Stéphane Sartoretto

Age of settlement and accumulation rate of submarine “coralligène” (−10 to −60 m) of the northwestern Mediterranean Sea; relation to Holocene rise in sea level

Morphological and chronological studies have been carried out on coralline algal buildups (“coralligene”) situated between 10 and 60 m depth near Marseilles, and in Corsica (France). Despite the presence of occasionally sizeable quantities of iron hydroxide, these constructions prove to be a reliable material for radiocarbon dating. Ages obtained using this method range from 640±120 yrs B.P. (Corsica, Scandola Natural Reserve, −15 m) to 7760±80 yrs B.P. (Marseilles, Grand Congloue, −52 m). Internal erosion surfaces within the buildups give evidence of discontinuous development. The accumulation rate of the coralligene constructions is very low (0.006–0.83 mm yr−1 according to the depth and time period). The higher values (0.53–0.83 mm yr−1) were recorded for the deeper constructions. They correspond to a period between 8000 and 6000 yrs B.P. After 6000 yrs B.P., the only appreciable accumulation rates (0.11–0.42 mm yr−1) were recorded for constructions situated between 10 and 35 m depth, whereas the accumulation rates of deep coralligene (> 50 m) appear to be low or zero. The age of the large constructions (overhang: ⩾ 80 cm in width) is positively correlated with depth (r = 0.95; p < 0.005). Their development occurred during the Flandrian transgression. The oldest structures, today situated at 50 to 60 m depth, started to develop when water depth was probably no greater than 10 to 15 m. Apart from in strongly shaded fissures on rocky coasts and areas subjected to heavy sedimentation, the main framework building algal species was initially Mesophyllum lichenoides (Ellis) Lemoine, a high tolerant species to light, hydrodynamic energy and temperature. With the rise in sea level, the coralligene structure gradually became available to other less tolerant algal species (Lithophyllum, Lithothamnion), and the crustforming population diversified. Because of the good preservation of coralligene structures, the reliability of radiocarbon dating and the correlation between the age and bathymetric position of the large coralligene structures (except in areas of heavy sedimentation and fissures in shallow rocky coasts), these buildups are considered to be of use as biological indicators of variations in sea level.

An integrated method to evaluate and monitor the conservation state of coralligenous habitats: The INDEX-COR approach

A new method based on photographic sampling coupled with in situ observations was applied to 53 stations along the French Mediterranean coast, to assess the integrity of coralligenous reefs affected by different levels of anthropogenic pressure. The conservation state of the assemblages characterizing these habitats was then assessed by an index - the INDEX-COR - that integrates three metrics: (i) the sensitivity of the taxa to organic matter and sediment deposition, (ii) the observable taxonomic richness, and (iii) the structural complexity of the assemblages. The sensitivity of INDEX-COR was tested and showed good correlation with the Level of Pressure calculated for each station according to expert judgment and field observations.

Comparative mitogenomics, phylogeny and evolutionary history of Leptogorgia (Gorgoniidae)

Molecular analyses of the ecologically important gorgonian octocoral genus Leptogorgia are scant and mostly deal with few species from restricted geographical regions. Here we explore the phylogenetic relationships and the evolutionary history of Leptogorgia using the complete mitochondrial genomes of six Leptogorgia species from different localities in the Atlantic, Mediterranean and eastern Pacific as well as four other genera of Gorgoniidae and Plexauridae. Our mitogenomic analyses showed high inter-specific diversity, variable nucleotide substitution rates and, for some species, novel genomic features such as ORFs of unknown function. The phylogenetic analyses using complete mitogenomes and an extended mtMutS dataset recovered Leptogorgia as polyphyletic, and the species considered in the analyses were split into two defined groups corresponding to different geographic regions, namely the eastern Pacific and the Atlantic-Mediterranean. Our phylogenetic analysis based on mtMutS also showed a clear separation between the eastern Atlantic and South African Leptogorgia, suggesting the need of a taxonomic revision for these forms. A time-calibrated phylogeny showed that the separation of eastern Pacific and western Atlantic species started ca. 20Mya and suggested a recent divergence for eastern Pacific species and for L. sarmentosa-L. capverdensis. Our results also revealed high inter-specific diversity among eastern Atlantic and South African species, highlighting a potential role of the geographical diversification processes and geological events occurring during the last 30Ma in the Atlantic on the evolutionary history of these organisms.

A new genus of soft coral (Cnidaria, Octocorallia) from the Republic of Congo (Pointe-Noire Region)

Abstract A new genus of soft coral from the Republic of Congo is described, Complexum gen. n. Nine West African octocoral species previously described in the genus Alcyonium by Tixier-Durivault (1955) are referred to this new genus, and a new species is described and figured, Complexum pusillum sp. n. The new species is characterized by having encrusting growth form and abundant spiny clubs in the surface of the polyparium. It colonizes shallow calcareous rocky banks (5 to 20 m depth) existing in coastal water of the region of Pointe-Noire. Based on molecular phylogeny this new genus is well separated from Alcyonium species.

CIGESMED : Coralligenous based Indicators to evaluate and monitor the "Good Environmental Status" of the Mediterranean coastal waters

Melih Ertan CINAR1, FERAL2 J-P., ARVANITIDIS3 C., DAVID2 R., TAŞKIN4 E., DAILIANIS3 T., DOĞAN1 A., GEROVASILEIOU5 V., DAĞLI1 E., AYSEL6 V., ISSARIS3 Y., BAKIR1 K., SALOMIDI3 M., SINI5 M., ACIK6 S., EVCEN1 A., DIMITRIADIS5 C., KOUTSOUBAS5 D., SARTORETTO7 S., ONEN1 S. and with contributors* 1 Ege University, Faculty of Fisheries, Izmir, Turkey; 2CNRS-IMBE, France; 3HCMR, Greece; 4CBU, Turkey; 5NMPZ, Greece; 6DEU, Turkey; 7IFREMER, France *(list on www.cigesmed.eu)