Toxicity assessment of organophosphorus in Ruditapes decussatus via physiological, chemical and biochemical determination: A case study with the compounds γ-oximo- and γ-amino-phosphonates and phosphine oxides.

Organophosphorus derivatives are widely used in human health care and have been detected in aquatic ecosystems. These compounds may pose significant risks to non-target exposed organisms and only limited studies are available on bioconcentration and the effects of organophosphorus derivatives on marine organisms. The aim of this work was to evaluate the possible toxic effects of two concentrations (20 and 40 µg/L) of γ-oximo- and γ-amino-phosphonates and phosphine oxides in mediterranean clams Ruditapes decussatus exposed for 14 days using different biomarkers and the changes of filtration and respiration rate. The use of clams in ecotoxicity evaluation is thus mandatory to assess the feasibility of assessing oxidative stress on R. decussatus after being exposed to γ-oximo- and γ-amino-phosphonates and phosphine oxides. The oxidative status was analyzed by measuring oxidative stress biomarkers RNS and ROS production in mitochondria, superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferases (GSTs), lipid peroxidation (LPO) and acetylcholinesterase (AChE), whose alteration was indicative of organophosphorus exposure, in both gills and digestive gland of the clams. No significant alterations in RNS, ROS production, SOD, CAT and AChE activities and MDA content were observed in both organs of clams treated with γ-oximophosphine oxides. It was possible then to hypothesize that γ-oximophosphine oxides may have probably exerted an incomplete alteration of antioxidant defenses and damage, which was changed by the activation of defense mechanisms. On the contrary, oxidative stress parameters were changed after exposure to γ-amino-phosphonates and phosphine oxides. In addition, metals accumulation, filtration and respiration rates were altered following exposure to all the studied organophosphorus compounds.

Ecotoxicity of polybrominated diphenyl ether (BDE-47) on a meiobenthic community with special emphasis on nematodes: Taxonomic and trophic diversity assessment.

The response taxonomic and trophic of meiobenthic organisms, especially marine nematodes to polybrominated diphenyl ether (BDE-47) was studied using a community from Bizerte lagoon (Nord-East Tunisia). Four concentrations of BDE-47 [D1 (2.5 µg/kg dw), D2 (25 µg/kg dw), D3 (50 µg/kg dw), and D4 (100 µg/kg dw)] were applied, and responses were determined 30 days after exposure. Species abundance and all univariate indices were significantly affected in all treated microcosms compared to the control. The non-parametric cluster based on species abundance separated the nematode population into two groups: control + all treated microcosms. After grouping nematode species according to their trophic diversity, their abundance showed differential responses. The non-metric multi-dimensional scaling analysis and cumulative k-dominance based on the abundance of trophic groups abundances reflected significant separation between the control microcosm and each treatment condition. The correspondence analysis 2D plot generated from nematode species and trophic groups abundance showed the control microcosm was dominated by microvores, represented by two species of Terschellingia. However, when treated with the highest concentration of BDE-47, the community was occupied by the resistant trophic groups of facultative predators and epigrowth feeders represented by Metoncholaimus pristiurus and Paracomesoma dubium, respectively.

Ethinylestradiol (EE2) residues from birth control pills impair nervous system development and swimming behavior of zebrafish larvae.

The ubiquitous use of ethinylestradiol (EE2), an active constituent of birth control preparations, results in continuous release of this synthetic estrogen to surface waters. Many studies document the untoward effects of EE2 on the endocrine system of aquatic organisms. Effects of environmental EE2 on the nervous system are still poorly documented. We studied effects of pico- to nanomolar concentrations of EE2 on early nervous system development of zebrafish larvae. EE2 disrupted axonal nerve regeneration and hair cell regeneration up to 50%. Gene expression in larval brain tissues showed significantly upregulated expression of target genes, such as estrogen and progesterone receptors, and aromatase B. In contrast, downregulation of the tyrosine hydroxylase, involved in the synthesis of neurotransmitters, occurred concomitant with diminution of proliferating cells. Overall, the size of exposed fish larvae decreased by 25% and their swimming behavior was modified compared to non-treated larvae. EE2 interferes with nervous system development, both centrally and peripherally, with negative effects on regeneration and swimming behavior. Survival of fish and other aquatic species may be at risk in chronically EE2-contaminated environments.

Using meiobenthic taxa, nematofauna biological traits, and bacterial abundance to assess the effects of the polybrominated diphenyl ethers compound: Case study of tetrabromo diphenyl ether BDE-47.

Trophic web structuring in aquatic sediments is dependent on the biological interactions between metazoans and microbial communities. The presence of pollutants in these biotas can therefore impact the meiofauna structure via the modification of the microbial communities. The current study examined in a laboratory bioassay the response of meiobenthic communities, particularly marine nematode taxa from the Bizerte Lagoon to the effect of the most detected polybrominated diphenyl ether in this aquatic environment, BDE-47. Four doses [D1 (2.5 ppb Dry weight (DW)), D2 (25 ppb DW), D3 (50 ppb DW), and D4 (100 ppb DW)] were gradually applied and sediment microcosms were incubated for 30 days in the presence or absence of meiofauna. Our results show that BDE-47-enriched sediments decreased the meiofaunal taxa and bacterial abundance. A lower taxonomic diversity of the nematodes' general structure was observed with all doses used. The numerical analysis of the two dimensional (2D) non-metric multidimensional scaling (nMDS) plots and the evolution of the relative abundances of each functional group of nematode genus assemblages revealed that the abundance of all biological traits was modified. Nevertheless, only three of the functional traits, adult length, feeding group, and amphid shape, showed a clear difference between the control and the treated microcosms. The similarity percentage analysis (SIMPER) revealed that the average dissimilarity between nematode genera communities and biological traits increased with BDE-47-enriched sediments. The nMDS second-stage ordination of inter-matrix rank correlations for matrices including genera and biological traits showed that the amphid shape was the functional trait closest to the generic distribution. Finally, the Principal Component Analysis (PCA) for the nematode biological traits and bacteria indicated a positive correlation of these microbes with the functional groups [1A, Cr, and ef], and a negative correlation only with the "cla"-type tail shape.