O objetivo deste trabalho foi comparar a composição e a diversidade da comunidade fitoplanctônica nos braços Rio Grande e Taquacetuba (Represa Billings) e determinar os fatores que regulam sua estrutura. Foram realizadas coletas em fevereiro, maio, agosto e novembro de 2005, nas quais foram coletadas amostras de água em 6 profundidades. Foram realizadas coletas em fevereiro, maio, agosto e novembro de 2005, nas quais foram coletadas amostras de água em 6 profundidades. Foram analisadas as variáveis físicas e químicas da água e a comunidade fitoplacntônica. No Rio Grande foram identificados 72 táxons distribuídos em 7 classes. Foi observada alta diversidade e uniformidade e o corpo dágua foi classificado com oligo/mesotrófico. Observou-se abundância relativa alternada entre as classes Zygnemaphyceae, Bacillariophyceae, Euglenophyceae e Chlorophyceae; entre C- e R-estrategistas e entre os grupos funcionais D, X1, W1 e T. Verticalmente, foi observada alternância entre classes abundantes devido às características morfológicas e/ou diferentes requerimentos fisiológicos. No Taquacetuba, foram identificados 66 táxons distribuídos em 7 classes. Foi observada baixa diversidade e uniformidade e o corpo dágua foi classificado com eu/supereutrófico. Observou-se dominância de cianobactérias R-estrategistas, principalmente das associações S1 e Sn. Aparentemente, a dinâmica do fitoplâncton no Taquacetuba é controlada por exclusão competitiva e distúrbios, pois a dominância das cianobactérias inibiu o crescimento de outras classes, enquanto no Rio Grande, a grande diversidade foi mantida pela presença de distúrbios. Os padrões observados podem ser explicados às diferenças nas variáveis físicas e químicas, nos funcionamentos das captações de água e aos diferentes fins para os quais estas águas são captadas. O Rio Grande tem suas águas constantemente tratadas com sulfato de cobre para o controle da biomassa algal e manutenção da qualidade da água compatível para o abastecimento público. Porém, a sulfatação como uma medida paliativa deve ser utilizada com cautela e mais estudos são necessários a fim de evitar problemas ainda desconhecidos a longo prazo. O Taquacetuba tem suas águas revertidas sem tratamento para a Represa Guarapiranga, podendo estar comprometendo a qualidade da água da Guarapiranga, que abastece grande parte da população da cidade de São Paulo. / The aim of this work was to compare the phytoplankton community composition and diversity in Rio Grande and Taquacetuba branches (Billings Reservoir) and to determinate its controlling factors. Water samples were collected in six depths on February, May, August and November 2005. Physical and chemical variables and the phytoplankton community were analyzed. In Rio Grande, 72 phytoplankton taxa were found, distributed among 7 classes. High diversity and uniformity were observed and water body was classified as oligo/mesotrophic. Relative abundance alternate among Zygnemaphyceae, Bacillariophyceae, Euglenophyceae and Chlorophyceae; among C- e R-strategists e among assemblages D, X1, W1 e T. Vertically, alternation of abundant classes was observed due to morphologic characteristics and/or different physiological requirements. In Taquacetuba, 66 phytoplankton taxa were found, distributed among 7 classes. Low diversity and uniformity were observed and water body was classified as eu/supereutrophic. Cyanobacteria R-strategist dominated, especially S1 e Sn assemblages. Apparently, phytoplankton dynamics in Taquacetuba is controlled by competitive exclusion and disturbs, because cyanobacteria dominance inhibit the growth of other classes, while the high diversity in Rio Grande is kept by the presence of disturbs. These patterns observed can be explained by differences on physical and chemical variables, on water intake functioning and on water destinations. Rio Grande is constantly treated with copper sulfate to control algae biomass and to maintain good water quality to public supply. Although, sulfatation as a palliative measure need to be cautious and more studies are necessary to avoid problems still unknown in long term. Taquacetubas water is transferred without treatment to Guarapiranga Reservoir. It could be compromising the water quality of Guarapiranga, which supply a great part of São Paulo city population.

