The aim of this thesis was to review the current state of knowledge, occurrence and distribution of two polydorid (Polychaeta: Spionidae) genera, Polydora and Dipolydora, in estuaries of subtropical eastern Australia. The existing taxonomy of the polydorid group is confused and descriptions include many relative terms. A numerical taxonomy approach using Primer 6 was taken to identify species groups and characters. A standardized set of multivariate morphological characters was developed and resemblance analysis functions used to create species cluster groups. SIMPER (similarity percentages) analysis on the same dataset was used to identify the diagnostic characters for each of these species cluster groups and to identify new characters which could be useful in species diagnosis, particularly for frequently occurring incomplete specimens.Prior to this study 3 Polydora species and 4 Dipolydora species were recorded from subtropical eastern Australia. The present study found 12 Polydora species and 10 Dipolydora species from estuaries and bays of subtropical eastern Australia.Two Polydora species are new (Polydora sp. P1 and Polydora cf. woodwicki) and 7 are potentially new species (P. cf. latispinosa; P. cf. websteri; P. sp. P2S; P. sp. P3S; P. sp. P4S; P. sp. P5S and P. sp. P6S) having been described from single specimens. Polydora cornuta Bosc, 1902 is recorded from New South Wales for the first time. Polydora cf. calcarea is reported from mudblisters in oysters. The Australian form of Polydora hoplura Claparède, 1870 and P. haswelli Blake and Kudenov, 1978 are described more fully than in existing literature.Three Dipolydora species are new (Dipolydora sp. D1; D. cf. flava and D. sp. D2) and 4 from single specimens are potentially new (D. cf. aciculata/ cf. giardi; D. sp. D3S; D. sp. D4S and D. sp. D5S). Dipolydora tentaculata (Blake and Kudenov, 1978) and Australian forms of Dipolydora flava (Claparède, 1870) and Dipolydora socialis (Schmarda, 1861) are described more fully than in existing literature.Prior to this study one Dipolydora and no Polydora were recorded from the Tweed- Moreton bioregion. This study reports 6 species of Dipolydora and 5 species of Polydora from this bioregion.Dipolydora penicillata (Hutchings and Rainer, 1979) and Carazziella victoriensis Blake and Kudenov, 1978 are recommended for synonymy.It is recommended that Polydora ciliata (Johnston, 1838) be reinstated and Dipolydora ciliata (Johnson, 1838) removed from the Australian polychaete checklist following identification of an error in description translation.Important gaps in collections were identified for polydorids associated with oysters from estuaries over the whole subtropical region; and for polydorids from the Tweed-Moreton IMCRA bioregion.

Recent sedimentary records have indicated that climate in low latitude, continental environments have varied significantly throughout the mid to late Holocene. In subtropical North America, major climatic phenomena such as the migration of the Intertropical Convergence Zone (ITCZ) and the Bermuda High have been shown to play a major role in this variability. Specifically, the northward migration of the ITCZ and the eastward position of the Bermuda High during summer months leads to warmer and wetter conditions over subtropical North America, and vice versa. A quantitative approach to understanding hydrologic dynamics (i.e. atmospheric circulation patterns, relative humidity) associated with these and other phenomena is necessary to accurately reconstruct the behavior of these hydrologic parameters in the past. Previous studies have shown that the hydrogen isotopic composition of algal material is a direct reflection of source waters, and that hydrogen isotopic enrichment in terrestrial material relative to aquatic biomass is a function of evaporative processes associated with the level of relative humidity in a given environment. This study utilizes a lacustrine system to provide a modern calibration that will attempt to develop a new climatic proxy for relative humidity and further examine varability in the behavior of environmental waters. This calibration was then applied to a sedimentary record to examine hydrologic variability in the geologic past.

