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1.
《Oceanologica Acta》1998,21(2):263-269
A study of the recent sedimentation of the ria de Gernika (Bay of Biscay) is undertaken to characterise different steps of its Holocene filling. Sedimentological and micropalaeontological analysis of six cores sampled in the ria, completed with absolute dating (14C, and based upon 210Pb exc.), allow us to identify three phases in the filling of the ria that are limited by two transgressive shifts (3500 and 2500 yr. B.P.) already described in other areas of the Bay of Biscay. In the first phase, lithologies as well as benthic foraminifera and ostracode assemblages are typical of coastal marine palaeo-environment. During the second phase the euryhaline waters progessively occupy the central area of the estuary. Here the presence of allochthonous microfauna, particularly of planktonic foraminifera, indicates an increase of exchanges with marine waters that can reach the inner areas of the estuarine system. The last phase (2500 yr. B.P. to the present), which corresponds to the recent and active sedimentation, is marked by an impoverishment of the microfaunas, the filling of some channels and the increase of salt marshes. The estimated sedimentation rate for the upper decimetres of the cores (0.73-1.29 cm·yr−1) shows faster sedimentary filling of the ria with anthropic action evidenced by the presence of metallic contaminants and hypohaline microfauna. 相似文献
2.
《Oceanologica Acta》1998,21(5):645-654
Intensity and spectral characteristics of the fluorescence of water samples collected along the transect Cherbourg-Isle of Wight during four cruises for excitations at 370, 313 and 270 nm have been investigated within the framework of the FluxManche II program. Seasonal and spatial differences appeared to reflect on the one hand, variations in terrestrial inputs, and on the other hand, waters masses structuring. The observed linear variation of the fluorescence intensity with salinity indicates a gradual dilution of the continental humic material in going from the coasts to the central part of the English Channel. The largest signal was observed for the English coastal waters in agreement with important terrestrial inputs from the Solent river. While the fluorescence intensity was not found to be correlated with the DOC, it shows a good correlation with the nutrients. This result could indicate both a supply from terrestrial inputs and an almost simultaneous autochtonous regeneration. As similarly reported for waters in the eastern part of the French coastal zone, excitation at 313 nm gives evidence for the presence of two classes of fluorescent dissolved organic matter. These two fluorescent components are indicative of the simultaneous presence of continental humic substances and substances whose assignment to marine humic substances or to heterotrophic related substances are still an open question. As compared to the eastern part of the Channel along the French coasts, excitation at 270 nm indicates a lower content of protein-like compounds which may be related to a lower biological activity along the transect or may be due to the fact that the samplings were made out of the phytoplanktonic bloom period (April–May 1995). 相似文献
3.
《Oceanologica Acta》1998,21(5):677-694
Microphytobenthic biomass was estimated in the Bay of Brest (1994) and the western English Channel (Trezen Vraz, 1993) using spectrophotometry. Best results (42 % difference) were obtained with an instantaneous extraction procedure at room temperature, compared with the cold extraction procedure. Chlorophyll biomass in sediment was higher in the western English Channel (65–215 mg Chl a m−2) than in the Bay of Brest (10–113 mg Chl a m−2), in contrast to total pigment biomass (Chl a + pheo a : 88–254 mg m−2 at Trezen Vraz vs. 131–934 mg m−2 in the Bay of Brest). This study emphasized decreasing pigment biomass from the estuary to the open sea. Low benthic pigment biomass in the Bay, compared to eutrophic ecosystems, agrees with previous studies on the pelagic system, suggesting that there is no eutrophication in the Bay of Brest. Microphytobenthic blooms were strongly correlated with environmental factors, such as river floods, light intensity, water temperature and the spring/neap tidal cycle. Turbidity and light could be limiting factors at Roscanvel, i.e. the deepest site facing gyre circulation. The latter would favour sedimentation of silt particles at the sediment-water interface. Microphytobenthos population dynamics would be also dependent on the spring/neap tidal cycle, since maximum chlorophyll biomass occurred at neap tides at all three sites in the Bay of Brest, in contrast to the western English Channel. Lower temporal variations of pigment biomass in sediment were observed in the Channel, compared with the Bay of Brest; maximum chlorophyll biomass in sediment was found to occur three to four weeks after the phytoplankton blooms. 相似文献
4.
