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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).

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.

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

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)

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

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.