A planície costeira do Rio Grande do Sul apresenta vários lagos subtropicais rasos com origem semelhante e uma grande amplitude de tamanho, distância e conectividade entre lagos, e desta maneira é aqui considerada como apropriada ao endereçamento de questões tais como diversidade e metabolismo do bacterioplâncton, um tópico atual de pesquisa. Em uma primeira abordagem, nós acessamos a diversidade bacteriana usando a técnica de Hibridização in situ Fluorescente (FISH) em um sub-conjunto destes lagos e inesperados padrões biogeográficos foram encontrados, a despeito da baixa resolução taxonômica empregada por esta técnica. Uma vez que os resultados do FISH têm sido relacionados também ao estado fisiológico das células, além de diversidade, nós procuramos por uma explicação alternativa para situações metabólicas bacterianas associadas aos fatores testados. Os resultados mostraram que as macrófitas exercem um efeito negativo sobre o fitoplâncton através de mecanismos antagonistas e que este último, por sua vez, afeta as bactérias, além de um possível efeito direto sobre o fitoplâncton e o bacterioplâncton pela liberação de compostos alelopáticos e substâncias húmicas. A competição entre o fitoplâncton e as bactérias sob condições de alta densidade algal pode igualmente criar condições inadequadas para o metabolismo bacteriano. Estes resultados indicam que fatores locais podem ter um efeito importante sobre a distribuição de estados metabólicos do bacterioplâncton. Em uma segunda abordagem, nós examinamos em detalhe a transição a partir da zona litoral dominada por macrófitas até a zona pelágica dominada pelo fitoplâncton, acompanhando as respostas contínuas do bacterioplâncton à mudança de dominância de produtor primário, uma vez que os resultados da primeira abordagem demonstraram que importantes respostas das bactérias estão associadas a estes dois habitats putativos. Os resultados também indicaram um padrão de inibição na presença de macrófitas aquáticas, potencializado pelas altas cargas de substâncias húmicas dos massivos banhados circundantes. O bacterioplâncton aumentou em densidade, biovolume e biomassa em direção às zonas pelágicas, mas a Eficiência de Crescimento Bacteriana indicou que as bactérias possivelmente tenham melhor performance metabólica em locais de dominância bem definida. Mudanças na estrutura da comunidade incluindo zooplâncton, fitoplâncton e bacterioplâncton foram encontradas, confirmando constatações prévias sobre o papel estruturador das macrófitas em lagos rasos, com a comprovação adicional de que este papel aplica-se também às bactérias. / The coastal plain of Rio Grande do Sul state presents several subtropical shallow lakes with similar origin and a wide range of size, distance and connectivity between lakes, and therefore is considered as suitable to address questions such as bacterial diversity and metabolism, a current research subject. In a first approach we assessed bacterial diversity using the technique of Fluorescent in situ Hybridization (FISH) in a sub-set of these lakes and unexpected biogeographic patterns arised, despite the low resolution employed by this technique. Since FISH results might be linked also to physiological status of cells, rather than diversity itself, we looked for an alternative explanation for bacterial metabolic situations associated with the drivers tested. Our results showed that macrophytes exert a negative effect on phytoplankton through antagonistic mechanisms and the latter, at its turn, affects bacteria, besides a possible direct effect on phyto- and bacterioplankton by release of allelopathic compounds and humic substances. Competiton between phytoplankton and bacteria in high algal density areas can create also inadequate conditions for bacterial metabolism. These results indicate that local factors can have an important effect on bacterioplankton metabolic status distribution. In a second approach we examined in detail the transition between a macrophyte dominated littoral zone to a phytoplankton dominated pelagic zone, following the continuous responses of bacterioplankton to the shift of primary producer dominance, since our previous results from the first approach showed that important responses of bacteria are associated to this two putative habitats. Overall data showed also a pattern of inhibition in the presence of aquatic macrophytes, potentialized by high loads of humic substances from surrounding massive wetlands. Bacterioplankton increased in density, biovolume and biomass towards pelagic zones, but Bacterial Growth Efficiency indicated that bacteria might perform better in well defined dominance sites. Changes in community structure of zooplankton, phytoplankton and bacterioplanton was found, confirming previous statements about the structuring role of macrophytes in shallow lakes, with the additional comprovation that this role applies also for bacteria.

Submitted by (ana.araujo@ufrpe.br) on 2016-07-06T20:01:40Z No. of bitstreams: 1 Jose Edson Rodrigues Guedes Gondim.pdf: 2993772 bytes, checksum: e59c03e20951f28e1850a28da2ba540e (MD5) / Made available in DSpace on 2016-07-06T20:01:40Z (GMT). No. of bitstreams: 1 Jose Edson Rodrigues Guedes Gondim.pdf: 2993772 bytes, checksum: e59c03e20951f28e1850a28da2ba540e (MD5) Previous issue date: 2015-03-02 / The physical, chemical and biological aspects of three estuaries of Pernambuco were studied to verify the different patterns of human impacts in these environments. Water quality and sediment parameters were collected from estuaries of Rio Botafogo and Carrapicho (north coast of PE) and Rio Maracaípe (Southern coast of the state) in the period from July to December 2011. These estuaries have different characteristics in your area, Rio Botafogo in the vicinity of the basin has more industries, Rio Carrapicho more shrimp and agriculture in general and the Rio Maracaípe is almost urban. The parameters observed regarding the sediment significant differences were identified in the presence of trace metals between the estuary of the Rio Botafogo with the Rio Maracaípe. As for the water the most significant difference was identified in total and fecal coliform estuary Rio Maracaípe regarding the Rio Carrapicho. Individually it was observed that the Rio Botafogo estuary is contaminated by iron (Fe) and mercury (Hg) due to evictions of industries and the estuary has Maracaípe contamination by fecal coliform or resulting from poor sanitary conditions of their area. The principal component analysis showed patterns of different characteristics within each of estuaries and also between them. For the phytoplankton was not identified any significant change in their communities. / Os aspectos físicos, químicos e biológicos de três estuários de Pernambuco foram estudados para verificar os diferentes padrões de impactos antropogênicos nestes ambientes. Parâmetros de qualidade da água e do sedimento foram coletados dos estuários do Rio Botafogo e Carrapicho (litoral norte de PE) e do Rio Maracaípe (Litoral Sul do Estado) no período de julho a dezembro de 2011. Estes estuários possuem características diferentes em sua área, o Rio Botafogo no entorno da sua bacia possui mais indústrias, o Rio Carrapicho mais carcinicultura e a agricultura em geral e o Rio Maracaípe é praticamente urbano. Nos parâmetros observados referente ao sedimento foram identificadas diferenças significativas na presença de metais traços entre o estuário do Rio Botafogo com o do Rio Maracaípe. Já para a água a diferença mais significativa foi identificada nos coliformes totais e termotolerantes do estuário do Rio Maracaípe com relação ao Rio Carrapicho. Individualmente foi observado que o estuário do Rio Botafogo encontra-se contaminado por ferro (Fe) e mercúrio (Hg) devido aos despejos das indústrias e que o estuário do Rio Maracaípe possui uma contaminação por coliformes fecais ou termotolerantes decorrente das péssimas condições sanitárias da sua área. A análise de Componentes Principais evidenciou os padrões de diferentes características dentro de cada um dos estuários como também entre eles. Para os fitoplâncton não foi identificado nenhuma mudança significativa em suas comunidades.