The aim of this thesis was to review the current state of knowledge, occurrence and distribution of two polydorid (Polychaeta: Spionidae) genera, Polydora and Dipolydora, in estuaries of subtropical eastern Australia. The existing taxonomy of the polydorid group is confused and descriptions include many relative terms. A numerical taxonomy approach using Primer 6 was taken to identify species groups and characters. A standardized set of multivariate morphological characters was developed and resemblance analysis functions used to create species cluster groups. SIMPER (similarity percentages) analysis on the same dataset was used to identify the diagnostic characters for each of these species cluster groups and to identify new characters which could be useful in species diagnosis, particularly for frequently occurring incomplete specimens.Prior to this study 3 Polydora species and 4 Dipolydora species were recorded from subtropical eastern Australia. The present study found 12 Polydora species and 10 Dipolydora species from estuaries and bays of subtropical eastern Australia.Two Polydora species are new (Polydora sp. P1 and Polydora cf. woodwicki) and 7 are potentially new species (P. cf. latispinosa; P. cf. websteri; P. sp. P2S; P. sp. P3S; P. sp. P4S; P. sp. P5S and P. sp. P6S) having been described from single specimens. Polydora cornuta Bosc, 1902 is recorded from New South Wales for the first time. Polydora cf. calcarea is reported from mudblisters in oysters. The Australian form of Polydora hoplura Claparède, 1870 and P. haswelli Blake and Kudenov, 1978 are described more fully than in existing literature.Three Dipolydora species are new (Dipolydora sp. D1; D. cf. flava and D. sp. D2) and 4 from single specimens are potentially new (D. cf. aciculata/ cf. giardi; D. sp. D3S; D. sp. D4S and D. sp. D5S). Dipolydora tentaculata (Blake and Kudenov, 1978) and Australian forms of Dipolydora flava (Claparède, 1870) and Dipolydora socialis (Schmarda, 1861) are described more fully than in existing literature.Prior to this study one Dipolydora and no Polydora were recorded from the Tweed- Moreton bioregion. This study reports 6 species of Dipolydora and 5 species of Polydora from this bioregion.Dipolydora penicillata (Hutchings and Rainer, 1979) and Carazziella victoriensis Blake and Kudenov, 1978 are recommended for synonymy.It is recommended that Polydora ciliata (Johnston, 1838) be reinstated and Dipolydora ciliata (Johnson, 1838) removed from the Australian polychaete checklist following identification of an error in description translation.Important gaps in collections were identified for polydorids associated with oysters from estuaries over the whole subtropical region; and for polydorids from the Tweed-Moreton IMCRA bioregion.

Durante décadas, a visão prevalente em ecologia de microrganismos era de que os fatores ambientais locais seriam os únicos agentes estruturantes das comunidades e dos padrões de coexistência das espécies. Entretando, estudos recentes têm fornecido evidência de que processos ligados a dispersão possam ser tão importantes quanto o ambiente local na estruturação das comunidades, reacendendo o debate em torno da hipótese clássica sobre a ubiquidade dos microrganismos. Neste estudo, nós examinamos os padrões de coexistência do fitoplâncton e os possíveis determinantes da variação espacial na composição das comunidades em 9 lagoas do sul do Brasil. Nós testamos se as espécies fitoplanctônicas apresentam um padrão não aleatório de coexistência através de um modelo nulo e se distância espacial ou a distância ambiental possuem relação com a similaridade na composição das comunidades. Nós também investigamos se as variáveis ambientais locais são bons preditores da abundância das espécies. Na análise de coexistência, nós não observamos um padrão significativo de estruturação dentro das lagoas, mas encontramos um padrão não-aleatório e segregado das espécies ao longo das lagoas, indicando que as espécies coexistem menos do que o esperado ao acaso nesta escala. A similaridade na composição das comunidades mostrou correlação significativa com a distância ambiental, mas não foi correlacionada com a distância geográfica entre os sítios. Além disso, a variação na abundância das espécies apresentou correlação significativa com as variáveis ambientais locais (transparência da água, condutividade, nitrato e ortofosfato). Em conclusão, nossos resultados apoiam a visão de que a variação espacial do fitoplâncton é melhor explicada pelo ambiente local. Nós não testamos a influência de variáveis históricas e filogenéticas sobre esses padrões, que podem ser temas de estudos futuros, a fim de elucidar ainda mais essas questões. / For decades, the main hypothesis in microbial ecology was that local environment would be the only mechanism structuring communities and patterns of species coexistence. However, recent studies have provided evidence that processes related to dispersion can be as important as the local environment for shaping biological communities, stimulating new debates on the classical hypothesis about the ubiquity of microorganisms. In this study, we examined the phytoplankton coexistence patterns and possible