Search

The amphipod Ericthonius didymus Krapp-Schickel, 2013 is reported for the first time outside its type locality in European waters, from the French Atlantic coast and from the Azores, Portugal. In particular, a large population was recorded in Arcachon, France. Molecular analyses were made to confirm the validity of three closely related Ericthonius species: E. didymus, E. convexus and E. pugnax. An identification key is provided, distinguishing Ericthonius species into three groups, based on the presence or absence of stridulating ridges on coxa 2 and posterodistal lobe on basis of male pereopod 5.

An examination of some benthic amphipods belonging to the genus Cheirocratus from Arcachon Bay revealed that they exhibited a combination of morphological character states that distinguished them from all previously described Cheirocratus species. In the form of the gnathopods, Cheirocratus pseudosundevallii is very close to two other European species: C. sundevallii and C. intermedius. An actualized key to the species of Cheirocratus is provided.

Hermit crabs are well-known to shelter many epibiotic, endobiotic or endolithic species in their shell, and examination of shells inhabited by hermit crabs in Arcachon Bay reveals the presence of several such species. Among them is the amphipod Monocorophium acherusicum, a species originally described from European waters and now known to be well distributed throughout the world, but not previously recorded to be commensal with hermit crabs, as reported herein.

Laticorophium baconi (Amphipoda, Corophiidae) was recorded for the first time in European marine waters from buoy fouling communities at the Sant Carles de la Rapita marina (Alfacs Bay, Eastern Mediterranean Spanish coast). Presence of juveniles, adult males, brooding and ovigerous females were indicative of a well-established population. An entire description of the species, together with a dichotomous key to Corophiini genera characterized by urosome segments fused with uropod 1 ventrally inserted, are provided. This record supports the view that L. baconi may have been overlooked and/or potentially confused with otherCorophiini species such as Apocorophium acutum in previous studies

International audience; Mercury (Hg) and methyl mercury (MeHg) concentrations have never been measured in sediments of coastal lakes of Aquitaine, although high concentrations of Hg have been measured in fish. Our objective was to characterize benthic biogeochemical processes and the distribution of Hg in lake sediments and to connect these results with fish contamination. For this, we mapped and characterized sediments. We measured sediment Hg and MeHg content, and biogeochemical parameters. We identified organic deposits in deep areas, and sandy sediments in shallow areas. Sediments were anoxic below the sediment–water interface. The average Hg concentration in organic sediment was 213 μg kg−1 dry weight. Sandy sediments had an average Hg concentration of 4 μg kg−1 dw. We measured concentrations below 6 μg kg−1 dw in sediments from streams that drain the catchment. Similar concentrations in the four lakes suggest that the source of total Hg was not a point source in a given lake. The highest MeHg concentrations were found in the upper centimetres of organic sediments, where sulphate reduction occurred. MeHg represented 2.53% of total Hg for Lake Carcans-Hourtin, less in other lakes. The proportion of MeHg in sediment followed lake water sulphate concentrations. High sulphate concentrations resulted from agricultural activity in the Lake Carcans-Hourtin catchment. Our results corroborate the hypothesis that Hg methylation is linked to sulphate-reducing activity. High fluxes of sulphate from a drainage basin may induce large proportions of potentially bioavailable MeHg in lake sediment, even in non-polluted areas. The Hg methylation activity in the sediment reflected the exposure of predatory fish to MeHg.

The common bait wormMarphysasanguinea(Montagu, 1813), originally described from the south coast of England, is the type species of the genus. This species has been widely reported from all around the world and has been considered as cosmopolitan until recently. This is partly because the original description was very brief and poorly illustrated, and also because all species superficially look similar. In order to clarify the situation,M.sanguineawas redescribed and a neotype was designated by Hutchings and Karageorgpoulos in 2003. Recently, specimens from Cornwall, close to the type locality, were sampled, examined morphologically, and used to obtain COI gene sequences for this species. Molecular results permitted us to confirm the identity and presence ofM.sanguineaalong the French coasts and to highlight the presence of inaccurate sequences of this species on GenBank. Use of this “false” cosmopolitan species at a worldwide scale by many biologists is also discussed in this paper.

