French Mediterranean Sea Research Articles

Ecodynamics of PAHs at a peri-urban site of the French Mediterranean Sea

The PAH contamination level and biochemical composition of sinking particles and surficial sediments (0–0.5 cm layer) were assessed at a rural coastal site in the northwestern Mediterranean Sea. Surficial sediment contamination (≈20 ng g−1) was considerably lower than at other Mediterranean sites, yet particles collected in sediment traps had 6–8 times more PAH. Contaminated particles were mostly marine in origin. Temporal variation of contamination levels correlated with organic content of the particles, but some of the observed variability could be attributed to seasonal changes in pyrolytic PAH production. Sinking organic particles were potentially as readily digestible as surficial sediments for prospective consumers however, transfer of PAHs along the benthic food chain is probably enhanced because of the particles' higher nutritional value.

Caractérisation de sédiments marins pour une mise en dépôt à terre et en remblai

ABSTRACT To reuse dredged sludge for earth structures such as unconfined or non embankments, a methodology is proposed to characterize marine sediments. This concerns physical, hydraulic and consolidation properties which constitutes a basis for the design of any embankment with sediments. A series of 8 marine sediments coming from the French Channel coast (2) and Mediterranean sea (6) is studied using different sedimentation, oedometric and creep testing. All the results are analyzed and presented in this paper. The main data are relative to the grain size distribution and Atterberg limits and relationships between permeability and void ratio or concentration. Finally some consolidation data are summarized in comparison with compressible soils.

Multibeam sonar detection of suspended mussel culture grounds in the open sea: Direct observation methods for management purposes

The exploitation of offshore mussel farms is becoming important throughout the world, but monitoring this activity remains a difficult task. Here, we propose a specific method for this purpose. A total of 140 long-lines were monitored on a mussel culture ground in the French Mediterranean Sea during four experimental surveys deploying multibeam sonar devices mounted on poles (Reson Seabat 6012, 455 kHz) on small boats. This allowed geo-referenced observations to be made of the submerged mussel long-lines, as well as three-dimensional (3D) drawings of the long-line structures and the sea bed shapes, using long-line longitudinal sonar sampling. Three sonar data-analysis methods were applied: (i) direct two-dimensional (2D) visual interpretation of raw sonar video images; (ii) indirect 2D long-line drawings; and (iii) 3D digital long-line reconstructions. The development of these acoustic methods in shallow water provides scientists, managers and local authorities with a tool for observing the 3D position (geographical position and depth) of mussel cultures, for counting each structure by the ‘long-line echo-counting’ method, for monitoring their shape in situ, and for classifying the mussel rope segments into three growth categories (‘in growth’, ‘full’ and ‘empty’). The use of acoustic tools for monitoring underwater mussel culture grounds, for management purposes and for scientific studies, could be extended to other artificial structures in shallow water environments.

Seasonal changes in phosphatase activities in Toulon Bay (France)

We studied the characteristics of the phosphatase activity (Km and Vmax) in total seawater and in particulate material of the three main plankton classes (0.25-5, 5-90 and >90 microm) in a coastal marine ecosystem of Toulon Bay (French Mediterranean Sea). The measurement of the hydrolysis of sodium paranitrophenylphosphate (pNPP), a substrate of phosphatase, revealed low and high affinity components in unfiltered seawater and in particulate matter. In unfiltered seawater, the low affinity activity was predominant from October to March during phytoplankton development. The high affinity activity dominated from April to June and was significantly correlated with the bacterial abundances. The phosphatase behaviour in the particulate material differs from that in the unfiltered seawater. The activity of the three particulate classes was generally much lower than that of unfiltered seawater, particularly the low affinity activity. The >90 microm size fraction consisted in greater part of zooplankton. In this size class, the activity (nmol l(-1) h(-1)) of the low affinity component was predominant from May to August, when the abundance of the larvae of copepods (copepodites) was highest. Its high specific activity (Activity/Protein concentration as nmol l(-1) h(-1) microg(-1)) was particularly elevated during this period. The 5-90 microm fraction consisted of phytoplankton cells, especially Dinoflagellates. Between September and January, the activity (nmol l(-1) h(-1)) of this size class was mostly supported by the low affinity component. The specific activity (nmol l(-1) h(-1) microg(-1)) of the high affinity component was highest in June and August. No significant correlation was found between phosphatase activities and chlorophyll a or total cell abundance. In return temporary relationships with specific taxa exist in particular with Ceratium spp., Gymnodinium spp. and Protoperidinium spp. The contribution of the 0.25-5 microm size class exceeded rarely 20% of the total particulate activity. Between June and August, high specific activities (nmol l(-1) h(-1) microg(-1)) were observed for its high affinity component. In autumn, strong rainfall increased the phosphate and nitrate concentrations and led to a drop in salinity, which probably explains the low phosphatase activities (nmol l(-1) h(-1)) and cell densities observed during this period.