《Oceanologica Acta》1999,22(3):353-364
The Bay of Guaratuba, whose area is approximately 45 km2, is a basin, situated to the south of Brazil (25° 52′ S; 48° 39′ W) and connected to the Atlantic ocean. In its northern part, a region of mangrove is found, under the influence of seasonal fluvial contributions, dominated by Laguncularia racemosa. The depth exceeds 6 m in some places. According to the period of the year, salinity varies between 3 and 37, and temperature between 15 and 28 °C. Several of the present fish species are exploited by commercial and recreational fisheries. This work describes characteristics of the fish populations occupying this mangrove, and temporal and spatial evolution of populations of the main species from available data on their biology. Between September 1993 and August 1996, fish samplings have been undertaken monthly by trawl, according to the same fishing effort (20 min), in channels of this ecosystem. Size, numerical abundance and weight of each individual of species were measured, as well as surface and bottom temperatures and bottom salinity. Species richness, Shannon-Weaver's diversity index were calculated and abundances were processed by the multivaried analysis. The global species richness is 61 species, distributed in 28 families; the better represented species are Sciaenidae (10), Gerreidae (5), Carangidae (5), Ariidae (4), Haemulidae (3), Serranidae (3), Bothidae (3). Each year, the number of species varies between 41 and 44, and a group of eight species represents between 80 to 90 % of the density and 75 % of the biomass. The constancy of this dominance is the main characteristic of this fish assemblage. The most represented species in abundance is Pomadasys corvinaeformis is the first two years, then Stellifer rastrifer. The group of eight main species is shared by 15 species in total, of which 13 for the density and 14 for the biomass. The most important monthly catches take place in winter season, during which one observes a decrease of water temperature and an increase of salinity. These species, however, being likely to be replaced by others according to the year or the season; one never finds the same composition in the assemblage which preserves always the same structures. Seasonal differences between seasons under marine (winter) and continental (summer) influences play a major role on the dynamics of fish in the Guaratuba mangrove. This ecosystem plays a functional role in the achievement of the life cycle of many permanent or temporary species. Those having succeeded to reach high levels of abundance are not represented in a uniform way in the course of the year, even when they reside permanently in the ecosystem. Periodic displacement strategies for self regulation of stocks abundance, are necessary mechanisms for these populations, which thus success to coexist in occupying the mangrove. 相似文献
5.
《Oceanologica Acta》1999,22(2):179-191
The grain size of mature coastal sands changes rapidly in response to the variation of the energy regime which provokes either erosion or deposition of fractions of the textural assemblage. Whatever the dynamic conditions, questions of paramount importance such as the size of grain populations transported simultaneously, the most common size of the grains in movement and the grain-size range of the sediment fraction involved are still poorly understood. The present paper deals with an attempt to describe this fraction without any consideration of the processes responsible for the observed changes. A major problem results from the fact that the distribution of the mobilized fraction cannot be known and described by direct comparison between the initial and the final grain-size curves. The only way to characterize the mobile fraction between two subsequent grain-size states is to simulate various kinds of removal or deposition. The first question is to express the shape of the actual distributions of the sediments mathematically. The simple Gaussian approximation being irrelevant, distributions can be expressed using advanced computer programmes which can provide mathematical expressions for all distributions. The cubic-spline approximation was chosen. The mobile fraction was assumed to have a Gaussian distribution. Various tests were made in order to simulate qualitative phenomena observed in nature (bimodality, grain-size parameter changes…) and to assess the three parameters which define the characteristics of the fraction deposited or removed: modal value, dispersion of the mobile population and relative amplitude of the change. An application was carried out on the Senegalese coast offshore from the Senegal delta and on the Mediteranean coast in the Gulf of Lions. It suggests that the dynamic agents have a great selectivity. Further developments are considered. 相似文献
6.
