Menzel Jemil Research Articles

First detection of the invasive protozoan Haplosporidium pinnae in the critically endangered bivalve Pinna nobilis in the Southern Mediterranean Sea (Bizerte Lagoon, Tunis) and update of its current status

Pinna nobilis (Linnaeus, 1758) populations have been severely damaged in the last few decades, and since early autumn 2016, a mass mortality event (MME) has drastically impacted populations in the Mediterranean Sea. Accordingly, the aim of the present study was to improve the knowledge on the status of P. nobilis populations in the Bizerte Lagoon (Tunisia) between 2016 and 2022. Before the MME, P. nobilis was found in the lagoon at depths from 1.5 to 6 m, with a density ranging from 2 to 30 ind/100 m². After the MME, mortality reached 100% in the monitored area, except in the eastern part of the Bizerte Lagoon near the Menzel Jemil site, where some living specimens were detected. Moreover, in 2022, successful recruitment was observed in the lagoon. Additionally, our results revealed the presence of Haplosporidium pinnae and Mycobacterium sp. in some living specimens sampled in the Bizerte Lagoon after the MME. This finding constitutes the first detection of both pathogens in Tunisia and in the entire Southern Mediterranean Sea.

Composition of a molluscan assemblage associated with macrophytes in Menzel Jemil (Bizerte lagoon, SW Mediterranean Sea)

AbstractThe molluscan species composition and diversity associated with macrophytes was studied throughout 1 year at Menzel Jemil station (Bizerte lagoon, north‐west of Tunisia). A total of 7,539 individuals belonging to 13 species were collected. The molluscan assemblage was mainly composed of gastropods (98.12%, nine species), followed by bivalves (1.88%, four species). Hydrobia acuta ranked first with 49.97% of total abundance, followed by Bittium reticulatum (17.97%), Tritia mutabilis (11.38%), Haminoea navicula (8.98%), Phorcus articulatus (5.17%) and Cerithium vulgatum (3.94%). The large number of juvenile molluscs collected confirms the importance of macroalgae and seagrass for mollusc recruitment. Significant temporal variations of species richness, density and diversity indices of the mollusc assemblage have been observed during the year. Multivariate analyses applied to our data revealed significant relationships between the macrophyte composition and associated molluscan assemblage. The BIOENV analysis indicated that water temperature, phosphates concentration and macrophyte biomass were environmental variables most closely associated with the temporal variation of molluscan assemblage.

Temporal variation and structure of macro-epifauna associated with macrophytes in the Bizerte lagoon (Tunisia, SW Mediterranean Sea)

ABSTRACTThe temporal variation in composition and abundance of the macro-epifauna associated with seaweeds (Ulva lactuca, Cladophora sp., Gracilariopsis longissima and Gracilaria bursa-pastoris) and seagrass (Cymodocea nodosa) was investigated at Menzel Jemil station in the Bizerte lagoon. Twelve replicate samples (25 x 25 cm frame) were collected monthly from October 2009 to September 2010. Sampling data yielded 21,575 invertebrate specimens from floating seaweeds and the seagrass, belonging to 40 taxa, of which 18 species were arthropods, 13 molluscs, three echinoderms, three fishes, two polychaetes and one cnidarian. Crustaceans were the most dominant and the most species-rich group and Idotea balthica basteri the most abundant species, accounting for 28.94% of the total abundance. Minimum (9.25 ± 5.56 species) and maximum (19.75 ± 3.2 species) values of mean species richness were observed in December and June, respectively. Species richness and density of macro-epifauna showed similar trends to plant biomass and the highest values of both indices coincided with periods of maximal plant biomass. Mean values of Shannon’s index H′ and evenness J′ were low, ranging from 0.34 ± 0.02 bit to 1.08 ± 0.06 bit, and from 0.23 ± 0.03 to 0.52 ± 0.07, respectively. The high dominance of herbivores and detritivores highlighted the substantial role played by macrophytes as food source for associated macro-epifauna species. Multivariate analyses also indicated significant seasonal differences for the macro-epifauna assemblage and revealed significant relationships with environmental variables. According to the canonical correspondence analysis, concentrations of phosphates and nitrites, and temperature were the variables that explained the variation of the macro-epifauna abundance in the Bizerte lagoon.

