Décembre 2005 - 45- and 70-Base DNA supramolecular polymerizations on quartz crystal microbalance biosensor
Auteurs : Lazerges M., Perrot H., Rabehagasoa N., Antoine E., Compere C.
Keywords : Supramolecular polymerizations of 45- and 70- base DNAs on the surface of an in-situ time-resolved 27 MHz quartz crystal microbalance biosensor
Décembre 2005 - Distribution of silver in mussels and oysters along the French coasts: Data from the national monitoring program
Auteurs : Chiffoleau J.F., Auger D., Roux N., Rozuel E., Santini S.
Distribution and behavior of many trace elements in the aquatic environment has been well characterized, but little is known about silver (Ag) concentrations in coastal waters, even though this element ranks among the most toxic to marine invertebrates (Calabrese et al., 1977 ; Fisher and Hook, 1997 ; Webb and Wood, 1998). Studies conducted by Flegal et al. (1995), River-Duarte et al. (1999), and Ndung'u et al. (2001), provided the first valuable data on Ag distribution in the oceanic environment, indicating that this element is found in very low concentrations in the dissolved phase. However, although silver concentrations in coastal waters do not reach the nanomolar range (Smith and Flegal, 1993 ; Squire et al., 2002), formation of a stable chloro complex enhances bioavailability and toxicity to biota (Luoma et al., 1995). Experimental studies have shown that Ag is toxic to some living organisms at environmentally realistic levels (Bryan and Langston, 1992). Silver found in the aquatic environment mainly originates in effluents from sewage treatment plants (Rozan and Hunter, 2001). Silver can therefore be used as a tracer of wastewater discharges in coastal waters (Martin et al., 1988 ; Sañudo-Wilhelmy and Flegal, 1992), for instance through the use of sentinel organisms, which concentrate bioavailable contaminants in their tissues (Stephenson and Leonard, 1994 ; Jiann and Presley, 1997 ; Riedel et al., 1998 ; Muñoz-Barbosa et al., 2000).
This study concerns biological monitoring as a means of providing a synoptic view of silver contamination in French coastal waters. The National Network for the Observation of Marine Environment Quality (RNO, the French Mussel-Watch) which has been regularly measuring concentrations of various chemical contaminants in oyster and mussel tissues for 25 years (Claisse, 1989), has been monitoring silver levels since 2003. This valuable database including data collected at 80 sampling sites distributed along the French coasts (Fig. 1), is used as a reference to provide the spatial distribution of a given contaminant (Chiffoleau and Bonneau, 1994), identify trends of contamination/decontamination (Chiffoleau et al., 2001), and detect peak concentrations due to accidental events (Chiffoleau et al., 2004). Mussels (Mytilus edulis and Mytilus galloprovincialis) and oysters (Crassostrea gigas) are collected twice a year in February and November. Sample collection (size of samples, size of animals) and treatment (cleaning, depuration, removal of soft parts from the shells, draining, homogenization, and freeze-drying) are performed according to the OSPAR Convention guidelines and the method described by Claisse (1989).
Keywords : Monitoring, silver, coastal water, mollusks
2005 - Morphological evolutions of a macrotidal bay under natural conditions and anthropogenic modifications, River, Coastal and Estuarine Morphodynamics : RCEM
Auteurs : Cayocca F.
Editions Gary Parker and Marcelo H. Garcia, Vol. 2, pp.151-159.
2005 - Allelopathic interactions among marine microalgae. In : D.V. Subba Rao Edt. Algal cultures, analogues of blooms and applications
Auteurs : Arzul G., Gentien P.
Science Publishers, Enfield (NH) USA pp 131-161.
2005 - Chapter I. Contaminants in sediments
Auteurs : Claude Alzieu, Pierre Michel, Jean-François Chiffoleau, Bernard Boutier, Alain Abarnou
Editions Ifremer, Dredging and marine environment. pp. 27-58. 2005, Ref. OU0501
L'accès des navires aux zones portuaires est assuré par le dragage de quantités importantes de sédiments. Les matériaux dragués ne peuvent être immergés que s'ils présentent toutes les garanties d'innocuité pour le milieu marin. Après un rappel sur la géochimie et la toxicité des différents contaminants qui sont adsorbés sur les sédiments, le présent ouvrage propose une approche globale de l'évaluation des risques environnementaux liés aux immersions. Les méthodes, de caractérisation des risques à partir de l'analyse chimique (Géodrisk) et de tests de toxicité sélectionnés, de bioévaluation de la qualité des sédiments par la définition d'un Indice d'évaluation de l'endofaune côtière (I2EC) et de biomonitoring actif des zones d'immersion, sont décrites de manière détaillée. Cette démarche ascendante et itérative, appliquée au contexte réglementaire français, permet de satisfaire aux recommandations des conventions internationales et en particulier aux lignes directrices OSPAR. Cet ouvrage pluridisciplinaire s'adresse aux scientifiques, techniciens et gestionnaires de l'environnement portuaire et marin.
2005 - General presentation of the Douarnenez Bay. Chapter 1. Présentation générale de la baie de Douarnenez. Chapitre 1
Auteurs : Claude Augris, Alain Ménesguen, Franck Dumas, Joël Rolet, Bernard Hallegouët
Editeur Ifremer, Atlas of the marine environment of the Douarnenez Bay (Finistere, France, Brittany). Atlas thématique de l'environnement marin de la baie de Douarnenez (Finistère, France). pp. 9-22. 2005. Ref. AT0501
On s'imagine toujours les fonds marins comme une vaste étendue monotone qui prolonge le littoral, cet espace de loisir, de découverte et de rêverie. C’est rarement le cas ! L’Atlas de la baie de Douarnenez le démontre. Pour cela, il vous faudra examiner dix grandes cartes, d’environ 1,3 m2 chacune, et lire les commentaires dans un livret d’accompagnement. Avec vos connaissances, ou vos souvenirs, en géologie et en biologie, vous allez découvrir le fond marin (n’oubliez pas de chausser des lunettes 3D pour voir en relief !), ainsi que la vallée sous-marine enfouie sous une couche meuble de sables et graviers, qui a été artificiellement dégagée. En référence à la légende locale, cette vallée a été nommée vallée d’Ys. Comme en plongée, vous observerez la nature des fonds ainsi que la faune qui y vit. Au final, rien ne vous sera inconnu sur l’état actuel et le devenir de cette baie.
