Characterization of microplastics in the surface waters of an urban lagoon (Bizerte lagoon, Southern Mediterranean Sea): Composition, density, distribution, and influence of environmental factors.

Compared to open sea environments, there is still limited knowledge about microplastic levels in semi-enclosed systems such as coastal lagoons. This work aims to assess the levels of MPs in the waters of an urban lagoon (Bizerte lagoon, northern Tunisia) and to study the effects of environmental factors on their distribution and abundance. Average concentration of total MPs was found to be 453.0 ± 335.2 items m-3. The upper 25 cm water layer of the lagoon is most likely to contain ~16.99 × 109 MPs items (which correspond to a total mass of 42.47 t). Fibers were the primary MPs types encountered, and most of MPs particles identified were white and clear-colored. Polyethylene and polypropylene were the predominant polymer types in Bizerte lagoon. Among the various potential plastic sources of MPs, unmanaged domestic plastic wastes are likely to be the major source of plastic pollution in the lagoon. Several environmental factors appeared to influence the distribution and density of MPs in the lagoon waters. These information contribute to better understand the dynamics of MPs in lagoons and to develop environmental management actions.

Microplastics in edible mussels from a southern Mediterranean lagoon: Preliminary results on seawater-mussel transfer and implications for environmental protection and seafood safety.

This study assesses the microplastics (MPs) levels in mussels (Mytilus galloprovincialis) and seawater from a southern Mediterranean lagoon (Bizerte lagoon, Northern Tunisia) and discusses the potential effects of its consumption on human health. Polyethylene was the most abundant in mussels and seawater, followed by polypropylene and cellophane. The lowest and highest average MPs concentrations were recorded in the lagoon channel and southern area of the lagoon, respectively, for both mussels (2.6 ± 1.7-12.0 ± 1.4 items mussel-1) and seawater (0.2 ± 0.1-0.7 ± 0.2 items L-1). Mussels in areas highly polluted with fibers and polyethylene were found to have higher potential to ingest and/or adhere higher numbers of these particles. The annual dietary intake of MPs by Tunisians through the consumption of local mussels was estimated at 4.2 items capita-1 year-1. Even though MPs are not biodegraded and can be excreted by humans, their potential human health risks are discussed in this paper.

Bio-monitoring of metal impact on metallothioneins levels in the gastropod Phorcus turbinatus (Born, 1778) in the northeastern and the eastern coasts of Tunisia.

This work is an evaluation of metal contamination degree in Phorcus turbinatus and a monitoring of metals impact on metallothioneins functioning. The gastropod was sampled from six stations along the northeastern and eastern coasts of Tunisia during four seasons (2014-2015). Our results suggested that sedimentological metallic contents (Copper, Zinc and Cadmium) vary significantly depending on stations and not significantly according to seasons except for copper. Nevertheless, differences were no significant between stations and significant between seasons as for ambient factors, metallic intrinsic contents and metallothioneins rates. The monodonta tissue seems to be enriched in the four analyzed metals (Cu, Zn, Cd and Hg) and this species seems to have an ability to accumulate metals. Metal effect on the protein induction may be linked to physicochemical factors (temperature, O2 and Cu contents in sediment). In fact, metallothioneins levels were positively correlated to the dissolved oxygen rates and negatively linked to temperature.

Metal bioaccumulation in two edible cephalopods in the Gulf of Gabes, South-Eastern Tunisia: environmental and human health risk assessment.

Samples of Octopus vulgaris and Sepia officinalis were collected from four areas in the Gulf of Gabes, south-eastern Tunisia, and their edible tissues (mantle and arms) were analyzed for cadmium, copper, mercury, and zinc. While the concentrations of metals showed significant differences between the sampling sites, no differences were revealed between the tissues of the two species. The spatial distribution of metals analyzed showed similar pattern for both tissues of the two species, with the highest concentrations found in the central area of Gabes Gulf, and the lowest in the northern and/or southern areas. From a human health risk point of view, the highest values of estimated daily intake, target hazard quotient, and hazard index were found in the central area of Gabes Gulf. Although the results of these indices were, in general, not alarming, the health risks posed by the consumption of cephalopods on local consumers cannot be excluded.