Tese(mestrado) - Universidade Federal Do Rio Grande, Programa de Pós-graduação em Oceanografia Biológica, Instituto de Oceanografia, 2013. / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-11-18T12:52:36Z No. of bitstreams: 1 AMABILE.pdf: 5765676 bytes, checksum: a4926b187c0614bc4d913a29b23870ab (MD5) / Approved for entry into archive by Angelica Miranda (angelicacdm@gmail.com) on 2013-11-18T19:07:50Z (GMT) No. of bitstreams: 1 AMABILE.pdf: 5765676 bytes, checksum: a4926b187c0614bc4d913a29b23870ab (MD5) / Made available in DSpace on 2013-11-18T19:07:50Z (GMT). No. of bitstreams: 1 AMABILE.pdf: 5765676 bytes, checksum: a4926b187c0614bc4d913a29b23870ab (MD5) Previous issue date: 2013 / Imagens de satélite da cor do oceano detectam intensas florações do fitoplâncton durante primavera e verão ao longo da quebra de plataforma Argentina, mas são escassas as medidas ópticas in situ na região. O objetivo geral desta tese foi investigar a variabilidade das propriedades ópticas das florações do fitoplâncton na quebra de plataforma Argentina e arredores. Entre 2006 e 2009, seis cruzeiros foram conduzidos com diversas medidas biológicas e físicas, incluindo medicões bio-ópticas, dentre as quais algumas inéditas na região. As seguintes medidas foram consideradas: coeficientes spectrais de absorção da luz pelo material particulado, que inclui o fitoplâncton e detritos; coeficiente de atenuação da luz pelo material particulado a 660nm; irradiância descendente e radiância ascendente da luz com alta resolução espectral, a partir das quais se obtém os coeficientes da atenuação difusa e a reflectância do sensoriamento remoto in situ; reflectância do sensoriamento remoto medida por satélite; concentração de clorofila-a total e fracionada por classes de tamanho do fitoplâncton estimada pelo método fluorimétrico; concentrações de clorofila-a e pigmentos acessórios do fitoplâncton, obtidas por HPLC; abundância taxonômica relativa do fitoplâncton estimada por CHEMTAX; e fator de tamanho celular do fitoplâncton estimado pelos espectros de absorção da luz pelo fitoplâncton. Grande variabilidade foi observada nos coeficientes de absorção, atenuação (e espalhamento) e atenuação difusa da luz para uma dada concentração de clorofila-a e vice-versa. Grande parte dessa variabilidade pôde ser explicada por variações no tamanho celular do fitoplâncton e, portanto, ao efeito “pacote”. A variabilidade nos espectros de reflectância do sensoriamento remoto (propriedade óptica aparente) medidos in situ revelou o fitoplâncton como componente dominante nas propriedades ópticas das florações na região. Porém, a variabilidade nos coeficientes específicos (i.e., normalizados por clorofila-a) de absorção e espalhamento (propriedades ópticas inerentes), devido a variações no tamanho celular do fitoplâncton, influenciou o desempenho de modelos bio-ópticos para estimar concentração de clorofila-a por satélite. As principais situações de composição taxonômica do fitoplâncton que ocorrem durante as florações na região (dominância por diatomáceas, haptofíceas, e com contribuições destes grupos e de outros, sem dominância) foram refletidas de forma coerente nos comportamentos espectrais de absorção da luz pelo fitoplâncton, indicando o potencial em discriminar as assembleias das florações na região através de dados ópticos. Particularmente, a identificação de dominância de diatomáceas e haptofíceas, a partir de um comprimento de onda, e também pelo fator de tamanho celular do fitoplâncton, que pode ser estimado por satélite, indica o potencial em identificar a dominância de tais grupos taxonômicos por sensoriamento remoto na região. / Satellite images usually detect intense phytoplankton blooms during spring and summer along the Argentina shelf break. Because in situ optical measurements are scarce in the region, six cruises were conducted from 2006 to 2009 to measure several physical, biological, and optical properties. Some of the bio-optical properties were gathered for the first time in the region. The aim of this thesis was to characterize the optical properties of phytoplankton blooms along the Argentina shelf break e adjacent areas. For this purpose, the following measurements and data were considered: light absorption coefficients of particulate material that includes phytoplankton and detritus; light attenuation coefficient of particulate material at 660 nm; hyperspectral downwelling irradiance and upwelling radiance, from which one obtains the vertical attenuation coefficients for downwards irradiance and upwards radiance and in situ reflectance of remote sensing; total and size-fractionated chlorophyll-concentration, estimated by fluorimetric method; concentrations of chlorophyll-a and accessory pigments of phytoplankton obtained by HPLC; relative taxonomic abundance of phytoplankton estimated by CHEMTAX; a cell size parameter for phytoplankton estimated from the phytoplankton absorption spectra. Large variability was observed for absorption coefficients of phytoplankton, scattering of particles and the vertical attenuation coefficients for downwards irradiance for a given chlorophyll-a concentration. Such variability could be largely explained by variations in cell size of phytoplankton and therefore the "package" effect, as indicated by the cell size parameter. The characterization of the variability in the remote sensing reflectance (apparent optical property) measured in situ revealed phytoplankton as the dominant component on the optical properties of algal blooms in the region. Nevertheless, the variability in absorption and scattering coefficients (inherent optical properties) due to variations in cell size of phytoplankton was shown to impact the performance of bio-optical models that relies on band reflectance ratios of remote sensing to retrieve chlorophyll-a from satellite. The main taxonomic composition of the phytoplankton blooms (dominance of diatoms, haptophytes, and mixed contributions of these and others groups, but with no dominance) was consistently reflected on the spectral shape of light absorption of phytoplankton. Our results indicate a potential to discriminate phytoplankton assemblages in the region through optical data. Particularly, the identification of diatoms or haptophytes using one wavelength or through a phytoplankton cell size parameter, which can be estimated from satellite, has a potential of identifying the dominance of such taxonomic groups from remote sensing in the region.