Seagrass ( Zostera marina L.) bed recolonisation after anoxia-induced full mortality

Recolonisation of Zostera marina, following complete destruction caused by an anoxic crisis, was studied in the Thau lagoon (French Mediterranean Sea) from February 1998 to September 1999. The recolonisation took place surprisingly rapidly as biomasses similar to those from untouched areas were reached only nine months after seed germination. The recolonisation success was partly due to a high seedling survival rate as well as a rapid vegetative recruitment (ranging from 0.012 to 0.042 per day). Two phases of recovery could be observed: a rapid multiplication of shoots during the first 3 months was followed by an increase in biomass due to elongation of leaves. During the first year of recolonisation no flowering shoot was observed whilst reproductive effort was considerable during the second year. In case of two consecutive anoxic crises at the same site, the recovery would have probably been much slower, since the annual seedbank would have been depleted.

Vernalization requirement of wild beet Beta vulgaris ssp. maritima: among population variation and its adaptive significance

Summary Seven populations of Beta vulgaris ssp. maritima (wild beet) situated along a latitudinal cline were studied for their vernalization requirement and its consequences for fitness. Various cold regimes were applied in glasshouses and experimental gardens with plants of different ages. Three additional experimental sites (on the French Mediterranean, Atlantic and North Sea coasts) situated near three of the sampled populations, and thus including a reciprocal transplant design, were used to evaluate the influence of latitude under natural conditions. Survival and plant size were measured over 3 years. The vernalization requirement was greater in plants from more northern origins. The level of cold required to allow flowering overcompensated for the colder springs, so that northern plants in northern sites flowered less than southern plants in southern sites. Young seedlings were more difficult to vernalize than plants that had already developed vegetative rosettes. Differences in vernalization requirement seem to be an adaptive response to spring temperatures and season length in a particular latitude. A whole winter vernalization almost always led to flowering in the subsequent year whatever the latitude or geographical origin. Plants from the Atlantic and Channel coasts showed the highest lifetime reproductive success at all sites. Southern populations were better adapted to disturbed habitats as shown by their higher first‐year reproductive success. The North Sea population had a lower reproductive success than the Atlantic populations, even in its native environment.

STATIS-CoA: A methodological solution to assess the spatio-temporal organization of species assemblages. Application to the demersal assemblages of the French Mediterranean Sea

The organizational patterns of demersal assemblages (fish, crustaceans and cephalopods) in the Gulf of Lions were investigated on the basis of a set of six bottom trawl surveys performed between 1994 and 1999 (MEDITS programme). The use of a recent multitable method (STATIS-CoA) provided a detailed representation of the stable and variable parts of the spatial organization of demersal assemblages during the studied period. We showed that demersal assemblages of the Gulf of Lions were organized along a coast-open sea gradient. At the scale of the Gulf, we showed that this gradient can be split into three areas: 1) the coastal region and the continental shelf (10 to 200 m depth), 2) the upper slope (200 to 500 m) and 3) the deeper slope (500 to 800 m). Associated to this bathymetric structuring we found a species-richness gradient which decreases from the coast to the upper slope. Our analysis showed that this spatial organization pattern was highly persistent during the course of the study. However, some species caught in the slope area exhibited a strong variability of their spatial distribution mainly during the 1999 survey. From a methodological point of view, STATIS-CoA offers a rigorous theoretical framework for the simultaneous analysis of a three-dimensional set of data. Applied in the field of fisheries ecology, this method (1) constitutes a relevant way to analyse the spatial organization of species assemblages and its pattern of changes, and (2) could be of particular interest to treat the MEDITS data both at a local and at the North Mediterranean Sea scales.

Analysis of oxygen rate time series in a strongly polluted lagoon using a regression tree method

This article presents results on daily forecasts of dissolved oxygen rates in a lagoon, the ‘Etang de Berre’, situated close to the French Mediterranean sea coast and submitted to particular meteorological conditions and freshwater inputs. To provide estimates of the response variable y (dissolved oxygen), a set of jointed decision rules is constructed by successive binary splitting of the predictor space composed of wind speed and freshwater flow data. The prediction model is displayed in the shape of a binary decision tree. We propose a transfer procedure in order to improve the prediction error of the tree model. Results obtained on the ‘Etang de Berre’ data set allow to describe and precise the effects of the environmental variables on the dissolved oxygen dynamics. The transfer procedure applied after the tree building process gives gains of prediction accuracy of about 17%.

