The aim of this research is to study the formation mechanism of Barrier Layers (BL) in the western tropical Atlantic and their influence on the tropical Atlantic climate at both short and long timescales. Many Coupled General Circulation Models (CGCMs) tend to overestimate the salinity in the Atlantic warm pool or the Northwestern Tropical Atlantic (NWTA) and underestimate the surface salinity in the subtropical salinity maxima region. Most of these models also suffer from a seasurface temperature (SST) bias in the NWTA region, leading to suggestions that the upper ocean salinity stratification may need to be improved in order to improve the BL simulations and thus the SST through BL-SST-Intertropical Convergence Zone (ITCZ) feedbacks. We used a CGCM to perform a set of idealized numerical experiments to understand the sensitivity of the BL and consequently SST in the NWTA region to freshwater flux and hence the upper ocean salinity strati cation. We find that the BL of the western tropical Atlantic is quite sensitive to upper ocean salinity changes in the Amazon River discharge region and the subtropical salinity maxima region. The BL phenomenon is further manifested by the formation of winter temperature inversions in our model simulations. However, in the region of improved BL simulation, the SST response is not statistically significant. SST response to Tropical Cyclones (TCs) is studied for the Atlantic region using a high-resolution coupled regional climate model (CRCM) and observational data sets. The presence of a BL, defined as the layer below the mixed layer that separates the base of the isothermal layer from the base of the isohaline layer, is found to modulate the SST response. The amplitude of TC-induced surface cooling is reduced by more than 35 percent in the presence of a BL, as a consequence of the weak thermal stratification. Furthermore, in locations when the BL exhibits a temperature inversion, TC-induced mixing can result in weak surface warming. BLs considerably reduce the rightward bias for tropical storms, but the effect is less conspicuous for TCs. The enthalpy flux into the atmosphere at the air-sea interface is enhanced by 16 percent and the increase in upper ocean potential energy due to TC-induced mixing is reduced by 25 percent in the presence of BLs. The results from the coupled model are supported by an observational analysis performed using re-analysis data sets, as well as data from Argo floats and TRMM satellite. As previous modeling and observational studies have indicated that the surface cooling caused by TC-induced mixing acts as a negative feedback for its intensity, results from our study suggest that BLs may have potential implications for TC intensity prediction.

An eddy-permitting 2-1/2-layer Reduced Gravity Ocean (RGO) model is developed. Compared with the conventional 2-1/2-layer RGO models, the new model has improvements in subsurface thermodynamics, vertical mixing scheme and open boundary conditions. Using this new 2-1/2-layer RGO model as a dynamical tool, a systematic investigation of the role of oceanic processes in controlling tropical Atlantic sea-surface temperature (SST) response to Atlantic Meridional Overturning Circulation (AMOC) changes is carried out by varying the strength of northward mass transport at the open boundaries. It is found that the North Brazil Undercurrent (NBUC) reverses its direction in response to a shut-down of the AMOC. Such circulation change allows warm waters of the northern subtropical gyre enter the equatorial zone, giving rise to a prominent warming in the Gulf of Guinea and off the coast of Africa. Sensitivity experiments further show that the SST response behaves nonlinearly to AMOC changes. The rate of SST changes increases dramatically when the AMOC strength is below a threshold value. This nonlinear threshold behavior depends on the position of subsurface temperature gradient. The new RGO is coupled to an atmosphere general circulation model (AGCM) (CCM3.6). The coupled model is capable of capturing major features of tropical Atlantic variability. With the aid of this coupled model, a series of experiments with different combinations of oceanic and atmospheric processes are carried out to elucidate the relative importance of the oceanic processes and atmospheric processes in AMOC-induced tropical Atlantic variability/change. It is found that the oceanic processes are a primary factor contributing to the warming at and south of the equator and the precipitation increase over the Gulf of Guinea, while atmospheric processes are responsible for the surface cooling of the tropical north Atlantic and southward displacement of ITCZ. The sensitivity of the coupled system to different strength of the AMOC is further investigated. It is found that equatorial SST and precipitation response also behaves nonlinearly to AMOC changes. The impact of AMOC changes on Tropical Instability Waves (TIWs) is assessed. It is found that the activity of TIWs is reduced in response to the AMOC-induced equatorial SST warming. Correlation analysis suggests that AMOC may affect TIW activities by modifying SST gradient north of the equator.