Made available in DSpace on 2014-07-29T16:22:04Z (GMT). No. of bitstreams: 1 Dissertacao Carla Patricia P Alves.pdf: 1914575 bytes, checksum: 1e548e27bdfb0a8d68e317095b54fcc7 (MD5) Previous issue date: 2011-03-28 / The river-floodplain systems are environments submitted a lateral overflow of river channel due the rains and/or underground waters. They are controlled by the type of climate, morphology and local effects. The lowland lakes are also highly productive because of the rich sources of primary carbon. The sediments transport and suspended and dissolved matter are done by the rivers between the land and aquatic phases. These phases strongly influence nutrient cycling, primary and secondary production and decomposition. The phytoplankton dynamics in tropical floodplain lakes is as variable as the seasonal and isolation patterns of flooding. For this reason, the aims of this work were i) to assess the rotation influence of potamophase and limnophase upon the phytoplankton of the Curuai Lake (PA, Brazil) and about the connectivity between other lakes, and ii) to evaluate the phytoplankton dynamics in a nictemeral cycling related to changes in CO2 in water, and what phytoplankton groups which were most important in this process. The phytoplankton community and environmental variables of the floodplain lakes of the Curuai Lake were sampled in the potamophase and limnophase (2009) and in a nictemeral cycling (2010). The informations summarized were obtained through the principal component analysis (PCA), canonical correspondence analysis (CCA), redundancy analysis (RDA) and nonmetric multidimensional scaling (MDS). The community structure was different among the periods with greater richness, density and phytoplanktonic biovolume in limnophase. There was predominance of Cryptophyceae (mainly Cryptomonas brasiliensis Castro, Bicudo & Bicudo) in potamophase and Cyanophyceae [Dolichospermum circinalis (formerly Anabaena circinalis) (Rabenh. ex Bornet et Flah.) Wacklin et al.] in limnophase, both influenced by environmental variables. In addition, the high phytoplanktonic biomass was favored by the highs temperatures and also responsible by the CO2 depletion in water caused by photosynthesis, which is reflected for the high carbon content in phytoplankton organisms. Despite the entry of water in the floodplain that connects the lakes, these environmental were distinct in relation a phytoplankton composition and a limnological variables. The phytoplanktonic community in Curuai Lake showed daily variation of biovolume because of high temperature and light availability. The development of persistent cyanobacteria bloom, with species predominance of Dolichospermum genius [functional group H1, D. spiroides (formerly A. spiroides) (Klebahn) Wacklin et al.] and Microcystis protocystis Crow (functional group M) caused the CO2 depletion in lake surface layer during the period of increased photosynthesis. The cyanobacteria bloom occurred mainly due to the attributes of group, which became it expressive competitors in relation another microalgae ones. / Os sistemas rio-planície de inundação são ambientes sujeitos ao transbordamento lateral do canal do rio pelas chuvas e ou águas subterrâneas e são controlados pelo tipo de clima, morfologia e efeitos locais. Esses ambientes são também altamente produtivos por causa das ricas fontes de carbono primário. O transporte de sedimentos e matéria suspensa e dissolvida é feito pelos rios entre as fases terrestre e aquática, influenciando fortemente o ciclo de nutrientes, produção primária, secundária e decomposição. A dinâmica do fitoplâncton em lagos de planícies de inundação tropicais é tão variável quanto os padrões sazonais de alagamento e isolamento. Por esta razão, os objetivos deste trabalho foram: i) verificar a influência da alternância da potamofase e limnofase sobre o fitoplâncton do Lago Grande de Curuai (PA) e sobre a conectividade entre os lagos e ii) avaliar a dinâmica do fitoplâncton em um ciclo nictimeral relacionada às mudanças do CO2 na água, bem como quais grupos fitoplanctônicos desempenharam maior importância nesse processo. Para isto, a comunidade fitoplanctônica e variáveis ambientais dos lagos da várzea do Lago Grande de Curuai foram amostrados na potamofase e limnofase (2009) e num ciclo nictimeral (2010). A síntese das informações foram obtidas através de análise de componentes principais, análise de correspondência canônica, análise de redundância e escalonamento multidimensional não-métrico. A estrutura da comunidade foi distinta entre os períodos com maiores riqueza, densidade e biovolume fitoplanctônico na limnofase. Houve predomínio de Cryptophyceae (principalmente Cryptomonas brasiliensis Castro, Bicudo & Bicudo) na potamofase e Cyanophyceae [Dolichospermum circinalis (antes Anabaena circinalis) (Rabenh. ex Bornet et Flah.) Wacklin et al.] na limnofase, influenciadas pelas condições ambientais. Além disso, a alta biomassa fitoplanctônica foi favorecida pelas altas temperaturas e também responsável pela diminuição do CO2 na água pela fotossíntese, refletida pelo alto conteúdo de carbono no fitoplâncton. Apesar da entrada de água na várzea que conecta os lagos, os ambientes foram distintos quanto à composição do fitoplâncton e às variáveis limnológicas. A comunidade fitoplanctônica no Lago Grande de Curuai apresentou variação diária do biovolume propiciadas pela alta temperatura e disponibilidade de luz. O desenvolvimento de floração persistente de cianobactérias, com predomínio de espécies do gênero Dolichospermum [grupo funcional H1, destaque D. spiroides (antes A. spiroides) (Klebahn) Wacklin et al..) e de Microcystis protocystis Crow (grupo funcional M) causou a depleção de CO2 na camada superficial do lago durante o período de maior fotossíntese. A floração de cianobactérias ocorreu principalmente devido aos atributos desse grupo que o tornam competidores expressivos em relação aos demais grupos de microalgas.

Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2018-11-22T21:12:08Z No. of bitstreams: 1 Dayane_Souza_2014.pdf: 1723109 bytes, checksum: 778032d6a7f0e2a7082f2ca51ee1f72f (MD5) / Made available in DSpace on 2018-11-22T21:12:08Z (GMT). No. of bitstreams: 1 Dayane_Souza_2014.pdf: 1723109 bytes, checksum: 778032d6a7f0e2a7082f2ca51ee1f72f (MD5) Previous issue date: 2014-09-05 / Ecological works with the phytoplankton community as a basis for monitoring aquatic environments are frequent and of great importance, especially in environments that have undergone anthropogenic actions, such as impoundments, which modify the chemical, physical and ecological attributes of aquatic environments. On the other hand, there is also a concern to know the biodiversity of the various aquatic environments, for which, floristic surveys are of extreme importance throughout Brazil, especially in the state of Santa Catarina, where they are scarce. For that, the environmental variables and the phytoplankton community were evaluated, with focus on Reynolds functional groups (RFGs) in the area of influence of a subtropical small hydropower (SHP) plant in the state of Santa Catarina. The collections were carried out in two phases: pre and post-impoundment, from 2007 to 2013. Statistical analyzes were performed in order to resize the data and to correlate the abiotic and biotic variables. 449 taxa were recorded, distributed in 11 taxonomic groups and 14 RGFs. RGF C, represented by centric diatoms, was dominant in the pre-damming phase. In the post-damming phase, besides RGF C, co-dominance of RGF P (Aulacoseira granulata var. Granulata), RGF N (dehmids), RGF J (chlorophytes) and RGF H1 (cyanobacteria heteocytes) occurred. Low phytoplankton biological volume values were recorded for the Santa Laura SHP in general, however, the highest among the phases was after damming, in the lacustrine region of the reservoir. Also in the state of Santa Catarina, a taxonomic survey of the genus Eunotia Eherenberg in the river Hercílio municipality of Ibirama was carried out. The samples were collected quarterly (April, July and October/2009), in four sampling stations, totaling 12 samples. The study resulted in the identification of 30 taxa of the genus Eunotia, of which four were determined at the generic level. Of the species identified, nine are new citations for the state of Santa Catarina and five for Brazil. / Trabalhos ecológicos com a comunidade fitoplanctônica, como base para monitoramentos de ambientes aquáticos são frequentes e de grande importância, principalmente em ambientes que sofreram ações antropogênicas, como represamentos, os quais modificam atributos químicos, físicos e ecológicos dos ambientes aquáticos. Por outro lado, há também uma preocupação em se conhecer a biodiversidade dos diversos ambientes aquáticos, para tanto, levantamentos florísticos são de extrema importância em todo o Brasil, principalmente no estado de Santa Catarina, onde são escassos. Para tanto, foram avaliadas as variáveis ambientais e a comunidade fitoplanctônica, com enfoque em Grupos Funcionais Fitoplanctônicos (GFs) na área de influência de uma PCH subtropical, no estado de Santa Catarina. As coletas foram realizadas em duas fases: pré e pós-represamento, no período de 2007 à 2013. Análises estatísticas foram realizadas a fim de redimensionar os dados, e correlacionar as variáveis abióticas e bióticas. Foram registrados 449 táxons, distribuídos em 11 grupos taxonômicos e 14 GFs. O GF C, representado pelas diatomáceas cêntricas, foi dominante na fase pré-represamento. Na fase pós-represamento, além do GF C, ocorreu co-dominância dos GF P (Aulacoseira granulata var. granulata), GF N (desmídeas), GF J (clorofíceas) e GF H1 (cianobactérias heteocitadas). Foram registrados baixos valores de biovolume fitoplanctônico para a PCH Santa Laura no geral, porém, os maiores entre as fases foi após o represamento, na região lacustre do reservatório. Ainda no estado de Santa Catarina, foi realizado um levantamento taxonômico do gênero Eunotia Eherenberg no rio Hercílio município de Ibirama. As coletas foram realizadas trimestralmente (abril, julho e outubro/2009), em quatro estações de amostragem, totalizando 12 amostras. O estudo resultou na identificação de 30 táxons do gênero Eunotia, sendo que destas, quatro foram determinadas em nível genérico. Das espécies identificadas, nove são novas citações para o estado de Santa Catarina e cinco, para o Brasil.

