Asari (=Manila) clam, Ruditapes philippinarum, is the second bivalve mollusc in terms of production in the world and, in many coastal areas, can beget important socio-economic issues. In Europe, this species was introduced after 1973. In Arcachon Bay, after a decade of aquaculture attempt, Asari clam rapidly constituted neo-naturalized population which is now fished. However, recent studies emphasized the decline of population and individual performances. In the framework of a national project (REPAMEP), some elements of fitness, stressors and responses in Arcachon Bay were measured and compared to international data (41 publications, 9 countries). The condition index (CI = flesh weight/shell weight) was the lowest among all compared sites. Variation in average Chla concentration explained 30% of variation of CI among different areas. Among potential diseases, perkinsosis was particularly prevalent in Arcachon Bay, with high abundance, and Asari clams underwent Brown Muscle Disease, a pathology strictly restricted to this lagoon. Overall element contamination was relatively low, although arsenic, cobalt, nickel and chromium displayed higher values than in other ecosystems where Asari clam is exploited. Finally, total hemocyte count (THC) of Asari clam in Arcachon Bay, related to the immune system activity, exhibited values that were also under what is generally observed elsewhere. In conclusion, this study, with all reserves due to heterogeneity of available data, suggest that the particularly low fitness of Asari clam in Arcachon Bay is due to poor trophic condition, high prevalence and intensity of a disease (perkinsosis), moderate inorganic contamination, and poor efficiency of the immune system. (C) 2015 Elsevier Ltd. All rights reserved.

Changes in (1) main sediment characteristics, and (2) benthic bacterial and macrofaunal communities were simultaneously addressed along an inner–outer transect within the West Gironde Mud Patch (Bay of Biscay, NE Atlantic), through the sampling of three stations (E: inner part, C: central part and W: outer part) during July 2010. Except in the top centimetre where a sandy layer was found at station E, all sediments were muddy and tended to be coarser and richer in photosynthetic pigments and particulate organic carbon and nitrogen at stations C and W than at station E. Maximum oxygen penetration depth was also lower at station E than at stations C and W. These results are consistent with: (1) the occurrence of strong hydrodynamics precluding current sedimentation in the inner part of the WGMP, and (2) conversely, inputs of particles originating from the Gironde Estuary in its central and outer part. Prokaryotic cell abundances were lower at station E than at stations C and W. Bacterial community composition also differed more clearly at station E as compared to stations C and W. Conversely, macrofaunal abundances and species richness decreased monotonously from station E to station W (i.e., along the inner–outer gradient). Macrofaunal composition strongly differed at station E on one side, and stations C and W on the other side. These results are consistent with the current paradigm regarding the long term effect of major rivers on benthic macrofauna given that strong hydrodynamics at station E precludes the sedimentation of fine particles originating from the Gironde Estuary. At last, we found no overall correlation between benthic bacterial and macrofaunal compositions, which may however clearly result from limitations in our sampling design.

Une approche de Microbial Source Tracking dite culture- et collection-dependante a ete developpee pendant 1 an pour faciliter l’identification des sources de pollution en cas d’episode de contamination fecale dans le bassin d’Arcachon (Gironde, France). Cette approche repose sur la comparaison d’une collection dite « environnementale » de genotypes obtenus dans des echantillons d’eau ou de sediment avec une collection dite « de reference » de genotypes provenant de matieres fecales d’origine connue (par exemple homme, animaux domestiques ou faune sauvage). La methode d’analyse consiste en l’isolement par culture sur milieu selectif d’indicateurs bacteriens de contamination fecale ( Escherichia coli et enterocoques fecaux) suivi d’un genotypage par Enterobacterial Repetitive Intragenic PCR (ERIC-PCR). Les caracteristiques genotypiques de chaque souche sont repertories dans une base de donnees.Pour E. coli , la base de donnees est constituee de 6 263 isolats obtenus a partir d’echantillons d’eau de mer ( n = 159), de sediments ( n = 119) et de feces d’animaux ou d’echantillons provenant de station d’epuration ( n = 169). La collection environnementale (3 565 isolats) contient 625 genotypes distinct dont 184, seulement, sont communs avec la collection de reference (2 698 isolats). Pour les enterocoques fecaux, elle est constituee de 3 941 isolats obtenus a partir d’echantillons d’eaux de mer ( n = 83), sediments ( n = 59) et feces d’animaux ou station d’epuration ( n = 128). La collection environnementale (2 013 isolats) represente 505 genotypes distincts dont seulement 137 sont communs avec la collection de reference (1 928 isolats). Seuls 29 % des 625 genotypes d’ E. coli et 27 % des 505 genotypes d’enterocoques fecaux etaient communs aux deux collections.L’analyse comparee des deux collections montre qu’une forte proportion de genotypes de la collection environnementale, 71 % pour E. coli et 73 % pour les enterocoques fecaux, n’ont ete detectes que dans l’eau ou les sediments. Cela peut suggerer l’existence d’une forte proportion de souches naturalisees.Des taux de classification correcte (ARCC) tres satisfaisants ont ete obtenus pour E. coli (65,2 %) et pour les enterocoques fecaux (ARCC = 88,7 %). De plus, nous avons pu confirmer l’origine aviaire d’une forte proportion d’isolats recueillis dans l’eau et les sediments d’un etang regulierement frequente par des canards colverts et des foulques macroules. Les valeurs d’ARCC et les resultants obtenus sur un site test valident la base de donnees constituee.

The bacterial communities associated with the cockle (Cerastoderma edule) were investigated at the individual level through a 10-month monitoring programme. Temporal changes and those changes associated with a common parasite of the cockle, Bucephalus minimus, were investigated by monthly sampling of individuals, selected based on their shell length (cohort monitoring). Cockle bacterial community abundance (CBCA) and diversity (CBCD) were estimated by epifluorescence microscopy counts and automated ribosomal intergenic spacer analysis, respectively. CBCA showed a temporal pattern peaking at 30 × 106 cells per gram of cockle flesh and intervalval liquid in October and a significant 1.8-fold increase linked with B. minimus occurrence. CBCD was characterized by 112 ± 26 intergenic transcribed spacer (ITS) per individual and showed a relative homology between individuals (52 ± 6%, Jaccard similarity) in spite of more than 30% of rare ITS. Consistent with an undisturbed evolution of the condition index of the studied cohort individuals as an estimate of their physiological state, neither temporal nor parasite-induced change in CBCA has been related to marked changes in CBCD.

This study investigated some stress (metals, parasites) and response (immunity, metallothionein) factors in two cockle and two Manila clam populations. Data from eight seasons were averaged to obtain global baseline values. Stress/response characteristics of each population were compared to population health status that was determined through population dynamics parameters. Four different scenarios were discussed: (1) a lightly stressed cockle population with correct population health but with a risk of deterioration (hot spot); (2) a lightly stressed introduced cockle population threatened of extinction. In this case ecological factors were suspected; (3) a moderately stressed clam population with moderate adaptative response. The population was sustainable but the level of stress should not increase (hotspot); and (4) a stressed clam population and unfavourable ecological conditions preventing clam settlement. This monitoring highlighted that the discrepancy between population health and stress levels could be due to insufficient response by bivalves and/or by unfavourable ecological factors.