Sediment Toxicity Bioassays Using Ruditapes decussatus Embryos and Larvae to Assess the Contamination in Four Sites on the Coast of Tunisia

Abstract

This paper aims to assess the marine sediment quality along the Tunisian coast using clam Ruditapes decussatus embryos and larval bioassays tests. Elutriate samples prepared with sediment from four sites (Monastir Lagoon, Chebba, Mahres, and Zarat) were used for chemical analysis and clam bioassays tests (embryogenesis, larval growth. and metamorphosis). For embryogenesis test, five elutriates concentrations (12%, 25%, 50%, 75%, and 100%) were prepared. Metal concentrations were highest at the Mahres and Monastir Lagoon sites. Clam embryogenesis success was significantly (p < 0.05) reduced in all elutriates preparations at concentrations up to 50% except Chebba, where inhibition was evident at only the highest concentration (100%). Compared to the control (9.4 μm day⁻¹), larval growth rate was significantly (p < 0.05) reduced only in two sites, Monastir Lagoon (6.8 μm day⁻¹) and Zarat (5.6 μm day⁻¹). However, larval survival was lower (42.9%) in elutriates prepared from Mahres sediment compared to other studied sites and control treatment. We did not note any significant (p > 0.05) effect of elutriate preparations on clam metamorphosis; conversely, survival in this stage was significantly affected in three sites (Monastir: 59.0 ± 6.7%; Zarat: 52.1 ± 6.3%, and Mahres: 64.1 ± 5.4%) compared to the control (83.2 ± 4.7%). This work shows that both clam embryos and larvae are sensitive to contaminants and can be used to evaluate sediment contamination and monitor pollution.

Keywords:

• bioassay
• sediment elutriate
• embryogenesis
• larvae
• metamorphosis
• Ruditapes decussatus

Acknowledgements

The work described in this paper was partially supported by funds from the Tunisian Ministry of Higher Education, Scientific Research and Technology (Laboratoire d’Aquaculture de l’Institut National des Sciences et Technologies de la Mer).