Distribution of benthic foraminiferal assemblages in the transitional environment of the Djerba lagoon (Tunisia)

Abstract

The eastern edge of the Djerba Island represents an important tourist pole. However, studies describing the environmental processes affecting this Island are scarce. Although never studied before, the peculiar Djerba lagoon is well known by the local population and by tourists. In July 2014, surface sediment and seawater samples were collected in this lagoon to measure grain size, organic matter content and living foraminiferal assemblages to describe environmental conditions. Seawater samples were also collected and the concentration of 17 chemical elements were measured by ICP-OES. The results show that a salinity gradient along the studied transect clearly impacts seagrass distribution, creating different environmental conditions inside the Djerba lagoon. Biotic and abiotic parameters reflect a transitional environment from hypersaline to normal marine conditions. Living benthic foraminifera show an adaptation to changing conditions within the different parts of the lagoon. In particular, the presence of Ammonia spp. and Haynesina depressula correlates with hypersaline waters, whilst Brizalina striatula characterizes the parts of the lagoon colonized by seagrass. Epifaunal species, such as Rosalina vilardeboana and Amphistegina spp. colonize hard substrata present at the transition between the lagoon and the open sea.

Alien and cryptogenic Foraminifera in the Mediterranean Sea: A revision of taxa as part of the EU 2020 Marine Strategy Framework Directive

“…The tempera-ture requirements of tropical foraminifera restrict their distributional capacity and migration towards the colder western Mediterranean, which is influenced by cold water currents from the Atlantic Ocean. Some of the larger symbiont-bearing foraminifera have reached Sicily and Tunisia (Langer & Hottinger, 2000, Langer et al, 2012El Kateb et al, 2018;Damak et al, 2019;Guastella et al, 2019), entered the Adriatic Sea (Langer & Mouanga, 2016), and continue to their range expansion towards the northwestern Mediterranean with more than 10km/yr (Langer et al, 2012;Guastella et al, 2019).…”

“…The species is widely present in the eastern Mediterranean and the Ionian Sea (Blanc-Vernet, 1969;Langer, 2008;Guy-Haim et al, 2017;Manda et al, 2020;Triantaphyllou et al, 2005;Triantaphyllou & Dimiza in Siokou et al, 2013), has recently invaded the Adriatic Sea (Langer & Mouanga, 2016), the coast of Sicily (Guastella et al, 2019) and is present along the coast of Libya (Langer unpubl. data) and Tunisia (Blanc-Vernet et al, 1979;Glacon, 1962;Langer, 2008;El Kateb et al, 2018;Damak et al, 2019;Langer unpubl. data).…”

Foraminiferal-based biotic indices to assess the ecological quality status of the Gulf of Gabes (Tunisia): Present limitations and future perspectives

“…Brackish waters, as desalination byproducts, also influence the density of subtropical living benthic foraminifera (Chesher, 1975). Similarly, ecological responses of stress-sensitive benthic foraminifera to brackish water were observed in the Djerba lagoon, on the eastern coast by (El Kateb et al, 2018a). The FI', I LS , FSI and %TS std (FSI assigned species), show impacted environment while the Foram-AMBI, %TS std (Foram-AMBI assigned species), and the exp(H') bc show good ecological conditions at Skhira (Tables 2 and 3; Fig.…”

Evolutionary significance of the microbial assemblages of large benthic Foraminifera

“…(); 61, El Kateb et al . (); 62, Pascual & Martín‐Rubio (); 63, Lévy et al . (); 64, Fajemila & Langer (); 65, McCulloch (); 66, Ebrahim (); 67, Cushman (); 68, Fajemila, Langer, & Lipps (); 69, Fujita & Omori (); 70, Bicchi, Debenay, & Pages (); 71, Whittaker & Hodgkinson (); 72, Yamano, Miyajima, & Koike (); 73, Baccaert (); 74, Renema, Beaman, & Webster (); 75, Jell, Maxwell, & McKellar (); 76, Mamo (); 77, Araújo & Machado (); 78, Barbosa et al .…”