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Resume De 1885 a 1967, la temperature de l’eau de mer a ete quotidiennement mesuree a Marseille. Ces mesures servaient a corriger les enregistrements du maregraphe totalisateur utilise comme reference au nivellement national. Ces mesures (pres de 30 000) sont conservees sous forme manuscrites a l’Institut geographique national, ou nous les avons retranscrites et enregistrees sous forme de fichiers informatiques. L’etude de cette longue serie de temperatures, souvent evoquee, mais non examinee jusqu’a ce jour dans son integralite, pouvait etre tres utile, compte tenu des preoccupations actuelles sur le changement climatique et de la rarete de telles archives historiques pour le milieu marin. Par comparaison avec d’autres series pluriannuelles recentes de temperature de l’air et d’eau de mer de surface, il apparait que les minima hivernaux sont respectivement trop faibles, de 2 °C en moyenne, que ceux des eaux mediterraneennes, mais trop eleves par rapport a ceux actuels de l’air pour la region. Ce biais est consecutif au lieu ou etaient vraisemblablement realisees ces mesures de temperature : le puits du flotteur du maregraphe, c’est-a-dire en eau de mer confinee et non libre. Mais le fait que toutes ces donnees aient ete acquises selon le meme protocole pendant 83 ans autorise leur comparaison au cours du temps. Cette comparaison fait apparaitre une tendance au rechauffement de l’ordre de 0,66 °C en 100 ans pour les moyennes annuelles et de 0,76 °C pour les mois les plus chauds (juin a septembre).

Resume Entre juin 1999 et octobre 2002, des profils thermiques d'eaux cotieres ont ete realises (au moins mensuellement) en deux points de la Mediterranee, un dans le bassin oriental (Batroun, Liban ; 0–100 m) et un autre dans le bassin occidental (Marseille, France ; 0–55 m). Dans les deux sites, saisonnalite des traces thermiques et formation de la thermocline sont tres semblables. En revanche, a profondeur comparable, les temperatures sont plus elevees au Liban de 4 a 5 °C, et la thermocline estivale est plus longue (au moins six mois), permanente et plus profonde (40–50 m) qu'a Marseille (20–30 m), ou elle disparait frequemment en saison chaude, lors des refroidissements brusques consecutifs aux vents de nord-ouest. Cette specificite est due principalement aux differences entre les regimes de vents dominants sur les deux cotes. Documentant l'evolution temporelle d'eaux cotieres representatives au niveau regional des bassins mediterraneens, perennisee, cette observation couplee peut contribuer a apporter des enseignements sur des tendances a long terme et leurs consequences dans le cadre du rechauffement global de la Mediterranee. Pour citer cet article : M. Abboud-Abi Saab et al., C. R. Geoscience 336 (2004).

Resume Des enregistrements semi-continus (1/30 min) de parametres physico-chimiques ( T , S , OD et pH) ont ete realises de 1998 a 2000, a 1,50 m de profondeur dans des eaux littorales mediterraneennes (Marseille), associes a des enregistrements d'irradiance et de vitesse et direction du vent. Les donnees physico-chimiques ont ete traitees pour en synthetiser l'information a differentes echelles de temps (inter-annuel, saisonnier, quotidien et horaire) et, en particulier, examiner la reponse des parametres semi-conservatifs OD et pH aux variables hydroclimatiques. A l'echelle de la journee, des variations circadiennes importantes resultent d'une activite biologique variant avec l'eclairement, avec un fort couplage OD–pH. La reflexion menee sur ces donnees peut contribuer a la definition d'enregistreurs automatiques, outils d'avenir pour l'observation des eaux cotieres. Pour citer cet article : N. Bensoussan et al., C. R. Geoscience 336 (2004).

