Recent cooperative efforts between the University of Central Florida, the Florida Department of Environmental Protection, and the South Florida Water Management District explore the development of a two-dimensional, depth-integrated tidal model for the Loxahatchee River estuary (Southeastern Florida). Employing a large-domain approach (i.e., the Western North Atlantic Tidal model domain), two-dimensional tidal flows within the Loxahatchee River estuary are reproduced to provide: 1) recommendations for the domain extent of an integrated, surface/groundwater, three-dimensional model; 2) nearshore, harmonically decomposed, tidal elevation boundary conditions. Tidal simulations are performed using a two-dimensional, depth-integrated, finite element-based code for coastal and ocean circulation, ADCIRC-2DDI. Multiple variations of an unstructured, finite element mesh are applied to encompass the Loxahatchee River estuary and different spatial extents of the Atlantic Intracoastal Waterway (AIW). Phase and amplitude errors between model output and historical data are quantified at five locations within the Loxahatchee River estuary to emphasize the importance of including the AIW in the computational domain. In addition, velocity residuals are computed globally to reveal significantly different net circulation patterns within the Loxahatchee River estuary, as depending on the spatial coverage of the AIW.

A high-resolution, finite element-based, shallow water equation model is developed to simulate the tides in the South Atlantic Bight. The model is constructed to include all of the estuarine features along the southeastern United States seaboard: coastal inlets, rivers and tidal creeks, sounds and lagoons, intertidal zones including salt marshes and mangrove swamps, and the Atlantic Intracoastal Waterway. The estuaries are represented in the finite element mesh using triangular elements with side lengths on the order of tens of meters. Also incorporated into the model is a spatially distributed bottom friction parameterization, based on the various landcover and benthic characteristics in the domain. The motivation to use this comprehensive representation of the system was inspired by a desire to capably account for the full estuarine tidal physics. In this approach, no calibration is performed and the model is used as a tool to assess the physical processes it describes. Upon its development, the model is first validated by accurately simulating tidal hydrodynamics in the South Atlantic Bight including the described estuaries. Variants of the model are then constructed by selectively removing estuarine features from the domain. All model representations are subsequently applied in nearly identical simulations: the only differing factor between the simulations being the inland extent of the estuaries described. The solutions are compared with respect to including versus excluding the estuarine features of the domain. Where water surface elevations are shown to be unaffected by the estuarine features of the South Atlantic Bight, tidal velocities exhibit far more sensitivity. This effect is pronounced locally, with regional effects extending offshore. Further analysis is performed on cross-sectional flows recomposed locally and on tidal energetics diagnosed throughout the domain. It is discovered that the high frictional environment of the vast estuarine surface area plays a role in local and regional tidal circulation in the South Atlantic Bight.

Utilizing field and modeling methodology, the effects of benthic micro-communities and physical transport mechanisms on sediment nutrient flux were investigated for two nearshore sediment types on Virginia’s Eastern Shore. Subtidal sandy mineral sediments were conducive to water transport and subsequently influenced by groundwater discharge to a greater degree than less permeable organic silt-clay sediments. Sediment ammonium and dissolved inorganic phosphorus (DIP) fluxes were strongly dependent on benthic aerobic respiration rates for silt-clay sediments as compared to sandy substrates. In situ studies indicated a significant decrease in ammonium and DIP fluxes as a result of nutrient uptake by benthic microalgal communities. The importance of advective solute transport mechanisms within nearshore sediments was demonstrated by a one-dimensional, steady-state model for a conservative substance. By incorporating dispersive and advective transport mechanisms, model predictability for chloride sediment flux was significantly improved as compared to a diffusion based model. Model results indicated that velocity associated transport of solutes, driven by elevated upland hydraulic heads, are significant and can dominate over diffusive flux in sandy sediment. In contrast, silt-clay sediment solute fluxes were dominated by dispersive processes. The importance of sedimentary nutrient flux in a shallow coastal embayment was demonstrated by short water column DIN and DIP turnover times with respect to sediment nutrient fluxes, by the significance of ammonium and DIP sediment nutrient fluxes with respect to phytoplankton nutrient assimilation demands, and by the relative importance of benthic respiration with respect to water column primary productivity. In order to evaluate water quality impacts of groundwater discharge on a larger scale, a surface, groundwater, and in situ groundwater discharge water quality survey was conducted in a shallow estuarine embayment. Sediment inorganic nitrogen fluxes were elevated adjacent to agricultural fields without benefit of a vegetative buffer. Nitrogen contributions from direct groundwater discharge and groundwater derived creek inputs appear to be of significant importance in terms of water quality and phytoplankton nitrogen assimilation demands. In summary, this study highlights the importance of nearshore sediments with regards to estuarine nutrient water quality and ecological processes. Neglecting groundwater discharge as a nutrient source and transport mechanism and potential biotic effects occurring at the sediment-water interface may lead to serious misinterpretation of data and error in water quality strategies. / Ph. D.