determinants of spatial variation in community composition in 9 lakes of southern Brazil. First, we use a null model analysis for tested whether the phytoplankton species show a nonrandom pattern of coexistence. We also tested whether spatial distance or environmental distance act as potential factors controlling community composition. Finally, we investigated whether local environmental variables are good predictors of species abundance. We did not observe a significant pattern of coexistence species in the within-lakes analysis, but we found a nonrandom pattern of coexistence and segregation of species across-lakes analysis, indicating that the species coexist less than expected by chance on this scale. Phytoplankton community composition showed a strong positive correlation with the environmental distance but was not correlated with the geographical distance between sites. Moreover, the variation in the abundance of species showed significant correlation with local environmental variables (water transparency, conductivity, nitrate and orthophosphate). In conclusion, our results support the view that the spatial variation of phytoplankton is best explained by the local environmental conditions. We suggest that the influences of historical and phylogenetic variables on these patterns, here not measured, be analyzed in future studies, to further elucidate these questions.

Durante décadas, a visão prevalente em ecologia de microrganismos era de que os fatores ambientais locais seriam os únicos agentes estruturantes das comunidades e dos padrões de coexistência das espécies. Entretando, estudos recentes têm fornecido evidência de que processos ligados a dispersão possam ser tão importantes quanto o ambiente local na estruturação das comunidades, reacendendo o debate em torno da hipótese clássica sobre a ubiquidade dos microrganismos. Neste estudo, nós examinamos os padrões de coexistência do fitoplâncton e os possíveis determinantes da variação espacial na composição das comunidades em 9 lagoas do sul do Brasil. Nós testamos se as espécies fitoplanctônicas apresentam um padrão não aleatório de coexistência através de um modelo nulo e se distância espacial ou a distância ambiental possuem relação com a similaridade na composição das comunidades. Nós também investigamos se as variáveis ambientais locais são bons preditores da abundância das espécies. Na análise de coexistência, nós não observamos um padrão significativo de estruturação dentro das lagoas, mas encontramos um padrão não-aleatório e segregado das espécies ao longo das lagoas, indicando que as espécies coexistem menos do que o esperado ao acaso nesta escala. A similaridade na composição das comunidades mostrou correlação significativa com a distância ambiental, mas não foi correlacionada com a distância geográfica entre os sítios. Além disso, a variação na abundância das espécies apresentou correlação significativa com as variáveis ambientais locais (transparência da água, condutividade, nitrato e ortofosfato). Em conclusão, nossos resultados apoiam a visão de que a variação espacial do fitoplâncton é melhor explicada pelo ambiente local. Nós não testamos a influência de variáveis históricas e filogenéticas sobre esses padrões, que podem ser temas de estudos futuros, a fim de elucidar ainda mais essas questões. / For decades, the main hypothesis in microbial ecology was that local environment would be the only mechanism structuring communities and patterns of species coexistence. However, recent studies have provided evidence that processes related to dispersion can be as important as the local environment for shaping biological communities, stimulating new debates on the classical hypothesis about the ubiquity of microorganisms. In this study, we examined the phytoplankton coexistence patterns and possible determinants of spatial variation in community composition in 9 lakes of southern Brazil. First, we use a null model analysis for tested whether the phytoplankton species show a nonrandom pattern of coexistence. We also tested whether spatial distance or environmental distance act as potential factors controlling community composition. Finally, we investigated whether local environmental variables are good predictors of species abundance. We did not observe a significant pattern of coexistence species in the within-lakes analysis, but we found a nonrandom pattern of coexistence and segregation of species across-lakes analysis, indicating that the species coexist less than expected by chance on this scale. Phytoplankton community composition showed a strong positive correlation with the environmental distance but was not correlated with the geographical distance between sites. Moreover, the variation in the abundance of species showed significant correlation with local environmental variables (water transparency, conductivity, nitrate and orthophosphate). In conclusion, our results support the view that the spatial variation of phytoplankton is best explained by the local environmental conditions. We suggest that the influences of historical and phylogenetic variables on these patterns, here not measured, be analyzed in future studies, to further elucidate these questions.

