First and repeated records of the tropical-temperate crab Asthenognathus atlanticus Monod, 1932 (Decapoda: Brachyura) in the eastern part of the Bay of Seine (eastern English Channel, France)

International audienceAsthenognathus atlanticus Monod, 1932, has been reported for the first time from the eastern part of the bay ofSeine (eastern english Channel). A total of 30 specimens were collected between the years 2008 and 2011, along thenormandy coast from ouistreham to Antifer, mainly on mud and muddy sand habitats, between 10 and 25 m depth. thedistribution range of A. atlanticus has been previously known to cover eastern Atlantic coasts from Angola to the westernenglish Channel, where it reached its northern limits. it is also present in the western part of the Mediterranean Sea. thechanges in the sediment composition of the eastern bay of Seine have probably led to the development of a potentiallyfavorable habitat for this species. However, the data collected have not yet been sufficient to ascertain the origin, and themethod of introduction of the eastern english Channel specimens. in the discussion, we ponder if they might haveoriginated from the western english Channel populations, and was transported as larvae in the eastern english Channel;they could have originated from a more distant population, and have been brought to the eastern english Channel throughhuman activities. each hypothesis is possible in theory

Does the hydrodynamic, morphometric and sedimentary environment explain the structure of soft-bottom benthic assemblages in the Eastern Bay of Seine (English Channel)?

International audienc

First and repeated records of the tropical-temperate crab Asthenognathus atlanticus Monod, 1932 (Decapoda: Brachyura) in the eastern part of the Bay of Seine (eastern English Channel, France)

International audienceAsthenognathus atlanticus Monod, 1932, has been reported for the first time from the eastern part of the bay ofSeine (eastern english Channel). A total of 30 specimens were collected between the years 2008 and 2011, along thenormandy coast from ouistreham to Antifer, mainly on mud and muddy sand habitats, between 10 and 25 m depth. thedistribution range of A. atlanticus has been previously known to cover eastern Atlantic coasts from Angola to the westernenglish Channel, where it reached its northern limits. it is also present in the western part of the Mediterranean Sea. thechanges in the sediment composition of the eastern bay of Seine have probably led to the development of a potentiallyfavorable habitat for this species. However, the data collected have not yet been sufficient to ascertain the origin, and themethod of introduction of the eastern english Channel specimens. in the discussion, we ponder if they might haveoriginated from the western english Channel populations, and was transported as larvae in the eastern english Channel;they could have originated from a more distant population, and have been brought to the eastern english Channel throughhuman activities. each hypothesis is possible in theory

Multiscale patterns in the diversity and organization of benthic intertidal fauna among French Atlantic estuaries

Based on a parallel sampling conducted during autumn 2008, a comparative study of the intertidal benthic macrofauna among 10 estuarine systems located along the Channel and Atlantic coasts of France was performed in order to assess the level of fauna similarity among these sites and to identify possible environmental factors involved in the observed pattern at both large (among sites) and smaller (benthic assemblages) scales. More precisely this study focused on unraveling the observed pattern of intertidal benthic fauna composition and diversity observed at among-sites scale by exploring both biotic and abiotic factors acting at the among- and within-site scales. Results showed limited level of similarity at the among-site level in terms of intertidal benthic fauna composition and diversity. The observed pattern did not fit with existing transitional water classification methods based on fish or benthic assemblages developed in the frame of the European Water Framework Directive (WFD). More particularly, the coastal plain estuaries displayed higher among-sites similarity compared to ria systems. These coastal plain estuaries were characterized by higher influence of river discharge, lower communication with the ocean and high suspended particulate matter levels. On the other hand, the ria-type systems were more dissimilar and different from the coastal plain estuaries. The level of similarity among estuaries was mainly linked to the relative extent of the intertidal “Scrobicularia plana-Cerastoderma edule” and “Tellina tenuis” or “Venus” communities as a possible consequence of salinity regime, suspended matter concentrations and fine particles supply with consequences on the trophic functioning, structure and organization of benthic fauna. Despite biogeographical patterns, the results also suggest that, in the context of the WFD, these estuaries should only be compared on the basis of the most common intertidal habitat occurring throughout all estuarine systems and that the EUNIS biotope classification might be used for this purpose. In addition, an original inverse relation between γ-diversity and area was shown; however, its relevance might be questioned