INSTM Bulletin : Marine and Freshwater Sciences

Resistance profiling, evolution of biofilm formation and genetic diversity of Vibrio alginolyticus isolated from aquaculture systems

Rim LAJNEF, Miguel Angel MORIÑIGO, Abdennaceur HASSEN, Lotfi BEN ABDALLAH — Fri, 17 May 2024 00:00:00 +0000

This study analyzes 26 presumptive Vibrio alginolyticus strains extracted from two fish farms (Khenis and Hergla, East Tunisia) that raised sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). In addition, from a shellfish farm located in Menzel Jmil, North Tunisia that raises mussels (Mytilus edulis) and oysters (Crassostrea gigas).

We have evaluated (i) the discriminatory power of PCR-RFLP for identification of closely related strains, (ii) the antibiotic resistance of the V. alginolyticus strains and (iii) their ability to form a biofilm in aquaculture farm.

Results showed that there is great heterogeneity in the diversity observed via the PCR-RFLP method related to the number of 20 genotypes generated by the two enzymes SduI and FaqI tested. The heterogeneity was observed in both fish (aquaculture farm) and bivalve (shellfish farm) origins, as well as in the same sample.

For antibiotic resistance, all isolates present a high resistance to ampicillin, erythromycin, cefotaxime, kanamycin and doxycycline. The resistance is displayed by 15 distinct profiles.

The Multiple Antibiotic resistance (MAR) index was ranged from 0.55 to 0.80 for the isolates from the aquaculture farm of Hergla followed by the index aquaculture farm of Khenis (0.55 to 0.75). While for the shellfish farm of Menzel Jmil the index ranges from 0.50 to 0.65. This finding indicated high-risk sources of antibiotic contamination in the three locations. Isolates from aquaculture systems with strong biofilm formation have been found to be resistant to antibiotics, which may allow them to survive longer in these environments.

Present findings could be relevant in aquaculture systems and underscore the importance of the linkage between adhesion, antibiotic susceptibility, and genetic diversity of these pathogenic bacteria to avoid fish and shellfish diseases. The results will provide helpful guidance on how to use antibiotics to control Vibrio alginolyticus diseases in aquaculture to be healthy.

Age and growth of Carcinus aestuarii Nardo,1847 (Portunidae) and Maja squinado Herbst, 1788 (Majidae) in the Gulf of Gabes, Southeastern Tunisia, Central Mediterranean

Thu, 23 May 2024 00:00:00 +0000

The Mediterranean green crab, Carcinus aestuarii Nardo, 1847 (Crustacea, Brachyura, Portunidae), and the spider crab Maja squinado (Herbst) are common inhabitant of the shallow waters in the Gulf of Gabes (southern Tunisia, central Mediterranean).

The Von Bertalanffy growth parameters CW∞/CL∞, k and t₀ were estimated on the basis of Length-frequency modal progression analysis method. The values of CW∞ (mm), K (year^-1) and t₀ (year) would be, respectively, 95.61, 0.84 and -0.104 for males; 73.92, 1.11 and -0.149 for females in Carcinus aestuarii and, CL∞ (mm), K (year^-1) and t0 (year) would be, respectively, 172.46, 0.68 and -0.147 for males; 147.05, 0.6 and -0.175 for females in Maja squinado.

These results were obtained, as the first attempt to study age and growth of these two crustaceans which will be of a great use for their eventual stock assessment studies.

Effect of the green macroalgae Chaetomorpha linum liquid extract on the germination, growth and pigments concentration of the chickpea Cicer arietinum L., 1753

Leila CHEBIL AJJABI, Leila KTARI, Imen BEN DOUAOUA, Marwa MELKI — Tue, 04 Jun 2024 00:00:00 +0000

Fertilizer production and application are growing excessively with increased agricultural expenses and environmental damage. As alternatives, organic fertilizers issued from natural resources such as seaweed liquid extracts (SLE) are considered as potential plant biostimulant agents. In this study, the impact of the green algae Chaetomorpha linum SLE on seed germination, yield and pigmenting characteristics of the chickpea Cicer arietinum was investigated in laboratory settings and in pots. Several SLE concentrations varying from 1%, 3%, 5%, 8% to 10% were prepared using distilled water.

