<p> The Ontario shoreline of Lake Huron is one of the most populated areas, with reference to recreational purposes, in Ontario. However, with the rising water levels of the Great Lakes during 1972 and again in 1973, serious problems of beach erosion have resulted, particularly in the area of Grand Bend and Port Franks. This loss of sand has threatened cottages built on the dunes in addition to destroying breakwalls, steps, and boat launching ramps along the beach. It was with the idea of learning more about the beach, and possibly suggesting some methods of beach protection, that the research for this thesis was initiated. During the course of study, the author also became interested in the Ausable River and the associated flooding and erosion problems, with reference to past, present, and future attempts to solve or at least alleviate these difficulties. Thus, one section of the thesis is concerned with the Ausable River alone. </p> <p> The beach studied is actually the culmination of a series of raised beaches, formed during higher post-glacial lake stages. These raised beaches formed a bar separating the now non-existent Ausable Bay from Lake Huron, forming a lagoon eastward of the beach. This bar extends from Grand Bend, in a southwest direction, and culminates at Kettle Point. However, for the purposes of this thesis, that section between Grand Bend and Port Franks received the greatest amount of concentrated study. Over the years, the lagoon, formed by the growth of the bar has silted up, and is now drained for agricultural purposes. </p> <p> The modern beach was observed during the summer of 1972. This involved, profiling of a portion of the shore and offshore topography, procuring beach samples for later analysis, the use of sequential air photographs for observing changes over time, and the analysis of wind and wave data, along with many conversations with local residents and personal observations. </p> <p> The subsequent study of the above factors revealed several major conclusions regarding the beach. First, that it has good natural protection against erosion due to the abundance of sand s tored by the dunes. Second, the beach appears to be in an equilibrium state, however as lake levels fluctuate, so must the beach level, thus destroying the equilibrium for a period of time. With the lowering of the water level, the beach will become wider, exposing sand to the onshore winds, which will in turn rebuild the dunes with the blowing sand. Finally, because of the prximity of man-made structures to the beach, on the unstable dunes, some method of stabilizing the beach is necessary. That suggested is a groin system, designed and constructed by the local authorities. This would help prevent erosion and would eliminate the often vain and possibly dangerous, (to the natural environment), attempts by individuals to halt erosion. </p> <p> This is by no means a complete study of the area and its problems. Further consideration should be given to proposals which have been presented to the local conservation authority, and which were designed to alleviate some of these problems, particularly at Port Franks. The suggestions made here should also be given further thought. In addition to these practical problems, the actual growth of the original bar would provide an interesting subject for study. </p> / Thesis / Bachelor of Arts (BA)

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Since the construction of the causeway and the jetty during the early 1970’s in Saldanha Bay, various alterations to the coastline in the area of the Langebaan Lagoon mouth were observed. These alterations include the erosion of Langebaan Beach located near the town of Langebaan. An investigation was undertaken to identify the possible impact these structures had on the hydrodynamics and sediment transport of the Saldanha Bay and Langebaan Lagoon systems, focusing on the entrance to the Langebaan Lagoon. A two-dimensional numerical model was implemented for this investigation. The outdated information available for the generation of a bathymetry, which indicated the conditions prior to the erosion of Langebaan Beach, complicated the calibration process. However, calibration of the numerical model was acceptable. Due to the bathymetry not providing an indication on the current situation at the Langebaan Lagoon mouth, the results from