Between 1996 and 2000, 79 cruises have been achieved following always the same transect between Marseilles and the Rhone river's mouth. While cruising, salinity, temperature and fluorescence of surface waters (1.5 m) were recorded every minute, in association with precise GPS position. The whole set of data. (i.e. 128 measured points per cruise) constitutes the Sorcom series whose synthetic results ate presented here. Despite the high spatial and temporal. variability encountered between two successive cruises, the regularity and duration of the sampling strategy permitted to define coherent spatial zonation and temporal evolutions. In the Cape Couronne vicinity the dynamic of the eastern extension of the dilution plume clearly changes. Westward, waters are frequently under its influence, but more sporadically to the east, with a less pronounced gradient. In few cases, salinity lowering has been measured up to the gulf of Marseilles. In these two areas, which can be divided in two sub zones, seasonal evolutions are different. In the eastern area (Cape Couronne-Marseilles), the classical rhythm prevailing over marine waters is observed but with earlier phytoplanktonic bloom than usually reported. In the western part, and as getting closer to the Rhone river mouth, a weaker seasonal variability is observed for the phytoplanktonic biomass then salinity and temperature differences remain high. The better knowledge of the eastern dilution plume is of important socio-economical concern due to the numerous population living on this coast and the presence of pollutants in the river waters., Entre 1996 et 2000, toujours selon le même trajet entre Marseille et l’embouchure du Rhône, soixante dix neuf missions ont été conduites. Le navire en route, toutes les minutes sont réalisées dans les eaux de surface (1,5 m) des mesures de salinité, température, fluorescence ainsi qu’un positionnement GPS. L’ensemble de ces données (soit 128 points de mesure par sortie) constitue la série Sorcom dont la synthèse de ces résultats est présentée ici. Malgré la forte variabilité spatiale et temporelle pouvant se manifester d’une sortie à l’autre, la stratégie de l’étude et sa durée permettent de dégager une zonation spatiale et des évolutions temporelles. C’est au voisinage du Cap couronne que se situe un changement net dans la dynamique d’extension, vers l’est, de l’influence du Rhône. A l’ouest, les eaux sont en quasi-permanence sous cette influence et plus sporadiquement vers l’est, avec un gradient moins marqué, mais dans certains cas une dessalure peut être détectée jusqu’à Marseille. Dans ces deux parties, chacune pouvant être découpée en deux sous zones, les évolutions saisonnières sont différentes. Si dans la partie est (cap Couronne–Marseille) on retrouve le rythme classique des eaux marines (avec une première poussée phytoplanctonique plus précoce que ce qui est reporté habituellement), la partie ouest (cap Couronne–Rhône) voit se mettre en place, au fur et à mesure que l’on se rapproche de l’embouchure, une plus faible variabilité inter saisonnière pour la biomasse phytoplanctonique alors que les écarts de salinité et surtout de température restent importants. La connaissance de la branche est de dilution des eaux du Rhône, sans doute moins étudiée car ne correspondant pas à la direction privilégiée du panache, revêt une importance socio-économique particulière du fait de la population qui vit sur cette côte et de la présence, dans les eaux du fleuve, d’un cortège de polluants amenés par le drainage du bassin versant.

Marine microorganism activities are commonly assessed by bulk methods and assigned to the total cell count. The presence in significant amounts of ghost, dead, and damaged cells makes such as assignment a non-correct one. A Nucleic Acid Double Staining protocol (NADS) of fresh water bacteria (Barbesti et al., Cytometry 40 (2000) 214-218) has been adapted to resolve viable, damaged and dead cells in marine environments (Gregori et al., Appl. Environ. Microbiol. 67 (2001) 4662-4670). The present reports the first in situ application of this approach, conducted in the Bay of Marseilles in winter and spring periods at two sites with contrasted features.

The Rhone River is the major source of nutrients and particulate matter to the Mediterranean basin. Its influence on coastal sediments was investigated by searching for the presence of continental markers. The composition of coastal sediments situated in the area influenced by the Rhone River inputs was compared with surface water salinity time-series records (five years bi-monthly survey). Sediment samples were analysed for grain-size, total and organic carbon and nitrogen, pigments, trace metals, carbohydrates, protein and lipid content. Comparisons show that changes in sediments are associated with the mean extension of the dilution plume of the river. The organic carbon content of sediments does not exhibit spatial changes related to the variations in the overlying water column. A large amount of inorganic carbon is discharged into the sea by the river and results in dilution of the organic carbon in the deposited material. The CaCO3 fraction of the total carbon of sediments is influenced by the river inputs with lower values in front of the river mouth. Changes in the composition of organic matter are linked with the inputs of the Rhone River and associated with variations of concentrations of the chlorophyll b as a marker of the terrestrial origin of the organic matter. Chlorophyll b content of sediments showed statistically significant negative correlation with the five-year bi-monthly mean surface salinity values (slope=−0.0233, R2=0.9437, n=22, p

During summer 1999, a massive mortality of attached benthic invertebrates was reported at several points along the French Mediterranean coast, east of the Rhone River. Such a wide geographical extension suggested the occurrence of a climatic anomaly as a direct or an indirect cause of this phenomenon. The systematic observations of surface water temperature (1 record/30 min) and vertical thermal structure from 0 to 55 m (semi-monthly frequency) performed by the service of observation of centre d’oceanologie de Marseille since 1994 in the Gulf of Marseilles (northwestern Mediterranean) compared with historical data obtained for the summer periods (June till October) indicates a thermal anomaly during summer 1999. Although the surface temperatures do not strictly show exceptional values, the stability during long periods of high temperatures (24.1 °C ± 0.5 in September, n = 1 018) and the thermal structure of the water column are remarkable. The vertical temperature profiles of 1999 reflect a general warming of 2–3 °C in the water layer overlying the thermocline, accompanied by its deepening (up to 30–40 m). This situation can be explained by the scarcity of NW winds with a marked drop of their relative frequency during July and October 1999 (13–27 % versus 42 %, mean value calculated from the previous 12 years) and the short duration of these windy periods (between 30 min and 5 h as a mean). Parallel to this, a large number of no wind registrations (125–250 h/month as a mean) were observed during this period. A similar thermal stratification, of lesser amplitude, associated with comparable meteorological conditions was also observed in 1997. The hypothesis that this summer 1999 temperature anomaly could constitute a partial explanation for the recorded massive mortality is discussed.