Novembre 2005 - Pheopigment dynamics, zooplankton grazing rates and the autumnal ammonium peak in a Mediterranean lagoon
Auteurs : Yves Collos (Université Montpellier II), Julie Husseini Ratrema (Université Montpellier II), Béatrice Bec (Université Montpellier II), André Vaquer (Université Montpellier II), Thong Lam Hoai (Université Montpellier II), Claude Rougier (Université Montpellier II), Virginie Pons (Université Montpellier II), Philippe Souchu (Ifremer)
The dilution technique was used to estimate chlorophyll and pheopigment, net and gross production as well as zooplankton grazing over a 12-month period in a coastal lagoon in Southern France. Chlorophyll a (Cha) based gross growth rates of phytoplankton ranged from undetectable in February to 2.6 day(-1) in June, corresponding to 3.8 divisions per day. Cha-based grazing rates ranged from undetectable in February to 1.1 d(-1) in June. The seasonal growth pattern of picoplankton was similar to that of the whole community, with a peak in July, corresponding to four divisions per day. Grazing processes represented from 20 to 150% of the phytoplankton daily growth, and the grazing pressure was stronger on small phytoplankton cells than on larger cells. Gross growth rates of phytoplankton were related to zooplankton grazing rates, and both were related to water temperature. Mesozooplankton which escaped sampling or oysters had to be also invoked as additional sinks for the primary production. In the fall, pheopigment concentrations greater than chlorophyll concentrations coincided with high ammonium levels in the water column. Pheopigment a production rates were highly correlated to chlorophyll -based microzooplankton grazing rates. The pheopigment a to chlorophyll a ratio was correlated with aminonium concentrations and could be used an index of the balance between ammonium supply (degradation) and demand (uptake by phytoplankton). In addition, pheopigment degradation rates in absence of grazing could be related to irradiance, indicating photo-degradation of these compounds.
Octobre 2005 - Scaling of coastal phytoplankton features by optical remote sensors: comparison with a regional ecosystem model
Auteurs : Jean-Noel Druon (Ifremer) , S. Loyer (Atlantide) , Francis Gohin (Ifremer)
Different scales of hydrological and biological patterns of the Bay of Biscay are assessed using space-borne and airborne optical remote sensing data, field measurements and a 3-dimensional biophysical model. If field measurements provide accurate values on the vertical dimension, ocean colour data offer frequent observations of surface biological patterns at various scales of major importance for the validation of ecosystem modelling. Although the hydrobiological model of the continental margin reproduces the main seasonal variability of surface biomass, the optical remote sensing data have helped to identify low grid resolution, input inaccuracies and neglect of swell-induced erosion mechanism as model limitations in shallow waters. Airborne remote sensing is used to show that satellite data and field measurements are unsuitable for comparison in the extreme case of phytoplankton blooms in patches of a few hundred metres. Vertically, the satellite observation is consistent with near surface in situ measurements as the sub-surface chlorophyll maximum usually encountered in summer is not detected by optical remote sensing. A mean error (60C) of 50.5% of the chlorophyll-a estimate in turbid waters using the SeaWiFS-OC5 algorithm allows the quantitative use of ocean colour data by the coastal oceanographic community.
Septembre 2005 - Towards multidisciplinary indicator dashboards for coral reef fisheries management
Auteurs : Clua E., Beliaeff B., Chauvet C., David G., Ferraris J., Kronen M., Kulbicki M., Labrosse P., Letourneur Y., Pelletier D., Thébaud O., & Léopold M.
Aquatic Living Resources 18, issue 3, 199-213
The diversity of reef ecosystems, the multiplicity of reef resource uses and the breadth of the range of the island socio-cultural contexts concerned make coral reef fisheries (CRF) management in the South Pacific a complex task. The health and state of the targeted resources depend both on ecosystem characteristics (as determined by ecological and biological factors) and on fishing pressure, whose effects are only partly known. Increasing harvests from commercial and recreational fishing increasingly overlap with traditional subsistence activity, creating an important CRF management challenge. This paper presents a new approach to CRF assessment and monitoring by providing a set of multidisciplinary indicators. The fisheries system is assessed from three different viewpoints: ecology of targeted populations, exploitation and the broader socio-economic fishery context. The use of complementary indicators chosen from each of these fields could balance the chronic lack of human and financial resources for the management of these fisheries. We suggest the use of these indicators through an assessment grid or an indicator dashboard specifically adapted to given situations and management objectives determined through a participatory approach. The operational efficiency of this dashboard depends on i) dialogue between users, ii) the objectivity of the proposed monitoring, iii) the visual transcription of divergent/convergent interests amongst stakeholders, and iv) stakeholder involvement in the decision-making process. The use and constraints of such a tool are described with reference to Ouvea atoll (New-Caledonia, South Pacific) for which an analysis of available indicators for assessing fisheries status is presented.