the numerical model were approached with caution, providing an overview of the hydrodynamics present in Saldanha Bay and Langebaan Lagoon and would be able to broaden the understanding of the impact the causeway and jetty had on the hydrodynamics and sediment transport of Saldanha Bay and Langebaan Lagoon. Results provided by the sediment transport model only provide an indication on the effect tidal variations and wind forcing have on the bay and lagoon and not realistic total sediment transport rates due to the omission of wave action during the modelling process. Results from the numerical model, based on tidal oscillations and wind forcing only, have indicated that no major impact on the hydrodynamics and sediment transport were experienced due to the construction of the causeway and the jetty. During the investigation of the impact of various extreme water level and extreme wind conditions, it has been observed that a 1 in 100 year wind velocity across the longest fetch towards Langebaan Beach resulted in the greatest velocities prior to the construction of the causeway and the jetty, and after the construction of the causeway and the jetty tidal storms, or storm surge, generated the greatest velocities and thus the most sediment transport in the main channels of the mouth of the Langebaan Lagoon. From this investigation it was recommended that future studies would require an updated survey of the area, to ensure accurate modelling of the conditions as experienced during field surveys. Further recommendations on the investigation of sediment transport were the inclusion of wave action to provide realistic results. Wave action is a fundamental part of sediment transport along the coastline. / AFRIKAANSE OPSOMMING: Sedert die konstruksie van die breekwater en die kaai gedurende die vroeg 1970’s in Saldanhbaai, is verskeie veranderings aan die kuslyn in die gebied van die Langebaan strandmeer mond waargeneem. Hierdie veranderinge sluit in die erodering van Langebaan Strand, geleë naby die dorp van Langebaan. 'n Ondersoek is onderneem om die moontlike impak van die bogenoemde strukture op die hidrodinamika en sedimentvervoer van die Saldanhabaai en die Langebaan strandmeer stelsels, veral die strandmeer se kanale, met die fokus op die ingang na die Langebaan strandmeer te ondersoek. 'n Twee-dimensionele numeriese model is gebruik vir hierdie ondersoek. Die verouderde inligting van die seebodem wat beskikbaar was vir die opwekking van die numeriese model het die kalibrasieproses bemoeilik. Alhoewel hierdie proses bemoeilik is kon ‘n aanvaarbare kalibrasie bereik word. Aangesien die gemodelleerde area en die werklike area nie ooreengestem het nie is resultate van die numeriese model omsigtig benader en die resultate geskik gevind om die kennis oor die moontlike impak wat die breekwater en die kaai op die hidrodinamika en sedimentvervoer van Saldanhabaai en die Langebaan strandmeer het, te verbreed. Resultate uit die sedimentvervoer model verskaf slegs ‘n aanduiding van die sedimentvervoer wat deur gety veranderings en wind gegenereer word. Werklike sediment vervoer sal die effect van golfaksie ook in ag moet neem, wat in hierdie studie uitgesluit is. Golfaksie is van kardinale belang by sediment vervoer langs ‘n kuslyn. Resultate van die numeriese model, gebaseer op gety en wind alleen, het aangedui dat geen groot impak op die hidrodinamika en sedimentvervoer as gevolg van die konstruksie van die breekwater en die kaai in Saldanhabaai ervaar word nie. Gedurende die ondersoek van die impak van verskeie ekstreme watervlak en uiterste windtoestande, is dit opgemerk dat 'n 1 in 100 jaar windsnelheid oor die langste stryklengte na Langebaan Strand gelei het tot die grootste vloei snelhede in die hoofkanale voor die konstruksie van die breekwater en die kaai. Na die konstruksie van die breekwater en die kaai is gevind dat gety storms die grootste snelhede en dus ook die meeste sedimentvervoer gegenereer het by Langebaan Strand. Uit hierdie ondersoek is dit aanbeveel dat toekomstige studies opgedateerde opmetings van die gebied moet uitvoer wat akkurate modellering, gebaseer op die toestande soos in die veld, sal verseker. Verdere aanbevelings oor die ondersoek van sediment vervoer is die modellering van .golfaksie wat van kardinale belang is in sediment vervoer langs ‘n kuslyn en dus meer realistiese resultate sal lewer.