South African estuaries have high biodiversity value and provide many benefits to society, including food, real estate, a place for recreation and economic enterprise. However, they are facing growing human pressures such as urban encroachment, development in river catchments and interference in hydrological cycles. This dissertation provides an exploratory study of the environmental history of the Mgeni River Estuary, KwaZulu-Natal in an attempt to improve the understanding of the forces that drive environmental change. Through the application of the techniques and methodologies of environmental history, it explores the dynamics, characteristics and impacts of human interaction with the Mgeni River Estuary over time. It focuses on the emergence of a capitalist! industrial society in the twentieth century as this period has been characterised by the most significant environmental alteration and degradation. With the aid of the techniques and methodologies employed, the study highlights a complexity of natural and human events that have altered the estuary over time. Comparative analysis of aerial photographs between 1937 and 1996 reveals that physical changes to the estuary were linked to prevalent social and economic activities. The study describes cultural beliefs, modes of resource use and the political economy as significant and interwoven factors that facilitate environmentally intrusive activities. The study has provided insights into the complexity of factors that influence the rate and extent of change of an estuarine system. It concludes that to improve the understanding of the causes of environmental change, it is necessary to look further than the physical impacts on the environment to the attitudes and beliefs that underlie them. While the solutions to the problems facing the Mgeni River Estuary are not easily at hand, such analysis should assist policy makers and managers in finding a way to initiate more sustainable estuarine development in the future. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

The nutrient dynamics in two contrasting estuaries and in the adjacent nearshore environment along the south-east coast of South Africa was investigated seasonally. Due to an inter-basin transfer of water from the Gariep Dam to the Great Fish River, the Great Fish estuary is a fresh water dominated, terrestrially driven system with an annual fresh water inflow of 250 – 650 x 10⁶ m³ per year. In contrast, the Kariega estuary is a fresh water deprived, marine dominated system with a fresh water inflow estimated at 2.5 – 35 x 10⁶ m³per year. The reduced fresh water inflow into the estuary is attributed to regular impoundments along the Kariega River. Water samples were collected from surface and subsurface layers along the length of the estuaries as well as from a series of transects occupied in the nearshore environment. Samples were analysed for nitrate, nitrite, ammonium, phosphate and silicate. Temperature and salinity were recorded at each station. A Land-Ocean Interactions in the Coastal Zone (LOICZ) budget was constructed for each estuary to describe the role of ecosystem-level metabolism as either a sink or a source of phosphorus, nitrogen and carbon. Seasonal variation in physico-chemical properties and nutrient concentrations in the Kariega estuary was minimal due to constant low inflow, while in the Great Fish estuary, concentrations varied in response to changes in flow rate. Nutrient concentrations were consistently higher in the Great Fish estuary than in the Kariega estuary, largely reflecting differences in fresh water inflow. During periods of high flow (32.92 m³.s⁻¹in the Great Fish River) dissolved inorganic nitrogen (DIN) concentrations in the Great Fish estuary were an order of magnitude higher than those recorded in the Kariega estuary. Results of the LOICZ budgeting procedures revealed that in spite of the contrasting hydrodynamic features, the estuaries behave in largely the same manner – both predominantly sources of nutrients with heterotrophic processes dominating over autotrophic actions and both were net denitrifyers during all surveys. This was, however, due to different sets of processes operating in the two estuaries, namely low nutrient concentrations resulting in microbial activity in the Kariega estuary, and riverine influx of nutrients and phytoplankton combined with a short residence time of the water in the Great Fish estuary. In the marine nearshore environment, higher nutrient concentrations were recorded adjacent to the Great Fish estuary than offshore of the Kariega estuary. This was due to a surface plume of less saline water leaving the Great Fish estuary, which acted as an ‘outweller’ of nutrients. Offshore of the Kariega estuary, on the other hand, the nutrient concentrations were characteristic of marine waters due to a lack of fresh water outflow from the estuary. Nutrient concentrations in the marine environment adjacent to the Kariega estuary were, at times, higher than those recorded within the estuary. This observation supports previous statements which suggest that the Kariega estuary is not an ‘outweller’ of dissolved nutrients and particulate material, but rather an extension of the marine environment.