La diversité des écosystèmes coralliens, la multiplicité des modalités d'exploitation de leurs ressources et l'hétérogénéité des contextes socio-culturels insulaires rendent complexe la gestion des pêcheries récifo-lagonaires du Pacifique sud. La santé et l'évolution de ces ressources dépendent, d'une part, des caractéristiques propres de l'écosystème (obéissant à des facteurs biologiques et écologiques) et, d'autre part, de la pression de pêche dont certains effets seulement sont établis. La pêche traditionnelle aux fins de subsistance est aujourd'hui concurrencée par des activités à visées commerciales et récréatives, qui accroissent les prélèvements et soulèvent de nouveaux enjeux de gestion. L'article propose une approche pour l'évaluation et le suivi de ces pêcheries basée sur un ensemble d'indicateurs pluridisciplinaires. Le système "Pêche" est analysé de trois points de vue complémentaires : l'écologie des peuplements exploités, l'exploitation halieutique sensu stricto et le contexte économique et social plus large des pêcheries. La mise en place d'indicateurs issus de ces trois domaines vise à compenser le manque chronique de moyens financiers et humains pour la gestion des pêcheries coralliennes des îles du Pacifique sud. Nous suggérons que leur utilisation s'effectue au travers d'une grille d'évaluation ou tableau de bord répondant à des situations précises et des objectifs de gestion définis lors d'une approche participative. La portée opérationnelle de ce tableau de bord de gestion de la pêche repose sur i) la concertation engagée entre les usagers, ii) l'objectivité du suivi préconisé, iii) la transcription visuelle des intérêts convergents et/ou divergents des acteurs, et iv) leur implication dans le processus de décision. Les modalités et contraintes d'application de cet outil sont décrites sur l'exemple de l'atoll d'Ouvéa (Nouvelle-Calédonie, Pacifique Sud), pour lequel une analyse des indicateurs disponibles pour décrire l'état des pêcheries a été réalisée.
Keywords : Coral Reefs / Fishing / Co-Management / Indicators / Dashboard
Septembre 2005 - Phytoplankton seasonal dynamics in a Mediterranean coastal lagoon: emphasis on the picoeukaryote community
Auteurs : Béatrice Bec (Université Montpellier II), Julie Husseini Ratrema (Université Montpellier II) , Yves Collos (Université Montpellier II), Philippe Souchu (Ifremer), André Vaquer (Université Montpellier II)
The dynamics of the phytoplankton community were investigated in a marine coastal lagoon (Thau, NW Mediterranean) from February 1999 to January 2000. Dilution experiments, chlorophyll a (Chl a) size-fractionation and primary production measurements were conducted monthly. Maximum growth and microzooplankton grazing rates were estimated from Chl a biomass fractions to separate pico- from nano- and microphytoplankton and by flow cytometry to distinguish between picoeukaryotes and picocyanobacteria. In spring, the phytoplankton community was dominated by Chaetoceros sp. and Skeletonema costatum, which represented most of biomass (B) and primary production (P). Nano- and microphytoplankton growth was controlled by nutrient availability and exceeded losses due to microzooplankton grazing (g). Picoeukaryote and cyanobacteria growth was positively correlated with water temperature and/or irradiance, reaching maximum values in the summer (2.38 and 1.44 day(-1) for picoeukaryotes and cyanobacteria, respectively). Picophytoplankton accounted for 57% of the biomass-specific primary productivity (P/B). Picophytoplankton was strongly controlled by protist grazers (g = 0.09-1.66 day(-1) for picoeukaryotes, g = 0.25-1.17 day(-1) for cyanobacteria), and microzooplankton consumption removed 71% of the daily picoplanktonic growth. Picoeukaryotes, which numerically dominate the picoplankton community, are an important source of organic carbon for the protistan community and contribute to the carbon flow to higher trophic levels.
Août 200 5 - The Paracentrotus lividus populations from the northern Moroccan Atlantic coast: growth, reproduction and health condition
Auteurs : Bayed A., Quiniou F., Benrha A., Guillou M.
The condition of three intertidal Paracentrotus lividus populations, which inhabit an area between Rabat and Casablanca (Morocco) known by its high wave energy and its substantial anthropogenic disturbances were described. The growth rate of the juvenile sea urchins in this intertidal zone was low compared with more sheltered populations. A sharp increase in the gonad index was observed between January and March at the beginning of a period of algal production, and was concomitant with increases in seawater temperature and food consumption rate. This gonad index increase was followed by a single spawning period occurring between March and June, probably triggered by the phytoplankton bloom induced by upwelling conditions. Larval development in all three populations was severely inhibited and could be explained, in part, by high and generalized Cu contamination throughout the region. Specific contamination of particular populations by Pb or Hg was attributed to local industries and the incomplete dispersion of pollutants in spite of the high hydrodynamics along the Moroccan Atlantic coast. One of the three populations studied showed strong indications of abnormal development; the degradation of its condition appeared to be due to the presence of a wadi (temporary river) which can seasonally reduce the salinity, directly affecting the sea urchin physiology and indirectly enhancing the metal toxicity.
