Diversité spécifique de la macrofaune benthique dans la côte ouest de la baie de Tunis et la côte de l'île de Djerba (sud-ouest de la Méditerranée)

In this study, 21 stations were sampled, 11 in the Djerba island coast and 10 in the western coast of Tunis bay. Then, samples were sifted on a square mesh of 1 mm a side, and the animals collected were identified and counted. Lacking an efficient single index suitable for application in all situations, several traditional nonparametric indices of biodiversity were selected, calculated and discussed. Results show that the community composition is totally different in the two studied sites, and, within each site, several species are common, butthey exchange the leader ranks from one station to another. For biodiversity measurement and since results show varying values depending on indices at several stations, an arithmetic mean index was calculated at each station on the basis of the most similar indices. It shows that, overall, the biodiversity is significantly higher in Tunis bay coast than in Djerba coast. These results are more reliable considering the real environmental /anthropogenic constraints imposed on both sites. Indeed, Djerba coast is subject, these last decades, to strong industrial, urban and fishing activities, causing significant regression of benthic habitats, which can led to a reduction of the biodiversity.Dans cette étude, 21 stations ont été échantillonnées, 11 dans la côte de l'île de Djerba et 10 dans la côte ouest de la baie de Tunis. Ensuite, les échantillons ont été tamisés sur une maille carrée de 1 mm de côté, et les animaux capturés ont été identifiés et comptés. Faute d'un indice unique efficace et adapté à toutes les situations, plusieurs indices traditionnels de biodiversité ont été choisis, calculés et discutés. Les résultats montrent que la composition de la communauté est totalement différente dans les deux sites étudiés, et, à chaque site, plusieurs espèces sont communes, mais ils se substituent aux places des leaders d'une station à l’autre. Pour la mesure de la biodiversité et étant donné la grande différence dans les valeurs enregistrées par les indices retenus, une moyenne arithmétique a été calculée à chaque station sur la base des indices les plus cohérents. Elle montre que, globalement, la biodiversité est nettement plus élevée dans la baie de Tunis par rapport à la côte de Djerba. Ces résultats semblent être plus fiables tenant en compte les contraintes réelles environnementales et anthropiques imposées aux deux sites. En effet, la côte de Djerba est l'objet, ces dernières décennies, à de fortes activités urbaines et de pêche industrielle, entraînant une régression significative des habitats benthiques, ce qui peut conduire à la réduction de la biodiversité

Structuring factors of the spatio-temporal variability of macrozoobenthos assemblages in a southern Mediterranean lagoon: How useful for bioindication is a multi-biotic indices approach?

International audienceThe authors investigated the impact of the extension of the El Kantra Channel on the composition and structure of macrobenthic assemblages in Boughrara Lagoon (Gulf of Gabes, Tunisia along with the use of 4 biotic indices (AMBI, BENTIX, M-AMBI and TUBI). Thirteen stations were sampled seasonally in 2012–2013. Forty-one species were found in 2012–2013 not recorded in 2009–2010, including 20 species of polychaetes belonging to the trophic groups of deposit-feeders and carnivores which are expected to increase in areas disturbed by organic pollution. During the survey, we recorded a high fish mortality, essentially caused by the development of harmful algal blooms (HAB) which increased organic matter deposition, thus inducing polychaete development. This seems to weaken the bio-indicating power of biotic indices used here which, paradoxically, classified all sampled stations at a high ecological status. A review of these indices and their applicability to all marine environments is recommended

First record of Naineris setosa (Verrill, 1900) (Annelida: Polychaeta: Orbiniidae) in the Western Mediterranean Sea

International audienceThe Polychaeta Naineris setosa (Verrill, 1900) is reported for the first time in the Western Mediterranen Sea. Several specimens were collected in 2012 and 2013 in Boughrara Lagoon (Tunisia). The vector of introduction of N. setosa likely commercial shipping because Gabes is an international harbour with dense shipping traffic. A detailed description of specimens from Boughrara Lagoon is provided in this paper

Assessment of surface sediment dynamics and response of benthic macrofauna assemblages in Boughrara Lagoon (SW Mediterranean Sea)

International audienceA study was conducted in the spring of 2009, the winters of 2010 and 2013, and in the summer of 2012 at 13 stations in Boughrara Lagoon, Tunisia (southern Mediterranean). The country’s largest lagoon, it is considered to be an anthropogenically stressed area, though a major tourist centre—Djerba Island—is located along its northern shores. The lagoon bottoms were studied via analyses of grain size, surface sediment composition, total organic matter (TOM) and through the trophic and functional organisation of benthic macrofauna. The results indicate that the bottoms are composed of fine, medium or coarse sands and that sediment distribution is controlled by water movement. Estimation of TOM content revealed that the studied samples present both normal and imbalanced sediments. The structure and organisation of the lagoon’s benthic macrofauna are dominated by select deposit feeders and underwent significant changes during the period 2010–2013.Subjected for decades to increased pollution due to growing human activities in the surrounding area, Boughrara Lagoon now appears to be impacted by certain environmental/anthropogenic stressors, as indicated by the presence of pollution-tolerant bio-indicator species in the imbalanced area. The response of the lagoon ecosystem to changes in benthic sediment deposition provides a potential assessment tool for similar habitats elsewhere

