Gulf Of Tunis Research Articles

New marine leech species of Branchellion Savigny, 1822 (Hirudinida: Piscicolidae) and new host record of Pontobdella muricata in the Gulf of Tunis

New marine leech species of Branchellion Savigny, 1822 (Hirudinida: Piscicolidae) and new host record of Pontobdella muricata in the Gulf of Tunis

Contribution of GIS to the Forecast mapping of marine flooding risk of a coastal sebkha of Soliman (Gulf of Tunis – Tunisia)

Contribution of GIS to the Forecast mapping of marine flooding risk of a coastal sebkha of Soliman (Gulf of Tunis – Tunisia)

Risk Assessment of Trace Metals Using Chemical Speciation, Bioavailability, and Cluster Analysis Around Wadi EL Bey (Gulf of Tunis, Tunisia)

ABSTRACT The Wadi El Bey is one of the most vulnerable areas to pollution in the northeast of Tunisia, altered by anthropogenic and natural processes. This study uses the Community Bureau of Reference (BCR) approach and statistical tools, particularly the student’s t-test and the cluster analysis, to evaluate the danger of metals zinc (Zn), nickel (Ni), lead (Pb), cadmium (Cd), and copper (Cu) pose. This work is to assess the long-term evolution and mobility of heavy metals in the core soils of the Wadi El Bey River Bed. Heavy metals in SC1 followed the descending order Fe>Cu>Zn>Ni>Pb>Cd and in SC2 it was Fe>Cu>Zn>Ni>Cd>Pb. The (BCR) procedure showed that in soil cores SC1 and SC2, Ni was mainly associated with the exchangeable fractions (F1). However, the Zn and Cu were linked to the residual fractions (F4). The student’s t-test confirmed that the difference in vertical distribution between the SC1 and SC2 of Zn and Pb is statistically significant (p-value<.05) contrary to Ni (P = .06), Cd (P = .79), Cu (P = .38) demonstrated a common origin for these metals in the Wadi El Bey. The cluster analysis revealed that pH was the main responsible factor influencing the migration of Cu, Ni, and Zn toward the labile fractions in SC1. Whereas the total organic carbon influenced the Zn fixation in the most stable fraction in SC2. The use of pollution indices showed strong contamination by Ni, Cu, and Cd and moderate contamination by Zn and Pb. The risk assessment code (RAC) showed that Zn and Cu had a low to medium risk whereas medium to high risk for Ni. For better management and better control of heavy metal pollution in ecosystems with intermittent regimes, we advise a tertiary treatment of wastewater before evacuating it in Wadi el Bey.

Prokaryotic Diversity and Dynamics during Dinoflagellate Bloom Decays in Coastal Tunisian Waters

(1) Background: Harmful algal blooms (HABs) can negatively impact marine ecosystems, but few studies have evaluated the microbial diversity associated with HABs and its potential role in the fates of these proliferations. (2) Methods: Marine prokaryotic diversity was investigated using high-throughput sequencing of the 16S rRNA gene during the bloom declines of two dinoflagellates detected in the summer of 2019 along the northern and southern Tunisian coasts (South Mediterranean Sea). The species Gymnodinium impudicum (Carthage, Tunis Gulf) and Alexandrium minutum (Sfax, Gabes Gulf) were identified using microscopy and molecular methods and were related to physicochemical factors and prokaryotic compositions. (3) Results: The abundance of G. impudicum decreased over time with decreasing phosphate concentrations. During the G. impudicum bloom decay, prokaryotes were predominated by the archaeal MGII group (Thalassarchaeaceae), Pelagibacterales (SAR11), Rhodobacterales, and Flavobacteriales. At Sfax, the abundance of A. minutum declined with decreasing phosphate concentrations and increasing pH. At the A. minutum peak, prokaryotic communities were largely dominated by anoxygenic phototrophic sulfur-oxidizing Chromatiaceae (Gammaproteobacteria) before decreasing at the end of the survey. Both the ubiquitous archaeal MGII group and Pelagibacterales were found in low proportions during the A. minutum decay. Contrary to the photosynthetic Cyanobacteria, the photo-autotrophic and -heterotrophic Rhodobacterales and Flavobacteriales contents remained stable during the dinoflagellate bloom decays. (4) Conclusions: These results indicated changes in prokaryotic community diversity during dinoflagellate bloom decays, suggesting different bacterial adaptations to environmental conditions, with stable core populations that were potentially able to degrade HABs.

