in sediments with several total concentrations of particles, and different groups of sizes were identified ranging from 0.850 to 0.100 mm. Recoveries exceeding 90% for sediments with higher concentrations of microplastics and above 80% for those with lower concentrations emphasise the potential of this methodology. This is even more remarkable if it is taken into account that different sizes were also used in these experiments. The use of this technique will result not only in a more complete assessment of microplastic concentrations but also in higher repeatability in inter-laboratory comparisons. In addition, this methodology is also suitable for applying the extraction of different polymers of microplastics using other salt solutions such as NaI or ZnCl
2
.
This paper describes a study of the occurrence, levels and temporal evolution of PAHs in a bay characterized by persistent chronic impacts. A total of 40 samples, 20 of sediment and 20 of water, were ...taken at each of five different stations, in four sampling campaigns. Analyses of pollutants have been made using GC-MS. Results indicate that in a coastal environment subjected to chronic pollution by pyrolytic PAHs, episodes of petrogenic pollution, like oil-spills, can be identified by the combination of different source ratios. Results also indicate that, in the study area, PAHs are transported from superficial water to sediment. This conclusion is based on the degree of coincidence found in the presence/absence of individual PAHs in both compartments and in their petrogenic/pyrolytic nature, the positive sedimentation rate in the study area, together with the performance of the analyses of unfiltered water and the distribution of sources of PAHs found.
In coastal environments subjected to chronic pollution by pyrolytic PAHs, episodes of petrogenic oil-spills can be identified by combining source ratios.
This paper reports a study of the occurrence and levels of polycyclic aromatic hydrocarbons (PAHs) in a bay characterised by a chronic persistent impact. A total of 55 sediment samples were taken at ...different depths up to 111 m in two sampling campaigns. Chemical analyses were carried out by gas chromatography-mass spectroscopy. The results indicate that: (1) significant spatial variations exist, (2) levels of PAHs are related more strongly to the spatial distribution of sediments than to mineralogy/granulometry, (3) the sediments are slightly-to-moderately contaminated by PAHs, and (4) these PAHs derive from pyrolytic and petrogenic sources. Through use of an innovative data classification system (proposed according to depth and spatial location of sampling points), and using factorial and cluster techniques, five zones have been differentiated depending on the contamination level and source.
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