The First Evaluation of Microplastics in Sediments from the Complex Lagoon-Channel of Bizerte (Northern Tunisia)

Microplastics (MPs) in sediments from the complex lagoon-channel of Bizerte were investigated, for the first time, to evaluate the occurrence and abundance of MPs in Tunisia. After density separation in saline solution, MPs were counted by a stereomicroscope. The number of MPs was at the range of 3–18 items/g sediment (3000–18,000 items/kg dry sediment) and the most contaminated site was of Menzel Abderrahmane (MA) followed by Carrier Bay (CB), Menzel Jemil (MJ) and Channel of Bizerte (C). The MPs gathered during the survey varied in size from 0.3 to 5 mm, and appear in a variety of shapes and colours. The dominant shape was fibre (88.88% in MA, 91.00% in CB, 82.35% in C and 21.05% in MJ). The rest of MPs are fragments whilst no micro beads were found. Colours are clear, white, blue, green, red and black. Cities discharges, fishing activity and industrial production sites are the most likely sources of MPs. This first work provides original data on the presence of MPs that determines their bioavailability to organisms as seafood, and then possibly transfers of to human. The high MP concentrations registered in the complex lagoon-channel of Bizerte suggest that this site is a hotspot for MP pollution and there is an urgency to understand their origins and effects on marine life. The results will provide useful background information for further investigations.

Distribution of four isopods (Peracarida: Crustacea) in shallow waters of the Bizerte Lagoon (Tunisia, SW Mediterranean Sea)

The distribution of four isopods – Idotea balthica basteri (Pallas, 1772), Idotea chelipes mediterranea Charfi-Cheikhrouha, 1996, Sphaeroma serratum (Fabricius, 1787), and Paracerceis sculpta (Holmes, 1904) – at Menzel Jemil (Bizerte Lagoon, North Tunisia) was analysed and then related to the variation of temperature, depth and plant biomass. The abundance of isopods showed monthly fluctuations with maxima in August and minima in December 2010. The most dominant species was I. b. basteri followed by S. serratum, with a spatial gradient in the distribution pattern of isopod species in the study area. The high density of juveniles in algae and seagrass highlights the important role played by this habitat as a nursery for species. Both dominant species were tolerant to temperature variations, with some preference values (19.73–27.73°C in I. b. basteri; up to 28°C in S. serratum) and salinity (36.7–38.6 psu in I. b. basteri; 39–39.2 psu in S. serratum). Multiple regression analysis between environmental variables and species abundance showed a positive relationship with biomass of Gracilaria bursa-pastoris and Ulva lactuca for the two species of Idotea and Sphaeroma, respectively, while abundance of P. sculpta was positively related to temperature. Biotic and environmental linking (BIOENV) analysis confirmed the greatest influence of temperature and vegetation biomass on the temporal distribution of these isopod species. A spatial distribution pattern according to successive depths was revealed.

Bioaccumulation of trace metals in Hexaplex trunculus: spatial and temporal trends from 2004 to 2011 along the Tunisian coast.

Cd, Zn, Cu, As, Fe, Cr, Ni, Al, and Pb were analyzed in the edible and inedible parts of the muricid gastropod Hexaplex trunculus sampled along the Tunisian coast in 2004, 2007, and 2011. The concentration ranges (μg/g dry weight) in the whole soft tissue were 0.1-19.2 for Cd, 198.7-564.6 for Zn, 31.9-363.1 for Cu, 12.8-177.8 for As, 35.4-179.0 for Fe, 0.0-5.8 for Cr, 0.1-4.6 for Ni, 1.0-41.4 for Al, and 0.0-0.6 for Pb. The highest concentrations were recorded in Gabès for Cd, Menzel Jemil for Zn and Cu, Bizerte channel for As, Zarat for Cr and Pb, and Tunis North Lake for Fe, Al, and Ni. The European standards compiled by FAO for mollusks were exceeded in several localities. The temporal trends revealed a decreasing metal contamination in most sampling stations from 2004 to 2011. The calculated intake of metals (μg/week/kg body weight) through human consumption of the snail edible portion varied from 0.0 to 4.4 of Cd, 55.9 to 172.1 of Zn, 8.7 to 92.7 of Cu, 3.0 to 42.6 of As, 9.5 to 49.1 of Fe, 0.0 to 1.52 of Cr, 0.0 to 1.4 of Ni, and 0.3 to 11.4 of Al. Comparison of these metal intakes with those of the standard provisional tolerable weekly intake (PTWI) values stipulated by the WHO recommends precaution in terms of human consumption of this marine snail.