《Oceanologica Acta》1998,21(6):887-906
This paper presents an ecological modelling of the Bay of Seine (Eastern Channel) over the last twenty years, chosen as a typical case of eutrophication in a river plume. In the physical sub-model, the Bay is divided into 42 boxes and water fluxes between them are calculated automatically using Ifremer's “Elise” software. A two-layer, vertical thermohaline model is then linked with the horizontal circulation scheme in order to take vertical stratification into account. The biological submodel deals with two chemical elements, nitrogen and silicon, and splits phytoplankton into diatoms and flagellates. Results from this ecological model point out the spatial concordance of highest phytoplanktonic concentrations with the river plume spreading in the bay. Contrary to diatoms, flagellate production appears to be mainly confined to the eastern bay, due to the vertical haline stratification in front of the river mouth. As far as the whole bay is concerned, the interannual fluctuations of diatom production are related to the level of spring insolation, whereas silicon inputs regulate diatom production in the river plume. The flagellate summer production in the plume is enhanced by high water temperature and high N/Si ratios, which appear during dry years with low discharge regimes. Finally, interannual increase of flagellate production could be related to gradual increase of nitrogen loadings, contrasting with silicon loadings, which remained stable for twenty years. 相似文献
7.
《Oceanologica Acta》1998,21(6):939-950
The release of enteric pathogenic bacteria in aquatic environments poses the problem of the fate of these bacteria under the effects of environmental factors (solar radiation, salt concentration, temperature, nutrient level, pH, competition). Frequently, these bacterial cells, potentially pathogenic, enter into a non-culturable state on routine bacteriological plating media. However, the use of direct detection methods DAPI stained cells allows the visualization of these Viable but Non Culturable cells VNC. But, beyond the characterization of the viability of the cells electron transport activity, metabolic activity, membrane integrity, structure and/or quantity of DNA, what happens with the virulence of these cells? This problem was experimentally investigated according to the bacterial model Salmonella Typhimurium. The virulence of this strain, which is the agent of the murine typhoid, was evaluated on a mouse model. Experimentally, the effects of some environmental factors on the survival and on the maintenance of virulence of Salmonella Typhimurium were measured in microcosms exposed to UV radiation (four germicidal lamps 8 mW s−1 cm−2, wave length: 254 nm, salt concentration (Sea Salt Sigma, 37, nutrient starvation. The microcosms were simultaneously submitted to these three factors, with variable exposure times. For each of those times, the viability of the nonculturable cells which became nonculturable because of the exposure to the three factors was measured through different physiological states notable in the cells, after using different fluorescent dyes. The stained cells were observed by epifluorescence microscopy and analysed by image cytometry. So, the cellular populations are characterised by enumeration of respiring bacteria CTC, [39], metabolising bacteria YEK, [22] modified, bacteria owning an undamaged cytoplasmic membrane LD, Live/Dead BacLight Viability Kit. Molecular Probes Inc.; we also determined the quantity and/or structure of DNA of the cells fluorescence level of DAPI stained cells), After exposure to the three factors for one hour 13.56 J cm−2, while the plate count cell density rapidly decreased from #107 cells mL−1 to0.1 cell mL−1, physiological states of these viable but non-culturable cells are similar to those of non-exposed cells. On the other hand, after exposure for three hours, only 10 % of the cells deposit a CTC formazan-crystal and 20 % are substrate responsive cells enlarged cells in presence of Yeast Extract and Cephalexin: YEC. Half of the cellular population presents an undamaged cytoplasmic membrane and the level of fluorecence of DAPI stained cells is close to 85 %, which shows that the DNA of these cells is weakly damaged. After exposure to the three experimental factors for24 hours 315 J cm−2, weak replies to the physiological tests used in this study to characterize the viability of the non-culturable cellular population are observed CTC: 4 %; YEC: 2 %; LD: 11.8 % while the fluorescence level of DAPI stained cells remains firm at 80 %. At the same time, the virulence expression of VNC cells of Salmonella Typhimurium, evaluated by intraperitoneal injection to the mouse route which excludes uncontrolled parameters, unlike the per os route does not seem to be correlated with the cellular viability such as it has been evaluated in this study. A 30 min exposure (6.73 J cm−2) to the three environmental factors, leading to the non-culturability of almost the entire exposed cell population 0.08 culturable cell mL−1 whereas the level of viability of those culturable cells is closed to the one of non-exposed cells. The injection of 1000 of those cells 0.001 culturable cells in 100 μL inoculated into the mouse a group of ten mice does not cause any mortality four weeks post-inoculation, whereas the injection of the same dose of non-exposed cells leads to the death of all mice in the group one week post-inoculation. According to our preliminary experiments on Salmonella Typhimurium, the loss of the state of culturability and the loss of virulence towards mice by intra-peritoneal route, because of the exposure to associated effects of UV irradiation 254 nm, salinity 37 and nutrient starvation, seem to be concomitant. 相似文献
8.