To investigate the tropical Atlantic response to the remote El Nino-Southern Oscillation (ENSO) forcing, a Reduced Physics – Coupled Global Circulation Model (RP-CGCM) is developed, and four experiments are carried out. The results show that the RP-CGCM is capable of capturing the major features of Tropical Atlantic Variability (TAV) and its response to ENSO forcing. The SST response to the remote influence of ENSO may be divided into two stages. In stage one, the ENSO influences the tropical Atlantic SST primarily through the Troposphere Temperature (TT) mechanism, which predicts a uniform warming in the tropical Atlantic following the mature phase of El Nino. In the north tropical Atlantic (NTA), the Walker mechanism and the Pacific-North-American (PNA) mechanism work in concert with the TT-induced warming, giving rise to a robust SST response during the boreal spring in this region. In the south tropical Atlantic (STA), the southeasterly wind anomaly and increased stratus clouds work against the TT-induced warming, resulting in a much weaker SST response in this region. At this stage, the response can be largely explained by the ocean mixed layer response to changes in surface heat fluxes induced by ENSO. In stage two, ocean dynamics play a more active role in determining the evolution of SST. The cross-equatorial wind anomaly in the western to central equatorial Atlantic can change the SST in the eastern equatorial Atlantic through Bjerknes feedback and the SST in the central equatorial Atlantic through Ekman feedback. These feedback result in a cooling of SST in the equatorial south Atlantic (ESA) region which is so overwhelming that it cancels the warming effect induced by the TT mechanism and reverses the sign of the warm SST anomaly that is formed during stage one in this region. In general, the horizontal advection of heat plays a secondary role in the SST response to the remote influence of ENSO, except in the regions where the North Equatorial Countercurrent (NECC) dominates and the SST variability is strong. Entrainment is particularly important in maintaining the correct SST structure during boreal summer.

The SST bias in the tropical Atlantic exists in the early to latest generation of coupled general circulation models. The maximum bias is not on the equator but at 16°S, the cause of which has not been thoroughly studied. Newly released CMIP5 models provide a useful tool to investigate the contributions of different physical processes to the SST bias in this area in the coupled system. We tested three existing mechanisms and found that: 1) there is no significant relationship between the SST bias and surface heat flux bias; 2) deficient coastal upwelling is a contributing but not the sole source of the bias; and 3) the SST bias is correlated with temperature biases in the upstream equatorial region. The Angola-Benguela front is displaced southward by more than 10° in latitude in many CIMP5 models. Due to the huge temperature contrasts on two sides of the front, such a frontal displacement generates a very strong SST bias. The correlation between the SST bias and frontal location error in this region is significant at the 99% level, demonstrating that the SST bias in coupled GCMs is attributable to the models’ inability to reproduce a realistic position of the front and the consequent erroneous advection by the southward Angola current. This is due to both errors in the simulated surface wind field and systematic errors in ocean models. Ocean reanalysis datasets and a high-resolution regional model simulation suffer a similar pattern of SST biases. Although they produce a more realistic ocean circulation than coarser resolution simulations and alleviate some of the severe SST bias near the front, a warm bias overlies on a northward current to the south of the front, which actually comes from the north of the front through a subsurface passage. We identify a strong subsurface temperature bias caused by a too-deep and diffused simulated thermocline along the coast of Angola, originating from the equatorial thermocline, advected by the Angola Current and an undercurrent beneath the Benguela current, and then brought to the surface by the coastal upwelling along the Benguela coast, contributing to the warm SST bias south of the front.

This dissertation discusses the predictability of the atmosphere-ocean climate system on interannual and decadal timescales. We investigate the extent to which the atmospheric internal variability (weather noise) can cause climate prediction to lose skill; and we also look for the oceanic processes that contribute to the climate predictability via interaction with the atmosphere. First, we develop a framework for assessing the predictability of a linear stochastic system. Based on the information of deterministic dynamics and noise forcing, various predictability measures are defined and new predictability-analysis tools are introduced. For the sake of computational efficiency, we also discuss the formulation of a low-order model within the context of four reduction methods: modal, EOF, most predictable pattern, and balanced truncation. Subsequently, predictabilities of two specific physical systems are investigated within such framework. The first is a mixed layer model of SST with focus on the effect of oceanic advection.Analytical solution of a one-dimensional model shows that even though advection can give rise to a pair of low-frequency normal modes, no enhancement in the predictability is found in terms of domain averaged error variance. However, a Predictable Component Analysis (PrCA) shows that advection can play a role in redistributing the predictable variance. This analytical result is further tested in a more realistic two-dimensional North Atlantic model with observed mean currents. The second is a linear coupled model of tropical Atlantic atmosphere-ocean system. Eigen-analysis reveals that the system has two types of coupled modes: a decadal meridional mode and an interannual equatorial mode. The meridional mode, which manifests itself as a dipole pattern in SST, is controlled by thermodynamic feedback between wind, latent heat flux, and SST, and modified by ocean heat transport. The equatorial mode, which manifests itself as an SST anomaly in the eastern equatorial basin, is dominated by dynamic feedback between wind, thermocline, upwelling, and SST. The relative strength of thermodynamic vs dynamic feedbacks determines the behavior of the coupled system, and enables the tropical Atlantic variability to be more predictable than the passive-ocean scenario.