Molecular and morphological characterisation of two species of the genus Ellipsomyxa Køie, 2003 (Ceratomyxidae) from the gall-bladder of Liza saliens (Risso) off Tunisian coasts of the Mediterranean.

During examination of some species of the family Mugilidae, two coelozoic myxozoans were observed in the gall-bladder of the leaping mullet, Liza saliens (Risso). Spore morphology allowed us to allocate them to the genus Ellipsomyxa Køie, 2003, one of which is described here as new. Ellipsomyxa kalthoumi n. sp. was observed forming globular pseudoplasmodia and free spores floating in the bile. Mature spores are ellipsoidal, measuring 13-21 × 10-15 (17.2 × 13.2) µm and possessing two equal spherical polar capsules, 5-6 (5.5) µm in diameter, opening subterminally in opposite directions, with nine polar filament coils. Morphological data and molecular analysis of the small subunit rDNA sequences helped identify this parasite as a new species of Elliposmyxa. The second species identified as E. mugilis (Sitjà-Bobadilla & Alvarez-Pellitero, 1993) has oval spores with rounded ends, measuring 10-11 × 7-9 (10.5 × 8.0) µm and possessing two polar subspherical capsules, 2.7-3.0 (2.8) µm in diameter, opening subterminally in opposite directions. Spore morphometry and molecular study of the small subunit (SSU) of the rRNA gene identified this species as E. mugilis described from the same host in the Western Mediterranean off Spain. Phylogenetic analysis revealed Elliposmyxa as a monophyletic clade and showed that E. mugilis, E. syngnathi Køie & Karlsbakk, 2009, E. adlardi Whipps & Font, 2012 and E. gobii Køie, 2003 group in a subclade containing the Tunisian isolate of E. mugilis whereas E. kalthoumi n. sp. appears in a second subclade together with four Australian species, E. maniliensis Heiniger & Adlard, 2014, E. apogoni Heiniger & Adlard, 2014, E. nigropunctatis Heiniger & Adlard, 2014 and E. arothroni Heiniger & Adlard, 2014.

Ceratomyxa tunisiensis n. sp. (Myxosporea: Bivalvulida) from the Gallbladders of Two Carangid Fish Caught Off the Coast of Tunisia.

A new coelozoic Myxozoan species, Ceratomyxa tunisiensis n. sp., was found infecting the gallbladders of two carangid fish, Caranx rhonchus and Trachurus trachurus (Perciforme, Carangidae), from the Gulf of Gabès, on the southern coast of Tunisia. The parasite develops in spherical mono-, diplo-, or polysporic tropozoites in the gallbladder of the hosts. Mature spores are typical of the genus Ceratomyxa. They are transversely elongated and narrowly crescent-shaped with a slightly convex anterior and concave posterior, and measure 23 ± 0. 27 (20-25) µm width × 6 ± 0.26 (5-8) µm in length. Spore shell valves are symmetrical with rounded ends. Two spherical polar capsules situated on either side of the sutural line measure 2.2 µm (2.0-3.0) in diam. Periodical sampling of C. rhonchus and T. trachurus from Marsh 2012 to February 2013 showed that infection due to C. tunisiensis occurs in 59% and 69% of the examined fish, respectively. Molecular analysis based on the small subunit (SSU) rRNA sequence shows high genetic divergence with all other ceratomyxid species. A Maximum Likelihood phylogenetic tree shows association with the species C. leatharjecketi Fiala, kova, Kodadkova, Freeman, Bartosova-Sojkova, and Atkinson, 2015 reported from the gallbladder of Aluterusmonoceros (L.) caught in the Andaman Sea, off Malaysia. Nonetheless, the SSU rRNA sequences of C. tunisiensis and C. leatharjecketi have only a 90% similarity.