First record of Lepidonotus tenuisetosus (Annelida: Polynoidae) from Tunisia with distributional notes

Four species of the genus Lepidonotus (Annelida, Polynoidae) have been listed in the Mediterranean, including L. carinulatus (Grube, 1869), L. squamatus (Linnaeus, 1758), L. tenuisetosus (Gravier, 1902) and L. clava (Montagu, 1808), although recent studies confirmed only the presence of the two latter. Based on materials collected in the Radès Area (Gulf of Tunis, Western Mediterranean), we provide a characterization of a population of L. tenuisetosus based on key morphological characters and body width/length relationships and conclude that all previously known Mediterranean reports from Israel, Croatia, Greece, Spain and Turkey did not belong to L. tenuisetosus, but either to L. carinulatus , L. clava or to other, non-identified species. Therefore, our finding represents not only the first correct record of L. tenuisetosus for the Tunisian waters and the Western basin, but for the whole Mediterranean Sea, and allows us to discuss on the possible reasons explaining the presence of this and other species of Lepidonotus in the Mediterranean.

Discrimination between six commercially relevant and ecologically diverse fish species across the Gulf of Tunis using fatty acid composition and otolith shape analyses

Discrimination between six commercially relevant and ecologically diverse fish species across the Gulf of Tunis using fatty acid composition and otolith shape analyses

The Impact of Human on the Current Environmental State of the Coastal Sebkha of Soliman (Gulf of Tunis - Tunisia)

The Impact of Human on the Current Environmental State of the Coastal Sebkha of Soliman (Gulf of Tunis - Tunisia)

Investigating otolith mass asymmetry in six benthic and pelagic fish species (Actinopterygii) from the Gulf of Tunis

Otolith mass asymmetry can significantly affect the vestibular system functionalities; usually, the X values of mass asymmetry vary between −0.2 and + 0.2 (−0.2 &amp;lt; X &amp;lt; + 0.2). These values can change during a fish life and therefore they are not related to the fish total length. We collected a total of 404 fish specimens from the Gulf of Tunis, including three pelagic species: Sardina pilchardus (Walbaum, 1792) (74 otolith pairs), Trachurus mediterraneus (Steindachner, 1868) (66 otolith pairs), and Chelon auratus (Risso, 1810) (60 otolith pairs) and three benthic species: Gobius niger Linnaeus, 1758 (77 otolith pairs), Mullus barbatus Linnaeus, 1758 (60 otolith pairs), and Trachinus draco Linnaeus, 1758 (67 otolith pairs). The relation between the total length and the otolith mass asymmetry was first calculated and compared, and then was evaluated. The comparison of the otolith mass asymmetry between benthic and pelagic species showed a significant difference (P &amp;lt; 0.05), where the absolute mean value of X does not exceed the critical value (0.2) for all the studied species. No relation has been found between the magnitude of the otolith mass asymmetry and the length in both benthic and pelagic specimens. Environmental factors have an indirect effect on somatic growth and otolith accretion. The significant difference found in this study can be due to the difference between the benthic and pelagic environments.

Spatial distribution, contamination assessment and potential ecological risk of some trace metals in the surface sediments of the Gulf of Tunis, North Tunisia

To evaluate the trace metals contamination status in the Gulf of Tunis, forty one sediment samples were analyzed using different approaches. According to certain contamination and ecological risk indices (Contamination Factor, Geoaccumulation index and Ecological risk index), Hg has the highest contamination level while pollution by Ni, Pb, Cd and Cr was absent. The highest concentrations of trace metals were found in sediments collected from the offshore and coastal areas located opposite the main exchange points with the gulf particularly, the Mejerda and Meliane Rivers, the Khalij Channel, Ghar El Melh and El Malah lagoons, Tunis Lake and Sebkhat Ariana. However, further ecological indices (Potential ecological risk index, Toxic unit and Mean effect-range median quotient) and comparison with sediment quality guidelines suggest that in addition to Mercury, Cr, Pb and Ni concentrations are detrimental to biota in both the offshore and areas near to the exchange points with the gulf. Moreover, in these areas the results from sequential extraction and individual contamination factor calculation pointed to the mobility and bioavailability of Cr, Pb and Ni.