The frequency, occurrence and extent of sea-surface slicks were studied in open seas during a ship crossing from the eastern Mediterranean to La Reunion Island (Indian Ocean), via the Red Sea, by taking sea-surface photographs every 1 min 45 s and relating them to wind speed and direction records. During 10% of the recording time, slicks covered from 20% to 80% of the observed sea surface, and they covered the entire photographic field during 1% of the recording time. Slicks were observed only at wind speeds below 5 m/s, but in some cases, they were absent at lower wind speeds. Conversely, slicks were never observed at wind speeds higher than 6 m/s. Compared to that in coastal waters, the frequency of occurrence of slicks was lower (11% against 30%) at the surface of the open sea, mainly as a consequence of persistent bad weather (southwest monsoon period). Nevertheless, the records provide evidence that slicks are not rare in the open sea and that slick-forming meteorological conditions found in coastal areas are similar to those of open seas. These include the upper wind speed limit and the percentage of the sea surface covered by slicks in relation to wind speed. The daily rhythm of slick formation in coastal waters, due to diurnal changes in wind speed and direction, is absent in the open ocean.

For one month photographic records of the sea surface were taken (every five minutes) in a coastal area and used with records of wind speed and direction to determine the frequency of formation and spatial extent of slicks. The analysis of photographic records showed that slick sizes and occurrence frequencies decrease as a direct function of the wind speed. When the weather is under the influence of local winds (heat flux exchanges between the sea and the continent), a periodic rhythm occurs for a 24-h period: in the morning and late afternoon slicks are generally large (coverage ~35%) and frequent) (occurrence frequency ~65%), but in the middle of the day, when the winds increase to maximum velocity, slicks are small (coverage ~12%) and rare (occurrence frequency < 40%). During the night, a high slick coverage (39%) can be deduced from wind conditions. The comparison of the present data to the results of a previous experiment conducted in another coastal area, and the fact that meteorological conditions which have prevailed during this study were not particular, allow us to extend our conclusions to the larger coastal zones. In situ sampling in the surveyed area has shown higher concentrations of anionic detergents and hydrocarbons in slicks as compared to the surrounding rough surface waters (Garabetian et al., 1993). Thus, this daily rhythm of slick formation may have some important consequences for the dynamics of pollutant dispersion.

International audience; This article presents a comparison between simulated and in situ temperature data. The aim is to test the reliability of the Symphonie model on the short coastal area, few kilometres wide (~ 20 km) with a strait configuration. The in situ data comes from records collected by the team of the marine park of Strait of Bonifacio (South of Corsica). The results show a difference between the two sets of data in winter and in summer, where the variation of temperature is the most extreme.

International audience; The dynamics of Bonifacio strait (south of Corsica) are investigated in a comprehensive study at long term from two set of data. First, by moored ADCP put in middle of the strait during six weeks (4 November 2004 to 7 January 2005), at a depth of 40 m and at few Kilometers from coast. Second, by velocity profiles obtained with a 314.4 kHz Acoustic Doppler Current Profiler (ADCP) during seven cruises (Cyrce) covering entirety strait. From moored ADCP data, a study is made on time correlation between wind stress and current. Shipboard ADCP data permits to obtain a general view in totality of strait and mostly to observe spatial variability. This study shows that the circulation is governed both by wind stress and by general circulation of Mediterranean Sea.