《Oceanologica Acta》1999,22(3):337-352
We compared the ability of three direct methods (increment summation, loss summation and instantaneous growth rate coefficient), the size-frequency method, and eight indirect methods (Banse and Mosher, Benke, Brey, Edgar, Morin and Bourassa, Plante and Downing, Robertson and Schwinghamer et al.) to measure or to predict the secondary production of a Mediterranean population of the polychaete Ditrupa arietina. This comparison was carried out both on the 1994 cohort during its two-year lifespan and on the entire population during the two years of the study (1994–1996). Our results showed that all three direct methods are more or less equivalent. Results referring to the year 1994–1995 showed a strong overestimation of the actual production by the size frequency method. This is attributed to the existence of an average individual maximal size below which the actual production equals zero. During the same year, the results obtained using indirect methods were highly variable, partly, but not solely, due to the type of environment for which the regression models were built. The incorporation of temperature as an independent variable within the most recent regression models did not contribute to improving the quality of the predictions. Results referring to the year 1995–1996 confirm the incapacity of both the size frequency and the indirect methods to predict changes in the P/B ratio in relation with age structure and recruitment irregularities. These results are discussed in the context of inferring productivities both at the population and the community level. 相似文献
9.
《Oceanologica Acta》1998,21(4):597-607
The hydrothermal environment is characterised, among other things, by a high metal concentration, related to the convective sea-water circulation inside the oceanic crust and its interaction with basaltic rocks. The biological communities associated with the hydrothermal system can survive in this toxic environment owing to their ability to regulate their intracellular metal levels by excretion or accumulation of metal ions in non-toxic forms. Various detoxification processes have been previously studied within an hydrothermal organism: immobilisation and precipitation of the metal in lysosomal systems, or binding to specific and soluble ligands such as metallothioneins. The later are heat stable and characterised by a high content of cysteine. The quantification of Fe, Zn, Cu, Mn, Cd, Ag, Ba and Sr in the tissues of the vent mussel Bathymodiolus sp. indicates a high accumulation of these metals in two target organs, the gill and the digestive gland. This accumulation is in relation with high concentrations of metallothioneins, but the subcellular distribution of metals indicates a higher contribution of the insoluble compartment for detoxification processes. These results are compared with the literature data about metal bioaccumlation in Bathymodiolus thermophilus collected at the Galapagos Rift. 相似文献
10.
《Ocean & Coastal Management》1999,42(2-4):155-164
The purpose of this paper is to outline the wealth of experience obtained by Argentine and Uruguay through the reciprocal cooperation framework provided by the Treaty of the Rı́o de la Plata and its Maritime Front. This agreement, signed by both countries in November 1973, provided for the establishment of a Common Fishing Zone and an international governmental agency, the Comisión Técnica Mixta (Binational Technical Commission), whose main functions include achieving the rational exploitation of the marine resources in those waters.2 相似文献
11.
《Oceanologica Acta》1998,21(1):21-31
During the PROGEMA I cruise which took place on the south-western Pacific coast of Mexico (between 14° and 16° N, 92° and 96° W), 3.5 kHz echosounding profiles, surface samples and cores as well as hydrological and oxygen minimum measurements down to 2250 m water depth were made in the Gulf of Tehuantepec. Chemical, sedimentological, mineralogical, X-ray and BEM analyses of waters, core and surface samples provided new data which permit a better knowledge of the Gulf of Tehuantepec margin, where tectonic activity is due to an active subduction.On the shelf of the gulf, the distribution pattern of quaternary deposits is affected by a double tectonic forcing and by eustatic oscillations of the sea level. The first tectonic control is linked to the existence of north-south tectonic troughs in the Tehuantepec Isthmus, in which the atmospheric circulation between the Gulfs of Mexico and Tehuantepec is accelerated by the Venturi effect. The resulting winds, called “Tehuanos”, play an important role in the forcing of surface circulation in the Gulf of Tehuantepec, inducing a deviation of the general circulation and thus forcing the distribution pattern of terrigenous sediment supply according to two physiographically and mineralogically distinct provinces, inherited from the past tectonic evolution, which are separated by the Tehuantepec axis.
