Metallothioneins as a biomarker of metallic pollution in Donax trunculus Linnaeus, 1758 (Mollusca Bivalvia) from the Gulf of Annaba (Algeria) Laboratory of Applied Animal Biology, Badji Mokhtar University, 23000 Annaba, Algeria *Corresponding author: noureddinesoltani@univ-annaba.org; noureddinesoltani36@gmail.com ABSTRACT In recent years, the Gulf of Annaba has observed an increase in the pollution level, in particular by heavy metals. The present experiment aimed to assess pollution by measuring the rate of metallothioneins (MTs), a biomarker of metallic contamination, measured in the digestive gland of Donax trunculus Linnaeus, 1758 (Mollusca Bivalvia) an edible mollusk widely used in biomonitoring of water quality. This sentinel species was sampled during two seasons (win- ter and summer 2019) at two sites in the Gulf of Annaba (Northeast Algeria): El Battah site far from any source of pollution and Sidi Salem site exposed to various sources of pollution. The biochemical analyzes reveal spatio-temporal changes. The levels of proteins recorded in the two studied sites were higher in summer and values from El Battah individuals were sig- nificantly higher compared to those from Sidi Salem. In addition, they show an induction in MT rates in individuals from the two sites (Sidi Salem and El Battah) in summer with higher values recorded in individuals from Sidi Salem. This difference is related to the proximity of sources of contamination at Sidi Salem compared to El Battah. The rates of MTs vary also according to abiotic factors such as hydrodynamics or temperature which can explain the sig- nificant seasonal difference with a more marked induction in summer. Conclusively, our study shows the sensitivity of D. trunculus to chemical stress induced by heavy metal contamination as evidenced by an induction of MTs with significant effects of both sites and seasons. INTRODUCTION The development of human activities is re- sponsible for the chronic pollution of the environ- ment by organic and inorganic contaminants (Larba & Soltani, 2014; Breitwieser et al., 2020; Douafer et al., 2020). The marine environment, and in particular coastal areas, receives a large amount of contaminants from urban, agricultural, port and industrial activities. These contaminants cause increased pollution of marine ecosystems and have a significant toxic impact on the health of living organisms (Amamra et al., 2019; Ham- dani et al., 2020). However, the increase in ocean pollution caused by toxic metals has resulted in bioaccumulation of toxic metals in marine ani- mals, particularly bivalves such as clams, and the consequent toxicity associated with heavy metals in these animals (Mengxu et al., 2020). Thus, bio- monitoring is an important tool to determine the KEY WORDS Pollution; Gulf of Annaba; Donax trunculus; Biomarker; Proteins; Metallothioneins. Amina Yezli, Abdelmalek Salahi, Asma Boukari & Noureddine Soltani* Biodiversity Journal, 2022,13 (4): 767–774 https://doi.org/10.31396/Biodiv.Jour.2022.13.4.767.774 Received 31.05.2022; accepted 24.09.2022; published online 24.10.2022