ASSESSMENT OF TRACE ELEMENTS UPTAKE ON THE INVASIVE CRAB PORTUNUS SEGNIS HEPATOPANCREAS USING A MULTIVARIATE BIOCHEMICAL APPROACH

In the current investigation, we evaluated the biological consequences of trace elements contamination in the two Tunisian gulfs (Gabes gulf and Tunis gulf) on the blue swimming crabs hepatopancreas (Portunus segnis). The concentrations of three trace elements (cadmium, copper, and lead) in the hepatopancreas P.segnis were evaluated. Additionally, acetylcholinesterase (AChE), metallothioneins (MTs), hydroxide peroxidase (H2O2) and advanced oxidation protein products (AOPP) levels, were chosen as measurements to evaluate the environmental effects on the two crabs’ populations from different gulfs. Macromolecular (lipids, proteins, and DNA) were also determined in P.segnis hepatopancreas. The results of trace elements bioaccumulation in soft P. segnis hepatopancreas showed a high pollution in the Gabes gulf as evidence by significant accumulation of cadmium, cooper, and lead. These findings were confirmed by significant increases of metal pollution index (MPI) and metallothioneins (MTs) levels in the hepatopancreas of P. segnis from Gabes gulf than these from Tunis gulf. Consequently, the trace elements accumulation in P.segnis from Gabes gulf conduct to the generation of lipid peroxidation processes as documented by the high levels of H2O2and LOOH. A significant decrease of AChE activity was recorded in crabs collected from Gabes gulf as compared to these from Tunis gulf. The present study revealed depletion of proteins and lipids contents, while DNA showed significant degradation on crab hepatopancreas collected from Gabes gulf comparing to Tunis gulf. These evidences must be taken in consideration when using P. segnis as an ecological indicator species in the biomonitoring programs.

First record of Marphysa chirigota (Annelida: Eunicidae) in the Mediterranean Sea (Gulf of Tunis)

To date, the genus Marphysa is represented by only three species, Marphysa sanguinea, Marphysa aegypti and Marphysa birgeri in the Mediterranean Sea. Combining morphological, molecular data (16S rRNA and cytochrome c oxidase subunit I mitochondrial loci) and environmental information, we are here presenting the first Mediterranean report of Marphysa chirigota, based on the specimens collected at Radès Station (Gulf of Tunis, western Mediterranean). The current information on the distribution of of the Marphysa species strongly supports that M. sanguinea inhabits hard bottoms and has a restricted distribution close to its type location (south English coast and nearby NE European Atlantic). The specimens from Radès Station, as well as all those reported as M. sanguinea along the Tunisian coast, were found in the shallow water soft bottoms. Therefore, we suggest that the presence of M. sanguinea in Tunisia seems is doubtful, and all Marphysa species reports from Tunisia might correspond to M. chirigota.

Distribution and assessment of trace metal contamination in the surface sediments of the Meliane River and the Coast of the Gulf of Tunis (Tunisia, Mediterranean Sea)

The Meliane River, the second longest and most important river in Tunisia, is one of the major rivers that flow into the Gulf of Tunis. However, it is known by its significant discharges of urban and industrial activities that have seriously affected the quality of the aquatic ecosystem. The highest amounts of Cadmium (Cd), Copper (Cu), Lead (Pb), Zinc (Zn), Nickel (Ni), Chromium (Cr) and Manganese (Mn) in the surface sediments of the Meliane River indicate that the downstream part is the most polluted area. The chemical speciation shows that the majority of the trace metals are bound to a reducible fraction (Zn, Mn, Cr and Ni) and the Pb and Cu are bound to the oxidizable fraction. The Cd is linked to the exchangeable fraction, which indicates its high mobility and toxicity. Both the contamination and enrichment factors values of some trace metals are elevated in the downstream part of the Meliane River. The percentage of the risk assessment code in Cd is 59.8%, which presents a very high environmental risk. Therefore, the spatial distribution of trace elements in the surface sediments is characterized by its high concentration of metals in the downstream part of the Meliane River. These concentrations decrease as a function of change in the physicochemical parameters from the freshwater-saltwater mixing zone to marine stations.