Estuaries are unique coastal bodies of water where water derived from land meets the sea. In order to preserve estuaries and minimise the effects of human interference in these sensitive areas, an understanding of the hydrodynamics is essential. South Africa has 259 estuaries, of which approximately 70% are temporary open. The aim of the project was to provide data to analyse the effect of different flow scenarios on the frequency, timing and duration of mouth closure for temporary open estuaries. To achieve the project aim, two case studies were undertaken, namely Mhlanga and Mdloti Estuaries. Achieving the terms of reference required monitoring of the mouth state, water level, flow rates and developing an understanding of breaching mechanisms. Observations of the mouth were used to monitor its state and initially photographs were used to monitor the water level within each estuary. During 2003 a continuous water level monitor was developed and placed in each estuary. Velocity readings were taken upstream of the estuaries at discrete time intervals and converted to flow rates using the velocity area method. A photographic survey of the berm at Mhlanga Estuary was used to observe the effect of beach processes on the mouth area. The survey observed the estuary as it shifted from closed through to open, then partially open and finally closed again, providing information on mouth mechanisms. The continuous water level monitoring provides useful information for Mhlanga Estuary in terms of breaching patterns, tidal exchange when in the open state and an indication of the time scales involved in mechanisms which change the mouth state. Similar information for Mdloti Estuary was not available as the estuary did not breach since the installation of the water level monitors, however salinity profiles from 2002 provided qualitative information on the existence of a saline intrusion into the estuary. The relationship between flow and mouth state is complex and relies on other influences such as water level and systems losses. In general estuaries will breach under high flows and remain closed under low flows, however in between these two regimes the estuary mouth state is less predictable based on flow alone. Mhlanga Estuary repeatedly breached at low tide. During the open phase tidal influence was both observed and captured by water level monitors despite the perched nature of the estuary. Closure generally occurred at high tide trapping saline water within the estuary. The two case studies provided a good basis for exploring the affects of different flow conditions on estuaries, with Mdloti Estuary experiencing the effects of the Hazelmere Dam and abstractions, while Mhlanga Estuary has increased flow due to the discharge of treated effluent to the system. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2004.

Sistemas estuarinos são locais de transição entre ambientes marinhos e fluviais, cujas forçantes influenciam a dinâmica e a distribuição das propriedades químicas, biológicas e sedimentares. Aproximadamente 60 % de todas as grandes cidades se desenvolveram ao redor de estuários que, por serem ambientes abrigados, favorecem a navegação e instalação de portos. O objetivo geral do trabalho foi de identificar os processos sedimentares atuantes em um trecho do canal de acesso ao Porto de Santos (Trecho 1 do Porto organizado), compreendendo 12 km de comprimento desde a embocadura da baía de Santos até a entrada no Canal do Porto, utilizando um conjunto de dados de diferentes períodos (entre 2010 e 2016), provenientes de diferentes fontes acústicas, visando contribuir para a melhor compreensão da dinâmica sedimentar do Sistema Estuarino de Santos. Foram utilizados dados obtidos com um duplo chirp (frequências entre 2-8 kHz e 10-20 kHz) e dados de batimetria multifeixe. A metodologia consistiu na comparação de levantamentos batimétricos (executados em diferentes períodos) e de forma complementar foram utilizados os dados obtidos com a fonte acústica chirp. As análises proporcionaram a identificação de indícios de erosão e de assoreamento no Trecho 1 do canal do Porto de Santos. Em alguns locais, foi possível relacionar os padrões de erosão e de assoreamento com a hidrodinâmica local e, assim, sugerir tendências nos processos sedimentares atuantes na área de estudo. Sem dragagem a tendência do Trecho 1 do Porto de Santos é de assoreamento. O Trecho 1 foi divido em 2 setores com comportamento distintos. O setor A (próximo à embocadura do canal) é, naturalmente, mais profundo, o sedimento de fundo não é depositado em grande quantidade nesse local devido à intensidade da velocidade das correntes que ocorrem no setor. Há indícios de instabilidade das encostas no trecho mais estreito do canal, da ocorrência de lama fluida e de gás raso nesse