Mots clés : Growth, Moroccan Atlantic, Reproduction, Juvenile, Population
Août 200 5 - Ditty Modelling report. Coastal lagoon modelling: An integrated approach
Auteurs : Annie Chapelle, Cédric Bacher (Ifremer), P. Duarte (Fernando Pessoa University), Annie Fiandrino (Ifremer), L. Galbiati, D. Marinov (JRC Ispra), J. Martinez (Murcia University), A. Norro (Royal Belgian Institute for Natural Sciences), A. Pereira (Fernando Pessoa University), Martin Plus (Ifremer), S. Rodriguez (Murcia University), G. Tsirtsis (Aegean Univ., Mytilini, Greece), J. M. Zaldívar (JRC Ispra)
Juillet 2005 - Vers des tableaux de bord d'indicateurs pluridisciplinaires pour la gestion des pêcheries coralliennes
Auteurs : Eric Clua (EPHE-CNRS), Benoit Beliaeff (Ifremer), Claude Chauvet (LERVEM), Gilbert David (Institut de Recherche pour le Développement, La Réunion), Jocelyne Ferraris (EPHE/Université de Perpignan), Mekhi Kronen (Secretariat of the Pacific Community), Michel Kulbicki (Institut de Recherche pour le Développement, New Caledonia), Pierre Labrosse (Secretariat of the Pacific Community, New Caledonia), Yves Letourneur (Centre d'Océanologie de Marseille), Dominique Pelletier (Ifremer), Olivier Thebaud ((Ifremer), Marc Leopold (Institut de Recherche pour le Développement, New Caledonia
La diversité des écosystèmes coralliens, la multiplicité des modalités d'exploitation de leurs ressources et l'hétérogénéité des contextes socio-culturels insulaires rendent complexe la gestion des pêcheries récifo-lagonaires du Pacifique sud. La santé et l'évolution de ces ressources dépendent, d'une part, des caractéristiques propres de l'écosystème (obéissant à des facteurs biologiques et écologiques) et, d'autre part, de la pression de pêche dont certains effets seulement sont établis. La pêche traditionnelle aux fins de subsistance est aujourd'hui concurrencée par des activités à visées commerciales et récréatives, qui accroissent les prélèvements et soulèvent de nouveaux enjeux de gestion. L'article propose une approche pour l'évaluation et le suivi de ces pêcheries basée sur un ensemble d'indicateurs pluridisciplinaires. Le système « Pêche » est analysé de trois points de vue complémentaires : l'écologie des peuplements exploités, l'exploitation halieutique sensu stricto et le contexte économique et social plus large des pêcheries. La mise en place d'indicateurs issus de ces trois domaines vise à compenser le manque chronique de moyens financiers et humains pour la gestion des pêcheries coralliennes des îles du Pacifique sud. Nous suggérons que leur utilisation s'effectue au travers d'une grille d'évaluation ou tableau de bord répondant à des situations précises et des objectifs de gestion définis lors d'une approche participative. La portée opérationnelle de ce tableau de bord de gestion de la pêche repose sur i) la concertation engagée entre les usagers,
ii) l'objectivité du suivi préconisé, iii) la transcription visuelle des intérêts convergents et/ou divergents des acteurs, et iv) leur implication
dans le processus de décision. Les modalités et contraintes d'application de cet outil sont décrites sur l'exemple de l'atoll d'Ouvéa (Nouvelle-Calédonie, Pacifique Sud), pour lequel une analyse des indicateurs disponibles pour décrire l'état des pêcheries a été réalisée.
The diversity of reef ecosystems, the multiplicity of reef resource uses and the breadth of the range of the island socio-cultural contexts concerned make coral reef fisheries (CRF) management in the South Pacific a complex task. The health and state of the targeted resources depend both on ecosystem characteristics (as determined by ecological and biological factors) and on fishing pressure, whose effects are only partly known. Increasing harvests from commercial and recreational fishing increasingly overlap with traditional Subsistence activity, creating an important CRF management challenge. This paper presents a new approach to CRF assessment and monitoring by providing a set of multidisciplinary indicators. The fisheries system is assessed from three different viewpoints: ecology of targeted populations, exploitation and the broader socio-econornic fishery context. The use of complementary indicators chosen from each of these fields could balance the chronic lack of human and financial resources for the management of these fisheries. We suggest the use of these indicators through an assessment grid or an indicator dashboard specifically adapted to given situations and management objectives determined through a participatory approach. The operational efficiency of this dashboard depends on i) dialogue between users, ii) the objectivity of the proposed monitoring, iii) the Visual transcription of divergent/convergent interests amongst stakeholders, and iv) stakeholder involvement in the decision-making process. The use and constraints of such a tool are described with reference to Ouvea atoll (New-Caledonia, South Pacific) for which an analysis of available indicators for assessing fisheries status is presented.
Juillet 2005 - Hydrological and biogeochemical dynamics of the minor and trace elements in the St. Lawrence River
Auteurs : B. Rondeau (St. Lawrence Centre, Environment Canada), Daniel Cossa (Ifremer), P. Gagnon (St. Lawrence Centre, Environment Canada), T. Pham (St. Lawrence Centre, Environment Canada), C. Surette (St. Lawrence Centre, Environment Canada)
Surface water samples from the St. Lawrence River were collected in order to study the processes controlling minor and trace elements concentrations (Al, Fe, Mn, Cd, Co, Cu, Ni and Zn), and to construct mass balances allowing estimates of the relative importance of their natural and anthropogenic sources. The two major water inputs, the upper St. Lawrence River, which drains waters originating from the Lake Ontario, and the Ottawa River were collected fortnightly over 18 months. In addition, other tributaries were sampled during the spring floods. The output was monitored near Quebec City at the river mouth weekly between 1995 and 1999. Dissolved metal concentrations in the upper St. Lawrence River carbonated waters were lower than in the acidic waters of the tributaries draining the crystalline rocks of the Canadian shield and the forest cover. Biogeochemical and hydrodynamic processes occurring in Lake Ontario drive the seasonal variations observed in the upper St. Lawrence River. Biogeochemical processes relate to biological uptake, regeneration of organic matter (for Cd and Zn) and oxyhydroxide formation (for Mn and Fe), while hydrodynamic processes mainly concern the seasonal change in vertical stratification (for Cd, Mn, and Zn). In the Ottawa River, the main tributary, oxyhydroxide formation in summer governs seasonal patterns of Al, Fe, Mn, Cd, Co and Zn. The downstream section of the St. Lawrence River is a transit zone in which seasonal variations are mainly driven by the mixing of the different water masses and the large input of suspended particulate matter from erosion. The budget of all dissolved elements, except Fe and Zn, was balanced, as the budget of particulate elements (except Cd and Zn). The main sources of metals to the St. Lawrence River are erosion and inputs from tributaries and Lake Ontario. Direct anthropogenic discharges into the river accounted for less than 5% of the load, except for Cd (10%) and Zn (21%). The fluxes in transfer of dissolved Cd, Co, Cu and Zn species from the river to the lower St. Lawrence estuary were equal to corresponding fluxes calculated for Quebec City since the distributions of dissolved concentrations of these metals versus salinity were conservative. For Fe, the curvature of the dilution line obtained suggests that dissolved species were removed during early mixing.