Alarming coastal vulnerability of the deltaic and sandy beaches of North Africa

The arid coasts of North Africa, extending over 4633 km from the Gulf of Tunis to the Nile Delta, are undergoing pronounced shoreline retreats and coastal floodings that are reported as a consequence of the ongoing sea level rise resulting from global warming. Of particular interest are the abnormal shoreline dynamics for deltaic and sandy beaches, which are severely impacted by abrupt decadal variabilities in both climatic and anthropogenic drivers resulting in their increased vulnerability to disturbances from coastal hazards. Unfortunately, the evolution, distribution and impacts of these drivers remain largely unquantified, let alone understood, for these extensive arid coasts that harbor the major portion of North Africa’s population as well as unique and fragile marine ecosystems. To address this deficiency, we use GIS-based multi-criteria approaches combined with analytic hierarchy process to map the Coastal Vulnerability Index and the Socioeconomic Vulnerability Index along these coasts to investigate the amplitude and extent of shoreline deterioration resulting from sudden fluctuations in sediment transport to the coastline. We use the western bay of the Gulf of Tunis, the coasts of Tripoli and the Nile Delta as three validation sites for our vulnerability assessment. The statistical Integrated Coastal Vulnerability Index map reveals that 47% of arid North African coasts are characterized by high to very high vulnerability. In particular, we observe that the densely populated deltaic coasts in both Tunisia and Egypt are 70% more vulnerable than any others coast in the eastern Mediterranean Basin. These abnormally high-vulnerability extensive areas are also correlated with significant deterioration of coastal aquifers and hence in crop production, compromising local food security and resulting in increasing outflow migration trends. Both Tunisia and Egypt observed dramatic increases in the net population outflow migration by respectively 62% and 248% between 2000 and 2016, mostly from coastal areas. Our source analysis of the amplitude and extent of these high coastal vulnerabilities suggests that they result from the anthropogenic drivers of damming and rapid urban growth over the last few decades rather than the effects of global warming.

Age, growth and mortality of the striped seabream Lithognathus mormyrus (Linnaeus, 1758) in the Gulf of Tunis (Central Mediterranean Sea)

AbstractDespite the high commercial value of the striped seabream Lithognathus mormyrus (Linnaeus, 1758) in the Gulf of Tunis, biological data on its age, growth and exploitation rate are lacking. With the aim of estimating growth parameters, 516 individuals, ranging from 6–27.5 cm total length and from 3.5–293.5 g total weight, were collected from the artisanal fishing fleet between February 2014 and July 2016. The somatic growth presented a positive allometry and was described by the equation TW = 6.54 10−3TL3.213. The monthly analysis of the marginal increment of the otoliths revealed that only one annulus was deposited per year. The estimated von Bertalanffy growth parameters were: L∞ = 30.18 cm, k = 0.303 year−1 and t0 = −1.42 years. Total and natural instantaneous rates of mortality were respectively Z = 0.784 year−1 and M = 0.698 year−1. Exploitation rate (E = 0.1) showed that the Gulf of Tunis stock of L. mormyrus is not overexploited. The estimated length class giving highest yield (Lopt) was 17.15 ± 1.71 cm.