The response of the tropical Atlantic Ocean to wind stress forcing on seasonal and interannual time scales is examined using an ocean data assimilation product from the Geophysical Fluid Dynamics Laboratory (GFDL), and an ocean general circulation model which incorporates a three dimensional flux correction technique to correct biases of the mean state of the ocean. On a seasonal time scale, we investigated the impact of the annual migration of the ITCZ on the exchange pathways of the northern tropical Atlantic. The results indicate that seasonal variation of the zonal slope of the thermal ridge along the boundary between the north equatorial countercurrent and north equatorial current in response to changes in the ITCZ controls, to a large extent, the amount of water participating in the equatorial circulation. These changes can be explained in terms of a simple dynamical model where local Ekman pumping dominates thermocline variation in the western part of the basin, and Rossby wave adjustment comes into play in the eastern basin. On an interannual time scale, we examined the upper heat budget of the equatorial Atlantic in order to identify the key mechanisms by which wind-driven ocean dynamics control SST variability during the onset and peak phases of the Atlantic zonal mode. It is found that, in contrast with Pacific ENSO, both Bjerknes and Ekman feedbacks act together to force the zonal mode, although their relative importance and dominance depend on season and location.

In the western tropical Atlantic, the North Brazil Current retroflection periodically sheds large anticyclonic rings, which then propagate northwestward. Between 1998 and 2000, the North Brazil Current Rings Experiment sampled a large number of these rings by shipboard and moored acoustic Doppler current profiler. Ten of the sampled rings are analyzed in this study, focusing on their sea surface dynamic properties. The rings exhibit a radial structure consisting of two regimes, an ``inner'' core region in near solid body rotation and an ``outer'' ring regime with an approximately exponentially decaying structure. The observations show a sharp change in vorticity at the regime transition and the presence of a strong opposite vorticity shield bounding the inner solid body core. We show that Gaussian models, commonly used to represent the surface expression of these and other rings, are adequate for determining the sea surface height anomaly but tend to poorly estimate other properties such as the maximum swirl velocity. Therefore, we propose a new two--part model as a better approximation of the rings' radial structure. According to the cyclogeostrophic balance approximation, the sea surface height distribution across the inner ring has a parabolic shape, while the outer ring has an exponential structure similar to the velocity field. Interestingly, many of the observed rings have an intensity very close to the theoretical limit for anticyclones at these latitudes, which is believed to be due to inertial instability. A climatology of the NBCR is developed from 17 years of satellite altimetry. Usually 5 to 7 NBCR are observed per year, leading to an average of 6.1 rings per year, higher than the previously accepted 5.5 rings per year. A new methodology, more robust and consistent, is developed to track the rings, showing an impressive skill. The methodology can be applied to any velocity field, including irregular data grids. In contrast to what was previously believed, the NBCR do have a seasonal cycle. While so clear in the number of generated rings the seasonal cycle is explicit in the rhythm of formation. The rings are usually formed every 30--70 days, being more frequent during the Spring, when they are generated in a regular pace of near 40 days. In the Fall, the rings are less frequent, with a longer and variable time interval between them. The generation of North Brazil Current Rings (NBCR) has been proposed from numerical simulations to result from westward propagation Rossby waves originating from the instability of the North Equatorial Countercurrent (NECC). Other mechanisms, such as instability of he North Brazil Current where it crosses the equator, are also possible, and the precise mechanisms controlling NBCR formation are still undetermined. Here the ``NECC wave mechanism'' for generation of the near surface NBCR is evaluated for the first time from observations -- 18 years of satellite altimetry. Using a Complex Principal Component analysis on maps of absolute dynamic topography, it is shown that the NECC is the origin of the coherent propagating rings along the NBCR corridor. In agreement with the results proposed from previous simulations, the modal solution has a longer wavelength before the retroflection and shorter wavelength along the ring corridor. The seasonal signal of the wave energy in the NECC is also found to be coherent with the seasonal production cycle of the rings, after taking into account phase lags due to wave propagation. It is therefore confirmed that the of NBCR shedding is defined by wave processes arising in the NECC. Further, in contrast with prior understanding, the NBCR are shown to have a seasonal signal that follows the seasonal cycle of the NECC intensity.