Juillet 2005 - Three dimensional (3D) ecological modelling of the Bay of Seine (English Channel, France)
Auteurs : Philippe Cugier, Alain Ménesguen, Jean-François Guillaud (Ifremer)
Journal of Sea Research (54, 104–124)
A three-dimensional model, based on the coupling between a hydrodynamic part taking into account sediment dynamics (S iAM-3D) and an ecological part which accounts for the main biological compartments and processes, has been developed to study nutrient cycles (nitrogen, phosphorus, silica) and their contribution to phytoplankton stock regulation in the Bay of Seine (French coast of the English Channel). The role of each nutrient in phytoplankton production has been identified. Spring phosphorus and summer silicate limitation of diatom growth is observed and confirmed by the model. The simulations show a shift from spring nitrogen to spring phosphorus limitation of diatom growth between the 1970s and the 1990s which is related to an increase in Seine river nitrogen loading and a decrease in phosphorus. Several scenarios of nutrient input reductions were investigated and show a greater sensitivity of flagellates to these reductions. The use of an original numerical method to track the nutrient coming from different sources shows the non-negligible impact of offshore inputs in annual plankton production. In some cases, 50% of the annual diatom production could be related to open sea nitrogen loading. The annual production of flagellates supported by the open sea loading did not exceed 36%.
Keywords : Marine eutrophication; Diatoms; Flagellates; 3D ecological modelling; Nutrients; Bay of Seine (France)
Juin 2005 - Harmful Algal Blooms in Stratified Environments
Auteurs : Gentien P., Donaghay P., Yamazaki H., Raine R., Reguera B., and Osborn T.
Contact : Patrick.Gentien@ifremer.fr
Juin 2005 - The Global, Complex Phenomena of Harmful Algal Blooms
Auteurs : Glibert P.M., Anderson D.M., Gentien P., Granéli E., and Sellner K.G.
Marine and fresh waters team with life, much of it microscopic, and most of it harmless; in fact, it is this microscopic life on which all aquatic life ultimately depends for food. Microscopic algae also play an important role in regulating atmospheric CO sub(2) by sequestering it during production and transporting it to deeper waters. Yet some of the micro-scopic "algae" cause problems when they accumulate in sufficient numbers, due either to their production of endogenous toxins, or to their sheer biomass or even their physical shape. These are known as the harmful algae, or, when in sufficient numbers, harmful algal blooms (HABs). These blooms were formerly called "red tides" because many were composed of dinoflagellates containing red pigments that in high densities colored the water red, but blooms may also be green, yellow, or brown, depending on the type of algae present and their pigmentation. As with all blooms, their proliferation results from a combination of physical, chemical, and biological mechanisms and their interactions with other components of the food web that are for the most part poorly understood. Most HABs are dinoflagellates or cyanobacteria, but other classes of algae, including diatoms, have members that may form HABs under some conditions. As stated by J. Ryther and co-workers many years ago, "...there is no necessity to postulate obscure factors which would account for a prodigious growth of dinoflagellates to explain red water. It is necessary only to have conditions favoring the growth and dominance of a moderately large population of a given species, and the proper hydrographic and meteorological conditions to permit the accumulation of organisms at the surface and to effect their future concentrations in localized areas".
Contact : Patrick.Gentien@ifremer.fr
Mai 2005 - Assessing the impact of removing reserve status on the Abore Reef fish assemblage, New Caledonia
Auteurs : Ferraris, J., Pelletier D., Kulbicki M. & Chauvet C.
We propose a statistical approach based on multivariate analysis and general linear models to test the consequences of removal of reserve status from the Abore Reef fish assemblage of the Abore Reef reserve, New Caledonia. Consequences on fish density were examined at the level of fish assemblage, accounting for habitat. Fish counts and habitat-related information were collected before and after the removal of reserve status, both inside and outside the reserve. Species groups were constructed on the basis of additional information on behavioural characteristics and taxonomy.
The impact of the removal of reserve status was assessed by using 2 habitat proxies corresponding to 2 spatial scales and by considering several criteria for grouping species. Habitat appeared to be a determining factor in explaining density variations. Significant positive effects were found for several species groups such as macrocarnivores, piscivores, herbivores, Lethrinidae and Siganidae. A counterintuitive negative effect was observed for Acanthuridae. No significant differences between the area which remained closed to fishing and the area open to fishing were found for the other species groups. The approach allows for a synoptic diagnosis of the impact of changes in reserve status at the fish assemblage level. It could be used to develop and select potential indicators for monitoring such impacts on fish assemblages in coral reef ecosystems and in other contexts.
Keywords : Marine reserve · Reef fish assemblage · Habitat · Coral reefs · Fishing impact · Ecological indicator · South Pacific
Avril 2005 - Synergic effect of goldmining and damming on mercury contamination in fish
Auteurs : Boudou A., Maury-Brachet R., Coquery M., Durrieux G., Cossa D.
Since the late 1980s, several studies have shown that human populations in the Amazon basin are exposed to high mercury levels in their fish diet. Gold mining, which releases the metal during the amalgamation process and erodes soils naturally rich in mercury, is regarded as the main contamination source. Here, we present the results of a comparative study of mercury distribution in the water and fish of two adjacent rivers in French Guiana, with and without gold mining activities. As a consequence of a marked difference in suspended particulate matter between the two systems, total mercury concentrations in unfiltered water samples were higher in the mined river (25.4-34.9 ng L-1) as compared to the reference one (2.1-5.4 ng L-1). Surprisingly, no significant differences were observed in mercury concentrations between 13 common fish species at upstream sites. In sharp contrast, mercury concentration of fish caught downstream a hydroelectric reservoir, where the two rivers flow, was up to 8-fold higher than that upstream. Mercury speciation measurements allowed one to relate these differences in fish to the water distribution of monomethylmercury, the mercury chemical species that biomagnifies along aquatic foodwebs. Indeed, mean dissolved monomethylmercury concentrations were low and similar in both rivers (0.03-0.06 ng L-1), while they were 10 times higher (up to 0.56 ng L-1) in the water outflowing the hydroelectric dam. Dissolved monomethylmercury determinations along a water column profile suggest that methylation of inorganic mercury occurs in the deep anoxic part in reservoir. We conclude that mercury mobilization related to gold mining is not solely sufficient to account for high concentrations in fish and that environmental conditions that favor mercury methylation, such as anoxia, are needed.