local. O setor B era, naturalmente, mais raso em 1960, período em que o canal passou a ter a sua configuração atual, sugerindo a formação de um delta de maré vazante no setor, onde a velocidade das correntes são mais lentas, quando comparadas com o setor A. / Estuarine systems are sites of transition between marine and fluvial environments, whose forcing influences the dynamics and distribution of chemical, biological and sedimentary properties. Approximately 60% of all large cities have developed around estuaries because they are sheltered environments, allowed the navigation and harbors installation. The objective of the study was to identify the sedimentary processes in a section of Santos Harbor channel, comprising 12 km in length from the mouth of the bay to the entrance in the Port Channel. It was used a data set from different periods (2010-2016), from different acoustic sources, aiming to contribute to a better understanding the sedimentary dynamics in the Santos Estuary System. It was used a double chirp data with frequencies between 2-8 kHz and 10-20 kHz and multibeam bathymetry data. The methodology consisted in the comparison of bathymetric surveys performed in different periods and in a complementary way used the data obtained from a double chirp. The analyzes allowed an identification of erosion and silting in Section 1 of Santos Port Channel. It was possible to relate erosion and silting patterns to local hydrodynamics and to suggest trends in sedimentary processes in the study region. Without dredging, the trend of Section 1 from the Santos Harbor was of silting. The Section 1 it was divided into 2 sectors with different behavior. Sector A is naturally deeper; the sediment is not deposited in large quantities at this location because of the currents velocities that occurring there. In this site there is evidence of instability of the slopes in the channel\'s narrowest section, the occurrence of fluid mud and shallow gas. Sector B was naturally shallower in 1960, when the canal became its current configuration, suggesting the formation in this site of an ebb tide delta, where the currents velocities are slower when compared to sector A.

O complexo estuarino-lagunar de Cananéia-Iguape vem sofrendo diversos impactos antrópicos desde à abertura do canal artificial Valo Grande, que alterou significativamente o setor Norte do sistema com o aumento da influência fluvial. O assoreamento da região, vem sendo um problema recorrente, impactando a pesca, o turismo e a navegação. Este trabalho visa entender a dispersão do aporte terrígeno na região a partir da modelagem numérica, com dados atualizados, para melhor reprodução da simulação no estuário. Os resultados do modelo mostraram altas concentrações dos componentes biogeoquímicos no setor Norte do sistema e baixa influência da maré, ocasionando alta retenção destes elementos na região. O setor Sul apresentou baixa influência do rio e alta influência marinha, com valores de silicato e fosfato dissolvidos e matéria inorgânica em suspensão dentro do esperado para um sistema estuarino preservado. O modelo apresentou um bom comportamento para a região, com bons resultados hidrodinâmicos e de qualidade da água. Ressalta-se a importância de um contínuo monitoramento da região e o uso de modelo para acompanhar o desenvolvimento geomorfológico e as alterações biogeoquímicas do estuário para auxiliar em medidas preventivas com o intuito de minimizar o impacto antrópico no sistema. / The estuarine-lagoon complex of Cananéia-Iguape has suffered several anthropic impacts since the opening of the Valo Grande artificial channel, which significantly altered the northern sector of the system with the increase of fluvial influence. The silting up of the region has been a recurrent problem, impacting fishing, tourism and navigation. This work aims to understand the dispersion of the terrigenous contribution in the region with numerical modeling and updated data, for better reproduction of the simulation in the estuary. The results of the model showed high concentrations of the biogeochemical components in the northern sector of the system and low tidal influence, causing high retention of these elements in the region. The southern sector showed low river influence and high marine influence, with expected values of dissolved silica and phosphate and inorganic suspended matter for a preserved estuarine system. The model showed a good behavior for the region, with good hydrodynamic and water quality results. It is emphasized the importance of continuous monitoring of the region and the use of a model to monitoring the geomorphological development and the biogeochemical alterations of the estuary to assist in preventive measures with the intention of minimizing the anthropic impact in the system.

