Patricia Aissa

The use of acetylcholinesterase activity in Ruditapes decussatus and Mytilus galloprovincialis in the biomonitoring of Bizerta lagoon.

The variations of acetylcholinesterase activity, considered to be a biochemical biomarker of organophosphorus and carbamate compounds, was followed in Mediterranean clams (Ruditapes decussatus) and mussels (Mytilus galloprovincialis) as a function of season and sampling sites in the lagoon of Bizerta (Tunisia). Results show that acetylcholinesterase activity in clams collected from station A was the lowest and was so throughout the year. This low activity may be due to the input of non-treated waste waters in the lagoon. Heavy metal contamination has been reported in the sediments of this area, suggesting that acetylcholinesterase activity in clams may be inhibited by this type of pollution. Clams harvested from station F, a site adjacent to an agricultural area, were characterized by a decrease in acetylcholinesterase activity, especially after rain periods. Clams from station J presented the highest activity throughout the greater part of the year. This phenomenon may imply that this location is less affected by pollutants inhibiting AChE activity than the others. In the mussels from station C, located in the channel from the lagoon to the Mediterranean and submitted to pollutants (urban wastes from Bizerta and hydrocarbons from the maritime traffic), acetylcholinesterase activities were lower than in those from station J. In conclusion, the variations in acetylcholinesterase activity observed between stations in both species may be the result of pollution and of the environmental conditions.

Characterization of aerobic polycyclic aromatic hydrocarbon-degrading bacteria from Bizerte lagoon sediments, Tunisia

Aims:  To characterize polycyclic aromatic hydrocarbon (PAH)‐degrading bacteria from sediments of the Bizerte lagoon, and to determine their ability to resist other pollutants such as antibiotics and heavy metals.

Bacterial community structure of sediments of the Bizerte lagoon (Tunisia), a southern mediterranean coastal anthropized lagoon.

In order to estimate how pollution affects the bacterial community structure and composition of sediments, chemical and molecular approaches were combined to investigate eight stations around the Bizerte lagoon. Terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR-amplified 16S rRNA genes revealed that each station was characterized by a specific bacterial community structure. The combination of this data with those of chemical analysis showed a correlation between the bacterial fingerprint and the pollutant content, principally with hydrocarbon pollution. The composition of the bacterial community of two contrasted stations related to the pollution revealed sequences affiliated to α, β, γ, δ, ε subclass of the Proteobacteria, Actinobacteria, and Acidobacteria in both stations although in different extent. Gamma and delta subclass of the Proteobacteria were dominant and represent 70% of clones in the heavy-metal-contaminated station and 47% in the polyaromatic hydrocarbon (PAH)-contaminated. Nevertheless, most of the sequences found were unaffiliated to cultured bacteria. The adaptation of the bacterial community mainly to PAH compounds demonstrated here and the fact that these bacterial communities are mainly unknown suggest that the Bizerte lagoon is an interesting environment to understand the capacity of bacteria to cope with some pollutants.

Effect of permethrin, anthracene and mixture exposure on shell components, enzymatic activities and proteins status in the Mediterranean clam Venerupis decussata

Anthracene (ANT) and permethrin (PER) are two of the more toxic compounds reaching the marine environment. This study aimed to determine the impact of these molecules on Venerupis decussata, an economically important species cultured on the Tunisian coast. Shell structure and its possible transformation upon exposure to the two contaminants were studied by X-ray diffraction and gravimetric analyses. Results revealed a phase transition in shell composition from aragonite to calcite after PER exposure, to a mixture of PER and ANT (Mix) but not for ANT alone. Catalase (CAT), superoxide dismutase (SOD) and glutathione transferase (GST) activities were determined in digestive gland and gills after exposure to ANT, PER and Mix to assess the impact of the contamination on the oxidative status of V. decussata. Enzyme activities increased in the digestive gland after PER treatment and in the gills after ANT treatment. PER exposure significantly reduced the levels of free thiols and increased levels of carbonylated proteins in the digestive gland, as compared to controls. In contrast, ANT exposure significantly reduced free thiols and increased the number of carbonylated proteins in the gills. Mix induced additive effects as measured by both enzymatic and proteomic approaches. The present study suggests that PER has a strong effect on shell structure; that PER and ANT exposure generate compound-dependent oxidative stress in the tissues of V. decussata and that a mixture of the two compounds has synergistic effects on biochemical response.