L’industrialisation de l’étang de Berre au cours du 20ème siècle s’est accompagnée d’importants rejets en éléments traces métalliques (ETM) qui ont été en partie accumulés dans les sédiments et sont aujourd’hui susceptibles d’être remobilisés vers la colonne d’eau ou d’être intégrés dans le réseau trophique et d’entrainer un risque écotoxicologique.La reconstitution de l’évolution temporelle et spatiale de la contamination des sédiments montre que les niveaux de contaminations actuels des sédiments de surface sont les plus bas depuis plusieurs décennies en lien avec l’efficacité des réglementations sur les rejets industriels mises en place dans les années 1970. Ces niveaux sont faibles à modérés en surface mais de très fortes contaminations existent quelques centimètres sous la surface des sédiments.Le rôle des oxy-hydroxydes de Fe ou de Mn et des sulfures dans le contrôle de la mobilité des ETM dans le sédiment et leurs flux à l’interface eau/sédiment a pu être démontré grâce à la modélisation du transport et des réactions des composés chimiques et des ETM dans les eaux interstitielles, de leurs profils de concentrations dans la fraction réactive de la phase particulaire et d’expérimentations en conditions contrôlées au laboratoire. L’oxygénation de la colonne d’eau constitue le principal paramètre influençant cette mobilité et ces flux, et l’influence d’une réoxygénation des fonds dans le Grand Etang est discutée.Enfin, la biodisponibilité des ETM et le stress (géno)toxicologique qu’ils peuvent constituer pour un organisme benthique cible, le polychète Nereis succinea, ont été évalués par l’estimation des fractions potentiellement biodisponibles dans les sédiments (extractions chimiques et Diffusive Gradient in Thin-films), par la mesure des concentrations bioaccumulées et par l’utilisation de biomarqueurs de défense (métallothionéines) et de dommages (tests de génotoxicité). Certains ETM qui sont fortement bioaccumulés représentent un risque potentiel et pourraient être impliqués dans la dégradation de la macrofaune benthique. / The industrialization of the Berre lagoon in the 20th century was accompanied by large releases trace metals, which were partially accumulated in sediments and are now likely to be remobilized to the water column or be integrated into the food chain and cause an ecotoxicological risk.The reconstruction of the temporal and spatial trends of sediment contamination shows that current levels of contamination of surface sediments have been the lowest for decades in agreement with the effectiveness of regulations on industrial releases set up in the years 1970. These levels are low to moderate in surface but very high contamination exist a few centimeters below the sediment surface.The role of Fe and Mn oxy-hydroxides and sulfides in controlling the mobility of ETM in the sediment and fluxes at the water/sediment interface has been demonstrated through the modeling of transport and reactions of chemical compounds and trace metals in the pore waters, their concentration profiles in the reactive fraction of the particulate phase and experiments under controlled laboratory conditions. The oxygenation of the water column is the main parameter influencing the mobility and fluxes and the influence of reoxygenation of bottom water column in the Grand Etang is discussed.Finally, the bioavailability of trace metals and adverse effects they may constitute for a target benthic organism, the polychaete Nereis succinea, were evaluated by estimating the potentially bioavailable fraction in sediments (chemical extractions and Diffusive Gradient in Thin-films), by measuring bioaccumulated concentrations and by the use of biomarkers (metallothioneins and genotoxicity assays). Some highly bioaccumulated trace metals pose a potential risk and might be involved in the degradation of the benthic macrofauna.

Devant l'intérêt croissant pour l'environnement et la conservation de la biodiversité, comprendre les principaux mécanismes des cycles biogéochimiques ayant lieu dans les écosystèmes coralliens et lagonaires est une priorité. Un modèle 3D couplé physique-biochéochimique a été mis en place sur le lagon de Nouvelle-Calédonie (NC) : un 'hot spot' de biodiversité sous l'influence de divers forçages d'origines naturelles et anthropiques.Les interactions terre-lagon ont été abordées à travers l'étude d'un événement extrême La Nina (2008) qui cause de fortes précipitations, amenant d'importants apports dans le lagon.Les résultats du modèle fournissent une vue synoptique de la réponse biogéochimique-physique du lagon, mettant en évidence que la totalité du lagon fût impacté par les apports des rivières et un hydrodynamisme plus actif, où les concentrations en chlorophylle-a ont été doublées.L'interaction complexe océan-lagon a été abordée à travers la modélisation des processus d'upwelling du Sud Ouest (SO) de la NC. Quatre étés australs ont été simulés, mettant en évidence l'importance des processus d'upwelling qui représentent un important forçage de la production primaire au SO de la NC. Une analyse lagrangienne du transport a montré que les eaux issues de l'upwelling peuvent atteindre le lagon SO sous certaines conditions, un phénomène pouvant avoir des conséquences sur le recrutement larvaire et l'enrichissement du lagon. Le modèle 3D couplé est un outil robuste pour l'étude de cet environnement très variable et complexe. Il peut représenter une aide à la décision des managers ainsi qu'un support d'analyse et de planification d'échantillonnage