Mars 2005 - Modelling the eutrophication of the Seine Bight (France) under historical, present and future riverine nutrient loading
Auteurs : Cugier P., Billen G., Guillaud J.-F., Garnier J., Ménesguen A.
Journal of Hydrology, special issue on nutrient mobility within river basins. Journal of Hydrology 304, 381–396
Because of the occurrence of episodic blooms of toxic dinoflagellates, eutrophication of the Seine Bight is a subject of growing concern. In order to better understand the relationships between these processes and human activity in the Seine watershed, two models have been used in connection:
• A model describing nutrient (N, P, Si) transfer processes at the scale of the whole Seine Basin (RIVERSTRAHLER [Billen, G., Garnier, J., Ficht, A., Cun, C., 2001. Modelling the response of water quality in the Seine River Estuary in response to human activity in the watershed over the last 50 years. Estuaries 24, 977–993]), allowing human activity (agricultural practices, waterscape management, urban wastewater management, etc.) to be related to fluxes delivered to the sea.
• A model of 3D hydrodynamic and ecological model of the Seine Bight (SiAM-3D/ELISE [Cugier, P., 1999. Modélisation du devenir à moyen terme dans l'eau et le sédiment des éléments majeurs (N, P, Si, O) rejetés par la Seine en baie de Seine. Thèse de doctorat, Univ. de Caen, p. 241; Cugier, P., Le Hir, P., 2000. Modélisation 3D des matières en suspension en baie de Seine Orientale (Manche, France). C. R. Acad. Sci. Paris, Sciences de la Terre et des planétes 331, 287–294]), capable of reproducing the spatio-temporal variations of sediment transport, thermo-haline stratification and phytoplanktonic development in the plume of the Seine river.
The models are validated by their ability to reproduce observed trends of interannual variations of nutrients delivered by the Seine during the last 50 years, as well as the response of the marine system in terms of diatoms and dinoflagellate development, for which data are available from 1976 to 1984 for the former and from 1987 to 1997 for the latter. The results show clearly that dry years, where silica inputs show a deficit with respect to nitrogen and phosphorus, are those where summer blooms of dinoflagellates are particularly pronounced.
Various scenarios of human activity in the watershed are simulated by the two models, including a reconstitution of the ‘pristine’ state, a historical state corresponding to the situation at the end of the 18th century, as well as several scenarios corresponding to the present situation with alternative policies of wastewater nitrogen and/or phosphorus treatment.
Keywords : Eutrophication, Seine Bigh, Seine river, Nitrogen, Phosphorus, Silica
Mars 2005 - Monitoring and modelling of the coastal environment using SST, solar fluxes, chlorophyll a concentration ans inorganique suspended particulate matters
Auteurs : Francis Gohin, Alice Vanhoutte-Brunier (Ifremer)
Remote sensing observations can be used as forcing data into biogeochemical models. We can mention amongst those data the solar Irradiance at sea surface, as derived from METEOSAT visible imagery, and the inorganic Suspended Particulate Matter, SPM, which can be derived from the SeaWiFS or MODIS marine reflectance. These quantities are all essential in modelling the irradiance available for the photosynthesis in the water column over the continental shelf. Chlorophyll concentration maps can be used for validating the biogeochemical models or for assimilation and a better estimation of key biological parameters. Doing so, biologists generalize the procedures already applied by physical oceanographers who use satellite SSTmaps to validate the outputs of their physical models.
As for other domains related to the environmental and climatic change, the remote sensing data are essential for monitoring the variability of the coastal seas. In the different browsers developed at IFREMER, satellite derived chlorophyll and inorganic SPM are associated to the in situ measurements provided by the conventional networks (SOMLIT/CNRS/INSU), REPHY (IFREMER). Three browsers are now available at IFREMER providing SST (AVHRR/ SAF Ocean and Sea Ice and the decadal climatology NOAA-SAF), chlorophyll and inorganic SPM concentrations (derived form SeaWiFS and MODIS) for the English Channel/Southern North Sea, the Bay of Biscay and the Occidental Mediterranean Sea. As it is a quantity used in the models, the solar irradiance, integrated over 10 day periods, will be added to the satellite maps shown in the browser. These data are also available, colocated, in NETCDF format. All those products are developed for the validation of the biogeochemical models and the monitoring of the environment quality (eutrophication risks and Harmful Algal Bloom occurrence) in the spirit of the european program GMES (Global Monitoring for Environment and Security).
Mars 2005 - Contribution to toxicity assessment of Dinophysis acuminata (Dinophyceae)
Auteurs : Marcaillou C, Mondeguer F, Gentien P.
Blooms of Dinophysis in French coastal waters are implicated in most bans on marketing commercial bivalves. However, the relation between Dinophysis cell density and shellfish toxicity is not always consistent. Discrepancies may be due to the simple fact that it is nearly impossible to compare an integral over a few days (shellfish toxin content) and water samples. Furthermore, it seems that cells may have a variable specific toxicity. This work focuses on the variability in cell toxicity taking into account recent findings and using liquid chromatography coupled to mass spectrometry with an ion trap and electrospray interface. Esterified analogues of okadaic acid (DTX-4 and diol-esters) have been identified in cultures of Prorocentrum lima, another okadaic acid producer. These analogues are inactive on some protein phosphatases, contrary to okadaic acid, and seem to protect the cell from harmful effects by the toxin and to be enzymatically hydrolyzed during cell lysis. In order to document specific toxicity and to validate the presence of these analogues, D. acuminata concentrates were subjected to two separate heating and freeze/thaw procedures, respectively inhibiting or promoting hydrolysis. This paper reports on the high variability of D. acuminata specific toxicity and the presence of esters found in half of the samples only.