Il s’agit de l’étude des successions écologiques du phytoplancton dans la lagune de Ghar El Melh au niveau de 5 stations pendant (i) un suivi bimensuel allant du janvier 2011 à janvier 2012 et (ii) un suivi saisonnier à partir du novembre 2012 à mars 2013. L’étude écologique a été consacrée au microphytoplancton en relation avec les facteurs abiotiques (température, salinité et nutriments) et biotiques (microalgues épiphytes, kystes des dinoflagellés, ultraplancton et ciliés). L’analyse hydrologique du milieu a montré une variation principalement saisonnière de la plupart des paramètres avec des valeurs élevées de la température et de la salinité en été et des concentrations exceptionnelles des nutriments en automne et en hiver. Le phytoplancton de la lagune de Ghar El Melh a été principalement dominé par les dinoflagellés et les diatomées avec une manifestation alarmante des espèces nuisibles atteignant plus que 70 % du peuplement. Ces proliférations ont été remarquées durant toute l’année avec une manifestation plus marquante dans les régions internes de la lagune ce qui est principalement tributaire à la température de l’eau, l’azote total, le nitrogène et l’orthophosphate. Une importante contribution des espèces épiphytes au phytoplancton a été signalée notamment celle du dinoflagellé toxique Prorocentrum lima. L’inventaire spécifique du phytoplancton dominé par l’espèce Prorocentrum micans (> 28 %) et d’autres espèces ne produisant pas de kyste a été en concordance avec les faibles valeurs enregistrées pour les kystes de dinoflagellés dans le sédiment où le maximum enregistré a été de l’ordre de 229 kystes g-1. Une part importante de l’ultraplancton a été représentée par le nanophytoplancton et les hétérotrophes procaryotes, dépassant largement les concentrations microphytoplanctoniques, ce qui est un indice de l’eutrophisation du milieu. Des corrélations hautement significatives ont été trouvées entre le microphytoplancton et les organismes microzooplanctoniques évoquant un probable rôle de ces derniers dans le contrôle des proliférations microalguales nuisibles. / We explored the distribution of the microphytoplankton community in relation to both abiotic (temperature, salinity and nutrients) and biotic factors (epiphytes microalgae, dinoflagellate cysts, ultraplankton and ciliates) in Ghar al Melh Lagoon at 5 stations during (i) a biweekly sampling from January 2011 to January 2012 and (ii) a seasonal sampling from november 2012 to march 2013. The results pointed out a seasonal variation of all parameters with high water temperature and salinity in summer and exceptional concentrations of nutrients in autumn and winter. Microphytoplankton was mainly dominated by dinoflagellates and diatoms with sequences of harmful species proliferation attaining more than 70 % of total phytoplankton. These sporadic proliferations occurred throughout the year with exacerbation in the inner parts of the lagoon mainly related to temperature and total nitrogen, nitrogen and orthophosphate. An important contribution of epiphytic species to phytoplankton abundance was recorded with especially the presence of the toxic dinoflagellate Prorocentrum lima. Microphytoplankton was dominated by Prorocentrum micans (> 28 %) and other non-cyst former species consistent with the low dinoflagellate cysts found at sediment surface (maximum = 229 cysts g-1 DS). Urtraplankton was chiefly represented by nanophytoplankton and heterotrophic prokaryotes, with low microphytoplanktonic abundance. This indicates that the lagoon is undergoing eutrophication. Significant correlations were reported between phytoplankton and microzooplankton suggesting a potential role of the former in controlling harmful microalgae proliferations.

Le système d'upwelling nord-ouest africain au large du Maroc, de la Mauritanie, de la Gambie et du Sénégal est le système le plus productif au monde en termes de productivité primaire. Elle se traduit par une importante biomasse de poissons principalement dominée par les petits poissons pélagiques qui sont les principales ressources vivantes exploitées de la région. Dans un contexte de gestion partagée par plusieurs pays des ressources halieutiques de la région, comprendre les facteurs qui contrôlent la répartition spatiale de ces populations et l'évolution de leurs abondances est un enjeu crucial pour les pêcheries et le développement socio-économique de la région. Le but principal de cette thèse est d'une part de décrire les variations saisonnières et interannuelles de l'environnement marin de l'upwelling des Canaries le long de la Côte nord-ouest de l'Afrique, et d'autre part de relier ces variations avec les dynamiques spatio-temporelles de ces principales espèces d'importance commerciale. Nous avons utilisé différents jeux de données disponibles et développé différentes approches afin d'avoir une vision la plus complète possible du fonctionnement de cet écosystème. Ainsi, nous avons combiné des données satellitaires, des données de campagnes scientifiques acoustiques, des statistiques de pêche et des analyses de formes d'otolithes. Le long des côtes NW africaines (10°-35° N), nos données nous ont permis d'identifier trois régions avec une saisonnalité et une intensité de l'upwelling bien différencié. La région présente une forte variabilité latitudinale et temporelle des conditions environnementales. La partie sud de la zone (~ entre 10° et 24°N) se caractérise par des eaux plus chaudes et plus riche en Chlorophylle-a que la partie nord. La majeure partie de la variabilité des paramètres environnementaux étudiés est due à la saisonnalité (>60%). Au cours de la période d'étude (2002-2012), nous avons noté une tendance significative au réchauffement allant de 0.01°C. à 0.04°C.an-¹ et un renforcement général de l'upwelling, mais une tendance à la baisse de la concentration en Chl a dans l'ensemble de la zone étudiée. Il existe un gradient latitudinal sud-nord de la phénologie du bloom de phytoplancton (période, durée et l'ampleur du bloom). Cependant, il n'y a pas de tendances interannuelles significatives de la phénologie du bloom phytoplanctonique ni de corrélations ou tendances avec les paramètres physiques de l'environnement étudié (SST, indice d'upwelling, vent). L'écosystème du courant des Canaries se caractérise par le couple sardines/sardinelles. L'anchois, bien que présent dans cet écosystème, ne joue pas un rôle aussi important que dans les autres systèmes d'upwelling. Les relations entre les abondances d'anchois, de sardines et de sardinelles avec les paramètres environnementaux ont été étudiées à différentes échelles à l'aide de modèles additifs généralisés (GAM). Les résultats de notre étude indiquent que les variations spatio-temporelles de l'abondance de l'anchois et de la sardinelle sont davantage contrôlées par le gradient thermique que par la productivité biologique. La sardine semble être plus contrôlée par une fenêtre environnementale optimale d'intensité d'upwelling et de température "optimal upwelling and temperature windows". Nous avons pu pour