The Influence of Environmental Factors on the Population Structure and Reproductive Biology of <i>Idotea balthica basteri</i> (Isopoda, Valvifera) of the Bizerte Lagoon (Northern Tunisia)

The reproductive biology of a natural population of Idotea balthica basteri (Pallas, 1772) collected from Menzel Jemil (Bizerte lagoon, Tunisia) was monthly studied from October 2009 to October 2010. Besides water temperature, salinity, turbidity, pH, and dissolved oxygen were measured. Based on the state of differentiation of individuals, the population was divided into 8 categories. Their numbers depend on the one hand to intrinsic factors imposed by the specimens and the structure of the population themselves, and to extrinsic factors due to the variability of environmental conditions on the other hand. Females were morphologically recognisable at smaller size than males. Reproductive activity, which was reflected through the presence of ovigerous females and juveniles, underwent fluctuations throughout the year, but it was continuous. Moreover, salinity, temperature, nitrates, and plant biomass have a noticeable effect on the fecundity and fertility. The Principal Component Analysis also confirmed that the richness of the water in nitrates would be favorable to fecundity and fertility of Idotea balthica basteri. However, higher phosphate concentrations, in April and May seem to have a positive effect on the sex ratio. Otherwise, the temperature would be responsible for increasing the percentage of ovigerous females.

Locomotor activity patterns of two sympatric species Orchestia montagui and Orchestia gammarellus (Crustacea, Amphipoda)

Freshly adult individuals of two sympatric species, Orchestia gammarellus and Orchestia montagui, collected in spring from the supralittoral zone of Bizerte lagoon (Northern of Tunisia) at Menzel Jemil, were housed in a controlled environment cabinet. Locomotor activity rhythm was recorded in isolated individuals and groups by infrared actograph every 20 min by a data-logger, at a constant temperature of 18 ± 0.5 °C under constant darkness. According to double-plotted actograms and waveform curves, results showed the presence of two different locomotor patterns; in fact, individuals of O. gammarellus concentrated their activity during the hours of subjective night, whereas O. montagui were active during the subjective night and beyond the subjective dawn. Furthermore, whatever the species studied, periodogram analysis indicated a distinct circadian pattern of activity. Moreover, whatever the experiment condition is, the most clearly defined rhythms were found in O. gammarellus. In contrary to O. gammarellus, the group effect on the locomotor rhythm parameters seems to be less marked in O. montagui. On the other hand, a highly inter-individual variability was observed in the activity time for these two species and especially for O. montagui groups.

Abundance and diversity of amphipods (Crustacea: Peracarida) on shallow algae and seagrass in lagoonal ecosystem of the Mediterranean Tunisian coast

Bizerte lagoon is a semi-enclosed marine ecosystem, where various types of human activities have been developed. To investigate the distribution and temporal variation of amphipod assemblage, monthly sampling was conducted at the Menzel Jemil site from October 2009 to September 2010. Atotal number of 3,620 specimens were collected from floating algae and seagrass allowing the identification of 10 amphipod species. Moreover, several indices, species richness, dominance, mean density, and diversity index were estimated to characterize the amphipode assemblage. Gammarusaequicauda wasthe most dominant species in all seasons. In addition, the minimum and maximum values of species richness of amphipod were observed in January (3 species) and April (8 species), respectively. The mean density and species richness were negatively correlated with plant biomass. Mean Shannon index (H')and evenness (J')were 1.62 ± 0.34 and 0.67 ± 0.16, respectively. Non-metric multidimensional scaling (MDS) analysis based on the mean species density showed three seasonal groups of samples. Therefore, canonical correspondence analysis (CCA) made it possible to summarize the overall situation for the species, monthly sampling, and environmental parameters on a single graph. Thus, the temperature, turbidity, and chlorophyll a content are the most often reported factors for the distribution and structure of amphipods in the Bizerte lagoon.