13 pages, 7 figures, 3 tables, Two large-scale mass mortality events (MMEs) of unprecedented extent and severity affecting rocky benthic communities occurred during the summers of 1999 and 2003 along the coasts of the NW Mediterranean Sea. These mortality outbreaks were associated with positive thermal anomalies. In this study, we performed an analysis of inter-regional and inter-annual differences in temperature (T) conditions associated with MMEs of the red gorgonian Paramuricea clavata by analyzing high resolution T time series (hourly records for 3 to 8 years) from four regions of the NW Mediterranean with differing hydrological conditions and biological impacts. High resolution records allowed a detailed analysis using classical and new descriptors to characterize T anomalies. We were able to determine that the MMEs were triggered by two main types of positive thermal anomalies, with the first type being characterized by short periods (2 to 5 days) with high Mean T reaching more than 27°C in some regions and being associated with high intra-day and intra-period variability, while the second type of anomaly presented long duration (near one month) at warm T (24°C) with low intra-period variability. Inter-regional patterns arose; some regions displayed both types of anomalies, while others exhibited only one type. The results showed that T conditions should be considered as the main factor that explains the observed inter-regional and inter-annual differences in mortality impacts. In explaining these differences, the late timing of T anomalies, in addition to their magnitude was found to be determinant. Finally, by combining thermotolerance experimental data with the maximal T stress conditions observed in the four regions, we were able to determine the differential risk of mass mortality across regions. We conclude that expanding high resolution T series is important for the development of sound management and conservation plans to protect Mediterranean marine biodiversity in the face of climate change, Funding: This work was supported by the Alßan Program (C. Crisci doctoral fellowship, fellowship code: E06D103213UY; www.programalban.org); Parc National de Port-Cros; The IFB Foundation (Institut Français de la Biodiversite´ ); Agence Nationale pour la Recherche (ANR) (MEDCHANGE Project (http://www.agencenationale-recherche.fr; http://sudek.esil.univmed.fr/medchange/spip); Ministry of Science and Innovation (Biorock project ref. CTM2009-08045). These funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Dr. Nathaniel Bensoussan is employed by IPSO-FACTO SARL; he contributed to the analysis of the data and the writing of the manuscript

Twenty-nine sea-surface microlayer samples, associated with their related bulk water, were collected in coastal waters of the northwestern Mediterranean Sea, and examined for the concentration and composition of their particulate sugar fraction. The monosaccharide content was assayed by high-performance liquid chromatography (HPLC) and fluorescence detection after dansylhydrazine precolumn derivatization. Samples were collected in both marine areas influenced by fresh water. As compared with bulk waters, accumulation of particulate organic matter in the surface microlayer was higher in marine than in brackish waters (about three-fold higher for particulate organic carbon (POC) and ten-fold higher for sugars). However, in brackish bulk waters, the concentrations of organic compounds (POC, particulate organic nitrogen (PON), chlorophyll a and sugars) were higher than in marine bulk waters. In all the samples the sugar content appeared to be directly linked to POC. All the surface microlayers were enriched in bacteria but phytoplanktonic pigments were less represented in microlayers than in other particulate organic fractions. In brackish waters, chlorophyll a concentrations were correlated with the percentage of monosaccharide carbon in POC, but the microbiomass could explain only a small part (5–10%) of the sugar concentrations recorded in surface microlayers. In all cases, glucose was the major monosaccharide form. In brackish waters, no change was noted in monosaccharide composition of the sugar fraction in surface microlayers as compared with their related bulk waters. In marine samples, a slight but significant depletion of glucose was recorded in the microlayers, and three forms (mannose, arabinose and rhamnose) exhibited higher percentages (+4%, +4% and +15%, respectively) in marine sea-surface microlayers. During mild acid hydrolysis of the particulate organic matter, the release of the ·Dubois-reactive compounds’ was faster in marine microlayer samples than in related bulk waters, and the relative concentration of glucose increased with time of hydrolysis in the two types of water. When hydrolysis was not complete, a compound which eluted at the beginning of the chromatogram and remained at a constant level throughout the hydrolysis, was detected.

Surface microlayer samples were collected with a rotating device at eight stations in a coastal area, and examined, with their related bulk waters, for their organic matter composition. At each station, sampling operations were conducted inside and outside slicks. With the exception of pigments, all the examined groups of compounds, particularly hydrocarbons and anionic detergents, exhibit accumulation in surface microlayer; enrichment is higher in samples collected inside slicks than outside. A decrease of the surface tension measurements is linked to the accumulation of organic matter in the slicks. In surface microlayers, the major part of the identified organic fraction, consists of carbohydrates and proteinaceous compounds rather than lipids. As far as could be deduced from an estimation of lipid, sugar- and protein-carbon, half the recorded particulate organic carbon weight is of an unidentified complex form. The study of hydrolysis kinetics of the carbohydrate particulate fraction shows that the organic matter is in a less condensed form in surface microlayers than in bulk water samples. A close relationship appears between pollutant accumulation and the lowering of surface tension in slicks. This has a direct consequence: the dampening effect on waves which smooths the surface of the sea, making slicks observable features of pollutant accumulation.