aux scientifiques. / In view of increasing environmental awareness and biodiversity conservation, understanding the main forcing mechanism driving biogeochemical cycles in coral reefs and lagoon coastal areas is a priority. We used a 3D coupled 'on-line' physical-biogeochemical model on the New Caledonia lagoon : a hot spot of biodiversity under several forcing from climate to human origin.Interactions between land and lagoon were investigated through the study of an extreme event La Niña (2008) that caused heavy rainfalls and large organic and inorganic inputs in the lagoon.Model results provided a synoptic view of the lagoon biogeochemical-physical response, highlighting that the whole lagoon was impacted by river inputs and stronger hydrodynamics were the chlorophyll-a concentration was almost double.The complex interaction between the ocean and the lagoon was investigated through the modeling of the South Western (SW) wind-driven upwelling. Four austral summers (2005-2008) were simulated and results were found to be in good agreement with measured data reported in previous publications, highlighting that upwelling processes represent strong drivers of the primary production in the SW of NC. A Lagrangian transport analysis showed that oceanic upwelled waters were able to reach the South West lagoon under certain conditions, representing an important issue for larvae recruitment and lagoon enrichment. The 3D coupled on-line biogeochemical-physical model was a robust tool to study such complex and highly variable environment. It could represent a support for decision makers to manage coastal areas as well as for scientists to plan sampling strategy or to analyse cruise data.

Os estuários são áreas de alta produtividade biológica. O estuário da Lagoa dos Patos constitui a área de criação, reprodução e alimentação de grande parte dos peixes que ocorrem no litoral sul do Brasil. A maior enseada rasa da zona estuarina é o Saco do Arraial, com hidrodinâmica singular, e palco de atuação pré-histórica de populações tradicionais na pesca. Atualmente, diversas comunidades de pesca atuam nesta enseada com explotação de peixe-rei (Odontesthes argentinensis), de siri (Callinectes sapidus), de tainha (Mugil sp) e, sobretudo, de camarão (Farfantepenaeus paulensis). Entre estas comunidades está a Coréia, situada na Ilha dos Marinheiros, segundo Distrito da cidade de Rio Grande. O presente trabalho tem como objetivo descrever o território de uma comunidade de pesca, a Coréia (Ilha dos Marinheiros RS), através de uma perspectiva etnooceanográfica. A perspectiva do território como conhecimento, não apenas o espaço, mas também o tempo é passível de ser apropriado constituindo os sinais de memória. Para atingir tais objetivos, um aparato metodológico, advindo das etnociências, foi utilizado: mapas cognitivo e vernacular, entrevistas abertas e semi-estruturadas, a técnica da turnê e a observação participante. As técnicas de coletas de dados foram utilizadas de forma a descrever o conhecimento das principais forçantes ambientais que conduzem a apropriação territorial em duas escalas: o território grupal e os pesqueiros. Os dados obtidos evidenciaram que as fronteiras territoriais são também limites do conhecimento ecológico tradicional e que três cenários ecológicos interanuais de tomadas de decisão, mediadas pelas técnicas de pesca, são construídos com base na interface de três principais forçantes ambientais percebidas: as chuvas, os ventos e o ciclo migratório das espécies. A partir da dinâmica estuarino-biológica construída (cenários), funda-se ou abole-se pesqueiros, bem como as relações sociais que deles emergem, o que confere flexibilidade às fronteiras do território grupal. / Estuaries are high biological productivity areas. The Patos Lagoon Estuary is the growth, reproduction and feeding area of the most of fish in southern coastline of Brazil. The biggest shallow cove in the estuary zone is Saco do Arraial, it has a particular hydrodynamic, besides, it has been a pre-historical setting of traditional fishing population. Nowadays, various fishing communities work in this cove exploting fishes (Odontesthes argentinensis and Mugil sp), the blue-crab (Callinectes sapidus) mainly the pink-shrimp (Farfantepenaeus paulensis). Among these communities is the Coréia, in Sailors Island, the second district of Rio Grande City. This paper aims to describe a fishing territory, the Coréia, from an ethnooceanographyc perspective. From the perspective of the territory as knowledge, not only space, but also time is apropriated; the later constituting memory signs. For these aims mental maps, open-ended and in-depth semi-structured interviewing, tour technique and participative research have been used. The data collection techniques were used in order to describe the knowledge from environmental forcings that defines territorial appropriation in two levels: communitarian and pesqueiros. The data showed that territorial lines are the limits of traditional ecological knowledge. Besides this, three inter annual ecological decision-making settings (decisions concerning fishing technique management) are built according to three environmental forcings (rains, winds and migratory cycle of fish) in relation to fishing technique management. From estuary-biological dynamic built (settings), reconstruct fishing places (pesqueiros) are established ou dismantled, as well as the social relations which arise from them. As a result, the borders of the group territory become flexible.