The use of foggage as winter feed for animal maintenance is unlikely to totally replace hay and/or silage, but should be used as an alternative for the early winter. The most important objective in producing foggage is to feed animals to at least maintain body weight through the winter season. As foggage is generally not a high quality feed, it usually can not be used for producing animals without supplementation. Using foggage can also mininise expensive inputs, such as labour and machinery. This is the single most outstanding advantage of using pasture foggage over hay, haylage, crop residues or silage. Although pastures also have establishment and fertilizer costs, these are less than costs associated with intensive annual crops. Many pastures are also perennial, which means less establishment costs. This emphasises the importance for less intensive farming systems. Depending on what the objectives of the farmer are, he can manage foggage to produce a high yield with a lower quality or vice versa. Thus it is critical to maintain a balance between yield and quality. Foggage quality was inversely related to the growing season after the pasture was closed-up and thus the quality will be lower with earlier closing-up time. Fertilisation, especially with nitrogen, will increase the nutritive value of the product (6% - 12%CP). The aim of this study was to determine which pasture provides the best foggage in different scenarios. The conclusion is, therefore, that a farmer must first decide on his management plan and where his foggage will fit in. Then it is recommended to choose the species (or accession) that is best adapted to his specific area of farming. Silk sorghum and Coastcross II had the best yields recorded. Smutsfinger grass was very palatable, had high digestibility and would, therefore, be recommended for quality in the higher rainfall eastern parts of the country. Because of their drought resistance, Molopo and Kleingrass will be recommended for the warmer areas with less rainfall and Molopo especially for small farmers who lack overall grazing management skills or infrastructure. / Dissertation (MSc (Agric) Pasture Science)--University of Pretoria, 2002. / Plant Production and Soil Science / unrestricted

The shortage of water in Mexico has made public and private institutions look at reservoirs as an alternative solution for present and future water supply. However, eighty percent of the existing reservoirs in Mexico are contaminated at some level, many severely. Water quality models are water-management tools used to diagnose water quality problems and the impact of various environmental conditions. They can be effective in assessing various measures of remediation leading to improved water quality. In most of the cases such water quality models have been successfully applied in reservoirs located in temperate climates. However, the use of water quality models in subtropical reservoirs, especially those in developing countries, have relatively little application because either basic data are not available or because they are not sufficient. In this study, a preliminary water quality model was developed for a subtropical reservoir to assess both the ability to collect adequate data and the model's underlying applicability in a subtropical region. The Aguamilpa reservoir is located in the western part of Mexico (Nayarit). It was built for power generation, irrigation and as a fishery. CE-QUAL-W2 is a two-dimensional hydrodynamic and water quality model suitable for long and narrow water bodies. Geometrically the Aguamilpa reservoir is long and deep, making it an ideal candidate to be modeled by CE-QUAL-W2. The model was developed for 1995 and 1996 because of a wider availability of historical data during this period. In addition to a preliminary model and assessment of applicability in this subtropical region, a monitoring and data acquisition plan was designed to identify the minimum required data which must be used to update, calibrate and simulate the water quality parameters. Once the model is calibrated, it may be used to simulate the water quality changes occurring with respect to environmental, climatological and anthropogenic effects. Further, the model may be used to prescribe operating procedures upstream as well as at the dam which can serve to improve the overall water quality. The development of the model at Aguamilpa can serve as a guideline for developing similar water quality models in this and other similar subtropical locations.

