Biochemical endpoints on juvenile Solea senegalensis exposed to estuarine sediments: the effect of contaminant mixtures on metallothionein and CYP1A induction

Abstract

Juvenile Solea senegalensis were exposed to fresh sediments from three stations of the Sado estuary (Portugal) in 28-day laboratory assays. Sediments revealed distinct levels of total organic matter, fine fraction, redox potential, trace elements (arsenic, cadmium, chromium, copper, nickel, lead and zinc) and organic contaminants (polycyclic aromatic hydrocarbons, polychlorinated biphenyls and a pesticide: dichloro diphenyl trichloroethane). Organisms were surveyed for contaminant bioaccumulation and induction of two hepatic biochemical biomarkers: metallothionein (MT) and cytochrome P450 (CYP1A), as potential indicators of exposure to metallic and organic contaminants, respectively. Using an integrative approach it was established that, although bioaccumulation is in general accordance with sediment contamination, lethality and biomarker responses are not linearly dependent of the cumulative concentrations of sediment contaminants but rather of their bioavailability and synergistic effects in organisms. It is concluded that metals and organic contaminants modulate both MT and CYP1A induction and it is suggested that reactive oxygen species may be the link between responses and effects of toxicity.

Transcriptomic analyses in a benthic fish exposed to contaminated estuarine sediments through laboratory and in situ bioassays

“…This information is in accordance with the present results considering that sediment C 1 is more contaminated by metals and arsenic than C 2 (although both have proximate levels of PAHs) and that exposure to sediment C 2 elicited the most significant up-regulation of this gene's transcription. Flatfish have been reported to rapidly catabolize PAHs (Varanasi and Gmur 1981), which is consistent with the overall strong correlations found between the transcription of the S. senegalensis CYP1A gene and the potential risk of the surveyed levels of sediment PAHs, confirming that, in spite the presence of multiple-class contaminants, measuring CYP1A transcripts produces results that can be better related to sediment CYP inducers than measuring CYP protein content (see for instance Costa et al 2009a). …”

“…1) and to previous research (e.g. Caeiro et al 2009;Costa et al 2009a). A reference (clean) site (R) was chosen for being the farthest from pollution sources.…”

“…The laboratory assays were performed in duplicate with a recirculation arrangement of 15-l capacity white polyvinyl tanks with blunt edges where 2 l of fresh sediments (providing a surface of approximately 525 cm 2 ) plus 12 l of clean seawater were allocated, following previous assays with the species (Costa et al 2009a). The photoperiod was set at 12 h light:dark and a weekly 25% water change was applied to ensure constancy of water quality parameters with minimal removal of suspended particles and dissolved contaminants: temperature was set at 18 ± 1°C, salinity = 32.1 ± 0.3, pH 8.0 ± 0.1, oxygen saturation = 56.5 ± 0.2% (supplied by constant aeration) and total ammonia was maintained within 1.6 ± 0.6 mg l -1 (the toxic unionized ammonia was restrained at 0.04 ± 0.02 mg l -1 ).…”

“…Jessen-Eller and Crivello 1998;Mouneyrac et al 2002;Gonzalez et al 2006) or in fact reports its up-regulation by organic contaminants (Costa et al 2009a). Still, the majority of research performed on MT induction in aquatic organisms for the purpose of ecological risk assessment focus on MT-like protein content and not its gene transcription.…”

Proposta conceitual de estudo para a integração e gerenciamento do uso de marcadores bioquímicos de contaminação ambiental

“…Nesse sentido, é importante a determinação de concentrações de misturas que causem efeitos não desejáveis em espécies não-alvo (CORY-SLECHTA, 2005;NEEDHAM et al, 2005;COSTA et al, 2009) …”