Life cycle and population dynamics of Idotea balthica basteri (Pallas, 1772), Isopoda Valvifera from the Bizerte lagoon (Southern Mediterranean Sea - Tunisia)

The population dynamics and life cycle of Idotea balthica basteri (Pallas, 1772) were studied at the Menzel Jemil (lagoon of Bizerte, Tunisia) based on monthly samples taken from October 2009 to September 2011. The presence of juveniles and gravid females throughout the sampling period showed that this species exhibits continuous reproduction. Sexual differentiation occurs in approximately 43–59 days. Females took 88–160 days (3–5.5 months) to reach sexual maturation, and males took 102 days (3.5 months). The fecundity and fertility values exhibited a great variation in the number of eggs and embryos or mancae inside the marsupium which was correlated with the length of the gravid females. The sex ratio underwent fluctuations throughout the sampling period but was always in favour of females. Size frequency distributions were analysed recognizing 24 cohorts during the sampling period. Six cohorts were identified in October 2009 and 18 cohorts in November 2009–September 2011. Among these latter cohorts, nine were tracked till they disappeared. The minimum average size of new cohorts ranged from 1.92 ± 0.31 to 2.97 ± 0.26 mm and the maximum values ranged from 12.83 ± 0.96 to 19.23 ± 0.56 mm. Life span was estimated at 10–14 months. I. balthica basteri, in the lagoon of Bizerte, is a semi-annual species with iteroparous females, and a bivoltine life cycle that produces two generations per year.

Associated and digenean fauna of the mussel Mytilus galloprovincialis cultured on shellfish tables in the lagoon of Bizerta (Tunisia)

1 - Shellfish tables used for the breeding in bags of the oyster Crassostrea gigas and the mussel Mytilus galloprovincialis are suitable support for rapid colonization by marine living organisms.2 - During the period, June 2008 to May 2009, monthly samples of M. galloprovincialis were collected from the mytiliculture farm situated in Menzel Jemil (Bizerta Lagoon). Specimens were analyzed to identify their associated and digenean fauna.3 - Overall samples contain 68 taxa belonging to 12 zoological classes. Crustaceans, Polychaetes and Bivalves dominated largely the associated fauna, with frequencies of 34.7%, 22.9% and 10.6% respectively. The Polychaete Myrianida pinnigera was identified for the first time in the Tunisian coast. The remaining groups of associated fauna (Ascidia, Ophiuroids, Gastropods, Actinaria, Gymnolaemata, Demosponges, Calcispongia, Turbellaria, and Echinids,) accounted for only 31.8%. Diversity indices showed a temporal variation of the taxonomic structure of listed groups related to the environmental conditions and the biological cycles.4 - The examination of ~1400 individual mussels showed the occurrence of a low number of Proctoeces maculatus sporocysts (Digenea, Fellodistomodae). Bag-shaped sporocysts containing, according to the maturation stage, germinal balls, daughter sporocysts and or cercariae colonize at the beginning of the infection, the digestive gland then gonads and totality of the mantle.

Dynamique saisonnière du genre Alexandrium (dinoflagellé potentiellement toxique) dans la lagune de Bizerte (Nord de la Tunisie) et contrôle par les facteurs abiotiques environnants