Polychaete diversity in Tunisian waters as of 2021: an update with special emphasis on Non-Indigenous species

International audienceThe last inventory of Tunisian polychaetes diversity by Ayari et al. (2009) is updated. New records were acquired from the literature and from the current study concerning species collected in the tidal channels of the Gulf of Gabès (2016-2017) and the re-examination of some species deposited in the collection of the Tunisian National Institute of Marine Sciences and Technologies. This inventory, reviewing the taxonomy, nomenclature, and biogeographic distribution of the Tunisian polychaetes, includes 390 species belonging to 52 families, among which the Serpulidae (41 species) and Syllidae (36 species) are the most diverse. In total, 37 species previously reported are currently removed from the Tunisian polychaetes list. An additional 121 new species are added, including 23 species collected in the tidal channels and 6 species in the reference collection previously misidentified as their congeners. Morphological differences between the latter are briefly discussed and figured. Among these species, Laonice bahusiensis, Laonice norgensis, and Scolelepis neglecta are extending their Mediterranean distribution, while Sternaspis thalassemoides and Caulleriella mediterranea are probably reported for the first time after their original description. In addition, this current inventory allows us to discuss the establishment status of 17 Non-Indigenous polychaete species (14 established, 1 casual, and 2 cryptogenic) found in Tunisian waters

First report of the invasive species Branchiomma bairdi McIntosh, 1885(Annelida: Sabellidae) along the Tunisian coast (Mediterranean Sea)

International audienceThe invasive sabellid polychaete Branchiomma bairdi McIntosh, 1885 was collected in the Boughrara Lagoon (southern Tunisian coast) between 2012 and 2013. This species was originally described from Bermuda and has been widely reported in the Caribbean Sea. It has been considered as non-indigenous species on the Pacific coast of Panama and the California Gulf. Recently, B. bairdi was recorded along the Italian and Turkish coasts, Australia, Canary and Madeira Islands. It was suggested that the commercial shipping is the most likely vector for the introduction of the species to Mediterranean Sea. A description of the species along with a discussion of its systematic position and ecology are provided

Diversité spécifique de la macrofaune benthique dans la côte ouest de la baie de Tunis et la côte de l'île de Djerba (sud-ouest de la Méditerranée)

In this study, 21 stations were sampled, 11 in the Djerba island coast and 10 in the western coast of Tunis bay. Then, samples were sifted on a square mesh of 1 mm a side, and the animals collected were identified and counted. Lacking an efficient single index suitable for application in all situations, several traditional nonparametric indices of biodiversity were selected, calculated and discussed. Results show that the community composition is totally different in the two studied sites, and, within each site, several species are common, butthey exchange the leader ranks from one station to another. For biodiversity measurement and since results show varying values depending on indices at several stations, an arithmetic mean index was calculated at each station on the basis of the most similar indices. It shows that, overall, the biodiversity is significantly higher in Tunis bay coast than in Djerba coast. These results are more reliable considering the real environmental /anthropogenic constraints imposed on both sites. Indeed, Djerba coast is subject, these last decades, to strong industrial, urban and fishing activities, causing significant regression of benthic habitats, which can led to a reduction of the biodiversity.Dans cette étude, 21 stations ont été échantillonnées, 11 dans la côte de l'île de Djerba et 10 dans la côte ouest de la baie de Tunis. Ensuite, les échantillons ont été tamisés sur une maille carrée de 1 mm de côté, et les animaux capturés ont été identifiés et comptés. Faute d'un indice unique efficace et adapté à toutes les situations, plusieurs indices traditionnels de biodiversité ont été choisis, calculés et discutés. Les résultats montrent que la composition de la communauté est totalement différente dans les deux sites étudiés, et, à chaque site, plusieurs espèces sont communes, mais ils se substituent aux places des leaders d'une station à l’autre. Pour la mesure de la biodiversité et étant donné la grande différence dans les valeurs enregistrées par les indices retenus, une moyenne arithmétique a été calculée à chaque station sur la base des indices les plus cohérents. Elle montre que, globalement, la biodiversité est nettement plus élevée dans la baie de Tunis par rapport à la côte de Djerba. Ces résultats semblent être plus fiables tenant en compte les contraintes réelles environnementales et anthropiques imposées aux deux sites. En effet, la côte de Djerba est l'objet, ces dernières décennies, à de fortes activités urbaines et de pêche industrielle, entraînant une régression significative des habitats benthiques, ce qui peut conduire à la réduction de la biodiversité