Spatial and interannual variations of phytoplankton diversity were characterized along the French Atlantic Coast in relation to physical factors and large-scale climatic indices using phytoplankton surveys conducted from 1993 to 2010 in four geographical areas. This study relates phytoplankton diversity to oyster recruitment success by comparing a 'specific' versus a 'functional' diversity approach. Functional diversity was represented by functional groups of different phytoplanktonic functional traits (size, shape, toxicity), relevant for oyster feeding during growth, reproduction and larval development. Phytoplankton diversity patterns along the French Atlantic coast corresponded to a geographical distribution mainly driven by a latitudinal gradient and hydrodynamic features as confirmed by the functional characteristics of the indicator species recorded for each geographical area (C-S-R strategies of Reynolds, specific habitat). This geographical typology was less clear for functional diversity. Only few functional groups were explained by physical factors: the non-toxic small and solitary cells were in particular related to temperature, with high densities observed in the southern areas. Even if temporal variation was less important in explaining the phytoplankton diversity patterns, the main drivers explaining the interannual pattern were the large-scale climatic indices, mainly the Atlantic Multidecennal Oscillation. Functional groups were readily explained by climatic indices than species even if the relationships cannot be applied generally because of the non-linearity of the correlations (local and temporal variations). However, the potentially toxic, small and linear phytoplankton were anticorrelated to NAO. The functional approach thus brings constructive elements concerning the relationships between the prey assemblage of oysters and their physical drivers. Redundancy and co-inertia analyses appeared as complementary analyses in investigating phytoplankton pattern of variation, being particularly useful in analyzing geographical and temporal diversity fluctuation, respectively. (C) 2012 Published by Elsevier Ltd.

L’Ifremer met en oeuvre, a l’echelle de l’ensemble du littoral metropolitain, une surveillance de la qualite du milieu marin cotier pour repondre aux objectifs environnementaux de la Directive Cadre sur l’Eau (DCE), aux obligations des conventions regionales marines (OSPAR et Barcelone) et aux objectifs sanitaires reglementaires concernant le suivi de la salubrite des coquillages des zones de peche et de production conchylicoles. Cette surveillance s’appuie sur plusieurs reseaux de surveillance : le reseau de controle microbiologique (REMI), le reseau de surveillance du phytoplancton et des phycotoxines (REPHY), le reseau d’observation de la contamination chimique (ROCCH) et le reseau de surveillance benthique (REBENT). Ces reseaux sont mis en oeuvre par les Laboratoires Environnement - Ressources (LER) qui operent egalement des reseaux de surveillance de la ressource : l'observatoire national conchylicole, qui remplace depuis 2009 le reseau REMORA (reseau mollusques des ressources aquacoles) et qui evalue la survie, la croissance et la qualite des huitres creuses elevees sur les trois facades maritimes francaises ; et le reseau de pathologie des mollusques (REPAMO).

La Directive Cadre sur l’Eau 2000/60/CE etablit un nouveau cadre pour une politique communautaire dans le domaine de l’eau. Elle fixe comme objectif general l’atteinte, a l’horizon 2015, d’un bon etat ecologique et chimique des masses d’eau souterraines et de surface, ces dernieres incluant les eaux cotieres et de transition (estuaires en particulier).

Ce rapport rend compte des resultats acquis en 2007 sur les parametres hydrologiques et le phytoplancton, dans le cadre des reseaux REPHY et ARCHYD (pour les points du Bassin d’Arcachon), et celui du controle de surveillance des masses d'eau du district Adour-Garonne qui ne faisaient pas l’objet de suivi avant la mise en œuvre de la DCE. Ce document contient des resultats concernant les elements de qualite physico-chimique (oxygene dissous et nutriments pour les deux types de masses d’eau, temperature et turbidite pour les masses d’eau cotieres exclusivement). Sont egalement inclues dans ce document les donnees d'evaluation de la qualite des masses d'eau vis-a-vis de l'indicateur « phytoplancton » calculees par Soudant et Belin (2009), sur la base des donnees contenues dans la base Quadrige pour la periode comprise entre le 01/01/2002 et le 31/12/2007 . L'explication des modes de calcul de cet indicateur et des differents indices qui president a son elaboration est rapportee en annexe.

