Résumé

ABSTRACT
The research carried out during the realization of this doctoral thesis is about the study of the impact of a possible pollution on the quality of the marine environment of Annaba gulf and this as part of biomonitoring program based on the use of a bioindicator species, Donax trunculus, an edible Bivalve Mollusc of Donacidae family. Sampling of this species was conducted monthly during 2016 at three sites in the gulf of Annaba; El Battah, considered as a
site of less pollution because far from any source of pollution; Echatt, site subject to agricultural and urban pollution; and Sidi Salem, site exposed to industrial pollution. In this context, we studied several aspects:
Spatio-temporal distribution and growth: the spatio-temporal distribution of the frequencies size classes of D. trunculus populations, revealed a better distribution of El Battah population, with a unimodal recruitment in the three sites and a maximum size of 38 mm. In addition, the biometric and weight study revealed a better growth ratio in individuals from El Battah compared to those from Echatt and Sidi Salem. Indeed, the condition index measured showed a positive correlation with seasonal variations, at individuals from the three sites, with higher indices during the spring corresponding to the reproduction period. These results were confirmed by the correlation and principal component analysis (PCA) applied, on the growth and condition index results. Physico-chemical parameters (temperature, pH, salinity, dissolved oxygen) were also determined in seawater from the three study sites, whose fluctuations are related to seasonal conditions.
Metallic contamination: the determination of some metallic trace elements (MTEs) in the sediment, water and flesh of D. trunculus revealed in the sediment the presence of a total of 20 chemical elements of a metallic (metals and metalloids) and non-metallic nature, with a high rate for Silicon (Si), and a relatively homogeneous mineralogical composition in the three sites.
Analysis of MTEs in seawater and the flesh of D. trunculus, showed the presence of two elements in the water, Copper (Cu) and Lithium (Li); and three elements in the flesh, Zinc (Zn), Copper (Cu) and Lithium (Li), with however low amounts considered as non-toxic.
Biochemical composition of the gonads: Seasonal determination of the gonado-somatic index in male and female gonads of D. trunculus individuals at the three study sites showed maximum values in females compared to males. The determination of the metabolites (proteins, carbohydrates, lipids) in the male and female gonads of D. trunculus showed a site effect with lower levels in individuals of Echatt and Sidi Salem compared to those of El Battah. In addition, a seasonal effect, was observed with higher rates in the spring corresponding to the start of the reproduction period. Comparison between the two sexes revealed that females accumulate more metabolic reserves and mobilize more energy than males during the reproductive process.
Biomarkers of environmental stress: concerning the biomarkers studied, we observed an
inhibition of acetylcholinesterase (AChE) and an increase in the activity of glutathione Stransferase (GST) and levels of malondialdehyde (MDA), translating a neurotoxic effect, and induction of the detoxification system and oxidative stress in individuals from the sites of Echatt and Sidi Salem compared to those of El Battah. The comparison between the seasons revealed more marked responses during spring and summer compared to the other two seasons. In addition, a tissue effect was highlighted with a more marked response in the gonad followed by the mantle and the digestive gland.
Parasitical impact: the examination of 360 individuals of D. trunculus collected at the three sites in the Annaba gulf allowed the collection of 8794 parasitic individuals distributed over the different tissues (mantle, gonad, digestive gland). The identification of these parasites revealed the presence of two species belonging to two families of trematode digenes Bacciger bacciger (Fellodistomidae; Rudolphi, 1819, Nicoll, 1924) and Postmonorchis sp (Monorchidae; Hopinks, 1941). The values of parasitic indices observed, show that the species Postmonorchis sp records the highest parasitic load (65.55%) compared to Bacciger bacciger (16.66%). The distribution of parasitic indices in D. trunculus at the level of the three sites shows that the site of Echatt has the highest parasite load compared to the other two sites. In addition, a tissue effect, was observed with a higher rate of infestation in the digestive gland compared to other tissues.
All the results obtained are related to the level of exposure of sites to the different sources of urban, agricultural, industrial and harbor pollution. In addition, D. trunculus appears as a choice model that can be used as a sentinel bioindicator species of pollution in the gulf of Annaba.

Keywords: Biomonitoring, Gulf of Annaba, Donax trunculus, Environmental stress, Bioindicator, Biomarker, Parasitism, Pollution.

Information

Item Type:	Thesis
Divisions:	» Laboratoire des Ecosystèmes Aquatiques et Terrestres » Faculté des Sciences de la Nature et de la Vie
ePrint ID:	2714
Date Deposited:	2021-09-05
Further Information:	Google Scholar
URI:	https://www.univ-soukahras.dz/fr/publication/article/2714

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