Seasonal and Spatial Variability of the Community and Trophic Structure of the Benthic Macrofauna within Tunisian Lagoonal and Marine Coastal Areas (Southwestern Mediterranean)

Abstract Three Tunisian lagoon and coast locations, diversely subjected to human activities and differing according to their degree of communication with the sea, were studied seasonally. Main environmental parameters and the trophic structure and biodiversity parameters of the benthic macrofauna were determined and analysed. Results show that the sites are quite different and each one has its own seasonal fluctuation linked certainly to environmental and anthropogenic factors. In the almost-enclosed lagoon of Ghar El-Melh with high salinity, selective deposit feeders dominate in spring and summer, and in the other seasons the trophic structure is rather balanced. In the southern lagoon of Tunis where environmental factors are more fluctuating and man-made activities of Tunis City and its suburbs are more important, the community is clearly more enriched because of the strong dominance of leader species. In this site, micrograzers dominate clearly all year, with a slight increase in winter. However, in the Bay of Tunis, which is a coastal area more open to the sea, the community is clearly less enriched and no dominance of the leader species was noted. In this site, the trophic structure seems to be clearly more balanced since most trophic groups are almost equally represented.

Mussel-farming effects on Mediterranean benthic nematode communities

Mussel aquaculture activities in coastal areas are growing rapidly throughout the world, inducing an increasing interest and concern for their potential impact on coastal marine environments. We have investigated the impact of organic loads due to the biodeposition of a mussel farm in a lagoonar ecosystem of the Mediterranean Sea (Bizerta lagoon, northern Tunisia) on the benthic environment. The most evident changes in the benthic habitat under the farm were a strong reduction of oxygen penetration into the bottom sediments and a large accumulation of chlorophyll a (concentrations up to 16 μg g–1), phaeopigments (concentrations up to 48 μg g–1) and total organic matter (concentrations up to 12%). Results from univariate analysis of the nematofaunal data show that the nematode abundance increased in all the stations located inside the mussel farm (I1, I2, I3) and the site I2, located in the centre of the mussel farm, was the most affected. At this site, Shannon-Wiener index H′, species richness (d), evenness (J′) and number of species (S) decreased significantly. Results from multivariate analyses of the species abundance data demonstrated that responses of nematode species to the organic matter enrichment were varied: Mesacanthion diplechma was eliminated at the most affected station (I2), whereas the abundances of Paracomesoma dubium, Terschellingia longicaudata and T. communis were significantly enhanced. Responses of free-living nematodes to mussel farm biodeposition (elimination of some species and increase or decrease of some others) could lead to food limitation for their predators that, ultimately, could alter entire communities and ecosystems. Consequently, we suggest that site-specific hydrodynamic and biogeochemical conditions should be taken into account when planning new mussel farms, and meiobenthic communities should be monitored before and after farm development to prevent excessive modifications of benthic assemblage structure.

Changes of benthic bacteria and meiofauna assemblages during bio-treatments of anthracene-contaminated sediments from Bizerta lagoon (Tunisia)

Sediments from Bizerta lagoon were used in an experimental microcosm setup involving three scenarios for the bioremediation of anthracene-polluted sediments, namely bioaugmentation, biostimulation, and a combination of both bioaugmentation and biostimulation. In order to investigate the effect of the biotreatments on the benthic biosphere, 16S rRNA gene-based T-RFLP bacterial community structure and the abundance and diversity of the meiofauna were determined throughout the experiment period. Addition of fresh anthracene drastically reduced the benthic bacterial and meiofaunal abundances. The treatment combining biostimulation and bioaugmentation was most efficient in eliminating anthracene, resulting in a less toxic sedimentary environment, which restored meiofaunal abundance and diversity. Furthermore, canonical correspondence analysis showed that the biostimulation treatment promoted a bacterial community favorable to the development of nematodes while the treatment combining biostimulation and bioaugmentation resulted in a bacterial community that advantaged the development of the other meiofauna taxa (copepods, oligochaetes, polychaetes, and other) restoring thus the meiofaunal structure. The results highlight the importance to take into account the bacteria/meiofauna interactions during the implementation of bioremediation treatment.

