Study on the Establishment of the Gastropod Lymnaea stagnalis (Linné, 1758) as a Bio-sentinel to Monitor the Water Quality of North Algerian Rivers: Case of the El-Malah River

Biomonitoring is a key solution for assessing the effects and risks of pollutants to preserve the most vulnerable ecosystems, including aquatic ecosystems. This study aims in establishing the gastropod Lymnaea stagnalis, as a sentinel species to assess the water quality of the El-Malah river in the Algerian North-West. Three sites were chosen along the river: upstream (US), midstream (MS), and downstream (DS). The responsiveness of the aquatic snails has been compared using physiological and biological markers: condition index (CI), volumetric condition index (VCI), acetylcholinesterase (AChE), glutathione s-transferase (GST), and catalase (CAT). Additionally, the occurrence of changes in biometric parameters of the specimens has also been treated: shell height (SH), shell thickness (ST) total weight (TW), and the ratio ST/SH. Snails from the site MS reacted in front to the water deterioration with low biometric values (ST 1.28 ± 0.17 cm; SH 1.83 ± 0.20 cm; TW 2.95 ± 0.69 cm), and condition indices values (CI 31.19 ± 3.58; VCI 2.09 ± 0.53 g.cm-3), thereby signaling smaller individuals compared to the population of site US. Whereas, no specimen was recorded in the site submitted to wastewaters discharge (DS). This indicates that the degradation of the water quality affected the growth and the viability of the snails. Furthermore, a significant induction in the GST activity (88.98 ± 10.72 nmol min-1mg-1), and a significant inhibition in the CAT activity (82.85 ± 9.49 μmol min-1mg-1) were recorded in the site MS, whereas no statistically significant variation was observed in AChE activity. L. stagnalis demonstrated biological and physiological variability between the studied contrasting sites of the El-Malah River. These results allow us to propose this species as a model in the ecotoxicology of western Algerian freshwaters.

Spatial distribution and biological effects of trace metals (Cu, Zn, Pb, Cd) and organic micropollutants (PCBs, PAHs) in mussels Mytilus galloprovincialis along the Algerian west coast

Native mussels Mytilus galloprovincialis are used as bioindicator organisms to assess the concentration levels and toxic effects of persistent chemicals, polychlorobiphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals using biomarker responses, such as catalase (CAT), glutathione s-transferase (GST), and condition indices, for the Algerian coast. The results show that mussels of Oran Harbour are extremely polluted by PCBs and PAHs, i.e., 97.6 and 2892.1μg/kg d.w., respectively. Other sites present low levels of pollution. Furthermore, high concentrations of zinc, lead and cadmium are found in mussels from fishing, agricultural and estuarine sites, respectively, while low concentrations of copper are found in all of the sites studied. CAT activity is negatively correlated with Cd and Cu, and Zn is positively correlated with GST and CAT. Site classification tools reveal the potential toxicity of coastal areas exposed to anthropogenic pressure and a gradient of toxicity along the Algerian west coast.

Integrated use of biomarkers and condition indices in mussels (Mytilus galloprovincialis) for monitoring pollution and development of biomarker index to assess the potential toxic of coastal sites

In this study, we are interested in spatial and temporal variations of the biological and physiological responses of mussels collected from contrasting marine sites regarding their levels of pollution. We measured both the conditions indices and the enzymatic biomarker expression: acetylcholinesterase (AChE), catalase (CAT) and glutathione S-transferase (GST) activity. The enzymatic biomarkers were chosen because they respond to environmental stress. Results show a significant interactions between biomarker variations and conditions indices in the industrial harbor site throughout the seasons. But no significant changes in the reference site. Furthermore, we classified the sites along the seasons according to their potential ecotoxicity, calculated based on the sum of the normalised values of the biomarkers. The results show a very high biomarker index in the impacted site with irregular changes between seasons. This biomarker index is therefore a valuable tool that could be used to classify the toxic potential of coastal sites.