- •-|A southeastern province related to the Caribbean Plate and fed by: (1) the rivers draining the Chiapas Massif; and (2) the Costa-Rica Current driving tropical and subtropical waters from Central America.
- •-|A northwestern province part of the North American Plate and fed by: (1) the Rio Tehuantepec which drains the Sierra de Oaxaca; and (2) the Californian Current.
- •-|shallow banks where the products of a present-day phosphatogenesis are concentrated because they are swept by upwellings. The latter are reinforced because the banks are situated south of the wind corridor;
- •-|tectonic depressions acting as sediment traps;
- •-|numerous canyons cutting the slope along brittle accidents, driving weak turbidity currents but which play an important role in the forcing of upwelling currents. Antarctic diatoms are found which are conveyed by the deep circulation from the South-Eastern Pacific and provide evidence that Antarctic Cold Water masses (AABW) rise towards the shelf.
12.
《Oceanologica Acta》1998,21(6):831-843
Shellfish farming leaves its mark on the environment in which it has developed, and the men who depend upon it. These changes have altogether balanced the lagoon cycle and have caused disastrous episodic events. Increased water clarity caused by the uptake of particulate material by shellfish farming allows seagrass to grow in deeper areas of the lagoon (down to five metres). Shellfish farming nutrient transformations increase ecosystem productivity, even if the filtration pressure keeps phytoplankton biomass at a low level. Storage of phosphorus and nitrogen in animal tissue limits eutrophication in this ecosystem. Transfer of oysters from growout facilities increases animal and vegetal specific diversity. The presence of large amounts of shellfish allows for the development of a masive benthos, while organic enrichment from biodeposition changes the specific composition of soft-bottom benthos. In the deeper areas, (less than six metres), where summer thermoclines limit oxygen transfer from surface water, the organically enriched substrate induces oxygen depletion and ammonium and nitrogen sulfide accumulation in the water column. This ecosystem dysfunction kills benthic populations, and sometimes reaches pelagic populations and affects the shellfish farming economy. 相似文献
13.
《Oceanologica Acta》1998,21(2):191-207
The Gironde estuary (France) discharges to the ocean an important amount of suspended particulate matter in the form of turbid plumes. The surface plume is more particularly studied from coastal oceanographic surveys and NOAA/AVHRR satellite data collected during a French programme of coastal oceanography (PNOC-Atlantic). The AVHRR reflectances are atmospherically corrected according to an algorithm based on the clear water concept. The comparison with suspended sediment concentrations are realised by direct and indirect calibrations. The correlations obtained show that at a same concentration the reflectance varies, probably because of varying particle (floc) size and composition. The shape and the surface measured from low resolution (4 km × 4 km) and high resolution (1 km × 1 km) AVHRR data are then compared to the forcings introduced by the fluvial output, the tide, neap and spring tide and the wind variations. The latter have an important effect on the orientation of the distal part of the turbid plume. 相似文献
14.
《Oceanologica Acta》1998,21(2):209-221
Coastal waters are generally a product of mixing between continental and oceanic originated water masses. Near river mouth areas, as in the Gironde estuary, oceanic waters are modified by the influence of freshwater discharge that introduces suspended and dissolved substances, including pollutants. Within PNOC (Programme National d'Oceanographie Côtière) our objective is to determine the extent of the influence of the Gironde estuary on to the Aquitanian continental shelf. Several cruises for collecting hydrological data have been carried out in this area. The data of every cruise were coupled with a NOAA-11 satellite passage. The recorded images have been analysed and were compared with the results given by a 3D mathematical model. The interaction among different dynamical factors (density, wind-driven and tidal circulation) controls the mixing and the transport of low salinity waters. 相似文献
15.