Effluent from on-site sewage treatment and disposal systems (OSTDS) is generally known to impact groundwaters and surface waters with nitrogen (N) and phosphorus (P) and other contaminants. Little research has quantified this problem along the Indian River Lagoon (IRL), especially in Indian River County (IRC) where there are 26,660 active systems. This study assessed the effects of OSTDS on contamination of surface and groundwaters along three urbanized canals and the St. Sebastian River in IRC, all of which flow into the Central IRL. Multiple lines of evidence were used to define the source of the nutrient loadings including the novel approach of using the artificial sweetener, sucralose, as an indicator of human sewage impact. Results indicate that areas with high densities of OSTDS are contributing N to surface waters and elevating N:P ratios through submarine groundwater discharge and promoting eutrophication in the Central IRL. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

O objetivo do presente estudo foi avaliar, através da análise de n-alcanos e de suas razões isotópicas, a influência da abertura do canal artificial do Valo Grande (VG) nas fontes de matéria orgânica (OM) do Sistema Estuarino-Lagunar de Cananéia-Iguape (CIELS). Os compostos foram analisados em quatro testemunhos, 22 sedimentos superficiais e em folhas de nove espécies de plantas dominantes na região de estudo. Os parâmetros avaliados nas folhas amostradas permitiram separar as espécies estudadas em monocotiledôneas e dicotiledôneas, e em vegetação lenhosa de mangue e de restinga. Esta separação foi útil na identificação das fontes de OM do CIELS. Os dados dos sedimentos superficiais mostraram que a principal fonte de OM no sistema é a vegetação de restinga. Esta se dá principalmente na região norte, onde está presente o VG. A influência fitoplanctônica, das macrófitas emersas e da vegetação de mangue é maior na região sul. Os dados dos testemunhos mostraram que a abertura do VG aumentou a contribuição da vegetação de restinga e das macrófitas aquáticas na OM presente ao longo do CIELS, diminuindo a influência fitoplanctônica e das macrófitas emersas. Assim, a qualidade e quantidade de OM do CIELS foram influenciadas pela presença do VG. / This study aimed to verify, through the use of n-alkanes and their isotopic composition, the influence of the Valo Grande artificial channel (VG) on organic matter (OM) sources of the Cananéia-Iguape Estuarine-Lagoon System (CIELS). The compounds were analyzed in four cores, 22 surface samples and nine dominants plants species leaves sampled on the studied area. The parameters evaluated on the leaves permitted to group the studied species in mono and dicotyledonous, and in mangrove and resting vegetation. This was useful to identify the OM sources on the CIELS. The surface sediment data showed that the CIELS OM is mainly composed by restinga vegetation. This occurs mainly on the northern region, where the VG is present. The influence of phytoplankton, of emergent macrophytes and of mangrove trees is higher on the southern region. The cores data showed that the VG opening increased the influences of Atlantic Forest and aquatic macrophytes on the CIELS OM, decreasing the emergent macrophytes and the phytoplankton influence. So, the type and the amount of OM on the CIELS are influenced by the VG presence.