This study addresses the susceptibility of atmospheric rivers (ARs) to the behavior of the North Atlantic Subtropical High (NASH). ARs are a major mechanism for meridional moisture transport often connected to heavy precipitation and mid-latitude troughs. The NASH, a semi-permanent anticyclone over the subtropical North Atlantic Ocean, has been shown to be significantly influential on precipitation variability over the southeastern United States. A self-organizing map (SOM) was trained on a 4 x 3 regular grid over 250 iterations using ERA5 derived 6-hourly 850 hPa Geopotential Heights ≥ 1535 gpm from 1979-2020. The 12 resulting "nodes" were analyzed with respect to ARs defined by objects of ERA5 derived integrated water vapor transport (IVT) > 500 m-1 s-1 with lengths > 2000 km. Composites of thresholded 850 hPa heights, AR-concurrent PRISM precipitation, AR spatial frequency distribution maps, and seasonal AR frequency histograms per node illustrate seasonal interactions between the NASH and ARs that demonstrate a tendency of more frequent ARs and higher mean AR-driven precipitation over the Mississippi embayment and Ohio River Valley in the summer months, believed to be representative of extreme moisture transport events, when the NASH exhibits increased intensity, spatial expansion, and southwestward migration. Conversely, AR frequency and AR-concurrent precipitation composites suggest wintertime events are mainly supported by dynamically-driven nor'easter and bomb type cyclones when the NASH is constricted, at higher latitudes, and further east. Findings suggest that extreme summertime water vapor transport events associated with an AR are enhanced by the warm season NASH due to its increased intensity and proximity to the eastern US that acts as a supplementary lifting mechanism amidst low dynamic influence. / Master of Science / This study aims to investigate the response of atmospheric rivers (ARs) to the behavior of the North Atlantic Subtropical High (NASH). ARs are a major vehicle for the poleward transport of moisture from the tropics and subtropics. ARs are often affiliated with heavy precipitation and mid-latitude cyclones and frontal boundaries. The NASH, a semi-permanent anticyclone over the subtropical North Atlantic Ocean, has been shown to be significantly influential on precipitation variability over the southeastern United States. A self-organizing map (SOM), a method of vector quantification, was trained on a 4 x 3 regular grid over 250 iterations using ERA5 derived 6-hourly 850 hPa Geopotential Heights ≥ 1535 meters from 1979-2020. The 12 resulting "nodes" were analyzed with respect to ARs defined by objects that result from masking the rate of transport of water vapor within a vertical column from 1000 hPa to 300 hPa of which that are greater than 2000 km long. Composites of thresholded 850 hPa heights, AR-concurrent precipitation, AR spatial frequency distribution maps, and seasonal AR frequency histograms per node illustrate seasonal interactions between the NASH and ARs that demonstrate a tendency of more frequent ARs and higher mean AR-driven precipitation over the Mississippi embayment and Ohio River Valley in the summer months, believed to be representative of severe precipitation events, when the NASH is stronger, larger, and further southwestward. Conversely, AR frequency and AR-concurrent precipitation composites suggest wintertime events are mainly supported by nor'easter and bomb type cyclones that occur when the Polar jet stream is strongest and when the NASH is constricted, at higher latitudes, and further east. Findings suggest that extreme summertime water vapor transport events associated with an AR are enhanced by the warm season NASH due to its increased intensity and proximity to the eastern US that acts as a supplementary lifting mechanism amidst low dynamic influence.