International audience; En 2007, étaient étudiées ici des températures mesurées quotidiennement à Marseille, au marégraphe, entre 1885 et 1967. Sur la base de l'information alors disponible, ces températures pouvaient être considérées comme celles de températures de surface de la mer. Ce n'était pas le cas : il s'agissait de températures prises à l'intérieur du bâtiment et les auteurs corrigent cette erreur en présentant ici la série authentique, retrouvée à la suite de la publication du précédent article. Cette série, plus courte (1895-1956) conduit à des conclusions proches de l'étude précédente. Il y a bien eu réchauffement significatif des eaux littorales méditerranéennes de surface, de +1,6°C en 61 ans, de +1,3°C durant les mois de janvier à mai + décembre et de + 2.2°C durant ceux de juin à novembre. C'est entre 1895 et 1925 que se rencontrent les moyennes mensuelles (sauf janvier) les plus froides et les minima annuels les plus bas (à l'exception de 1956) par rapport à 1925-1956.

11 pages, 8 figures, 3 tables, In the North West Mediterranean (NWM), mass mortality events (MME) of long-lived benthic species that have occurred over the last two decades have been related to regional warming trend. Gaining robust data sets on thermal regimes is critical to assess conditions to which species have adapted, detect extreme events and critically evaluate biological impacts. High resolution temperature (T) time series obtained during 1999-2006 from 5 to 40 m depth at four contrasted sites of the NWM were analyzed: Area Marina Protegida de les Illes Medes (NE Spain), Riou (Marseilles, France), Parc National de Port-Cros (France), and Réserve Naturelle de Scandola (Corsica, France). The seasonal pattern showed winter T around 11-13 °C, and summer T mainly around 22-24 °C near surface to 18-20 °C at depth. Stratification dynamics showed recurrent downwellings (>40 m) at Medes, frequent observation (1/3rd of the summer) of deep and cold upwelled waters at Riou, while Scandola exhibited stable summer stratification and highest suprathermoclinal T. Port-Cros showed an intermediate regime that oscillated between Riou and Scandola depending on the occurrence of northern winds. Data distribution study permitted to identify and to characterize 3 large scale positive anomalies concomitant with the mass mortality outbreaks of summers 1999, 2003 and 2006. The analysis of biological surveys on gorgonian populations showed significant impacts during the 3 years with temperature anomalies. Besides the degree of impact showed inter-annual differences which could be related to different T conditions concomitant to mortality events, from slight increase in T extreme of only 1-2 °C over short duration, to lengthened more classical summer conditions. Our results therefore support the hypothesis that shallow NWM populations of long-lived benthic species are living near their upper thermal thresholds. Given actual trends and projections in NWM, the repetition of new MMEs in the next decades is extremely likely. In such context, the acquisition of dedicated high resolution T series proves to be crucial for increasing our detection, understanding and forecasting abilities, This research was funded by the Parc National de Port-Cros, the IFB Foundation (Institut Français de la Biodiversité), the environmental department of the TOTAL-Fina-Elf group, an “Action Concertée Incitative” (ACI) program “Jeunes chercheurs 2003” (number JC5360) from the French Research Ministry, and the MEDCHANGE project funded by the “Agence Nationale pour la Recherche” (ANR)

The respective roles of regular echinoids and scarid fishes in the transformation of turf algae, the main food resource for reef herbivores, were investigated on French Polynesian coral reefs. The role of one species of parrotfish (Scarus sordidus) was compared with that of four species of echinoids. The degree and ways of degradation of the algal matter were determined by the organic matter percentage, the composition of the sugar fraction, and the concentration and composition of chlorophylltype pigments as assayed by HPLC analysis. Chemical analyses were performed on anterior and posterior intestines for scarids, intestinal contents and faeces for echinoids, and on fresh algal turf as a control of initial food quality. A decrease in mean percentage of organic matter in gut content was observed from intestine (9.7%) to faeces (7%) in sea urchins, but not in parrotfishes. The total sugar fraction decreased from fresh algal turf (32% of total organic matter) to echinoid (28%) to scarid (18%) gut contents. The ratio of insoluble to soluble sugars (I/S ratios) was higher in echinoids (2.6) than in scarid gut contents (1.0). A decrease in the total pigment concentration was measured from fresh algal turf to echinoid and it was found to be even lower in scarid gut contents. Chromatograms showed that the composition of chlorophyll-type pigments in scarid intestines was very similar to fresh algal turf, with a dominance of native forms, mainly chlorophyll a and b. On the contrary, degraded pigment forms dominated in echinoids. The main degraded products were pheophorbides in sea urchins, and chlorophyllides in parrotfishes. These results provided evidence for differentiation in digestive processes occurring in the two types of grazers. Echinoids released higher degraded algal material than did scarids. Thus, these two types of grazers play different roles in the recycling of organic matter on coral reefs.