Made available in DSpace on 2014-12-17T15:41:45Z (GMT). No. of bitstreams: 1 EmilyCTACpdf.pdf: 3591315 bytes, checksum: be24520b4ab67c175c58faec0f0ec20c (MD5) Previous issue date: 2008-07-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This study is an environmental diagnosis of the Jundia?-Potengi/RN estuarine system waters, using calculations of pollution indicator indices such as the Water Quality Index (WQI) and the Toxicity Index (TI). The samples were collected at twelve points on the estuary, at high and low tide, between August and November 2007, over four campaigns. The study area, located in a high impact region, has various activities on its banks such as: discharge of untreated or undertreated domestic and industrial sewage, shrimp farming, immunizer stabilization lakes, riverside communities, etc. All the parameters analyzed were compared to the limits of CONAMA Resolution No. 357 of 2005 for healthy and saline Class 1 waters. The results found prove the impact caused by various activities, mainly the parameters related to the presence of organic material, such as DQO, DBO, COT and thermotolerant colliforms. The IQA for most of the collection points was of medium quality. For the metals, although values above the Resolution limits were found, most of them were lower than the detection limits of ICP-OES used, indicating that they tend to be transported by the dynamic of the tides or rainfall and are deposited in bottom sediments, resulting in a TI of 1.0 in this water, when they are absent, which occurs in most cases, or 0.0, when heavy metals are found in these waters / O presente trabalho consiste em um diagn?stico ambiental das ?guas do sistema estuarino Jundia?-Potengi/RN, atrav?s de c?lculos de ?ndices indicadores de polui??o como o ?ndice de Qualidade da ?gua (IQA) e do ?ndice de Toxidez (IT). As amostras foram coletadas em doze pontos do estu?rio, em mar? alta e baixa, entre os meses de agosto e novembro de 2007, totalizando quatro campanhas. A ?rea de estudo est? localizada numa regi?o de alto impacto, tendo em suas margens diversas atividades como: lan?amento de esgotos dom?sticos e industriais sem tratamento ou fora dos padr?es de lan?amento, carciniculturas, lagoas de estabiliza??o de imunizadoras, comunidades ribeirinhas, etc. Todos os par?metros analisad s tiveram seus resultados comparados com os limites da Resolu??o CONAMA N? 357 de 2005 para ?guas salobras e salinas Classe 1. Os resultados encontrados comprovam o impacto ocasionado pelas diversas atividades, principalmente os par?metros relacionados com a presen?a de mat?ria org?nica, como DBO, COT e Coliformes termotolerantes. Assim, o IQA para a maioria dos pontos de coleta foi de qualida e M?DIA. Para os metais, embora tenham sido encontrados valores acima do que permite a Resolu??o, a maioria deles estavam abaixo dos limites de detec??o do ICP-OES utilizado, indicando que estes tendem a ser carreados pela din?mica das mar?s ou precipitam e se depositam nos sedimentos de fundo, dando a essa ?gua um IT igual 1,0, quando estes est?o ausentes, o que ocorre na maioria dos casos, ou 0,0 quando se encontram teores de metais pesados nessas ?guas

Submitted by Leticia Schettini (leticia@ufrrj.br) on 2016-09-19T13:26:00Z No. of bitstreams: 1 2009 - Leonardo Mitrano Neves.pdf: 932793 bytes, checksum: 1e42ee61916afbed6020d0c2430fa7a4 (MD5) / Made available in DSpace on 2016-09-19T13:26:00Z (GMT). No. of bitstreams: 1 2009 - Leonardo Mitrano Neves.pdf: 932793 bytes, checksum: 1e42ee61916afbed6020d0c2430fa7a4 (MD5) Previous issue date: 2009-03-05 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPQ / The estuarine systems influence fish assemblages, throughout their longitudinal gradients and remarkable salinity changes. Such assemblages adapt to different habitat constraints and change in spatial and temporal scales. The aim of this study was to assess the ichthyofauna composition and structure in three zones of the Mambucaba estuary (CZ ? coastal zone; MZ ? mixture zone and RZ ? river zone) and their relationship with environmental variables and habitat characteristics. Systematic fish collections (2 months in each seasons) were performed between October 2007 and August 2008, by using otter trawl at two sites in CZ (C1 e C2), beach seine at three sites in MZ (M1, M2, M3) and mesh trays at two sites in RZ (R1 e R2). At each fish sampling occasion, both surface and depth environmental variables of temperature, salinity, conductivity, turbidity and dissolved oxygen were taken and depth was measured. A total of 14,320 individuals, in 111 species (RZ ? 