Transcriptomic, Biochemical, and Histopathological Responses of the Clam Ruditapes decussatus from a Metal-Contaminated Tunis Lagoon

Abstract

This study was designed to investigate the molecular (transcriptional expression), biochemical (oxidative stress and neurotoxicity), and histopathological effects of metal contamination in the gill of clams (Ruditapes decussatus) sampled from the Tunis lagoon. The concentrations of five heavy metals (Cd, Pb, Hg, Cu, and Zn) in surface sediments and their accumulation in soft tissues of R. decussatus were evaluated in three sites (Z1, Z2, and Z3). A metal contamination state of Tunis lagoon sediments was noted with spatial variations with relatively high levels at Z2. Biomarker analyses showed an increase in glutathione S-transferase and catalase activities and lipid peroxidation levels and a decrease in acetylcholinesterase activity in the studied sites. Molecular investigation showed a significant overexpression of: cytochrome c oxidase subunit I, ribosomal RNA 16S, Cu/Zn superoxide dismutase, heat shock protein 70, and metallothioneins in the three sampling sites. Moreover, our data were correlated to severe and diverse histopathological alterations in the clam gills. The principal component analysis showed that the Z2 region is more affected by metal contamination than Z1 and Z3 regions. Current field results suggest the use of several combined biomarkers at different cell levels instead of individual ones in monitoring programs.

Assessment of oxidative stress, genotoxicity and histopathological responses in the digestive gland of Ruditapes decussatus collected from northern Tunisian lagoons

“…Furthermore, the average water residence time in the lagoon varies from 6.6 to 8.2 days, with 2.57 million m 3 day -1 of total water exchange with the sea (Jouini 2003). The zones close to this lagoon are characterized by the presence of activities such as harbours, tourism, agriculture, urban developments and industries (Chalghmi et al 2016). The Northern Lagoon of Tunis is part of the wetlands partially separated from the marine environment by a coastline, meeting both marine salty waters and continental fresh water (Ben Mosbah et al 2010).…”

“…This site is characterized by a sandy substrate and is supposedly less polluted after the restoration works in 1985 to 1988, as reported by Barthel (2006) and Chouba et al (2010). The HCA is located in the South Lake (36°47′12.40″N 10°13′12.88″E), in a highly polluted area with higher anthropic pressure than the other sampling sites (Chalghmi et al 2016). Indeed, this site is characterized by black sticky mud and water stagnation, with a strong smell of hydrogen sulphide (H 2 S), and is very rich in seaweeds with some fragments of shells (Kochlef 2003.…”

“…There are numerous studies focusing on TEs contamination in sediments and marine organisms from the northern coast of Tunisia (including the Tunisian Gulf and the Bizerte lagoon) (Chalghmi et al 2016, Ghannem et al 2016. However, investigation of the effect of TE contamination in bivalves from Ghar el Melh and the Northern and Southern Lagoons of Tunisia has so far been insufficient.…”

“…However, investigation of the effect of TE contamination in bivalves from Ghar el Melh and the Northern and Southern Lagoons of Tunisia has so far been insufficient. Previous studies have integrated the toxicity responses provided by the clam R. decussatus and contamination to assess the quality of some Tunisian lagoons (Chalghmi et al 2016). The current study is aimed at comparing the environmental quality of three lagoons with different contamination levels, a less contaminated area (LCA), a moderately contaminated area (MCA) and a highly contaminated area (HCA) on the northern Tunisian coastline by integrating water parameters, TE accumulation, biological responses, macromolecules and tissue injuries using the digestive gland of R. decussatus.…”

Combined effects of metal contamination and abiotic parameters on biomarker responses in clam Ruditapes decussatus gills: an integrated approach in biomonitoring of Tunis lagoon

“…5,6 Metal contamination is a matter of huge concern especially on marine environments due to their abundance, persistence and subsequent bioaccumulation. [8][9][10] Furthermore, it is also important to understand the interactions between metals and their spatio-temporal evolution specicity in coastal environments. Metals accumulated in sediments provide an historical input record of a local environment, whereas the metals accumulated in the biota indicate each metal's bioavailability.…”