Use of Tridacna maxima, a bivalve in the biomonitoring of the Saudi Arabian Red Sea coast.

The present study is an attempt to assess the effects of contamination of several sites in the Red Sea coasts of Saudi Arabia using bivalves as a biomonitoring tool. Oxidative stress biomarkers (including reduced glutathione level (GSH), glutathione-S-transferase activity (GST), Malondialdehyde level (MDA) and Catalase activity (CAT)), neurotoxicity acetylcholinesterase activity (ACHE), and genotoxicity micronucleus rate (MN) were measured in three distinct tissues - digestive glands, gills and mantle - of specimens of the giant clam Tridacna maxima, collected from five sites in Saudi Arabian Red Sea coast (Al-Khuraybah, Al-Wajh, Yanbu, Rabigh and Thuwal). Our results demonstrated that T. maxima showed differential biomarker responses according to the nature of pollutants and human activity that affect the coast. This study can be considered as the first one using biomarkers to assess the state of the Red Sea coast in Saudi Arabia which must be followed by periodic studies for surveillance of aquatic pollution.

Seasonal ecotoxicological monitoring of freshwater zooplankton in Bir Mcherga dam (Tunisia).

Dams represent large semi-closed reservoirs of pesticides and various organic and inorganic pollutants from agricultural and human activities, and their monitoring should receive special attention. This study evaluated the environmental health status of Bir Mcherga dam using zooplankton species. The dam has a capacity of 130 Mm3 and its waters are used for irrigation, water drinking supply, and fishery. Copepods and cladocerans (crustaceans) were collected in situ monthly between October and August 2012. Oxidative stress (CAT, MDA), neurotoxicity (AChE), and genotoxicity (micronucleus test) biomarkers were analyzed in two zooplankton species: Acanthocyclops robustus and Diaphanosoma mongolianum. High values of cells with a micronucleus were observed during summer. AChE activities were inhibited during early winter and summer. The high seasonal variability of CAT and MDA levels indicates that zooplankton is continuously exposed to different oxidative stresses. These results suggest that there is an obvious and continuous multi-faceted stress in Bir Mcherga reservoir and, consequently, an urgent monitoring of freshwater environments in Tunisia is needed, particularly those intended for human consumption and irrigation.

In situ genotoxicity assessment in freshwater zooplankton and sediments from different dams, ponds, and temporary rivers in Tunisia.

Tunisia water resources are limited. The country currently has 29 large dams, more than 1000 hill lakes, and 220 small dams which are essential for economic and social development given their contribution to irrigation, drinking water consumption, flooding protection, production of electrical energy, groundwater recharge, and industrial uses. Given the scarcity of these resources, it is crucial to be able to ensure the quality of freshwater environments, particularly those intended for human consumption. In this study, we meant to assess the health status of various freshwater ecosystems in different regions of Tunisia (north and center west) in order to detect genotoxic components in sediments and their potential effect on zooplankton (cladocerans). Sediment and cladoceran species were collected from dams, ponds, and temporary rivers in Tunisia. For each collection site, micronucleus (MN) assay was performed, in triplicates, using a pool of ten specimens of the same cladoceran species. MN occurrence in cladocerans varied from one site to another and MN frequencies varied between 0.67 and 22‰, suggesting the presence of genotoxic substances in certain sites. Sediment genotoxicity and mutagenicity were assessed using the SOS Chromotest and the Ames test. Sediment results showed that genotoxicity varies from one site to another displaying a quantitative and a qualitative variation of pollutant among the sites. These results suggest an urgent need for continuous monitoring of freshwater environments in Tunisia, particularly those intended for drinking water.