Some species of the genus Alexandrium are known as potential producers of saxitoxin, a neurotoxin that causes the paralytic shellfish poisoning (PSP) syndrome. Blooming of these species, especially in shellfish farms can affect the aquaculture production and harm human health. Seasonal dynamics of Alexandrium spp. abundance in relationship to environmental factors was investigated from November 2007 to February 2009 at six stations in the Bizerte lagoon, an important shellfish farming area situated in SW Mediterranean. The sampling stations represented different hydrological and trophic conditions: one station TJ (Tinja) is affected by the river plume; two stations (Chaara [Ch] and Canal [Ca]) are influenced by marine inflow (particularly in summer), industrial and urban effluents; and the three other stations (Menzel Abdelrahmen [MA], Menzel Jemil [MJ] and Douaouda [Do]) are located close to shellfish farms. Cell abundance of Alexandrium spp. varied among stations and months. Species of this genus showed a sporadic appearance, but they reached high concentration (0.67–7×105cells L−1). Maximal cell density was detected in autumn (November 2007; station MA), at salinity of 37.5, temperature of 16°C and NH4+ level of 55.45μM. During this month, Alexandrium spp. abundance accounted for a large fraction (61%) of the harmful phytoplankton. The statistical analysis revealed that Alexandrium concentrations were positively correlated with N:P ratio and NH4+ levels. Thus, the eutrophic waters of the lagoon favour the growth of Alexandrium, which seemed to have preference for N-nutrient loading from antrophogenic activities, as ammonium. Blooms of these potential harmful algae may constitute a potential threat in this coastal lagoon of the southern Mediterranean. Consequently, it is necessary to be well vigilant and to do regular monitoring of Alexandrium species.

Polymorphisme biochimique chez quelques halophytes autochtones du Nord Tunisien

Chemical polymorphism of some North Tunisian autochthonous halophytes. The study aims to explore and analyse osmoticums synthesized by four perennial halophytic Chenopodiaceae : Salicornia arabica, Atriplex portulacoides, Atriplex halimus and Suaeda fruticosa from Menzel Jemil, Soliman and Gammarth regions which belong to sub-humid and semi-arid bioclimatic zones. A sampling of aerial vegetative organs of these four halophytes has been made. Analyses focused on reducing sugars, starch, total proteins, soluble proteins and total lipids. Atriplex portulacoides harvested from Menzel Jemil station accumulates large amounts of starch, indicating a high photosynthetic activity. This could suggest that this species avoids drought and high salinity by an acceleration of its growth cycle and reproductive systems. Suaeda fruticosa is characterized by the highest levels in soluble sugars. This would mean that it is capable of synthesizing carbohydrate osmoticums for its osmotic adjustment. Atriplex sp. and Suaeda fruticosa have the highest levels of soluble protein indicating the possible intervention of amino acids in the regulation of intracellular osmotic pressure. This behavior was essentially observed at Soliman sampling site characterized by an upper semi-arid bioclimate and saline soils.

Imposex and butyltin concentrations in snails from the lagoon of Bizerta (Northern Tunisia)

Imposex and butyltin concentrations were assessed in Hexaplex trunculus, Conus mediterraneus, Cyclope neritea and Nassarius mutabilis from Menzel Jemil, and H. trunculus and Stramonita haemastoma from the Bizerta channel. All females of the five species exhibited the characteristic development of male sex organs (penis and/or vas deferens). In Menzel Jemil, H. trunculus and C. mediterraneus exhibit similar imposex levels and were most affected (VDS reading 3–4). The development of a bud penis or a vas deferens sequence behind the right ocular tentacle was reported in Cyclope neritea and N. mutabilis (VDS 1). The concentration of tributyltin (TBT) was similar for the four species. The monobutyltin (MBT) was only detected in C. mediterraneus while the dibutyltin (DBT) was found in all gastropods at similar proportions as TBT. In the Bizerta channel, imposex levels were similar in both H. trunculus and S. haemastoma but imposex degree was higher in H. trunculus. This finding was confirmed by higher TBT concentration recorded in female of H. trunculus. These results suggested that H. trunculus is the more suitable bioindicator for monitoring TBT pollution.

Relative Growth and Reproduction in Tunisian Populations ofHexaplex trunculuswith Contrasting Imposex Levels

The banded murex Hexaplex trunculus was sampled at Menzel Jemil and Bizerta Channel (Bizerta Lagoon, northern Tunisia) to study imposex, growth, and reproduction. Butyltin concentrations were analyzed in females from the 2 sampling sites using the gas chromatographic flame photometric detection technique. Results showed that the Bizerta Channel population was severely affected by imposex, which was confirmed by the high level of butyltins recorded in females from this site. Growth in shell width and shell weight was higher in Bizerta Channel, whereas growth in shell aperture and flesh weight was favored in Menzel Jemil. The assessment of reproductive activity, made by calculating fecundity and using 2 condition indices, showed that the Menzel Jemil population was reproductively more active.