Mobilisation and dynamics of energy reserves in different tissues of Donax trunculus (Bivalvia: Donacidae) in the Gulf of Tunis (eastern Mediterranean Sea, Tunisia)

Seasonal changes in condition index and the biochemical components (proteins, lipids and glycogen) of the gonad/digestive gland, foot, labial palp, mantle, gills and adductor muscles of Donax trunculus Linnaeus, 1758 from the Gulf of Tunis were monitored seasonally, from November 2006 to October 2007, in relation to environmental conditions and reproductive events. The condition index increased during late gametogenesis and the ripe stage, coinciding with enrichment of the water by phytoplankton, and decreased during late summer and autumn (i.e. the spawning and rest periods). Glycogen increased during early gametogenesis and peaked during winter, pointing to its mobilisation in the formation of active ripe gametes. The foot, gonad/digestive gland, and adductor muscle were the three major glycogen-reserve tissues. Protein content was high during the end of summer in the whole individual and during autumn in the gonad/digestive gland. Lipid content started to increase as gametogenesis began, reached its peak at gonad ripeness and during the early spawning stage (summer) and sharply declined due to the shedding of gametes (autumn). A transformation of glycogen for de novo synthesis of lipids, in the gonad/ digestive gland, was suggested during the later stages of the gonadic cycle, in support of gametogenesis. Temporal fluctuations in environmental factors, particularly temperature and food supply, drive the cycle of storage and utilisation of metabolic energy reserves which in turn govern gametogenesis in Donax trunculus.

Late Miocene-Quaternary thrusting in the Utique-Kechabta foreland basin of the Tell, Northern Tunisia

Northern Tunisia is characterized by a complex orogenic system, the Tell fold-and-thrust belt (FATB), part of the Maghrebides, associated, to the South, to the Atlas FATB intra-continental chain. The South Tellian Front (STF) separating the two FATBs is bounded by Upper Miocene to Quaternary of the Mejerda wedge-top basin to the South-West and Utique-Kechabta basin to the North-East. The first one corresponds to an extensional basin developed during the Late Miocene to Quaternary compressions. On the other hand, field mapping and seismic profiles interpretations indicate that the Utique-Kechabta is characterized by tectonic accretion, thrusting of the Tell onto its foreland basin. In Bizerte Area (to the North of Utique-Kechabta basin), the subsurface structures underneath the Tell are characterized by pop-up/pop-down structures and important horizontal displacement. These Tellian structures are transported toward the SE over the major decollement level which corresponds to the Triassic salt and bounded southeastwards by the South Tellian Front. The latter, separating the Tell, propagates through Utique-Kechabta basin within the Upper Miocene series and cutting through apical parts of Triassic diapiric structures with transported salt plugs. The drastic change of the structural style from the Mejerda to the Utique-Kechabta basins can be partly controlled by the evaporites differential repartition, from Tell to Atlas. A tentative facies distribution map of the Late Triassic is presented, and it shows an evaporitic dominant facies in onshore Tunisia and along its coast, except in and Gulf of Tunis characterized by carbonate facies. These carbonates are analog of the dolostones of Southern Sicily known as good source rock and then offer an interesting potential to the Petroleum exploration in North Tunisia.

Grain-size trend and ecological state of southern mediterranean coastal lagoons: Case of the Gulf of Tunis

Coastal lagoons are among the highest biological productive ecosystems; they offer a variety of habitats and feeding grounds for several species. These ecosystems are besmirched by human activities which entail the degradation to their environmental aspects. The purpose of this study is the identification of the grain-size characteristics and the unprecedented recognition of the vegetation cover, so as to assess the ecological state and the water body quality of Kalâat Andalous lagoon: a fast changing ecosystem under its dynamic sandy spit and human pressures. The methodology is based on the sedimentological analysis and the microfauna identification. The study of the environmental quality of the lagoon was built on an unprecedented identification of the macrophyte communities and the use of diversity indexes and the EXCLAME indicator; the latter combines the taxonomic composition and the species abundance. The sedimentological investigations showed that the northern and southern areas of the lagoon, as well as its channel area are all dominated by a sandy facies provided by the continental shelf i.e. the nearshore zone. The central area of the lagoon is characterized by the finest grain size facies (<0.063 mm) mostly supplied by the aeolian terrestrial fluxes and the delta flood yields. The harvested pelagic and benthic microfauna indicated that the lagoon is supplied by sediments of mixed continental-fluvial and marine origins. The inventory of macrophytes demonstrates the presence of 19 species, five of which are reference species. The dominant taxa are those of Green algae (53%) with several opportunistic and invasive species with a high outbreak altering the ecosystem's natural balance, then Brown algae (21%), Red algae (16%) and angiosperms (10%). Those results, along with the biodiversity indexes outcomes, revealed the quality loss of the ecosystem and the water eutrophication. The lagoon floristic communities are slightly unbalanced, which might be due to the natural disturbance and the anthropogenic activities. Those results conform to the EXCLAME indicator (EQRMAC = 0.24), illustrating the poor ecological state of the Kalâat Andalous lagoon water body.