The application of SLE significantly affected all assessed parameters over the control (0%). Use of SLE at the lowest concentration (1%) showed maximum seed germination, root and shoot length and contents of total chlorophyll, chl (a), and chl (b). Accordingly, the results suggest that C. linum SLE could be used as an alternative organic fertilizer because it is environmentally friendly and profitable. This extract, rich in plants growth components, could find its future use in various sectors.

Frequency histograms, condition parameters and size-depending metal accumulation in two species belonging to Phorcus genus

Wafa BOULAJFENE, Sabiha TLIG-ZOUARI — Tue, 02 Jul 2024 00:00:00 +0000

This work is a biological and ecotoxicological investigation in two Trochidae species Phorcus turbinatus and Phorcus articulatus taken from four stations, monthly for biological study and seasonally for size-depending metal monitoring. Our results related to biological characterization suggested mostly polymodal frequency histograms associated with a continual renewal of juveniles indicating a laying period spread over several months.

The condition index revealed similar values slightly decreasing during hot seasons probably due to the coincidence of the spawning period with the spring and the summer. As for the condition factor, it also presented close values with a slight increase during the periods of March-April, June-July and even September-November probably resulting from algal proliferation and trophic availability during those months.

The estimation of metal pollution indicators proposed an increasing classification of contamination related to the amounts of waste ejections at each locality coming from industrial activity, large fishing ports and mooring areas. Size-depending metal analyses revealed that despite the strong contamination, a moderate concentration decrease was associated with size growth. This life strategy would allow these species to counteract unfavorable conditions and ensure their persistence and thus justify their frequent use as bio-indicators of the state of health in coastal ecosystems.

Human health risk assessment of heavy metal(oid)s in four fish species harvested from the Bizerte lagoon (Tunisia)

Fri, 05 Jul 2024 00:00:00 +0000

This study investigated the levels of cadmium (Cd), lead (Pb), arsenic (As), iron (Fe), copper (Cu), and zinc (Zn) exposure in the child and adult populations in Tunisia. The heavy metal(loid) (HM) content in muscle and the organ mixture of four commercial species of fish widely available and consumed were determined (Sparus aurata, Dicentrarchus labrax, Liza aurata, Sarpa salpa).

The fish samples were prepared using a wet digestion method, and the HM analysis was carried out using an inductively coupled plasma mass spectrometry (ICP-MS). The results indicated that all fish organs had high amounts of Pb and As and high levels of Cd and Zn in some organs. Based on the exploratory data analysis, fish species can be differentiated according to their diet.

The estimated daily intake values for the children's population have exceeded the permissible levels for Cd and As, whereas they were only exceeded for As for the adult population. Only Fe's Target Hazard Quotient exceeded the permissible limit. The evaluation of the carcinogenic risk associated with the consumption of the four fish species from the Bizerte lagoon indicated a potential carcinogenic effect related to lead (Pb) exposure. In this lagoon, HM contamination of fish is requiring both a short-term and long-term approach to ensure the safety of marine products.

Cellular compartmentalization and accumulation of Aluminium in the halophyte of Arthrocnemum indicum

Dhouha BELHADJ SGHAIER — Fri, 19 Jul 2024 00:00:00 +0000

It has been demonstrated that halophytes had the potential to accumulate heavy metals and therefore had the remediation potential of soils affected by metals. In this context, Arthrocnemum indicum was supplied with increased doses of Aluminium (Al) (200, 500, 800 µM) alone or added to NaCl (200 mM). Results demonstrated that Al was found mainly in the cell wall in the shoots and the roots.

The addition of the salt displaced the localization of Al in the roots, it was found bound to intercellular and proteiccomponents. These results suggest that the subcellular distribution of Al plays an important role in avoidance of metal toxicity.