Bats of Jebel Mghilla National Park (central Tunisia): first survey and habitat-related activity

We surveyed the bat fauna of the Jebel Mghilla National Park (central Tunisia) in the five main habitats from the lowland to the summit: cultivated area, open juniper (Juniperus spp.) forest, Stipa tenacessima steppe, open and dense forest of Pinus halepensis, with a special emphasis on water bodies. We mist-netted three bat species: Eptesicus isabellinus, Myotis emarginatus and Myotis punicus. We also identified echolocation calls of Rhinolophus blasii, Rhinolophus ferrumequinum, Rhinolophus hipposideros, Tadarida teniotis, Miniopterus schreibersii, Pipistrellus kuhlii, Plecotus gaisleri and Hypsugo savii. Pipistrellus kuhlii and E. isabellinus were the most active and widely distributed species. The bat fauna was richer in the dense and open pine forest than in cultivated area and open juniper forest, but water bodies are also very attractive for bats.

Apodopsyllus gabesensis n. sp.: a new species of Paramesochridae (Copepoda: Harpacticoida) from the Gulf of Gabes (south-eastern Tunisia)

Several specimens belonging to a new species of Apodopsyllus were collected during a study on the diversity of meiobenthic communities in the Gulf of Gabès, a Mediterranean shallow-water bay at the south-eastern coast of Tunisia in July 2005. The new species Apodopsyllus gabesensis n. sp. shares the characteristics of the genus such as the lack of endopods from P2 to P4 and the soft and slightly cuticularized body. Apodopsyllus gabesensis n. sp. belongs to the few known species of Apodopsyllus that are described to have comparably distinct patterns of dorsal and lateral cuticular plates and pores. Besides a typical combination of characters that clearly distinguishes the new species from its congeners, the new species shows the following unique single characters: female P5 with a hitherto unknown combination of shape of the exopodal part and shape and setation of the baseoendopodal lobe with two small stout spines; male P6 with a particular shape, and a distinct armature of the exopodal spines in P2–P4 in the male that are pinnate with very short spinules contrary to the female where spines are smooth. The genus Apodopsyllus contains 26 species with the inclusion of the new species.

Influence of Bizerte city wastewater treatment plant (WWTP) on abundance and antibioresistance of culturable heterotrophic and fecal indicator bacteria of Bizerte Lagoon (Tunisia)

The waste water treatment plant (WWTP) of the city of Bizerte concentrates different types of chemical and biological pollutants in the Bizerte lagoon (Tunisia). Considering four upstream and downstream WWTP discharge stations, seventy nine, culturable bacterial strains were isolated and identified from water and sediment as fecal coliforms, fecal streptococci, pathogenic staphylococci and non-enterobacteriacea. Fecal coliforms were most abundant (2.5 105 bacteria/mg) in sediment of WWTP discharge. Leuconostoc spp (23.1%) and Chryseomonasluteola (23.1%) were the most prevalent culturable fecal indicator bacteria (FIB) isolated at the upstream discharge stations. However, Staphylococcus xylosus (13.9%) was the most prevalent culturable FIB isolated at the WWTP discharge stations. Moreover, high antibioticresistance phenotypes were present in all sampling stations, but especially in WWTP discharge station in both water and sediment. Resistance levels in water and sediment, respectively were amoxicillin (58.8%; 34.8%), penicillin (50%; 31.6%), oxacillin (60%; 33.3%), cefotaxim (55.2%; 39.1%), ceftazidim (66.7%; 50%), gentamycin (42.9%; 38.9%), tobramycin (50%; 25%), vancomycin (33.3; 71.4%), amikacin (66.7%; 0%) and ciprofloxacin (100%; 100%). Interestingly, ß-lactam antibiotic resistant FIB were mostly isolated from water as well as from sediments of upstream and WWTP discharge station. Canonical correspondence analysis CCA correlating antibiotic resistance profile with the abiotic data showed that, in water column, culturable bacterial strains isolated in upstream WWTP discharge stations were interestingly correlated with the resistance to amikacin, oxacillin, cefotaxim, ciprofloxacin and gentamycin, however, in sediment, they were correlated with the resistance to amoxicillin, oxacillin, céfotaxim and vancomycin. Serious ß-lactams and aminoglycosides acquired resistance appeared mainly in fecal streptococci and pathogen staphylococci groups.