Made available in DSpace on 2016-12-12T20:12:32Z (GMT). No. of bitstreams: 1 PGEF15MA042.pdf: 1375553 bytes, checksum: f93a1c6bfaca22be5ac8fae40f160f3c (MD5) Previous issue date: 2015-06-16 / The present dissertation aimed to understand the functional, phylogenetic and the floristic-structural organization of the tree component, along a topographic gradient in a forest in Upper Uruguay River region. Information of this nature is critical for the definition of conservation plans, since it allows inferences about the ecological strategies of species to occupy different environmental conditions. For this, 50 10 × 20 m permanent plots were allocated along different topographic sectors (lower, middle, upper), where all individual tree species with circumference at breast height (cbh) equal to or greater than 15.7 cm had the cbh measured, the height estimated and the botanical identity determined. For the 20 most abundant species, the following functional traits were determined: basic wood density, maximum potential height, leaf area, specific leaf area,leaves lifespan, regeneration and dispersal guilds. The floristic-structural organization was analyzed through Shannon (H ) and Pielou (J) Indices, NMDS (Non-metric Multidimensional Scaling), Permutational Multivariate Analysis of Variance (PERMANOVA), Indicator Species Analyzes and contingency table. The functional traits were analyzed by Rao Q Index and community weight means values for plots (CWM). The phylogenetic structure was 18 determined by Mean Pairwise Distance analysis and K statistic of phylogenetic signal. The functional and phylogenetic structures were compared among sectors by Analysis of Variance, for normal distributions, or Kruskal-Wallis, for non-normal distributions, followed by post hoc tests. The results demonstrated that the tree component showed floristic-structural and ecological strategies variations in function of topographic sectors. The taxonomic, functional and phylogenetic diversity was lower in the lower sector, with predominance of trees with low wood density, large leaves, with smaller values of specific leaf area, than sectors situated at upper positions in the terrain. It was concluded that the topography represented an important source of heterogeneity of the tree component in small spatial scale. The capacity of species occupy different sectors in relief was influenced by their functional traits, reflecting different ecological strategies, which are partly phylogenetically conserved / A presente dissertação teve como principal objetivo entender a organização florística-estrutural, funcional e filogenética do componente arbóreo, ao longo de um gradiente topográfico, em uma floresta na região do Alto Rio Uruguai. Informações desta natureza são fundamentais para a definição de planos de conservação, uma vez que permitem inferências sobre as estratégias ecológicas das espécies para se desenvolverem em condições ambientais distintas.Para isto, foram alocadas 50 parcelas permanentes de 10 × 20m, ao longo de diferentes setores topográficos (inferior, intermediário e superior), onde todos os indivíduos arbóreos com circunferência na altura do peito (CAP) maior ou igual a 15,7 cm, tiveram a CAP medida, a altura estimada e identidade botânica determinada. Para as 20 espécies mais abundantes, foram determinados os seguintes atributos funcionais: densidade básica da madeira, altura máxima potencial, área foliar, área foliar específica, regime de renovação foliar, guildas de regeneração e de dispersão.A organização florística-estrutural foi analisada por meio dos índices de Shannon (H ) e de Pielou (J), NMDS (Escalonamento Multidimensional Não-métrico), Análise de Variância Multivariada Permutacional (PERMANOVA), Análise de Espécies Indicadoras e tabela de contingência. Os atributos funcionais foram analisados por meio do índice de Rao Q e os valores médios dos