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To assess the potential of the sole as sentinel species for ecotoxicological monitoring, the present study compares contaminant levels and biological responses with two closely related flatfish species: the common dab and European flounder. Trace metals, organic contaminants and biomarkers were measured in the three flatfish species collected during the same oceanographic cruise in the Bay of Seine (France). Overall, sole showed lower concentrations of Hg, met-Hg, Cd, Zn and PBDE (lw), higher concentrations of Ag, Cu, PFOS (ww), PCBs, p,p' -DDE (lw) and OH-pyrene, a higher ability to metabolize PBDEs and higher genotoxic (Comet, Micronuclei) and neurotoxic (AChE inhibition) alterations. Sole was the species most frequently occurring in the bay and appeared sensitive to chemical contamination. We therefore recommend promoting the use of the common sole for ecotoxicological monitoring. • Chemical contaminants alone are not sufficient for assessing the fish health status. • The species with the most altered biomarker responses was not the most contaminated. • With regard to pollution, integrated monitoring is key to assess ecosystems' status. • The common sole is a suitable sentinel species for coastal pollution monitoring. [ABSTRACT FROM AUTHOR]

Frequencies of eight nuclear abnormalities (NAs) reflecting environmental genotoxicity and cytotoxicity, were examined in 739 specimens of herring ( Clupea harengus ), flounder ( Platichthys flesus ) and cod ( Gadus morhua ) collected between 2009 and 2017 at 50 study stations located in the Gulf of Gdansk and the southern part of the Gdansk Deep (the Baltic Sea). The highest levels of geno-cytotoxicity were recorded in fish caught at stations located in close proximity to chemical and conventional munitions dumping sites or in zones polluted by Chemical Warfare Agents (CWAs). The values of NAs were significantly higher (up to 51-fold compared with the reference level) in herring caught at seven stations and in cod from one station located close to the munitions dumping sites. Exceptionally high total genotoxicity (∑Gtox) risk was found for flounder collected from 18 (72.0%) stations, herring caught at 12 (38.7%) stations and cod caught at four (17.4%) studied stations. [ABSTRACT FROM AUTHOR]

Understanding the long-term effects of climatic factors on key species' recruitment is crucial to species management and conservation. Here, we analysed the recruitment variability of key species (Dicentrarchus labrax, Platichthys flesus, Solea solea, Pomatoschistus microps and Pomatoschistus minutus) in an estuary between 2003 and 2019, and related it with the prevailing local and large-scale environmental factors. Using a dynamic factor analysis (DFA), juvenile abundance data were grouped into three common trends linked to different habitat uses and life cycle characteristics, with significant effect of temperature-related variables on fish recruitment: Sea surface temperature and the Atlantic Multidecadal Oscillation. In 2010, a regime shift in the North Atlantic coincided with a shift in the common trends, particularly a decline in P. flesus and S. solea trend. This work highlights the thermophilic character of fish recruitment and the necessity to investigate key biological processes in the context of species-specific responses to climate change. [Display omitted] • We studied the recruitment variability of 5 fish species in an estuary for 17 years. • Dynamic factor analysis identified 3 trends linked to life history and habitat use. • Water temperature related variables were the main drivers for recruitment variability. • The direction of abundance trends of the study species inverted between 2010 and 2012. • Our work demonstrates the thermophilic nature of fish recruitment. [ABSTRACT FROM AUTHOR]

A multi-biomarker approach was developed to evaluate responses of European flounder ( Platichthys flesus ) in three contrasted estuaries over the English Channel: the Canche (pristine site), Tamar (heavy metals and PAHs contamination) and Seine (heavily pollution with a complex cocktail of contaminants). The condition factor and several biomarkers of the immune system, antioxidant enzymes, energetic metabolism and detoxification processes were investigated in young-of-the-year (0+) and one-year-old (1+) flounder. Results underlined the difference between the pristine site and the Seine estuary which showed a lower condition factor, a modulation of the immune system, a higher Cytochrome C oxidase activity, and an up-regulation of BHMT expression. The moderate biomarker responses in the Tamar fish could be linked to the specific contamination context of this estuary. Flounder life history traits were analyzed by otolith microchemistry, in order to depict how the fish use their habitat and thus respond to chemical stress in estuaries. [ABSTRACT FROM AUTHOR]