O presente trabalho propõe uma metodologia científica, com critérios bem definidos, para avaliar e quantificar o desempenho ambiental e a renovabilidade de processos de tratamento de esgoto, numa base única: a exergia. O desempenho ambiental é quantificado através do cálculo da eficiência exergética ambiental, definida como a razão da exergia do efeito útil do processo pela exergia total consumida dos recursos humanos e naturais, incluindo todas as entradas exergéticas. O cálculo da renovabilidade é feito por meio do índice exergético de renovabilidade definido como como a razão entre a exergia dos produtos pela soma das exergias não renováveis, a exergia destruída, a exergia de desativação e a exergia das emissões e residuos. A metodologia foi aplicada a três processos de tratamento de esgoto: dois biológicos (aeróbio e anaeróbio) e um físico-químico (TQA). O cálculo dos indicadores exergéticos foi realizado para cada um destes processos e foi observado que o processo com maiores valores de desempenho ambiental e renovabilidade, considerando o metano e o lodo do processo como efeito útil, foi o processo RAFA Lagoa Facultativa, com valores respectivamente de n<exerg,amb> (0,983) e lâmbda(7,060). A análise dos resultados mostrou que a metodologia proposta é uma ferramenta útil na avaliação e comparação do desempenho ambiental e da renovabilidade de processos de tratamento de esgoto. / This work proposes a scientific methodology, with well defined criteria, to assess and quantify the environmental performance and renewability of wastewater treatment processes on a single base: the exergy. The environmental performance was measured by calculating the environmental exergy efficiency defined as the exergy ratio of the useful effect of the process to the total exergy consumed by human and natural resources, including all the exergy inputs. The renewability calculation was done using the renewability exergy index defined as the exergy ratio of the products to the sum of the non-renewable exergy, destroyed exergy, deactivation exergy and the emissions and waste exergy. The methodology was applied to three wastewater treatment processes: biological (aerobic and anaerobic) and physicochemical (CEPT) processes. The exergy indicators were calculated for each of these processes and it was observed that the process with the higher environmental performance and renewability values, considering the methane and sludge of process as useful effect, was the Facultative Lagoon UASB process, with values, respectively, of n<env,exerg>(0.983) and lambda(7.060). The results analysis showed that the proposed methodology is a useful tool in the evaluation and comparison of environmental performance and renewability of wastewater treatment processes.

Les lagunes côtières sont des écosystèmes semi-fermés à l'interface de la terre et des océans et sous l'influence de ces deux compartiments. De par ces caractéristiques, elles sont soumises à de fortes variations spatiales et saisonnières de leurs ressources trophiques. De par leur nature fermée et peu profonde, elles vont amplifier la force des processus qui conditionnent la disponibilité des ressources alimentaires et par conséquent l'écophysiologie des organismes benthiques qui composent les assemblages associés. Ce travail de thèse se propose de caractériser l'écophysiologie trophique de deux espèces de bivalves filtreurs (Nodipecten subnodosus et Spondylus crassisquama) au sein d'une lagune du Pacifique Nord-est (Basse Californie, Mexique). Une approche mufti-tissus et multi-traceurs (isotopes stables, acides gras, stérols et analyse isotopique sur acides gras) a été adoptée afin de pouvoir caractériser l'écologie trophique des espèces, mais aussi leurs régulations physiologiques face aux variations environnementales. Deux facteurs clés se sont révélés largement explicatifs de la variabilité spatio-temporelle observée dans le régime alimentaire : la période (hiver vs été) et la localisation dans la lagune par rapport à l'embouchure. L'importance des apports de phytoplancton océanique a été démontrée dans l'ensemble de la lagune, avec une contribution plus importante de diatomées océaniques notamment en période estivale pour les individus à proximité de l'embouchure. Par ailleurs, les bivalves en fond de lagune semblaient davantage dépendre de la matière organique locale, en particulier issue du recyclage bactérien, voire de la production des herbiers de phanérogames. Ces contrastes spatiaux se reflétaient également dans la composition des membranes cellulaires, mettant en évidence les interactions entre apports trophiques et régulations métaboliques des compositions en acides gras chez ces deux bivalves. Cette thèse présente une approche intégrée dédiée à la compréhension des variations spatiales et saisonnières des ressources trophiques d'un écosystème lagunaire, ainsi que leurs répercutions trophiques et physiologiques sur les assemblages benthiques. / Coastal lagoons are semi-enclosed ecosystems at the interface between land and ocean and under