《Oceanologica Acta》1998,21(6):861-870
Nitrate and ammonium uptake rates were measured in spring and summer in deep and shallow wellmixed waters of the English Channel during different cruises between 1986 and 1994. In the deep waters, nitrate uptake was relatively low during phytoplankton development and ammonium uptake represented more than 70 % of the total uptake irrespective of the season. In the shallow waters, nitrate uptake during spring phytoplankton growth was high and represented about 75 % of the total uptake. Ammonium uptake became substantial towards the end of spring and summer. The high contribution of ammonium to the nitrogenous nutrition of phytoplankton over the whole of the well-mixed waters is related to a high rate of recycling of nitrogen in the water column. Ammonium regeneration by microheterotrophs can satisfy between 62 % and the totality of the phytoplankton nitrogen requirements. The high primary production in deep well-mixed waters is not supported by allochthonous nitrogen supply but by an intense in situ regeneration of nitrogen. The situation is similar in shallow well-mixed waters, except during the spring bloom. 相似文献
16.
《Oceanologica Acta》1998,21(2):371-381
Regular flights over the Bay of Biscay by the French Customs Air Service, have enabled us to record more precisely, from 1989 to 1995, the geographical locations of French and other European Community (EU) fishing boats. Data showed three main ‘métiers’ within the Bay of Biscay fishing fleet: French and Spanish bottom trawlers (61 %), French gill-netters and Spanish longliners. More than 80 % of gill-netters worked inside the territorial sea (12 nautical miles) and 60 % of them worked south of Noirmoutier (47°N). Longliners moved according to the seasons, from the edge of the continental shelf to the 50–100 m sounding lines. Since they work at night, only few pelagic trawlers have been recorded (records being made in daylight). The potters, liners and other small ‘métier’ boats of the bay were only located along the coast. The position of the French boats' positions according to their registration district showed that most boats worked close to their landing ports and that the overlap is small between the areas of two neighbouring fleets. Further analysis of the spatial distribution of boats in the French EEZ showed that Spanish boats were mainly recorded in the southern part of the Bay of Biscay, and that most were Basque. Belgian and Dutch beam trawlers fished their quota of sole off the ‘Pertuis Charentais’, the Gironde estuary and the ‘bassin d'Arcachon’. The 100 m sounding line appeared to constitute a demarcation line between the major fraction of the French fleet and other EU fishing boats. Although some fishing areas were only visited by boats practising a particular ‘métier’, others were coveted by everybody and, consequently, were areas with the most serious risk of conflicts. 相似文献
17.
《Oceanologica Acta》1998,21(6):923-935
As part of the Programme National d'Océanographie Côtière, the nutrient dynamics of the Bay of Seine were studied between 1992 and 1994 in order to complement work on ecological modelling. Firstly, the River Seine's nutrient fluxes were established: 80 000–130 000 t a−1 of dissolved inorganic nitrogen, 6 400–8 4001 a−1 of dissolved phosphorus and 20 000–77 000 t a−1 of dissolved silicium. Estuarine processes were taken into account. Consequences of nutrient loading for the bay were then evaluated at the pelagic level (nutrient and chlorophyll enrichments) and the benthic level (distribution of various phosphorus fractions in superficial sediments). The large continental inputs always induce concentration gradients in the water from the mouth of the river to the northwest of the bay. The northward spreading of fine particulate matter controls the distribution of adsorbed phosphate and iron-aluminium bound phosphate in sediments. In contrast, calcium bound phosphate, the main fraction in sediments, is not affected by river inputs. Organic phosphorus in sediments is related to phytoplankton blooms, with increasing concentrations during productive periods; afterwards the fast recycling prevents sedimentary accumulation. The nutrient depletions observed beyond the turbid plume during spring 1992 enabled the calculation of nutrient uptake rates, and the comparison of these rates with phytoplankton biomass (chlorophyll a + phaeopigments). Ratios of nutrient consumption to pigment concentration were estimated at 1 μmol μg−1 for nitrogen, 0.05 for phosphorus and 0.5 for silicate. These values, as N/P and Si/N uptake ratios (respectively 17.5 and 0.4), were similar to usual values. 相似文献
18.
一到夏天,坐落在美国海滨的美丽小城艾米蒂就热闹非凡,从世界各地赶来的游客都仰慕这里的海滨浴场,纷纷来这里避暑消夏。一天,艾米蒂警察局局长布劳迪接到海滨浴场管理人员打来的电话:“局长,刚刚有一位女士在浴场那边 相似文献
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