la première fois mettre en évidence l'existence d'une alternance temporelle d'abondance entre l'anchois et la sardine comme cela est connu dans d'autres systèmes d'upwelling. Enfin, pour contribuer à la connaissance sur la structuration des populations de la sardinelle ronde qui préoccupent les scientifiques et les gestionnaires des pêches, nous avons mené une étude sur l'analyse de la forme des otolithes. L'existence possible de plusieurs stocks de sardinelle en lien avec des structures océanographiques ne confortent pas la politique de gestion actuelle qui considère un stock unique au large de la côte NW africaine. / The North West African upwelling system off Morocco, Mauritania, Gambia and Senegal is the most productive system in the world in terms of primary productivity. This productivity results in a large fish biomass dominated by small pelagic fish which are the main living resources exploited in the region. In a context of shared management of fisheries resources by several countries in the region, understanding the factors that control the spatial distribution of populations of small pelagic fish and the evolution of their abundances is a crucial issue for fisheries and the socio-economic development of the region. The main objective of this thesis is to describe the seasonal and interannual variations of the marine environment of the Canary upwelling along the Northwest coast of Africa and to link these variations with the spatio-temporal dynamics of the main small pelagic species of commercial importance of this zone. We have used different sets of data available and developed different approaches in order to have a complete view of the functioning of this ecosystem. Thus, we have combined satellite data, acoustic scientific survey data, fishing statistics and analysis of otolith shapes. Along th NW African coasts ( 10° - 35° N), our data allowed us to identify three regions with a well-differentiated seasonality and intensity of upwelling. The region has a high latitudinal and temporal variability of environmental conditions. The southern part of the zone (between 10° and 24° N) is characterized by warmer and richer Chlorophyll-a waters than the northern part. The majority of the variability of the environmental parameters studied is due to seasonality (> 60%). During the study period (2002-2012), we noted a significant warming trend ranging from 0.01° C to 0.04°C. yr-¹ and a general reinforcement of ipwelling, but a downward trend in Chl a concentration in the whole study area. There is a south-north latitudinal gradient of the phenology of the phytoplankton bloom (period, duration and magnitude of the bloom). However, there are no significant interannual trends in phytoplankton bloom phenology or correlations or trends with the physical parameters of the environment studied (SST, upwelling index, wind). The Canary current ecosystem is characterized by the sardine/ Sardinella pair, Anchovy, althought present in this ecosystem, plays no more important role than in other upwelling systems. The relationships between the abundances of anchovies, sardines and sardinella with environmental parameters have been studied at different scales using generalized additive models (GAM). The results of our study indicate that the spatial and temporal variations of the abundance of anchovy and sardinella are controlled more by the thermal gradient than by the biological productivity. The sardine seems to be more controlled by an "optimal upwelling and temperature windows". We were able for the first time to demonstrate the existence of a temporal alternation of abundance between anchovy and sardine as is known in other upwelling systems. Finally, in order to contribute to the knowledge of population structure of the round sardinella that concern scientists and fisheries managers, we conducted a study of the shape of otoliths. The possible existence of several stocks of sardinella in connection with oceanographic structures do not support the current management policy which considers a single stock off the African NW coast.

Les diatomées sont une composante majeure des écosystèmes marins et sont caractérisées par une grande diversité. L’objectif général de cette thèse est d’étudier les facteurs de contrôle des diatomées dans la Zone Côtière Belge (ZCB). Pour ce faire, la modélisation par groupes fonctionnels et l’approche basée sur les traits sont combinées :la première fournit un cadre écosystémique utile pour étudier les interactions des diatomées avec les compartiments biotiques et abiotiques de l’écosystème, et la seconde permet de représenter de façon efficace leur diversité fonctionnelle.<p><p>Dans un premier temps, puisque la taille est reconnue comme un trait majeur affectant de nombreux aspects de la valeur sélective du phytoplancton, la dépendance au biovolume de différents traits des diatomées a été établie sur base d’observations disponibles dans la littérature. Cette revue a montré qu’un compromis sépare les diatomées sur base de leur biovolume :les petites espèces sont meilleures compétitrices pour l’acquisition des ressources mais plus sensibles au broutage, et inversement. <p>Sur cette base, un ré-analyse d’un jeu de données incluant des comptages et mesures de biométrie avec l’identification de 68 taxons dans la ZCB entre 1992 et 2000 a été réalisée, avec une attention particulière pour la structure en termes de taille de la communauté de diatomées. Un regroupement des diatomées en fonction de leur biovolume a été réalisé sur base de leur évolution saisonnière typique. L’analyse de leur évolution temporelle suggère que la communauté des diatomées est composée d’assemblages avec une évolution saisonnière et interannuelle distinctes qui répondent vraisemblablement différemment aux conditions environnementales.<p>Afin d’étudier plus en profondeur les facteurs environnementaux contrôlant la structure en termes de taille de la communauté des diatomées dans la ZCB, le module diatomées du modèle MIRO, qui représente l’écosystème planctonique de la ZCP, a été modifié afin d’inclure les dépendances à la taille de quatre traits des diatomées. Cet outil reproduit correctement l’évolution saisonnière du biovolume moyen de la communauté, qui est caractérisé par de plus petites diatomées au printemps qui maximisent l’acquisition de ressources tandis que la prévalence du broutage en été induit une transition vers des espèces plus grandes. Le modèle a également été exploité pour étudier la gamme de tailles viables dans la ZCB en fonction des conditions environnementales. <p>Les résultats du modèle basés sur les traits ont ensuite été analysés sur la période 1992-2000. Les simulations ont mis en évidence les interactions complexes entre les processus physiques, de contrôles par les ressources et par le broutage, qui sont susceptibles de déterminer la variabilité interannuelle de la structure en termes de taille des diatomées dans la ZCB. La comparaison de ce modèle adaptatif avec un modèle plus conventionnel qui ne représente pas de diversité interne aux diatomées suggère que le premier produit une réponse légèrement plus flexible que le dernier, mais que la rigidité de la réponse simulée demeure un problème avec le modèle adaptatif qui reste incapable de représenter des évènements extrêmes de biomasse ou de structure de la communauté. Cela suggère que des développements supplémentaires du modèle sont nécessaires, en particulier du module zooplancton.