18; MZ ? 50, and CZ - 66) were collected. Distinct fish assemblages were found for each zone, as indicated by low number of common species (14 - MZ and CZ; 8 - MZ and RZ; and 2 - CZ and RZ), and only one abundant species (> 1% of the total number of fish within the zone) being common in more than one zone (Eucinostomus argenteus in CZ and MZ). Such pattern can be related to high salinity variation in MZ and narrow (20 m) channel width connecting the estuary with the sea, which can limit fish movement (into/out of the estuary). In CZ, the three more abundant species were Paralonchurus brasiliensis, Ctenosciaena gracillicirrhus, Anchoa lyolepis, Larimus breviceps and Stellifer brasiliensis, with large contribution of fish from the Scieanidae family in this zone (18 species). Spatial changes inf fish species were not consistent in CZ, probably due to lack of spatio-temporal estuarine plume influence on depth environmental variables (ANOVA, p>0.05). Depth was the main factor to influence spatial changes for Diapterus rhombeus (negative association) more abundant in C1 (average depth = 10 m; ANOVA, p<0.05) and Micropogonias furnieri, P. brasiliensis and Pellona harroweri (positive association) more abundant in C2 (average depth = 17 m; ANOVA, p<0.00). Diapterus rhombeus and Etropus crossotus occured mainly in Spring and Summer, and Eucinosomus gula in Spring. The most abundant species in CZ, typical of high salinty influence, is a indication that this zone have characteristics to inner continental shelf. In MZ, most abundant species (Eugerres brasilianus, Eucinostomus melanopterus, Trinectes paulistanus, Gobionellus shufeldti, G. oceanicus, Geophagus brasiliensis, Centropomus parallelus and Citharichthys arenaceus) have higher number and weight of individuals in M1 (ANOVA, p<0.01), an adjacent lagoon connected to the main channel. In spite of the significant negative correlation between this species and salinity (r-Spearman>0.32, p<0.01), the more sheltered areas in M1 seem to be more important to determine this pattern than salinity itself. The site M1 also have more number of individuals and species (ANOVA, p<0.01), and larger number of fish of smaller size (CT median = 58mm) compared to M2 and M3, located in the main channel (median = 106mm) according to Median and Kruskall-Wallis tests (p<0.01; 2 = 1167.5), indicating the importance of this area for species recruitment. Low average similarity (SIMPER) for sites M2 (38.7%) and M3 (17.8%) indicate larger variability of assemblage in these sites, probably due to lesser habitat structure e higher dynamism. In RZ, the fish assemblage have few species (5) with abundance higher than 1% of the total number of fishes, being dominated by Dormitator maculatus, Astyanax sp and ix Microphis brachyurus lineatus, species typical of upper estuaries and lower river reaches. Spatial variation was detected for D. maculatus only, more abundant at R2, a site with abundant riparian vegetation, mainly grass. Dormitator maculatus was more abundant in Summer and Autumn, M. brachyurus lineatus, in Spring, Autumn and Winter and Astyanax sp was absent in Spring only. Patterns in fish assemblage structure were at large scale, primarily species-specific responses to dominant environmental gradient, while at small scale, results of association with the habitat. / Os sistemas estuarinos influenciam as assembl?ias de peixes, ao longo de seus gradientes longitudinais e das marcadas varia??es da salinidade. Estas assembl?ias se adaptam ?s diferentes condicionantes do habitat e variam em escalas espaciais e temporais. O objetivo do presente estudo foi avaliar a composi??o e estrutura da ictiofauna em tr?s zonas do estu?rio do rio Mambucaba (ZC ? zona costeira; ZM ? zona de mistura e ZR ? zona de rio) e suas rela??es com as vari?veis ambientais e caracter?sticas do habitat destas zonas. Coletas sistem?ticas de peixes (2 meses por esta??o do ano) foram realizadas entre outubro de 2007 e agosto de 2008, com arrastos de fundo em dois locais da ZC (C1 e C2), arrasto de praia em 3 locais da ZM (M1, M2, M3) e peneira em 2 locais da ZR (R1 e R2). Em cada amostragem de peixes, foram tomadas, para a superf?cie e fundo, as vari?veis ambientais de temperatura, salinidade, condutividade, turbidez e oxig?nio dissolvido, bem como medida a profundidade. Um total de 14320 indiv?duos, constitu?dos por 111 esp?cies (ZR ? 