Forecasting physicochemical variables by a classification tree method. Application to the Berre Lagoon (south France).

The dynamics of the "Etang de Berre", a brackish lagoon situated close to the French Mediterranean sea coast, is strongly disturbed by freshwater inputs coming from an hydroelectric power station. The system dynamics has been described as a sequence of daily typical states from a set of physicochemical variables such as temperature, salinity and dissolved oxygen rates collected over three years by an automatic sampling station. Each daily pattern summarizes the evolution, hour by hour of the physicochemical variables. This article presents results of forecasts of the states of the system subjected to the simultaneous effects of meteorological conditions and freshwater releases. We recall the main step of the classification tree method used to build up the predictive model (Classification and Regression Trees, Breiman et al., 1984) and we propose a transfer procedure in order to test the stability of the model. Results obtained on the Etang de Berre data set allow us to describe and predict the effects of the environmental variables on the system dynamics with a margin of error. The transfer procedure applied after the tree building process gives a maximum gain in prediction accuracy of about 15%.

Variation of heavy metal contents of the green alga Caulerpa Taxifolia (VAHL) C. Agardh in its area of expansion in the French Mediterranean Sea

Concentrations in cadmium, copper, mercury, nickel, lead and zinc were determined by atomic absorption spectrophotometry in 72 samples of the green alga Caulerpa taxifolia collected in its area of expansion in the French Mediterranean Sea. The data obtained was used to carry out a statistical study on the two main parts of the thallus (pseudo‐stolons and pseudo‐leaves), in regard to the seasons, the geographical and bathymetrical localisations and the distance from sources of pollution. The highest concentrations were those of copper and zinc, followed by lead and nickel, then by cadmium and mercury to a lesser extent. The samples collected near the most heavily populated places such as Monaco and Menton harbours, showed the highest concentrations of heavy metals. It seems that pseudo‐leaves concentrate metals more than pseudo‐stolons and that the metallic charge increases with the depth. However, these results are significant only for some of the metals. The presence of heavy metals in rather large quantities in this alga may carry a toxicological risk for the fauna that feeds on it and may be a hindrance for a possible industrial exploitation. But, it is difficult to assess the degree of this risk. Thanks to its ability to concentrate metals, however, Caulerpa can be used as a biological indicator in the "in situ”; assessment of the metallic pollution of the sea.

Smoking and age-related macular degeneration. The POLA Study. Pathologies Oculaires Liées à l'Age.

To assess the associations between age-related macular degeneration (ARMD) and smoking. The POLA study is a population-based study taking place in the town of Sète, located on the French Mediterranean Sea border. The presence of early and late ARMD was assessed in 2196 participants on the basis of 50 degrees color fundus photographs using an international classification system. After adjustment for age and sex, current and former smokers showed an increased prevalence of late ARMD (odds ratio [OR] = 3.6, 95% confidence interval [CI] = 1.1-12.4; OR = 3.2, 95% CI = 1.3-7.7, respectively). An increased risk was present in participants who smoked more than 20 pack-years (OR = 3.0, 95% CI = 0.9-9.5 for 20-39 pack-years; OR = 5.2, 95% CI = 2.0-13.6 for 40 pack-years and more). In addition, the risk of late ARMD remained increased until 20 years after cessation of smoking (OR = 9.0, 95% CI = 3.0-27.0 for 1-9 years; OR = 4.0, 95% CI = 1.3-12.0 for 10-19 years; OR = 1.3, 95% CI = 0.4-4.3 for 20 years and more). Smoking was not significantly associated with early signs of ARMD. This study further confirms the adverse effect of tobacco on late ARMD. Former smokers seem to remain at high risk for ARMD.