The aim of this study was to distinguish between sources of the complex variety of Marennes-Oleron Bay suspended particulate organic matter (SPOM) contributing to the tropho-dynamics of the Marennes-Oleron oyster farming bay. Basic biomarkers (Chl a, C/N and POC/Chl a ratios), carbon and nitrogen stable isotopes from SPOM were analyzed and the microalgae community was characterized. The sampling strategy was bimonthly from March 2002 to December 2003; samples were taken from an intertidal mudflat. Four main sources contributed to the SPOM pool: terrigenous input from rivers, neritic phytoplankton, resuspended microphytobenthos and periodic inputs from intertidal Zostera noltii meadows. Seasonal fluctuations were observed in both years of the study period: (1) SPOM collected in the spring of 2002 (delta C-13 = -25 parts per thousand to -23 parts per thousand) was mainly composed of fresh estuarine inputs; (2) SPOM from the summer and fall of 2002 and 2003 was predominantly neritic phytoplankton (delta C-13 = - 22 parts per thousand to - 19 parts per thousand); (3) SPOM from the winter of 2002, spring of 2003 and winter of 2003 (delta C-13 = -21 to -23 parts per thousand) was composed of a mixture of decayed terrigenous river inputs and pelagic phytoplankton, which was predominantly resuspended microphytobenthos. In the summer of 2003-the warmest summer on record in southern France and Europe-SPOM was particularly enriched for C-13, with delta C-13 values ranging from -14 parts per thousand to -12 parts per thousand. Pulses in delta C-13 values, indicative of C-13-enriched decaying materials, extended into the fall. These were attributed to benthic intertidal inputs, including both resuspended microphytobenthos and Z. noltii detritus. Changes in SPOM sources in Marennes-Oleron Bay may lead to differences in the quality of the trophic environment available for reared oysters. (c) 2007 Elsevier Ltd. All fights reserved.

Phytoplankton distribution and primary productivity were investigated in the Bay of Seine (eastern English Channel, France) in spring and early summer of 1992 and 1994. In 1992, the horizontal distribution of phytoplankton species was determined over the whole Bay of Seine. In 1994, species distribution and primary productivity were studied along the salinity gradient of the Seine plume and in the neighbouring marine waters. Phytoplankton distribution was characterised by the permanent diatom dominance from early spring to early summer. The spring bloom did not occur uniformly over the bay, but was initiated in the marine waters, in the middle of the bay and progressed towards the coast where it developed, in June, in the diluted waters of the Seine plume. Phytoplankton distribution was also characterised by the dominance of large diatoms (Rhizosolenia) in marine waters and by the dominance of small species (Skeletonema costatum, Asterionella glacialis) in the plume waters. The greatest abundance of large diatoms was generally encountered below the euphotic zone. This accumulation seemed to be related to cell sedimentation and advection of marine waters below the diluted plume waters. The daily carbon productivity range was 1.4 to 3 g m−2 d−1. The highest values were measured in the plume waters (S > 28), suggesting the primary productivity in the plume was more controlled by light than by nutrients. The photic zone productivity/ chlorophyll a ratios (P/B; producted carbon per unit of Chla) were close to 40 mg mg−1 d−1 in the plume waters. P/B exceptionally reached 90 mg mg−1 d−1 in early summer. This value corresponded to a fast growing population of S. costatum. In marine waters, P/B varied from 22 mg mg−1 d−1, in spring, to 43 mg mg−1 d−1, in early summer.

La gestion de l'eau constitue l'une des preoccupations majeures actuelles, aussi bien dans son utilisation quantitative que dans sa qualite sanitaire et environnementale. Si la protection des ressources en eau destinee a la production d'eau potable reste la principale priorite, l'utilisation de l'eau douce pour les activites humaines (urbaines, industrielles et surtout agricoles) et les rejets des eaux usees dans le milieu conditionnent en grande partie la qualite de l'environnement. Dans le cadre du SDAGE Loire-Bretagne, issu de la loi sur l'eau du 3 janvier 1992, trois SAGE ont ete programmes autour du pertuis Breton et concernent les bassins versants du Lay, de la Vendee (affluent de la Sevre Niortaise) et de la Sevre Niortaise. Ces trois SAGE sont coordonnes par une Commission de Coordination du Marais Poitevin qui a charge l'Agence de l'Eau Loire-Bretagne de proceder au lancement d'etudes. celles-ci doivent permettre de definir des objectifs de qualite et de quantite des eaux superficielles sur l'ensemble des bassins versants concernes, ainsi qu'au niveau des exutoires en mer des principaux cours d'eau, afin que les usages lies a l'eau soient preserves.

Les resultats du reseau REMI et de l’etude de salubrite 1998-2000 contractualisee entre la SRC Re-Centre-Ouest et l’IFREMER, ont etabli la responsabilite de la Sevre, du Lay et du Cure dans les episodes de contaminations microbiologiques du pertuis Breton. Toutefois, ces resultats ne permettent pas de preciser le role respectif de chaque cours d’eau. Des investigations complementaires s’averent necessaires pour repondre a cette question. Le present rapport synthetise l’ensemble resultat acquis au cours de cette etude.