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| Registros recuperados: 47 | |
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| Kempf, Marc; Merceron, Michel; Dosdat, Antoine. |
| Farmed sea fish production is at the moment relatively undeveloped in France (20 million alevins, 2,600 tonnes of fish, 165 million francs), but it has growth potential that is yet to be exploited. Installation plans are eliciting a great variety of reactions depending upon the areas of the shoreline. The various objections, often passionate, generally rely upon environmental arguments. And yet, objective data that would make it possible to evaluate the latter are in large part lacking. The government, accustomed to regulating fresh water, lacks benchmarks and experience in the marine environment. Property developers need basic outlines and data to build their cases. Scientists are called upon, in a national and international plan, to help aquafarming grow... |
| Tipo: Text |
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| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/1994/publication-2628.pdf |
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| Merceron, Michel. |
| At the end of July 1982, a massive number of fish and benthic invertebrates died in Vilaine Bay. The mass of fish concerned has been estimated at several tens of tonnes. The analysis of the event's conditions indicates that it was asphyxiation caused by a very pronounced depletion of dissolved oxygen in the bay's bottom waters. The appearance of toxic phytoplankton in the years that followed (Dinophysis) is aseparate topic of research by IFREMER. The most likely mechanism of that anoxia is a succession of events: (1) a first flood of Vilaine River inducing a vertical stratification of waters in Vilaine Bay, (2) an intense and superficial bloom of marine phytoplankton, (3) a stormy weather breaking up the stratification and mixing superficial... |
| Tipo: Text |
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| Ano: 1989 |
URL: http://archimer.ifremer.fr/doc/1989/publication-2833.pdf |
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| Menesguen, Alain; Aminot, Alain; Belin, Catherine; Chapelle, Annie; Guillaud, Jean-francois; Joanny, Michel; Lefebvre, Alain; Merceron, Michel; Piriou, Jean-yves; Souchu, Philippe. |
| In order to be able to count the cases of coastal eutrophication and to propose methods to monitor as well as to reduce these phenomena, first of all it is necessary to precisely define the word eutrophication itself. Instead of the strict etymological definition, that is to say a progression of the enrichment of a medium, we will rather retain the concept of a state enriched at a point such as it causes harmful effects on the ecosystem, and nuisances to man's activities. Based on the average chemical equations of the organic matter synthesis/degradation in the sea, this operational definition thus puts forwards the harmful consequences of enrichment, i.e. the production of an excessive algal biomass, sometimes unbalanced from the point of view of... |
| Tipo: Text |
Palavras-chave: Alexandrium; Phaeocystis; Monostroma; Ulva; Dilution plume; Water trapping; Anoxia; Nitrogen and phosphorus loadings; Red tides; Phytoplankton blooms; Green tides; Eutrophication; Alexandrium; Phaeocystis; Monostroma; Ulva; Panache de dilution; Confinement; Anoxie; Phosphate; Nitrate; Apports terrigènes; Eaux colorées; Blooms phytoplanctoniques; Marées vertes; Eutrophisation. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/2001/rapport-22.pdf |
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| Merceron, Michel; Antoine, Virginie; Auby, Isabelle; Morand, P. |
| Ulva spp., the algae most responsible for green tides in Brittany (France), are found on the foreshore and in the most beachward wave area (MBWA) of many bays during green tide phenomena. These algae have recently been seen drifting at greater depths (reaching -20 m). In view of the significant quantities of algae found at these depths, and the less favorable conditions for algal growth than in the intertidal zone, we attempted to determine if they could grow there. For that, during their maximum growth period (from May to July), algae were picked up at three stations located on the foreshore, in the MBWA and in the subtidal (deep) zones of the Bay of Douarnenez, and their nitrogen, carbon and chlorophyll a+b contents were determined, and their... |
| Tipo: Text |
Palavras-chave: Nutrients; Irradiance; Photosynthesis; Ulva sp.; Algal blooms; Eutrophication. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3527.pdf |
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| Kempf, Marc; Jacq, E; Le Guellec, C; Merceron, Michel; Monfort, Patrick; Nezan, Elisabeth; Ryckaert, Mireille. |
| This document presents a year-long (1994) environmental study conducted on a site of intensive farming of salmonids (mainly fario trout) in Camaret Bay. A set of parameters were considered for the body of water and the sea bed (flow patterns, hydrology, sedimentology, biology, chemistry) and complemented by video observations. The study concluded that there was a measurable effect from the farm in its current configuration, but that the impact was of a very limited intensity and scope that did not affect the environment in a substantial way. It is recommended that production growth be accompanied by a minimum amount of environmental assessment. |
| Tipo: Text |
Palavras-chave: Bretagne; Truite fario; Salmonidés; Environnement; Pisciculture marine. |
| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/1995/rapport-2834.pdf |
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| Merceron, Michel. |
| The 1998 survey of green tides on the Brittany coast was performed in the same way as that of 1997 in order to allow comparison. 11 includes an inventory ofail the concerned sites, and a precise assessment ofthirteen ofthem, the most loaded. On these ones, nitrogen fluxes were surveyed during the critical period, and the green seaweed stock on the beach and in the first waves was quantified. The climatic conditions were opposite between the two years, very dry in spring and summer 1997, and wet in 1998. The irradiance contrast was inverse, and less pronounced. The nitrate contents and mostly the flows were more important in 1998. They generated nitrogen fluxes about 3.3 times those of 1997. The total number of sites concerned in 1998 is clearly higher than... |
