Le mercure (Hg) est un élément métallique naturellement présent dans l'environnement qui connaît aussi un cycle d’émission anthropique. Le Hg est présent sous différentes formes inorganiques (mercure élémentaire Hg°; mercure ionique Hg2+) et organiques (e.g. méthylmercure MeHg). Le Hg peut être méthylé dans l'eau et les sédiments par le métabolisme des bactéries pour former du MeHg, la forme chimique la plus toxique qui est de plus bioamplifiée dans la chaîne alimentaire aquatique. Le travail effectué dans cette thèse « Etude de la spéciation et du devenir du mercure dans les eaux côtières » a répondu à trois objectifs: - Déterminer les formes chimiques du Hg dans les eaux côtières à des concentrations inférieures au ng/L (10-9 g/L).- Etudier les transformations du Hg (Méthylation, Deméthylation et Réduction) dans les eaux estuariennes et côtières et leur influence sur le cycle du Hg dans la zone littorale (panache turbide de l’Adour). Evaluer les émissions du Hg gazeux (Hg°) dans les zones estuariennes et côtières par l’utilisation des modèles semi-empirique d’échange gazeux à l’interface eau-atmosphère. / Mercury (Hg) is a metallic element naturally found in all the environmental media that could also be released by anthropogenic processes. Mercury is present in various chemical forms, inorganic (elemental mercury Hg°, ionic mercury Hg2+) and organic (e.g. methylmercury MeHg). Hg can be methylated in water and sediments by the metabolism of the bacteria to form MeHg, the most toxic Hg form which is biomagnified in the aquatic food chain. This work "Study of mercury speciation and fate in coastal waters" had three objectives: - Determination of the chemical forms of Hg in coastal waters at low concentrations, lower than ng/L (10-9 g/L). - Determination of Hg transformations (Methylation, Demethylation and Reduction) in estuarine and coastal waters and their influence on the Hg cycle in the coastal zone (turbid plume of the Adour River). - Evaluation of the emission of gaseous Hg (Hg°) in coastal and estuarine zone using semi-empirical gas exchange models at the water-air interface.

nÃo hà / A modelagem ambiental à uma importante ferramenta para projetos e estudos envolvendo a gestÃo ambiental, devido à complexidade dos sistemas ambientais. Com ela à possÃvel integrar um grande nÃmero de variÃveis e processos de forma a obter uma visÃo dinÃmica de tais sistemas e avaliar as suas condiÃÃes presentes e futuras. Neste trabalho sÃo apresentados os resultados de modelagens da qualidade bacteriolÃgica da Ãgua da Ãrea costeira de Fortaleza (Brasil), frente a diversas entradas de cargas contaminantes nas mesmas. Coliformes termotolerantes, usados como indicadores de qualidade de Ãguas de banho pelas normas brasileiras, foram numericamente modelados usando o SisBaHiA (Sistema Base de HidrodinÃmica Ambiental), usando-se cargas contaminantes provenientes de trÃs diferentes tipos de fontes: rios, galerias pluviais e emissÃrio submarino. Os modelos foram implementados de forma a representar as variaÃÃes de decaimento frente à radiaÃÃo solar e outros fatores ambientais. Foram obtidos valores relativamente prÃximos entre os resultados modelados e monitorados em campo em diferentes cenÃrios. Os resultados mostraram que as galerias pluviais sÃo as fontes de contaminaÃÃo mais importantes, respondendo por episÃdios de nÃo cumprimento dos padrÃes de qualidade de Ãgua de banho, especialmente durante os perÃodos chuvosos. AlÃm disto, os resultados mostraram nÃo haver riscos da pluma do emissÃrio submarino de Fortaleza alcanÃar as Ãreas de banho das praias da cidade. / The environmental modeling is an important tool for studies and projects involving environmental management, due to the complexity of environmental systems. With it you can integrate a large number of variables and processes in order to obtain a dynamic view of such systems and assess their present and future conditions. This paper presents the results of modeling the bacteriological quality of the water in the coastal area of ​​Fortaleza (Brazil), and against several entries contaminant loads in them. Fecal coliform, used as indicators of quality of bathing waters by Brazilian standards, were numerically modeled using SisBaHiA (System Base Environmental Hydrodynamics), using contaminant loads from three different sources: rivers, storm sewer and outfall . The models were implemented to represent the changes in decay forward to solar radiation and other environmental factors. Values ​​were relatively close results between modeled and monitored in the field in different scenarios. The results showed that the storm sewers are the most important sources of pollution, accounting for episodes of non-compliance with water quality standards for bathing, especially during rainy periods. Moreover, the results showed no risk of the outfall plume reaching Fortaleza bath areas the city beaches. .

