Experimental evidence that polystyrene nanoplastics cross the intestinal barrier of European seabass.

Plastic pollution in marine ecosystems constitutes an important threat to marine life. For vertebrates, macro/microplastics can obstruct and/or transit into the airways and digestive tract whereas nanoplastics (NPs; < 1000 nm) have been observed in non-digestive tissues such as the liver and brain. Whether NPs cross the intestinal epithelium to gain access to the blood and internal organs remains controversial, however. Here, we show directly NP translocation across the intestinal barrier of a fish, the European seabass, Dicentrarchus labrax, ex vivo. The luminal side of median and distal segments of intestine were exposed to fluorescent polystyrene NPs (PS-NPs) of 50 nm diameter. PS-NPs that translocated to the serosal side were then detected quantitatively by fluorimetry, and qualitatively by scanning electron microscopy (SEM) and pyrolysis coupled to gas chromatography and high-resolution mass spectrometry (Py-GC-HRMS). Fluorescence intensity on the serosal side increased 15-90 min after PS-NP addition into the luminal side, suggesting that PS-NPs crossed the intestinal barrier; this was confirmed by both SEM and Py-GC-HRMS. This study thus evidenced conclusively that NPs beads translocate across the intestinal epithelium in this marine vertebrate.

Scattering of individual particles from cytometry: tests on phytoplankton cultures.

This study presents an application of the Cytosense flow cytometer (CytoBuoy b.v., NL) for the analysis of the optical properties of phytoplankton cells. For the first time, the forward, sideward and backward cross sections (σFSC, σSSC and σbb ) were derived for two species morphologically different (Chlamydomonas concordia and Thalassiosira pseudonana). The objective of this work is to check the validity of the estimates before any applications in the frame of marine optics studies. Thus, estimates of σFSC and σSSC are tested with radiative transfer computations as no in situ measurements are available. A synthetic database is built considering homogeneous, multi-layered spheres, aggregates and cylinders. Scanning electron micrographs were performed to investigate the cell morphology to simulate particles as close as possible to the real cells. This set of numerical results represents a valuable database for many kinds of applications dealing with marine optics. Comparisons showed that the Cytosense estimates for the cultures are consistent with values predicted by the theory. In average, more than 92% of the Cytosense estimates were encompassed by predicted values. The backscattering cross section and the backscattering efficiency were compared with in situ measurements found in the literature wherever possible. Results showed that σbb and Qbb estimations fall within the range of the referenced values.

A combined measurement of metal bioaccumulation and condition indices in juvenile European flounder, Platichthys flesus, from European estuaries.

Condition indices and metal bioaccumulation of early life stages of juvenile flounder (5-10 cm) were determined in three anthropogenic estuaries (the Scheldt, Seine and Loire) and compared to a reference site (the Canche). Significant correlations were found between metal concentrations in sediment and (i) fish liver for Cd, Cu, Ni, Pb, V and Zn and (ii) fish gills for Cd and Mn. Metal accumulation in juvenile flounder from the three anthropogenic estuaries coincided with significantly lower Fulton's K indices (from 0.99 ± 0.03 to 1.06 ± 0.01 mg mm(-3)) compared to those from the Canche estuary (from 1.02 ± 0.01 to 1.13 ± 0.01 mg mm(-3)). This discrepancy in fish condition index increased with fish size and therefore, strongly depends on the time juvenile spend in estuary. Muscle lipid contents and Triacylglycerol to Sterol ratios were significantly lower in fish collected in the Scheldt (lipid content: 21.3 ± 3.6%), Seine (17.9 ± 19.8%) and Loire (19.5 ± 2.4%) estuaries compared to those originating from the Canche (38.3 ± 4.6%). This study highlights that combined measures of both fish metal contents and condition indices gives a relevant assessment of juvenile fish health growing in anthropogenic estuaries.

Metal concentrations, growth and condition indices in European juvenile flounder (Platichthys flesus) relative to sediment contamination levels in four Eastern English Channel estuaries.

The aim of the present study was to evaluate the effects of metal contamination on the biological responses of 0-group juvenile European flounder and to assess and compare the quality of four estuarine habitats located in the Eastern English Channel. Fish otolith growth and condition indices (RNA : DNA ratio, Fulton's K condition index) were measured and found to be significantly lower in individuals from the Seine estuary compared to those of the Canche, Authie and Somme estuaries. No obvious effects of hydrological condition or food availability on the flounder biological responses were observed. Sediments from the Seine showed the highest metal concentrations, bioavailable proportion and enrichment factors. Higher metal concentrations were observed in fish from the Seine compared to the other ones caught in less polluted estuaries. These results suggest that contaminants may have a negative impact on the early life history stage of flounder.

Growth and condition indices of juvenile turbot, Scophthalmus maximus, exposed to contaminated sediments: effects of metallic and organic compounds.

Since sediments have the potential to form associations with several classes of pollutants, they have been recognized as a possible and significant source of contamination for the benthic environment. Flatfish maintain a close association with sediments for food and cover, and are therefore more likely to be exposed to contaminated sediments, especially in coastal areas (e.g. nursery grounds). The assessment of these potential biological effects involves the use of adapted biomonitoring tools. The main objective of this study was to assess and compare the response of several physiological biomarkers measured on juvenile turbot (Scophthalmus maximus) exposed to contaminated sediments. Sediments were collected from three stations in a harbour in northern France (Boulogne-sur-Mer), in an anthropogenic French estuary (the Seine), and in a reference site (exposed sandy beach of Wimereux). Unexposed lab-reared juvenile turbots were exposed to sediments for 7 and 21 days in laboratory conditions. Sediments were analysed for metals, PAH and PCB contamination. Several fish growth and condition indices were individually analysed in fish according to the chemical contaminant availability in sediment, the metal concentrations in gills and the estimation of PAH metabolites in their bile. Significant decreases in growth rates, morphometric index, RNA:DNA ratio and the lipid storage index, based on the ratio of the quantity of triacylglycerols on sterols (TAG:ST), were observed with increasing level of chemical contamination. This decrease in the fish's physiological status could be related to the significant increase of several metal concentrations in contaminated fish gills and the significant increase of PAH metabolites in bile. In a field situation, such a reduction in growth and energetic status of juvenile fish could dramatically decrease their over-winter survival in contaminated nursery grounds.

Heavy metals in four fish species from the French coast of the Eastern English Channel and Southern Bight of the North Sea.

Shallow coastal waters act as nurseries for various fish species and have been recognized as essential fish habitat. We studied heavy metal concentrations in four fish species (plaice, dab, flounder and cod) as an indicator of large-scale habitat quality. The study took place along the French coasts between the Eastern English Channel and the Southern Bight of the North Sea. All species show different concentrations of measured metals (e.g., Cd, Cu, Mn and Pb) in liver but not in muscle. The highest concentrations are found for the flounder and the lowest for cod which is consistent with their habitat and diet. Although our results do not highlight levels of appreciable pollution within the study area, inter-site differences are mainly observed in the muscle tissues and are generally in agreement with the known environmental data (e.g., anthropogenic pressure). However, in the Bay of Seine, one of the most contaminated estuaries in Europe, metal concentrations are in the same range or even lower than those found in fish collected from areas distant from any anthropogenic pressures. At one site, the comparisons of the Cd, Cu and Pb concentrations between healthy and diseased dabs have been carried out on the muscle and liver tissues. The results of this preliminary study show a relationship between metal concentrations and the pathological status of the fish. The use of fish health as indicator of habitat quality is discussed.