Keywords : Okadaic-acid, Liquid-chromatography-electrospray-ionization-mass-spectrometry, Dinophysis-acuminata, Dinophysistoxins
Mars 2005 - Modélisation couplée physique-biogéochimie des processus du panache du Rio de la Plata
Auteurs : Martin Huret (Ifremer), Isabelle Dadou (LEGOS/CNRS), Franck Dumas (Ifremer), Pascal Lazure (Ifremer), Véronique Garçon (LEGOS/CNRS)
A coupled three-dimensional physical-biogeochemical model was developed in order to simulate the ecological functioning of the Rio de la Plata estuary and plume. The biogeochemical model reproduces the nitrogen cycle between five compartments: dissolved inorganic nitrogen, phytoplankton, zooplankton, detritus and dissolved organic nitrogen. The coupling is tested in seasonal climatological configurations and for the particular year 1999. The circulation is forced with Parana and Uruguay rivers discharges, NCEP wind and tide. The biogeochemical model includes loads of inorganic and organic nitrogen from both rivers. The model reproduces the correct tidal amplitudes in the estuary, as well as the most outstanding features of the observed horizontal and vertical structures of the salinity plume. Simulated surface chlorophyll a concentrations exhibit maximum values all year long seaward of the turbidity front, between the 0.5 and 15 isohalines, in agreement with SeaWiFS images of the area. The model simulates well the low primary production in the light-limited highly turbid tidal river (20 gC/m(2)/yr), the high production area in the frontal zone where it can reach 500 gC/m(2)/yr, and the nutrient-limited production in the outer estuary and inner shelf (300 gC/m(2)/yr), with realistic values in each case. According to the 1999 model simulation, the tidal river is the location of organic nitrogen remineralization with a consequent increase of the inorganic pool. At the entrance of the frontal zone, inorganic nitrogen represents about 75% of the whole nitrogen pool, it is reduced to 50% at its sea end-member. The outer estuary has the same sink role for inorganic nitrogen, suggesting that organic nitrogen is the major form exported to the shelf.
Février 2005 - Seasonal and longer term trends in sea temperature along the French North Sea coast, 1975 to 2002
Auteurs : D. Woehrlings (Ifremer), Alain Lefebvre (Ifremer), Genevieve Lehoerff (Ifremer), R. Delesmont (Institut Pasteur, Lille)
Regular sea temperature measurements have been made since 1975 at Gravelines (French coast of the Southern Bight of the North Sea) within the framework of a research programme aimed at monitoring the influence of the thermal discharge of a nuclear power plant. The sampling has yielded a 28-year time-series. Pluriannual natural fluctuations of temperature show cyclic patterns and long-term trends in good accordance with global climatic changes as revealed by the NAO (North Atlantic Oscillation) annual index.
Février 2005 - Relationship between land-use in the agro-forestry system of les Landes, nitrogen loading to and risk of macro-algal blooming in the Bassin d'Arcachon coastal lagoon (SW France)
Auteurs : Rutger De Wit (CNRS & Université Bordeaux 1), J. Leibreich (Cemagref-Bordeaux), F. Vernier (Cemagref-Bordeaux), F. Delmas (Cemagref-Bordeaux), H. Beuffe (Cemagref-Bordeaux), P. Maison (Cemagref-Bordeaux), J. Chossat (Cemagref-Bordeaux), C. Laplace Treyture (Cemagref-Bordeaux), R. Laplana (Cemagref-Bordeaux), V. Clave (Cemagref-Bordeaux), M. Torre (Cemagref-Bordeaux), Isabelle Auby (Ifremer), Gilles Trut (Ifremer), Daniele Maurer (Ifremer), P. Capdeville (Service Intercommunal d'hygiène et de Santé, Audenge, France)
Nitrogen loading to the Bassin d'Arcachon coastal lagoon (SW France) was evaluated by studying land-use and nitrogen output in its 3001 km(2) catchment. At present, the catchment is dominated by forestry (79%), while intensive agriculture occupies 9% of the surface. The N-output of two hydrological subunits, i.e. the Tagon subunit dominated by pine forestry and the Arriou 11 subunit comprising both forestry and intensive agriculture, were monitored for a seven year period (1996-2002). From these observations it was calculated that forestry contributes on average 1.6 kg total N ha(-1) yr(-1), which is dominated by organic nitrogen (DON+PON are 70% of N). On an areal basis, intensive agriculture contributes 26 times more than forestry, i.e. 41.6 kg total N ha(-1) yr(-1), which is mainly in the form of nitrate (65% of N). These data were upscaled to the catchment and the upscaling was validated by comparison to gauged nitrogen throughputs for the catchment of the Leyre river that is the major tributary to the system. Taking into account the other known N sources and the interannual variability in the catchment it was estimated that nitrogen loading to the lagoon was on average 90 kg ha(-1) yr(-1) (range from 54 to 126 kg ha(-1) yr(-1)). The sandy soils of the catchment have a clear potential for denitrification, but anoxic conditions (waterlogged) and input of organic matter to fuel this process are required. Currently, agricultural practices and spatial planning do not make use of this potential. Nitrogen loading in the Bassin d'Arcachon is reflected by 10-40 muM nitrate concentrations in winter, which became depleted during spring as a result of uptake by vegetation. Short-term uptake experiments showed that the macroalga Monostroma obscurum is well adapted to temperatures between 10 to 20degreesC and competitive with respect to the seagrass Zostera noltii when the nitrate concentrations are above 10 muM. Spring conditions with high nitrate and high insolation are therefore favourable for M. obscurum and this species presents a high risk for algal blooming. In contrast, the macroalga Enteromorpha clathrata well adapted to summertime temperatures around 25degreesC, forms occasionally blooms in the lagoon. This phenomenon is limited due to the low DIN concentrations in summer.