atributos ponderados para comunidade em cada parcela (CWM). A estrutura filogenética foi determinada por meio da análise de Mean Pairwise Distance (MPD) e pela estatística K para sinal filogenético de atributos funcionais. As estruturas funcional e filogenética foram comparadas entre setores por meio de Análise de Variância, para distribuição normal, ou Kruskal-Wallis, para distribuições não-normais, com testes post hoc.Os resultados demonstraram que o componente arbóreo apresentou variações florísticas-estruturais e de estratégias ecológicas em função dos setores topográficos. A diversidade taxonômica, funcional e filogenética foi menor no Setor inferior, que apresentou a predominância indivíduos com baixa densidade da madeira, folhas maiores e com menor área foliar específica, em relação as posições mais elevadas no relevo. Conclui-se que a topografia representou uma importante fonte de heterogeneidade do componente arbóreo em pequena escala espacial. A capacidade das espécies ocuparem diferentes setores no relevo foi influenciada por seus atributos funcionais, refletindo diferentes estratégias ecológicas, que, em parte são filogeneticamente conservadas

Submitted by dayse paz (daysepaz@hotmail.com) on 2016-04-06T14:58:58Z No. of bitstreams: 1 Disserta_o_Vanessa_Correa.pdf: 9516390 bytes, checksum: be0bd59f07a366880594f1ccedf35cb0 (MD5) / Approved for entry into archive by cleuza maria medina dos santos (cleuzamai@yahoo.com.br) on 2016-04-07T22:41:59Z (GMT) No. of bitstreams: 1 Disserta_o_Vanessa_Correa.pdf: 9516390 bytes, checksum: be0bd59f07a366880594f1ccedf35cb0 (MD5) / Made available in DSpace on 2016-04-07T22:42:00Z (GMT). No. of bitstreams: 1 Disserta_o_Vanessa_Correa.pdf: 9516390 bytes, checksum: be0bd59f07a366880594f1ccedf35cb0 (MD5) Previous issue date: 2013 / Este estudo teve o objetivo de conhecer a comunidade de diatomáceas epífitas nas macrófitas (Acrostichum danaefolium Langst. & Fisch, Schoenoplectus californicus (C.A. Mey) Soják, Myriophylum aquaticum (Vell) Verdc e Cabomba caroliniana A. Gray) em diferentes amostragens na Lagoa Pequena que compreende os ambientes (Arroio Pseudônimo, Praia da Lagoa Pequena, Entrada da Lagoa Pequena e Feitoria), de maio de 2011 a janeiro de 2012, totalizando 79 amostras coletadas. As amostras foram fixadas com formalina a 4%. Para estudo das formas de crescimento, em cada ponto foi coletada uma amostra (não fixada) para observação das diatomáceas. No ambiente foram medidas as variáveis físicas (temperatura, profundidade, transparência da água e vazão) e químicas (pH, condutividade elétrica, fósforo e nitrogênio). A flora em A. danaeifolium apresentou 157 spp, dentre os quais 26% de água doce, 50% estuarinos e 14% marinhos. Nitzschia apresentou maior diversidade (riqueza de espécies). Vinte e três espécies foram registradas pela primeira vez para o Rio Grande do Sul. Ocorreram diferentes formas de crescimento que formaram as guildas ecológicas de baixo perfil (formas adnatas), alto perfil (formas eretas, formadoras de cadeias, tubos, e pedúnculos de mucilagem) e guilda móvel (espécies móveis). Em S. californicus ocorreram 129 táxons distribuídos em 55 gêneros, e Nitzschia apresentou também maior número (25) de espécies. Em C. caroliniana ocorreram 38 táxons e formas de crescimento adnata, ereta, pedúnculo, cadeia tubo e móvel) e em M. aquaticum ocorreram 54 táxons e formas de crescimento adnata, pedúnculo, ereta, cadeia e tubo. Em ambas macrófitas foi encontrada guilda de alto perfil. A presença de diferentes formas de crescimento e guilda de alto perfil em todos locais estudados mostrou a complexidade da comunidade. A temperatura da água variou de 10-28,5º C, a profundidade 0,26-1,29 m, a transparência 0,20-0,76 m, a vazão 9,4-42,12 m³/s, o pH 7,0-8,8, a condutividade elétrica 0,62-16,96 mS.cm‾¹, o fósforo orgânico total 0,03-0,37 mg.L-1 , e o nitrogênio orgânico total entre 0,29 e 