14 pages, 3 figures, 4 tables, Late in summer 2003, extensive mass mortality of at least 25 rocky benthic macro-invertebrate species (mainly gorgonians and sponges) was observed in the entire Northwestern (NW) Mediterranean region, affecting several thousand kilometers of coastline. We were able to characterize the mortality event by studying six areas covering the main regions of the NW Mediterranean basin. The degree of impact on each study area was quantified at 49 sites by estimating the proportion of colonies affected in populations of several gorgonian species compared with reference data obtained in years without mortality signs. According to these data, the western areas (Catalan coast and Balearic Islands) were the least affected, while the central areas (Provence coast and Corsica-Sardinia) showed a moderate impact. The northernmost and eastern areas (Gulf of Genoa and Gulf of Naples) displayed the highest impact, with almost 80% of gorgonian colonies affected. The heat wave of 2003 in Europe caused an anomalous warming of seawater, which reached the highest temperatures ever recorded in the studied regions, between 1 and 3 °C above the climatic values (mean and maximum). Because this exceptional warming was observed in the depth ranges most affected by the mortality, it seems likely that the 2003 anomalous temperature played a key role in the observed mortality event. A correlation analysis between temperature conditions and degree of impact seems to support this hypothesis. Under the present climate warming trend, new mass mortality events may occur in the near future, possibly driving a major biodiversity crisis in the Mediterranean Sea, This research was partly supported by the IFB Foundation (Institut Français de la Biodiversité), the environmental department of TOTAL-Fina-Elfgroup, an 'Action Concertée Iniciative' (ACI) program 'Jeunes chercheus 2003' (number JC5360) from French Research Ministry, research grants CTM2006-01463 and CGL2007-66757

For 2 years photographic records of the sea surface were taken in a coastal area. These were used, in conjuction with records of the wind speed and direction, to determine the frequency of formation of slicks as an index of surface microlayer presence. Parallel collection of sea-surface samples provided evidence for a relation between the pictures and accumulation processes of organic matter in surface microlayers. Results show that slicks are present for more than 25% of the recording time; this frequency may reach more than 60%, depending on the hour and season. Slick formation is dependent on wind speed and slicks never exist at wind speeds greater than 7 m s −1 ; below this upper limit the highest probability of slick formation corresponds with wind speed values between 2 and 4 m s −1 , but in many cases, no slicks are formed under low wind speed conditions. (Slicks were found to require considerable time to form, following a decrease in wind speed, and to disperse, following an increase in wind speed. This dependence explains most of the seasonal and diurnal variations in slick occurrence.) Slicks are more frequent in the morning, and less frequent at midday and afternoon, because of wind induced by heat flux between the sea and continent in coastal areas. Despite the fact that it was not possible to take photographic records during the night, a high probability of slick formation during the night can be deduced from the recorded decrease in wind speed.

Marine microorganism activities are commonly assessed by bulk methods and assigned to the total cell count. The presence in significant amounts of ghost, dead, and damaged cells makes such as assignment a non-correct one. A Nucleic Acid Double Staining protocol (NADS) of fresh water bacteria (Barbesti et al., Cytometry 40 (2000) 214-218) has been adapted to resolve viable, damaged and dead cells in marine environments (Grégori et al., Appl. Environ. Microbiol. 67 (2001) 4662-4670). The present reports the first in situ application of this approach, conducted in the Bay of Marseilles in winter and spring periods at two sites with contrasted features.