Février 2005 - Seasonal variations in photosynthetic irradiance response curves of macrophytes from a Mediterranean coastal lagoon
Auteurs : Martin Plus (Ifremer) , Isabelle Auby (Ifremer) , Marc Verlaque (CNRS) , Guy Levavasseur (CNRS)
The main photosynthesis and respiration parameters (dark respiration rate, light saturated production rate, saturation irradiance, photosynthetic efficiency) were measured on a total of 23 macrophytes of the Than lagoon (2 Phanerogams, 5 Chlorophyceae, 10 Rhodophyceae and 6 Phaeophyceae). Those measurements were performed in vitro under controlled conditions, close to the natural ones, and at several seasons. Concomitantly, measurements of pigment concentrations, carbon, phosphorous and nitrogen contents in tissues were performed. Seasonal intra-specific variability of photosynthetic parameters was found very high, enlightening an important acclimatation capacity. The highest photosynthetic capacities were found for Chlorophyceae (e.g. Monostroma obscurum thalli at 17 degrees C, 982 mu mol O-2 g(-1) dw h(-1) and 9.1 mu mol O-2 g(-1) dw h(-1)/ mu mol photons m(-2) s(-1), respectively for light saturated net production rate and photosynthetic efficiency) and Phanerogams (e.g. Nanozostera noltii leaves at 25 degrees C, 583 mu mol O-2 g(-1) dw h(-1) and 2.6 mu mol O-2 g(-1) dw h(-1)/mu mol photons m(-2) s(-1) respectively for light saturated net production rate and photosynthetic efficiency). As expected, species with a high surface/volume ratio were found to be more productive than coarsely branched thalli and thick blades shaped species. Contrary to R-d (ranging 6.7-794 mu mol g(-1) dw h(-1), respectively for Rytiphlaea tinctoria at 7 degrees C and for Dasya sessilis at 25 degrees C) for which a positive relationship with water temperature was found whatever the species studied, the evolution of PII curves with temperature exhibited different responses amongst the species. The results allowed to show summer nitrogen limitation for some species (Gracilaria bursa-pastoris and Ulva spp.) and to propose temperature preferences based on the photosynthetic parameters for some others (N. noltii, Zostera marina, Chaetomorpha linum).
Janvier 2005 - Ability of taxonomic diversity indices to discriminate coastal lagoon environments based on macrophyte communities
Auteurs : David Mouillot (CNRS, Université Montpellier II) , Sylvain Gaillard (CNRS, Université Montpellier II) , Catherine Aliaume (CNRS, Université Montpellier II) , Marc Verlaque (Centre d'Océanologie de Marseille) , Thomas Belsher (Ifremer) , Marc Troussellier (CNRS, Université Montpellier II) , Thang Chi (CNRS, Université Montpellier II)
Lagoons are highly productive areas representing more than 50% of the coastline area in Languedoc-Roussillon (South of France, Mediterranean sea). These lagoons are very different in their environmental conditions, human influences, eutrophication levels and aquaculture intensity. Based on macrophyte communities associated with soft substrates, two indices of taxonomic diversity (the "average taxonomic distinctness" (Delta(+)) and the "variation in taxonomic distinctness" (Lambda(+))) were used to discriminate four of these lagoons (Thau, Salse-Leucate, Bages-Sigean and Mauguio). Bages-Sigean presented a significant higher average taxonomic distinctness (p < 0.05) and Salse-Leucate had a significant higher variation in taxonomic distinctness (p < 0.05) without considering exotic species. The index values were neither influenced by sample size nor by presence of exotic species. Thus, the "average taxonomic distinctness" was related to human activities and eutrophication level whereas the "variation in taxonomic distinctness" was more related the environmental variability, associated with the prime stressor of salinity in brackish coastal lagoons.
Janvier 2005 - Designing indicators for assessing the effects of marine protected areas on coral reef ecosystems: A multidisciplinary standpoint
Auteurs : Dominique Pelletier (Ifremer) , Jose Garcia Charton (Universidad de Murcia) , Jocelyne Ferraris (ORSTOM) , Gilbert David (IRD) , Olivier Thebaud (Ifremer) , Yves Letourneur (Université de la Méditerranée) , Joachim Claudet (Ifremer) , Marion Amand (Ifremer) , Michel Kulbicki (IRD) , René Galzin (EPHE UMR 8046 CNRS)
Cet article vise à identifier des indicateurs de l'effet des aires marines protégées (AMP) en milieu corallien, sur la base d'une synthèse bibliographique dans les domaines écologiques, économiques et sociaux, et principalement en milieu corallien. Nous recensons d'abord les différents effets attendus des AMP pour chacun des domaines, et les variables retenues pour les étudier. Les indicateurs écologiques potentiels sont évalués au travers de leur lien avec l'effet étudié (ici appelé "pertinence") et de leur "efficacité" qui regroupe les notions de précision, justesse et puissance statistique. Pertinence et efficacité sont respectivement mesurées par la fréquence d'utilisation et la proportion de résultats significatifs trouvés dans les articles recensés. Pour les aspects économiques et sociaux, le faible nombre de références ne permet pas une approche comparable à celle utilisée pour les indicateurs écologiques, et nous discutons donc de la question de l'identification d'indicateurs, et suggérons quelques pistes de recherche. Les principales conclusions de ce travail sont: i) le décalage entre les nombres de publications entre disciplines; ii) la nécessité de protocoles et méthodologies incluant des situations de contrôle pour évaluer les effets des MPA; iii) la faible efficacité de nombreux indicateurs écologiques; et iv) le nombre élevé d'effets peu ou pas étudiés ou démontrés à l'heure actuelle.
The present paper aims at identifying and assessing indicators of the effects of Marine Protected Areas (MPAs) in coral reef regions, based on a bibliography review in ecology, economics and social sciences. First the various effects Studied within each of these domains and the variables used to measure them were censused. Potential ecological indicators were assessed through their link with the question used (here termed "relevance") and their "effectiveness" which encompasses the issues of precision, accuracy and statistical power. Relevance and effectiveness were respectively measured by the frequency of use of each indicator and the proportion of significant results in the reviewed articles. For social and economic effects, the approach was not possible due to the low number of references: we thus discussed the issue of finding appropriate indicators for those fields. Results indicate: 1- the unbalance in literature between disciplines: 2- the need for protocols and methodologies which include controls in order to assess MPA effects: 3- an important proportion of ecological indicators with low effectiveness: 4- the large number of ecological effects still not studied or not demonstrated at present.