| Tipo: Text |
Palavras-chave: Bretagne; Nitrate; Prolifération; Ulve; Eutrophisation; Brittany; Nitrate; Proliferation; Ulva; Eutrophication. |
| Ano: 1999 |
URL: http://archimer.ifremer.fr/doc/1999/rapport-2665.pdf |
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| Merceron, Michel; Piriou, Jean-yves; Coic, Daniel. |
| The coastal marsh of Kervigen is located near by the bay of Douarnenez and its 22 hectares are almost entirely covered bV reeds. An experiment was there carried out to assess the nitrogen flux depletion of a sma/l stream, the Kerharo. The last one has a 45 I<m2, mostlv agricultural, drainage basin. Due to its nitrate loadings to the nexl sandy beach, it feeds a green algae (U iva) proliferation. In order to control its nitrogen fluxes, the stream was partly divelted through a part of the marsh (9 ha), before it was allowed ta go back to the main bed. Thus a collapsible weir was set up during severalsprings and summers, i.e. the growing period ofulva. The nitrate stripping off the going through flux is withina60 to 90 % range, thal is important (about... |
| Tipo: Text |
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| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/1997/acte-3335.pdf |
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| Merceron, Michel; Gaffet, Jean-dominique. |
| Current recordings were performed near the middle of the great breakwater of Cherbourg ("Grande Digue", inner side) during two months of the 1993 summer. The data show that, in this site, the currents drive mostly westwards. They are driving eastwards only during the first half of flood. In the tidal cycle, there is only one current slack, at law tide. The most important velocities are observed during the high tides : 0.5 to 0.6 m.s-1• The fish net pens, which are located there, tend to speed up the undemeath currents and, thus, contribute to scatter the farm effluents. The temperature and salinity records are also displayed. _ |
| Tipo: Text |
Palavras-chave: Courant; Cage; Élevage; Poisson; Cherbourg; Current; Net pen; Farm; Fish; Cherbourg. |
| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00082/19330/16924.pdf |
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| Sauriau, Pierre-guy; Merceron, Michel; Goulletquer, Philippe. |
| Marine fish farming is fairly recent in France and it is still in the process of being developed. On the Atlantic and Channel coasts, it deals mainly with Atlantic salmon (Salma salar), fario trout (Salmonella faria) with l,400 t in 1991, and turbot (Scophthalmus maximus) with 600 t. In Gravelmes a bass (Dicentrarchus labrax) and bream (Sparus auratus) farm (1,000 t) uses water which is heated (Mediterranean production for these two species is around 2,000 t). Although these figures are low compared to French shellfish farming (200,000 t) and foreign fish farms (150,000 t in Norway, for example), they are growing. |
| Tipo: Text |
Palavras-chave: Biocénoses; Conchyliculture; Algoculture; Mesure de Protection; Impact non trophiques; Impact; Aquaculture littorale; Aquaculture marine. |
| Ano: 1997 |
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| Merceron, Michel. |
| On tens of sandy beaches of Brittany, a green seaweed (Ulva) blooms during spring and summer. In the sites where the proliferation is the most important, the total biomass amounted to 20 000 t of wet weight in 1997, at the time of maximum. These "green tides" occur every year in nearly the same locations. They have a very harmful impact on local tourism. In many communes, beached and rotting algae are collected and dumped (43 000 m 3 as a whole in 1997). The main development of biomass takes place between the surf zone and the bare sand.The outbreak requires three coexisting conditions : 1) a sandy beach gently sloping, 2) a weak residual current (i.e. once the tidal back and forth movement has been filtered), 3) a nitrogen loading, even moderate (ammonium... |
| Tipo: Text |
Palavras-chave: Brittany; Eutrophication; Proliferation; Ulva; Marine algae; Bretagne; Eutrophisation; Prolifération; Ulves; Algues marines. |
| Ano: 1999 |
URL: http://archimer.ifremer.fr/doc/1999/acte-46.pdf |
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| Merceron, Michel. |
| De l'agglomération de CAEN à la mer, le canal double le cours de l'Orne sur une distance d'environ 14 km. Au port de OUISTREHAM le canal cominunique avec la mer par deux écluses, et en aval des écluses se trouve la confluence avec l'orne, Jusqu'au niveau des basses mers, le chenal est commun et il est encadré par deux enrochements d'axe N.S. sur une distance de 2 Km (cf. carte n°1). Les débits de l'Orne seraient respectivement de 2 m3/s en étiage, d'environ 21 m3/s en débit moyen et de 70 m3/s en crue. Ce fleuve alimente la sédimentation en matières fines qui se produit à la fois dans le chenal commun a l'aval, et dans l'avant-port soit entre le point de confluence et les écluses. La présente étude (carte n°2) porte sur : - la zone de sédimentation... |
| Tipo: Text |
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| Ano: 1980 |
URL: http://archimer.ifremer.fr/doc/00106/21684/19263.pdf |
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| Merceron, Michel. |
| The yearly study of Ulva in Brittany aims at building a time series of its proliferations and corresponding nutrient loadings. The goal is to detect results of wilful loading reductions, and to distinguish them from natural variations. This first actually quantified study is the starting bench-mark of the process. Forty-five concerned sites were listed in 1997. They are nearly the same as in 1988, 1991 and 1994 (previous rough census). The Côtes d'Armor and then the Finistère are the most affected departments. The Morbihan is less and file et Vilaine not at all. Ulva biomass was precisely quantified in about fifteen locations during the growing season, along with nitrogen loadings of local streams (mostly nitrate). The fluxes of nitrogen - the limiting... |
| Tipo: Text |
Palavras-chave: Bretagne; Nitrate; Prolifération; Ulve; Eutrophisation; Brittany; Nitrate; Proliferation; Ulva; Eutrophication. |
| Ano: 1998 |
URL: http://archimer.ifremer.fr/doc/1998/rapport-1580.pdf |
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| Registros recuperados: 47 | |
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