Platichthys flesus is often used as a sentinel species to monitor the estuarine water quality. In this study, we carried out an experimental contamination of fish using a PAHs/PCBs mixture, which was designed to mimic the concentrations found in the Seine estuary (C1) and 10 times these concentrations (C2). We used a proteomic approach to understand the molecular mechanisms implied in the response of P. flesus to these xenobiotics. We showed that 54 proteins were differentially accumulated in one or several conditions, which 34 displayed accumulation factors higher than two. 18 of these proteins were identified by MALDI TOF–TOF mass spectrometry. The results indicated the deregulation of oxidative stress- and glutathione metabolism-(GST, GPx) proteins as well as of several proteins belonging to the betaine demethylation pathway and the methionine cycle (BHMT, SHMT, SAHH), suggesting a role for these different pathways in the P. flesus response to chemical contamination. [ABSTRACT FROM AUTHOR]

Juvenile flounders ( Platichthys flesus ) , collected in two estuaries with similar temperature regimes (the heavily polluted Seine and the moderately contaminated Vilaine), were submitted to a common garden experiment. After an acclimation period, both populations were challenged by a thermal stress (9–24 °C for 15 days, then maintenance at 24 °C for 19 days). The condition factor of the Vilaine fish increased in both conditions, while it decreased for the heated Seine flounders after 34 days. The expression of genes related to the energetic metabolism was measured in the liver. The expression levels for ATP-F0 and COII were significantly reduced for heated vs . standard fish from both estuaries, while a decrease of the 12S expression was detected only in heated vs . standard fish from the Seine estuary. Thus, it is suggested that highly contaminated fish from Seine could display a lower tolerance to thermal stress, compared to moderately contaminated fish from Vilaine. [ABSTRACT FROM AUTHOR]

Contamination levels and profiles of 7 polychlorinated-p-dioxins, 10 polychlorinated furans (PCDD/Fs) and 12 dioxin-like polychlorinated biphenyls (dl-PCBs) were investigated in juvenile European flounder (Platichthys flesus) captured in different nursery areas in the northeastern Atlantic coast across its geographical distribution range. The toxic equivalent concentrations (WHO-TEQfish) were also determined in order to evaluate which P. flesus population was more exposed to dioxin-like toxicity. Juveniles caught in the Sørfjord (Norway) showed the lowest WHO-TEQfish concentration (0.052pg WHO-TEQfishg−1wet weight) whereas the highest value was observed in fish from the Wadden Sea (The Netherlands; 0.291pg WHO-TEQfishg−1ww), mainly due to the greater contribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin, the most toxic congener. Nonetheless, when comparing the results with existent tissue residue-based toxicity benchmarks, no adverse effects resulting from PCDD/Fs and dl-PCBs are expected to occur in flounder from the studied systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] The two estuaries differed markedly in POP levels and profiles. [•] PCA showed a clear distinction between the examined sites and marine regions. [•] The dominant contaminants, PCBs and DDTs, exceeded the PBDE levels by 4–42 fold. [•] POP profiles in fish were not quite closely reflective of those in sediments. [•] None of the POPs exceeded EAC, except for CB-118 in the Vistula River estuary. [ABSTRACT FROM AUTHOR]

Highlights: [•] Female flounder were sampled from the mouths of the two rivers and corresponding open sea sites. [•] Several differences in biomarkers between the sampling sites were found. [•] Salinity and pollution seem to be the main factors that affect the biomarkers. [•] Effects of chronic pollution were found in the mouths of both rivers. [ABSTRACT FROM AUTHOR]

The modifications of several biomarkers were investigated in flounder (Platichthys flesus) when exposed in the laboratory to sediment samples collected from the Northern Adriatic Sea. Besides clean sand used as a control substrate, fish were exposed to sediments sampled offshore the delta of the Po River, the harbour of Trieste, and from the industrial harbour of Venice (Porto Marghera). After six days of exposure, the enzyme activities ethoxyresorufin-O-deethylase (EROD), UDP glucuronyltransferase (UDPGT), glutathione S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx), were assayed in fish fiver. In addition, the contents of reduced glutathione (GSH), nonprotein thiols (SH), total sugars and extractable lipids were also determined in hepatic tissue, as well as the number of micronucleated hepatocytes and biliary concentrations of fluorescent aromatic compounds (FAC). Despite some variability within treatment groups, differences among exposed organisms were evident and consistent with known contaminant levels of sampled areas. Microsomal activities (EROD, UDPGT) and FAC levels were the most sensitive exposure indicators. Variations in the other biomarkers showed only tendencies which although not statistically significant were generally consistent with the contamination pattern. [ABSTRACT FROM AUTHOR]