<p>Finalement, une fonction écologique particulière est abordée dans une dernière section de cette thèse :la production d’une neurotoxine par certaines diatomées du genre Pseudo-nitzschia. Cette fonction a été incluse comme un métabolisme secondaire dans un modèle idéalisé de la croissance de Pseudo-nitzschia afin d’étudier les facteurs contrôlant la production de la toxine. Il est notamment montré que l’environnement lumineux est déterminant lorsque les conditions menant à la production de toxine sont rencontrées. <p><p>/<p><p>Diatoms are a key component of marine ecosystems and are characterized by an important diversity. The general objective of this thesis is to investigate the bottom-up and top-down controls of diatoms in the Belgian Coastal Zone (BCZ). This is done through the integration of their functional diversity into a coherent framework. In order to achieve this, Plankton Functional Type modelling and trait-based approaches are combined: the former provides an ecosystem context convenient to study the interactions of diatoms with biotic and abiotic compartments, and the latter allows an efficient representation of their functional diversity. <p><p>As a first step, since size is recognized as a master trait shaping many aspects of phytoplankton fitness, the cell volume dependences of diatom functional traits were compiled from observations available in the literature. This review showed that a trade-off distinguishes diatoms on the basis of their cell volume: smaller species are better competitor for resource acquisition but sensitive to grazing, and inversely. <p>On this basis, a re-analysis of a dataset including diatom cell counts and biometry with the identification of 68 taxa in the BCZ over the 1992-2000 period was carried out, with a focus on the size structure of the diatom community. A clustering of diatoms according to their cell volume was realized on the basis of their average seasonality. Investigation of their time evolution suggested that the diatom community in the area is composed of assemblages with distinct seasonal and interannual evolution that likely respond differently to environmental conditions.<p>In order to further investigate the bottom-up and top-down constrains on the size structure of the diatom community in the BCZ, the diatom module of the MIRO model, which represents the planktonic ecosystem of the BCZ, was modified in order to accommodate size-dependences of four diatom functional traits. This tool adequately reproduced the seasonal evolution of the mean cell volume of the diatom community, which is characterized by smaller diatoms in spring that maximize resource acquisition while the prevalence of grazing pressures in summer induces a shift towards larger species. The model was also used to investigate the range of viable diatom sizes in response to the bottom-up and top-down pressures in the BCZ.<p>Results of the trait-based adaptive model were then analysed over the 1992-2000 period. Simulations evidenced the complex interactions between physical, bottom-up and top-down processes that are likely to govern the interannual variability in the size structure of diatom in the area. Comparison of the adaptive model with a more conventional model resolving no diversity within diatoms suggested that the former produces a slightly more flexible response than the latter, but showed that the rigidity of the simulated response persists with the adaptive model which remains unable to catch extreme biomass and community structure events. This calls for further developments of other compartments of the model, more particularly zooplankton.<p>Finally, a peculiar ecological function is addressed on its own in the last section of this thesis: the toxigenicity of some species of the genus Pseudo-nitzschia. This function was added as a secondary metabolism in an idealized model of Pseudo-nitzschia growth in order to investigate the factors affecting toxin production. It notably showed that light was determinant under conditions leading to its production.<p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

Le gyre subpolaire de l'Atlantique Nord est le siège de la plus importante floraison (bloom) phytoplanctonique de l'océan global. Cet événement biologique majeur joue un rôle crucial sur le fonctionnement des écosystèmes océaniques et sur le cycle global du carbone. L'objectif de cette thèse est de mieux comprendre les processus bio-physiques qui contrôlent la dynamique du bloom phytoplanctonique et l'export de carbone à différentes échelles spatio-temporelles. Dans une première étude, basée sur des données satellites climatologiques, le gyre subpolaire a été biorégionalisé en fonction des différents cycles annuels de biomasse phytoplanctonique. Les conditions de mélange, couplées à l’intensité de la lumière de surface, contrôlent l’initiation du bloom printanier au sein des différentes biorégions. La nouvelle génération de flotteurs BGC-Argo a permis, dans une deuxième étude, d’explorer des processus à des échelles plus fines, en particulier pendant la période hivernale jusqu’à présent très peu étudiée. En hiver, des restratifications intermittentes et locales de la couche de mélange, liées à des processus de sous-mésoéchelle, initient des blooms transitoires qui influencent la dynamique du bloom printanier. Enfin, une troisième étude a montré que la variabilité haute-fréquence de la profondeur de la couche de mélange pendant la transition hiver-printemps joue aussi un rôle crucial sur l’export de carbone. / The North Atlantic Subpolar Gyre exhibits the largest phytoplancton bloom of the global ocean. This major biological event plays a crucial role for the functioning of marine ecosystems and the global carbon cycle. The aim of this thesis is to better understand the bio-physical processes driving the dynamics of the phytoplankton bloom and carbon export at various spatiotemporal scales.In a first study, based on satellite data at a climatological scale, the subpolar gyre is bioregionalized according to distinct annual phytoplankton biomass cycles. The light-mixing regime controls the phytoplankton bloom dynamics in the different bioregions.In a second study, the new generation of BGC-Argo floats allowed for processes to be explored at a finer scale, especially during the overlooked winter season. In winter, intermittent and local restratifications of the mixed layer, triggered by sub-mesoscale processes, initiate transient winter blooms impacting the spring bloom dynamics.Finally, a third study showed how the high-frequency variability of the mixed layer depth during the winter-spring transition plays a crucial role on carbon export.