Mitigation on Coastal Zone at French Mediterranean Sea and Applicability for Japan

Mitigation on Coastal Zone at French Mediterranean Sea and Applicability for Japan

A new genus and species of the deep-sea family coronarctidae (Tardigrada) from a submarine cave with a deep-sea like condition

Abstract A new genus and species of the deep-sea family Coronarctidae (Tardigrada, Arthrotardigrada), collected from a sublittoral submarine cave in the French Mediterranean Sea, is described and illustrated. Tardigrades were only present in the first centimetres of the cave sediment (1.5-2 cm), where the 80 % ofmeiofauna, largely dominated by nematodes, is also concentrated. Trogloaretus trionyehes gen. et sp. n. was only identified at the stations with complete darkness, mainly at the far end station. The new genus Trogloaretus shows several characters, distinguishing it from all known Coronarctidae: presence of only one somatic cirrus (cirrus E), three claws on each leg (reduction), and an absence of large accessory spine on the fourth pair oflegs. The presence of bar shaped placoids in the pharyngeal bulb may be regarded as a plesiomorphic character. These differences involve the modification ofthe previous diagnosis ofthe family Coronarctidae in order to accommodate the new genus Trogloaretus. Ecology and geographical distribution of Coronarctidae is reviewed.

Fine structure of spermatids and sperm of Dolioletta gegenbauri and Doliolum nationalis (Tunicata: Thaliacea): implications for tunicate phylogeny

In Dolioletta gegenbauri and Doliolum nationalis, collected in 1987 in the bay of Villefranche-sur-mer (French Mediterranean Sea), spermiogenesis is essentially the same. Early spermatids have a round head, a flagellum arising from a single centriole with short microtubules at 45° to its base, several mitochondria, and an acrosome 50 nm thick and 250 nm long with its long axis parallel to the plasma membrane. The acrosomal contents are dense, with a central denser plate. The nuclear envelope next to the acrosome is thickened and concave. In elongating nuclei, strands of chromatin become oriented parallel to the length of the nucleus and then twist helically. Although the mitochondria surround the nucleus, they remain relatively short and do not fuse into a single mitochondrion as in sperm of other tunicates. In very late doliolid spermatids, the acrosome undergoes exocytosis, and exposes fibrous material that stays associated with the tip of the sperm; no acrosomal tubule forms. Exocytosis at this stage may be triggered by fixation. If so, exocytosis probably occurs naturally at some time before fusion of sperm and egg. Sperm have elongate heads (1 μm×10 μm), with the anterior two-thirds of the nucleus surrounded by mitochondria. Spermiogenesis in doliolids, compared to that in other tunicates, is most like that in solitary members of the class Ascidiacea, except that in the latter the sperm mitochondria fuse and the acrosome appears incapable of exocytosis. In contrast, previous work has shown that salps (class Thaliacea) and colonial didemnid ascidians have an acrosomeless sperm with a spiral mitochondrion, while the class Appendicularia has a sperm with a midpiece, a compact head and an acrosome capable of exocytosis and acrosomal tubule formation. By outgroup comparison with echinoderms and acraniates, appendicularian sperm are plesiomorphic within the Tunicata. Thus, gamete morphology indicates that (1) solitary ascidians and doliolids had a common ancestor, (2) the popular idea that doliolids gave rise to appendicularians is incorrect, and (3) the Thaliacea are polyphyletic, doliolids having arisen very early from the ascidian lineage and salps having arisen later.

Die Morphologie und die Infraciliatur einiger Ciliaten (Protozoa: Ciliophora) aus dem Darm der Seeigel (Euechinoidea) Paracentrotus lividus und Arbacia lixula

Summary The morphology and the infraciliature of 3 ciliate species inhabiting the gut of the sea urchins Paracentrotus lividus Lamark and Arbacia lixula ( Linne ) from the French Mediterranean Sea (Banyuls-sur-Mer) are described. The redescriptions base on living observations and silver nitrate stained and biometrically characterized specimens. Cryptochilum echini Maupas , 1883, Entodiscus echini ( Russo , 1914) nov. comb, (for Colpidium echini Rirsso , 1914), and Pseudocohnilembus caeci ( Powers , 1935) nov. comb, (for Cohnilembus caeci Powers , 1935) belong to the order Scutico-ciliatida Small, 1967. Entodiscus echini ( Russo , 1914) and Entodiscus sabulonis Powers , 1935 are regarded as synonymous because they differ only by the caudal cilium which Russo (1914) obviously overlooked. Pseudocohnilembus caeci ( Powers , 1935) differs from the other species of the genus by its habitat and by many biometric characters. The poorly described Pseudocohnilembus cantabricus Fernandez-Leborans and Casto de Zaldumbide , 1984 is regarded as identical with the older known P. marinus Thompson , 1966, because with respect to morphology and infraciliary structures it is within the range of variability of this species ; and its name thus fall as synonym of P. marinus .