This study deals with the colonisation of experimental Porites blocks by epilithic and endolithic algal community in two atoll lagoons and two high-island lagoons in French Polynesia, exposed to different environmental conditions during a 5-year period. A qualitative analysis of the community (cyanobacteria and micro-algae) was carried out, and the relationship between the epilithic and endolithic strata observed. HPLC analysis of chlorophyll pigments was used to quantitatively determine the plant biomass, which was then compared to that of the algal turf of neighbouring reefs. The results show that these blocks are colonised according to two factors: the reef structure (atoll or high-island) and the degree of human disturbance. The epilithic and endolithic population dynamics differ. The density of the epilithic algal community and the species diversity increase with the degree of eutrophication and the amount of borers (sea-urchins, parrotfish), while the proportion of endolithic species remains low (34 %-59 %). This is especially marked in the high-island lagoons, where leaching has caused enhanced nutrient levels. An extreme case is the station at Faaa, a highly polluted harbour, where increased sea-urchin levels (44 ind. m(-2)) meant that the blocks disappeared completely in less than five years due to bioerosion. In the oligotrophic waters of the atoll lagoons, the losses of CaCO3 by bioerosion do not exceed 35 % per block, and the algal community is made up mainly of endolithic species (66 %-85 %). The algal biomass is lowest in the Takapoto atolls (10-11 mu g cm(-2)) and maximum in Tikehau atoll (23 and 56 mu g cm(-2)). The first microborers to settle in the ecological succession of the community are the cyanobacteria. These are gradually replaced by Ostreobium (Chlorophyceae borers), which become dominant in the blocks exposed to the lowest bioerosion rate. The richness and the density of the algal turf reflect the convergence of many ecological factors: it seems that the covering of epilithic algae or the richness of endolithic flora could be used as a global indicator of the quality and the health of a reef., Cette étude porte sur la colonisation par du feutrage algal épilithe et endolithe de bloes expérimentaux de Porites, mis en place dans deux atolls et deux îles hautes de Polynésie française et soumis à des contraintes environnementales différentes pendant cinq ans. La composition qualitative des peuplements (cyanobactéries et microalgues) et les relations entre «strateå épilithe et «strateå endolithe ont été observées. La quantification de la biomasse végétale a été effectuée par la mesure des pigments chlorophylliens analysés en HPLC. Des comparaisons ont étéétablies avec le feutrage algal des substrats récifaux avoisinants. Les résultats font apparaître des différences dans l'évolution de la colonisation de ces blocs selon deux facteurs: la structure récifale (atolls ou îles hautes) et le degré d'anthropisation des milieux. Par ailleurs, la dynamique de la colonisation est différente pour les populations épilithes et endolithes. La densité du feutrage algal épilithe et la diversité spécifique augmentent avec le degré d'eutrophisation des eaux et la quantité des organismes brouteurs (oursins, Scaridés), alors que la contribution des espèces endolithes dans ce feutrage reste faible (34 et 59 %). C'est le cas notamment dans les stations des îles hautes, enrichies en nutriments par le lessivage des sols. L'exemple extrême est représenté par la station de Faaa (ville de Papeete) où la forte pollution urbaine et le nombre élevé d'oursins bioérodeurs (> 44 ind. m2) ont entraîné la disparition des blocs en moins de cinq ans. Dans les atolls, les eaux sont oligotrophes, les pertes de CaCO3 par bioérosion ne dépassent pas 35 % par bloc, et le peuplement algal est constitué principalement d'espèces endolithes (66 % à 85 % de l'ensemble du peuplement). Sur les blocs de l'atoll de Takapoto, la biomasse du feutrage algal épilithe et endolithe est la plus faible et n'atteint que 10 à 11 μg chl a cm−2, alors qu'elle est maximale (23 et 56 μg chl a cm−2) aux deux stations de l'atoll de Tikehau. Dans la succession écologique, les premiers microperforants qui s'installent sont les cyanobactéries; celles-ci sont peu à peu remplacées par l'Ostreobium (Chlorophycée perforante) qui devient dominant dans les blocs soumis à la plus faible bioérosion. La richesse et la densité du feutrage algal reflétant l'intégration de nombreux facteurs écologiques, il apparaît que la couverture en épilithes ou la richesse en flore endolithe pourraient servir d'indicateur global de la qualité et de la santé d'un récif.

Changes in the composition and distribution of organic matter from the urban sewer of the City of Marseilles (France) were studied in superficial sediments (16 stations) and in suspended particulate matter collected by sewer sediment traps. Sugar and amino acid compositions were assayed by HPLC (high pressure liquid chromatography) analysis in parallel with determination of hydrolysis kinetics and the insoluble to soluble ratios. The organic matter from the sewage outlet and in sediments located near the outlet was more rapidly hydrolysed and exhibited lower I/S ratios than that of marine sediments. The monosaccharide composition and particularly the glucose/ribose, glucose/fucose and mannose/fucose ratios which varied strongly with increasing distance from the sewage outlet may constitute a fingerprint of the terrigenous matter in the marine environment. The variations in the amino acid spectra were comparatively smaller. Four major forms were dominant in the outlet itself, the superficial sediments and particle-traps and exhibited significant changes. Changes in the nitrogenous fraction could be attributed to changes in some minor or non-protein amino acids such as methionine and methionine sulfoxide.

The influence of sampling and sample treatment upon adenylic nucleotide (ATP, ADP, AMP) content of microplankton is studied. Changes in light conditions during nigh-sampling and extracting do not induce significant variations, in the adenylic nucleotide content of microplankton or in energy charge values. The contribution of zooplankton (size up to 200 µm) to microplankton adenosine values can be neglected for inshore surface waters and traditional sample volumes (about one liter). This result can been explained by the low density of zooplankton in such a small sample volume and by differences in efficiency of the extracting method used.