Significance of 2-methylhopane and 22,29,30Trisnorhop17(21)-ene biomarkers in holocene sediments from the Gulf of Tunis - Southern Mediterranean Sea

The investigation of lipid biomarkers in sediments deposited during the Holocene in the Lagoon of Tunis, located at the southern edge of the Mediterranean Sea, revealed two important hopanoid biomarkers: 2-methylhopaneand 22,29,30 trisnorhop-17(21)-ene. These compounds are considered of special interest because they reveal information about climate conditions during the Late Holocene sediment deposition. These hopanoids, or bacteriohopanepolyols (BHPs), indicate a considerable bacterial contribution to the organic matter preserved in these sediments.The occurrence of 2-methylhopanein substantial amounts indicates that cyanobacteria, Rhodopseudomonas palustris bacteria, and genus Desulfovibriobacteria communities made large contributions to the sediment's organic content. In addition, the presence of these bacteria communities have been interpreted as reliable indicators of hydrologic modifications associated with the development of wetland systems during the Late Holocene.The occurrence of 22,29,30trisnorhop17(21)-ene also suggests a considerable bacterial contribution to the organic matter and indicates an immature diagenesis stage. It also reflects the development of favourable conditions to the preservation and accumulation of organic matter within an anoxic depositional environment.

Study of organic pollution in superficial sediments of Meliane river catchment area: aliphatic and polycyclic aromatic hydrocarbons.

Organic contaminants can be accumulated in aquatic systems even at trace concentrations with potential threats to the environment and human health. The present study has been performed to evaluate the effects of organochlorines and polyaromatic hydrocarbons on surface sediments of the Meliane river catchment. Their determination provides an essential scientific approach for a better understanding of the expected sources and the processes of bioaccumulation. The concentrations of saturated hydrocarbons in extractable organic matter of the dry sediment were found ranging from 0.58 to 3 83μgkg-1 and PAHs content ranged from 63 to 131μgkg-1. These results indicated the adherence of Oued Meliane to the pollution of the Tunis Gulf. The fraction of saturated hydrocarbons extracted from the sediments of Oued Meliane included a majority of organic compounds of biogenic nature with a small oil input. In addition, characterization with the TAR index and the LMW/HMW index confirmed that terrigenous inputs in this fraction are more abundant than aquatic inputs. The characterization of PAHs fraction has shown its pyrolitic origin with a predominance of high molecular weight PAHs.

Ceratomyxa mennani n. sp. (Myxosporea: Bivalvulida) parasitizing the gallbladder of the dusky grouper Epinephelus marginatus (Serranidae) from Tunisian waters.

Ceratomyxa mennani n. sp. is a new coelozoic Ceratomyxa species found in the gallbladder of Epinephelus marginatus from the Gulf of Tunis, Tunisia. Mature plasmodia were disporic, ovoid in shape measuring 9-12μm in width and 11-14μm in length. Mature myxospores were slightly crescent-shaped with almost straight posterior margin, measuring 5.8 ± 0.2 (5.4-6.1) μm in length and 12.7 ± 0.3 (11.9-13.0) μm in thickness. The two valves were unequal with rounded ends. Polar capsules were spherical, equal in size with 2.1 ± 0.2 (1.9-2.6) μm in diameter. The binucleated sporoplasm filled the entire cavity of the myxospore. Molecular analysis of SSU rDNA sequences indicated that C. mennani n. sp. was distinct from all other Ceratomyxa sequences in GenBank. Phylogenetic analysis revealed that C. mennani n. sp. clustered with Ceratomyxa species infecting Epinephelinae fishes. Seasonal prevalence of infection over oneyear was significantly higher in winter and the lowest in autumn. This is the third report of Ceratomyxa species infecting the gallbladder of Epinephelus marginatus from Tunisia and the first study to include molecular data.