This study investigated the distribution, growth and reproduction of splendid ponyfish (Leiognathus splendens), the most dominant fish species in the catches of demersal trawls, along the coastal waters off southwestern Taiwan. Samples were collected once every 1-2 month (7-8 times per year), from January 2001 to January 2004 at seven stations, including Fangliao, Linbian, Dapeng Bay, Linyuan, Jhongjhou, Zuoying and Jiading, in southwestern Taiwan. The results showed that the distribution of L. splendens had significant differences among seasons, sites and water depths. The monthly mean abundance peaked in April, July and December, whereas lowest in January. L. splendens appeared in the north of Jhonhjhou only in the period from June to November. Based on their occurrence, the ponyfish could be separated into south and north groups at Linyuan. The south group can be further divided into inshore and offshore subgroups. The south group was more abundant than the north group. The size of L. splendens ranged from 15.32 mm to 121.01 mm (TL¡×total length), with an asymptotic length (L¡Û) of 128.20 mm and a catabolic growth coefficient (K) of 0.16(on a yearly basis). The ova diameter raged from 101.01 to 966.37 um with a peak between 500 and 600 um. The reproductive characteristic of L. splendens postulated as an asynchrouous spawner, who may spawn from March to May at Dapeng Bay and Linbian. The sex ratio (female/male) was less than 0.5 in total samples, and their first maturity length (L50) for female and male were 72.93 mm and 68.22 mm respectively. The distribution of L. splendens is associated with hydrology, season and ocean current. Higher abundance is normally coincided with low salinity, density, oxygen dissolution, and high water temperature and high value of Cpar (corrected irradiance-photosynthetically available radiation). The SCSW (South China Sea Water) and SCSSW(South China Sea Surface Water) with high temperature and low salinity flowing northward into the Taiwan Strait during the southwest monsoon season of May-September may deeply influence the northward distribution of the fish. Bigger fish and mature female capture during the spawning season from March to May, besides, smaller fish (TL¡Õ 20 mm) abundance on April, July and October. Additionally, the rainfall and nutrient wash away from onshore by typhoons, are the factors increase catches of L. splendens in the coastal waters of southwestern Taiwan.

This study aims to investigate the temporal-spatial distribution and reproduction of the Callionymidae, a dominant bottom-dwelling family at southwestern Taiwan. Samples were collected once every 1~2 month from January 2001 to January 2005 at seven stations, including Jiading, Zuoying, Jhongjhou, Linyuan, Dapeng Bay, Linbian and Fangliao, along the southwestern coast of Taiwan. A total of 5,846 samples was obtained, including 3 genera and 15 species. More species were found in this study than previous ones. The distribution of callionymids showed the significant variations in season, site and year. The highest abundance months occurred during March to October annually, with the most abundant at Jiading, then decreased in numbers southwards. Callionymus planus (52%)¡BCallionymus curvicornis (28%)¡BCallionymus virgis (7%) and Callionymus filamentosus (6%) were the top four dominant species. The four dominant species appeared abundantly around their spawning season. C. planus, C. curvicornis and C. filamentous were serial spawners, with peaking period at March-May, November-March and February-April, respectively. Both C. planus and C. curvicornis were most abundant at Jiading, and decreased southwardly, whereas the C. virgis and C. filamentosus were most abundant at Fangliao and Zuoying, respectively. All dominant species were revealed resource partitioning in relation to their reproductive activities. Callionymus planus that grew fast and recovered quickly among the callionymids, predominated in this area. Both C. planus and C. curvicornis showed significant reproductive isolation at the same area, both with a southward decrease in number. Calllionymus virgis separated from others and lived in the southmost site. Furthermore, C. filamentosus had a spawning period between C. planus and C. curvicornis.

This study aims to describe the spatial and temporal distribution of Platycephalids and the biology of the dominant species Suggrundus macracanthus, in the coastal waters off southwestern Taiwan. A beam trawl was adopted to collect fish samples from 7 stations, including Jiading, Zouying, Jhongjhou, Linyuan, Dapeng Bay, Linbian and Fangliao. Samplings were carried out on a 1-2 month interval, started from June 2000 and ended in August 2005. In total, 3,780 specimens were collected, including 9 genus 11 species. The distribution of Platycephalids varied in station, water depth and season. The lowest abundance were recorded at Jiading, then decreased from Zouying to Linyuan, and then increased southwards. Platycephalids eived more abundant in depth 25-55 m, and the number increased with depth 15-35 m. The highest abundance occurred from spring to summer. S. macracanthus (74%) were the top dominant species. S. macracanthus spawn once a year during February to April, with a peak in the frequency distribution of egg diameter. The recruitment of S. macracanthus occurred in the period from June to July, at near-shore waters of 15 m depth with mud and sand substrata. S. macracanthus take epibenthic shrimp as the major diet accounts for above 68%, including 59% of Metapenaeopsis palmensis. Other food items still had the fish, crab, Mollusca and Amphipoda. S. macracanthus juveniles nearly didn¡¦t ate crab, but the adult ate crab up to 12%.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

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