Wild fish (Cyprinus carpio, Mugil cephalus, Platichthys flesus) from an estuary of the NE Atlantic coast were investigated for plastic contamination (N = 128). From the 1289 particles recovered from fish samples, 883 were plastics. Among these, 84% were fibres and 97% were microplastics. Thirty-six polymers were identified. The number of microplastics (mean ± SD) per individual fish (MP/fish) was 8 ± 6 in C. carpio , 10 ± 9 in M. cephalus and 2 ± 2 in P. flesus. The means of MP/fish per body site were 6 ± 7 in gastrointestinal tract, 0.5 ± 1.1 in gills, 0.3 ± 0.7 in liver and 0.6 ± 1.2 in muscle samples. A few large fibres in liver (≤ 4841 μm) and muscle (≤ 5810 μm) samples were found. The results evidence the existence of high fish contamination by microplastics and reinforce the need of further research on plastic pollution in estuaries. [Display omitted] • Fish (flounders, mullets, carps) were studied for plastic (PL) contamination. • 883 PL were recovered, of which 97% were microplastics (MP). • 94% of fish had PL with a mean of 8 ± 8 PL per fish. • PL in the gastrointestinal tract, gills & muscle, and MP in the liver were found. • Fibres had size ≤ 4841 μm in the liver, and ≤ 5810 μm in the dorsal muscle. [ABSTRACT FROM AUTHOR]

Telomeres protect the coding sequence of chromosome ends and Telomere Length (TL) has been proposed as a biomarker of cellular aging, cumulative stress exposure and life-span in humans. With the aim to propose new biomarkers, a q-PCR protocol was adapted for the measurement of TL in the European flounder Platichthys flesus. The protocol was then applied in 2-year-old flounders from the Seine Estuary. The absolute TL in the flounder is 54 ± 13 kbp per genome (mean ± standard error). Considering relative or absolute TL, no correlation was observed with DNA damage and any of the measured contaminant concentrations (trace elements, metabolites of polycyclic aromatic hydrocarbons, polychlorobiphenyls, organochlorinated pesticides, polybrominated diphenyl ethers, perfluoroalkyl substances). Because sampling was limited, further investigations are required to state a possible impact of chemical pollution on flatfish telomeres. This is motivated by correlations observed with organochlorinated compounds when decreasing statistical significance (p ≤ 0.10). • A q-PCR protocol was adapted for telomere length (TL) measurement in flounders. • In fish from Seine Estuary, the absolute TL is 55 ± 12.8 kbp per diploid genome. • No correlation between TL and DNA damage was observed. • TL is positively correlated with organochlorinated compounds for p -values ≤0.10. • More studies are required to state if TL could be a marker of chemical stress. [ABSTRACT FROM AUTHOR]

To investigate the presence of sub-lethal contaminant effects in flounder (Platichthys flesus) populations in English estuaries, 16 sitesfrom 7 estuaries were sampled in September-December 1997. Determination of hepatic ethoxyresorufin O-deethylase (EROD) activity revealed that significant (p<0.05) induction of the mixed function oxygenase (MFO) system was apparent in flounder from several industrialised estuaries compared to the relatively unpolluted reference site - the Aldeestuary. The estuaries in increasing order of observed mean EROD activity were: Alde, Southampton Water, Humber, Tyne, Wear, Tees, Mersey. No significant gender differences in EROD induction or other measured variables were discovered for any site. Limited analytical data suggest a close link with EROD induction and hepatic polycyclic aromatic hydrocarbons (PAH)/polychlorinated biphenyls (PCB) concentrations but no strong correlations were discovered between EROD activity induction with any other measured variable across all estuaries. However, in the Tyne estuary strong negative correlations were discovered between mean female EROD and female gonado-somatic index (GSI) and femalecondition factor (CF) of r=-0.84 and -0.80, respectively. It is suggested that the `out of season' correlation of reproductive parameterswith EROD could be linked to contaminant interference, perhaps by xeno-oestrogens. It is clear that flounder populations in English industrialised estuaries are exhibiting widespread sub-lethal contaminant effects and more research is essential to understand the potential implications of this for reproduction and disease that could be affecting the future viability of these populations. [ABSTRACT FROM AUTHOR]