International audience; Estuarine ecosystems have been described as a mosaic of habitats exhibiting different physical, biological and chemical properties and processes. These habitats are of primary importance for fishes, providing refuges and/or food for juveniles. While it is well known that habitats contribute also to the structuration of meio- and macrobenthic assemblages, this concept of habitat has never been associated to zooplankton communities, a major food resource for many pelagic fishes during summer in North-European estuaries. The objective of this work was thus to assess if estuarine habitats, in addition to the salinity gradient, structured zooplankton communities as well. Sampling was conducted at high tide during summer in a highly turbid system, the Gironde estuary, for which primary production and thus food resource at the basis of the food web is strongly limited. The results showed that even if the upstream-downstream estuarine gradient was the main factor structuring zooplankton at the scale of the estuary, there was a significant difference of zooplankton assemblages between samples collected over subtidal areas and those collected over intertidal areas. More particularly, the estuarine gradient was associated to the distribution pattern of species while difference between subtidal and intertidal samples were mainly due to difference in the level of abundance of species. Stable isotope analysis revealed that these zooplanktonic omnivorous species may be attracted to intertidal mudflats by microphytobenthos availability and that some planktivorous fishes, in particular Alosa fallax, preferentially fed on this zone. The role of intertidal habitats in structuring zooplankton assemblages suggests that this habitat strongly participates to the production of planktivorous species and that it represents a biotic vector of carbon resources toward subtidal areas. The loss of tidal flats habitats could thus have consequences on the functioning of pelagic system as well.

This paper presents new records of Spio symphyta Meisner et al., 2011 and Spio martinensis Mesnil, 1896 (‘Polychaeta’: Canalipalpata: Spionidae) from Arcachon Bay (southern Bay of Biscay). For both species the new records represent an extension of their known distributional range. The two species have probably been present in Arcachon Bay for several years but were confused with other species of the genus Spio. Spio symphyta was identified at five locations in Arcachon Bay in 2009 and 2013 and S. martinensis at three stations in 2012 and 2013. A detailed and illustrated description of specimens from Arcachon Bay is provided. Important characters of Spio spp. occurring in the area are compared.

The Asiatic isopod Paranthura japonica Richardson, 1909 was collected in 2007 in Arcachon Bay (SW France), where the species occurs in a variety of habitats, both in the intertidal and at shallow depths. This species, native to the Sea of Japan, may have been accidentally introduced in Arcachon Bay with oyster transfers or as fouling on ship hulls.

The mysid Heteromysis (Heteromysis) microps is reported for the first time in the Bay of Biscay. During surveys carried out between March and September 2015 in Arcachon Bay, mysid specimens were fortuitously collected from Upogebia pusilla burrows. Details on morphology, colour pattern and behaviour of H. microps are provided. Commensalism was frequently mentioned for Heteromysis species but never reported for H. microps. In this study, commensalism seems to be proved between the mysid and its host U. pusilla.

A new species of Elasmopus is described and figured from specimens collected in different benthic communities of Arcachon Bay. It can be distinguished from its closest relative E. rapax by the palmar ornamentation of male gnathopod 2 propodus (shelf and 2 teeth). It preferentially lives on hard bottoms (in mussel fouling of navigation buoys, Sabellaria spinulosa reefs, algal rocky bottoms, Laminaria and Saccorhiza bulbs and as epibiont on the carapace of Maja brachydactyla) but also less abundantly on naked sandy bottoms. An identification key of Atlantic and Mediterranean European species is also given.

Additional records of Elasmopus vachoni Mateus and Mateus, 1966 together with description of its its poorly-known mouthparts is provided, based on material from Tarifa Island (southern Spain). The known geographical distribution of this species extends from the Gulf of Guinea to the northern part of the Iberian Peninsula, all along its Atlantic and Mediterranean coast, also extending to Canary and Azores Archipelagos. Additionally, an identification key of Elasmopus species mentioned in European waters (ERMS area) is also given.

International audience; 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-site scale by exploring both biotic and abiotic factors acting at the among- and within-site scales. Results showed a 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 EuropeanWater Framework Directive (WFD). More particularly, the coastal plain estuaries displayed higher among-site 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.

The Asian date mussel Musculista senhousia, previously recorded from the Pacific coast of North America, Australasia andthe Mediterranean, is reported for the first time from the Atlantic coast of Europe in Arcachon Bay, where it occurs intertidallyand to depths of 5 m. It has been present in Arcachon Bay since 2002 and has since been found in 2006 withintwo further inlets of the Bay of Biscay, Hossegor Lake and the Bidasoa estuary. Their appearance is probably associatedwith oyster transfer from Thau lagoon in the Mediterranean Sea to Arcachon Bay.