the influence of these two compartments. Owing to these characteristics these ecosystems are submitted to spatial and seasonal variations in their trophic resources. Because of their enclosed and shallow nature, lagoons amplify the intensity of processes conditioning the availability of food resources and consequently the ecophysiology of the benthic organisms which compose associated assemblages. This thesis aims to characterize the trophic ecophysiology of two species of suspension feeding bivalves (Nodipecten subnodosus and Spondylus crussisquomo) within a lagoon of Northeast Pacific (Baja California, Mexico). A mufti-tissue and multi-tracer approach (stable isotopes, fatty acids, sterols, and isotope analysis on fatty acids) was used in order to characterise the trophic ecology of both species, as well as their physiological regulations against environmental variations. Two key factors have been found to explain the observed spatio-temporal variability: the period (winter vs summer), and the location in the lagoon with respect to the distance from the mouth. The importance of oceanic phytoplankton inputs has been highlighted throughout the lagoon, with a greater contribution of oceanic diatoms particularly during the summer period for individuals near the mouth. Bivalves from the inner lagoon seemed more dependent of local organic matter, in particular resulting from bacterial recycling, or even from the production of eelgrass. These spatial contrasts were also reflected in the composition of cell membranes, highlighting the interactions between trophic contributions and metabolic regulation of fatty acid composition in both bivalves. This thesis presents an integrated approach to understand spatial and seasonal variations of the trophic resources of a lagoon ecosystem, as well as their trophic and physiological repercussions on benthic assemblages.

A população de foraminíferos e tecamebas no SELCI evidenciou variação espacial, caracterizando alta dominância de hialinos e porcelanáceos no verão, e aglutinantes no inverno. Essa distribuição da microfauna estava associada a maior influência marinha dos setores externos e a forte influência do regime regional de chuvas nos setores internos. Constatou-se como bioindicadores a espécie Pararotalia cananeiaensis indicando o alcance da cunha salina nas porções internas do sistema, os miliolídeos indicando ambientes com renovação de águas marinhas e fluxos mais energéticos no sistema, o gênero Miliammina spp. e as tecamebas indicando ambientes de baixa salinidade. Através do Ic foi possível detectar o impacto do balanço entre as influências continentais e marinhas no sistema, com a intrusão salina sazonalmente distinta, devido às próprias condições regionais e geomorfológicas do sistema. Na tentativa de encontrar ambientes hipóxicos foi aplicado o IAE, porém este índice não gerou resultados satisfatórios neste sistema estuarino, visto que outros fatores representaram ser variáveis mais importantes do que a concentração de oxigênio dissolvido. O cálculo da BFAR foi testado revelando que a geomorfologia do SELCI foi um fator determinante na distribuição das espécies e que a BFAR foi uma medida qualitativa do fluxo de MO no sistema. Através das análises estatísticas multivariadas foi possível determinar as associações da microfauna, sendo estas condicionadas, nas duas campanhas, principalmente pelos fatores salinidade, substrato e profundidade. / The population of foraminifera and thecamoebians in the CILES (Cananéia-Iguape Lagoon Estuarine System) evidenced spatial variation, characterizing high dominance of hyalines and porcelanaceous during the summer and agglutinated in the winter. This microfauna distribution was associated to stronger marine influence in the outer sections and to strong regional pluviosity in the inner sections. The bioindicator species were Pararotalia cananeiaensis, evidencing the extent of the salt water wedge in the inner portion of the system, the miliolidae, indicating environments with renewal of marine water and more energetic fluxes in the system and the gender Miliammina spp. and thecamoebians indicating areas of low salinity. Trough the Ic it was possible to identify the impact of the balance between marine and fresh waters influence in the system, with saline intrusion seasonally distinct, due to the system\'s own regional and morphological conditions. An attempt to identify hypoxia areas was made using the AEI (Ammonia-Elphidium Index) test, however, this index did not reveal satisfactory results in this estuarine system, since other factors seem to be more representative than the dissolved oxygen concentration. The geomorphology of the CILES was proved to be a determinant factor in the distribution of the species through the BFAR (Benthic Foraminifera Accumulation Rate) calculation, which was also a qualitative measure of the flux of organic matter (TOC) in the system. Statistical analysis proved that the associations of microfauna, was driven, in both campaigns, by salinity, substract and depth.