18; ZM ? 50 e ZC - 66) foram coletados. Assembl?ias de peixes distintas foram identificadas para cada zona, indicadas pelo baixo n?mero de esp?cies comuns (14 - ZM e ZC; 8 - ZM e ZR; e 2 - ZC e ZR), e com apenas uma esp?cie abundante (> 1% do numero total de peixes na zona) comum em mais de uma zona (Eucinostomus argenteus na ZC e ZM). Tal padr?o pode estar relacionado ? maior variabilidade da salinidade existente na ZM e a estreita (20 m) largura do canal de conex?o com o mar, fatores que podem ser limitantes aos movimentos (entrada/sa?da) de peixes. Na ZC, as tr?s esp?cies mais abundantes foram Paralonchurus brasiliensis, Ctenosciaena gracillicirrhus, Anchoa lyolepis, Larimus breviceps e Stellifer brasiliensis, com a maior participa??o de peixes da fam?lia Sciaenidae nesta zona (18 esp?cies). As varia??es espaciais das esp?cies foram pouco consistentes na ZC, provavelmente relacionado a influencia da pluma estuarina n?o ter provocado mudan?as espa?o-temporais nas vari?veis ambientais de fundo (ANOVA, p>0,05). A profundidade foi o principal fator respons?vel pela separa??o espacial encontrada para Diapterus rhombeus (associa??es negativas) mais abundante em C1 (profundidade m?dia = 10 m; ANOVA, p<0,05) e Micropogonias furnieri, P. brasiliensis e Pellona harroweri (associa??es positivas) mais abundantes em C2 (profundidade m?dia = 17 m; ANOVA, p<0,00). Diapterus rhombeus e Etropus crossotus ocorreram principalmente na primavera e ver?o, e Eucinosomus gula na primavera. As esp?cies mais abundantes da ZC, t?picas de ?guas com maior influencia salina, ? um indicativo de que esta zona tem caracter?sticas mais associadas ? plataforma continental interna. Na ZM, a maioria das esp?cies mais abundantes (Eugerres brasilianus, Eucinostomus melanopterus, Trinectes paulistanus, Gobionellus shufeldti, G. oceanicus, Geophagus brasiliensis, Centropomus parallelus e Citharichthys arenaceus) apresentou maior n?mero e peso de indiv?duos em M1 (ANOVA, p<0,01), uma lagoa adjacente conectada ao canal principal. Apesar das correla??es negativas significativas observadas entre estas esp?cies e a salinidade (r-Spearman>0.32, p<0,01), as ?reas mais abrigadas em M1 parecem ser mais determinantes neste padr?o do que a salinidade em si. O local M1 tamb?m apresentou o maior n?mero de indiv?duos e de esp?cies (ANOVA, p<0,01), com maior n?mero de peixes de menor tamanho (CT mediana = 58mm) do que dos locais M2 e M3, situados no canal principal (mediana = 106mm) de acordo com o Teste das Medianas e Teste de Kruskallvii Wallis (p<0,01; 2 = 1167,5), indicando a import?ncia desta ?rea para o recrutamento das esp?cies. A baixa similaridade m?dia (SIMPER) para os locais M2 (38,7%) e M3 (17,8%) indicam uma maior variabilidade na assembl?ia destes locais, possivelmente devido a menor estrutura??o do habitat e maior dinamismo. Na ZR, a assembl?ia de peixes apresentou poucas esp?cies (5) com abund?ncia maior que 1% do n?mero total de peixes, sendo dominada por Dormitator maculatus, Astyanax sp e Microphis brachyurus lineatus, esp?cies t?picas de ?reas lim?trofes entre a zona superior do estu?rio e a zona baixa de rio. Varia??es espaciais foram detectadas apenas para D. maculatus, mais abundantes em R2, um local com abundante vegeta??o marginal composta principalmente por gram?neas. D. maculatus foi mais abundante no ver?o e outono, M. brachyurus lineatus, na primavera, outono e inverno e Astyanax sp foi ausente somente na primavera. Os padr?es na estrutura da assembl?ia de peixes s?o, em maior escala, primariamente resultado das respostas individuais das esp?cies ao gradiente ambiental dominante, enquanto em menor escala, resultado das associa??es com o habitat.