Chlorophyll and its breakdown product contents were determined by both high pressure liquid chromatography (HPLC) and the fluorimetric method in surface microlayer and related bulk water samples collected in the western Mediterranean Sea. Differences in chlorophyll α measurements between the two methods are enhanced in highly loaded organic matter water samples such as surface microlayers. In several samples, pheophytins, which are commonly reported to be present in surface microlayers, were detected by the fluorimetric method, but not by HPLC. In most cases, the accumulation processes of pigments can be recorded in surface microlayers, but with small differences in pigment composition when compared with that of related bulk waters. Enrichment factors for chlorophyll are often higher than those of its degradation products. On the other hand, the low reported values of phytoneustonic productivity provide evidence for an inhibition of phytoplankton organisms transported to the sea-air interface; these organisms should be stressed but alive. These results also support the hypothesis that pigments could be actively photo-oxidized by the high level of solar radiation prevailing in surface microlayers.

Discriminating approach of various microplanktonic-stage contributions to whole electron transport system (ETS) measurements in sea-water sampless. b. Bacateria Data obtained from cultures of natural bacterial populations were applied to various water samples in order to determine both the phytoplanktonic and bacterial contributions to whole ETS water-sample measurements. The bacterial part was estimated both by cell enumerations and HPLC muramic-acid measurements and the phytoplankton contribution by enumeration and chlorophyll levels. An appropriate first-order equation is adequate to low carbon content samples but must be corrested for highly organic loaded samples in order to obtain a better adjustment between the sum of the “estimated” phytoplanktonic and bacterial ETS and the really-measured ETS concentrations in the water samples.

Influences of unsalted waters penetration, in the Gulf of Fos, are marked as much on the primary step structuration level as on the component cellular physiology one. At their outlet, the weak structuration and the considerable biomasses resulting from an intense eutrophication go with a strong mortality clearly shown as well as by ATP/chlorophyll ratio than these of ATP, ADP and AMP inside the adenylic nucleotides pool. The primary step acquires a larger maturity in the salt share of the south eastern area. Spectrum variations of the population specific cellular volumes in terms of population importance can in a certain measure explain the intracellular rate variations into biochemical components.

Discriminating Approach of Various Microplanktonic-stage Contributions to Whole ETS Measurements in Sea-water Samples. a. Phytoplankton Data obtained from algal cell cultures were applied to various sea water samples in order to estimate the specific contribution of phytoplanktonic organisms to whole ETS (electron transport system) measurements of these samples which have been collected at eleven stations in the northwest Mediterranean Sea. When the phytoplankton ETS contributions were quantified by cell enumerations or by other indirect-biomass-indicator measurements, the results are in good accordance to the recorded ETS measurement values of the sample. More specific of the phytoplankton stage is the index used for such an estimation (as chlorophyll a), and better is the relationship between both estimated and measured ETS values.

Based on the information obtained from the Gulf of Fos, France, we propose herewith a generalized model to characterize the physical, chemical and biological parameters and their interrelationship in the eutrophic coastal system. This system is characterized by having high concentration of suspended materials, especially the mineral fraction (C/N > 30). Nutrients concentrations are very high, except in diluted basins. The N-NO3/P-P04 ratio is usually low, due to the preferential assimilation of nitrates and the presence of polyphosphates from sewage waters. The concentrations of phaeopigments are always high (more than 50%), due to the mortalities of freshwater originated phytoplankton, the resuspension of dead vegetal materials, and the grazing of zooplankton. We noted in diluted water of eutrophic system the biomass is high, but the diversity is relatived low, among adapted cells with low " energetic charge". Whereas in oceanic water, the biomass is less, the diversity and energetic charge are increasing. This may indicate that phytoplankton communities have to make an effort to grow and duplicate. In comparing zooplankton populations from eutrophic to oligotrophic waters, biochemical diferentiations were observed for a same species, which may due to the difference in salinities and the presence of chemical pollutants.

Muramic acid, a constituent of procaryotic cell walls, was assayed by high-pressure liquid chromatography in samples from several marine environments (water column, surface microlayer, and sediment) and a bacterial culture. It is used as a microbial biomass indicator. The method gave a good separation of muramic acid from interfering compounds with satisfactory reproducibility. A pseudomonad culture had a muramic acid content of 4.7 � 10 −10 to 5.3 � 10 −10 μg per cell during growth. In natural water samples, highly significant relationships were found between muramic acid concentrations and bacterial numbers for populations of 10 8 to 10 11 cells per liter. The muramic acid content in natural marine water decreased from 5.3 � 10 −10 to 1.6 � 10 −10 μg per cell with increasing depth. In coastal sediments exposed to sewage pollution, concentrations of muramic acid, ATP, organic carbon, and total amino acids displayed a parallel decrease with increasing distance from the sewage outlet. Advantages of muramic acid measurement by high-pressure liquid chromatography are its high sensitivity and reduction of preparation steps, allowing a short time analysis.