1,20 mg.L-1 . A maior temperatura e o baixo nível da água influenciaram a composição da guilda de alto perfil, que prevaleceu durante todo período. O maior valor de condutividade (verão) permitiu a presença de espécies marinhas no Arroio Pseudônimo e Feitoria. O Arroio Pseudônimo teve maior riqueza de espécies provavelmente por ser mais protegido, do que os outros locais. Em menor temperatura (10º C) e condutividade (0,65 mS.cm‾¹) também se observou a formação de tubos de mucilagem e a guilda de alto perfil no Arroio Pseudônimo. Espécies dulcícolas (Nitzschia spiculoides Hustedt, N. subacicularis Hustedt, N. fonticola var. pelagica Hustedt e S. martyi Hèribaud-Joseph) e marinha (C. peltoides Hustedt) foram tolerantes as variações de condutividade na Lagoa Pequena. A morfologia das macrófitas aquáticas influenciou a comunidade de diatomáceas que apresentou maior riqueza de espécies e gêneros em macrófitas de arquitetura complexa (C. caroliniana e M. aquaticum). / The study aimed know the diatom community epiphytic on macrophytes (Acrostichum danaefolium Langst. & Fisch, Schoenoplectus californicus (C.A. Mey) Soják, Myriophylum aquaticum (Vell) Verdc and Cabomba caroliniana A. Gray) at different samplings in Lagoa Pequena comprising enviroments (Arroio Pseudônimo, Lagoa Pequena beach, Lagoa Pequena entrance and Feitoria) from may 2011 to january 2012, totalizing 79 samples collected. All samples were fixed with 4% formalin. In order to study the crecimento forms, in each point was collected a sample (unfixed) for observation of diatoms. In the environment were measured physical variables (temperature, depth, water transparency and flow) and chemical (pH, electrical conductivity, phosphorus and nitrogen). The flora in A. danaeifolium presented 157 spp, among them 26% freshwater, 50% estuarine and 14% marine and Nitzschia presented the highest diversity (species richness). Twenty-three species were recorded for the first time to Rio Grande do Sul. There were different forms growth that formed guilds ecological of low profile (forms adnate), high profile (forms erect, chains, tube, and stalked of mucilage) and guild mobile (species mobile). In S. californicus occurred 129 taxa distributed in 55 genera and Nitzschia presented also the greatest number (25) of species. In C. caroliniana occurred 38 taxa and forms growth adnate, erect, stalked, chain, tube and mobile) and in M. aquaticum occurred 54 species and forms of growth adnate, stalked, erect, chain and tube. In both macrophytes were found guild of high profile. The presence of distinct growth forms and guild high profile in all study sites showing the complexity of the community. The water temperature varied from 10-28,5º C, the depth 0,26-1,29, the transparency 0,20-0,76 m, the flow 9,4-42,12 m³/s, the pH 7,0-8,8, electrical conductivity 0,62-16,96 mS.cm‾¹, the total organic phosphorus 0,03-0,37 mg.L-1 , and the total organic nitrogen 0,29-1,20 mg.L-1 . Highest temperature and low water level influenced the composition of guild high profile, which prevailed throughout the period. Higher conductivity values (summer) allowed the presence of marine species in the Arroio Pseudônimo and Feitoria. The Arroio Pseudônimo had greater species richness probably because is more protected than the other sites. In the lowest temperature (10º C) and conductivity (0,65 mS.cm‾¹) also observed the formation of mucilage tubes and guild high profile in the Arroio Pseudônimo. Freshwater species (Nitzschia spiculoides Hustedt, N. subacicularis Hustedt, N. fonticola var. pelagica Hustedt and S. martyi Hèribaud-Joseph) and marine (C. peltoides Hustedt) were tolerant to conductivity variations in Lagoa Pequena. The morphology of aquatic macrophytes influenced the diatom community that presented highest richness of species and genera in macrophytes of complex architecture (C. caroliniana and M. aquaticum).