Made available in DSpace on 2014-06-11T19:26:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-31Bitstream added on 2014-06-13T20:34:25Z : No. of bitstreams: 1 barros_lcp_me_botfca.pdf: 1858043 bytes, checksum: fb53061efb50a949388de9ae4d407603 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Esta pesquisa teve como objetivo principal realizar levantamento etnobotânico junto à comunidade rural do Bairro dos Marins, no município de Piquete, a respeito do conhecimento sobre as plantas medicinais com atividades de controle do colesterol, pressão arterial e problemas renais. Outros objetivos a alcançar disseram respeito à ocorrência e à freqüência das doenças na comunidade; verificar como os moradores reconhecem e nomeiam as doenças estudadas; identificar quais espécies de plantas medicinais são conhecidas e usadas pelos moradores, sua forma de utilização e preparo; e entender como todas as casas do Bairro. A escolha do entrevistado de cada unidade residencial teve como critério que este fosse responsável pelo sustento da família. Foram entrevistadas 74 pessoas, mediante entrevistas estruturadas e semi-estruturadas. Foram coletados dados sócio-culturais e levantados os problemas de saúde mais recorrentes na comunidade e as plantas usadas para tratar cada um deles. Na segunda etapa foram entrevistados profissionais e agentes da área da saúde do Programa de Saúde da Família (PSF). Nessa etapa foi utilizado roteiro com perguntas. Para a terceira etapa foi usada a técnica de amostragem “bola de neve”, que consistiu em conversar com algumas pessoas da comunidade e perguntar se conheciam moradores que tinham significativo conhecimento sobre plantas medicinais, com esta técnica foram indicadas 15 pessoas. Para complementar a pesquisa foram escolhidos mais cinco entrevistados pelo método conhecido como amostragem por julgamento, o critério para escolha destes foi o maior número de espécies medicinais citadas durante a primeira etapa e conhecimento e uso das plantas para as três enfermidades propostas neste estudo. Durante a realização da terceira etapa optou-se por utilizar entrevistas semi-estruturadas... / The main objective of this research was to do an ethnobotanical survey in the rural community Marins, Piquete municipality, on their knowledge about medicinal plants with activity on cholesterol control, blood pressure and kidney problems. Other objectives were to evaluate the occurrence and the frequency of the diseases in the community, to verify how the inhabitants know and name the studied diseases, to identify which species of medicinal plants are known and used by the inhabitants, how they prepare and use each one and to understand how the exchange of information works in the community.The collection of data was based on methods used in Anthropology, like semi-structured and structured interviews and also participant observation. In order to facilitate the research, the interviews were divided in three stages. In the first stage all the houses of the community were visited. The person who was responsible for the family support was chosen as the one who would be interviewed. Seventy four people were interviewed by using semi-structured and 74 structured interviews. Sociocultural data were collected, as well as the community’s most common health problems and the plants used to treat each problem. In the second stage, professionals and healthcare workers from the healthcare family program (PSF) were interviewed. On the third stage, it was used the “snow ball” technique, which consists on talking to some people of the community and asking them whether they know some inhabitants who have a significant knowledge about medicinal plants. Fifteen persons were indicated with the use of this technique. To complete the research, five more persons were interviewed by the method know as judgment sampling. The criterion used to choose these five interviewed was the greatest number of medicinal plants species mentioned on the first stage and the...(Complete abstract click electronic access below)

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-02-16T13:22:40Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertaçãofinal_CynthiaLima.pdf: 1671444 bytes, checksum: a618adc7ce746bd89739101831df619e (MD5) / Made available in DSpace on 2017-02-16T13:22:40Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertaçãofinal_CynthiaLima.pdf: 1671444 bytes, checksum: a618adc7ce746bd89739101831df619e (MD5) Previous issue date: 2016-06-29 / CNPq / Este estudo descreve a distribuição vertical de eufausídeos na presença de uma termoclina permanente em águas oligotróficas do Atlântico Tropical (00º 55 'N, 29º 21' W). A amostragem foi realizada de junho de 2010 à outubro de 2011, com arrastos verticalmente estratificados de 100 a zero m durante o dia e à noite. Densidades foram analisadas quanto a sua relação com a profundidade, estações e sazonalidade. A média total da densidade de eufausídeos foi de 2,65 ind. m-³, com valor máximo de 30,4 ind. m-³. A comunidade foi composta principalmente de larvas (80%). As larvas de Euphausia foram mais abundantes, com 56,4% de todos os indivíduos. Eufausídeos foram sempre mais abundantes durante a noite. A distribuição vertical ontogenética de eufausídeos apresentou três padrões: (i) larvas caliptopis foram mais abundantes na camada de transição (ii) larvas furcilia na camada de mistura superior (iii) e para os adultos, os padrões variaram de acordo com a espécie. Padrões de distribuição distintos podem ser descritos para três espécies de Euphausia (E. americana, E. tenera e E. similis) e duas espécies de Stylocheiron (S. carinatum e S. suhmii), sugerindo que espécies congêneres desses dois gêneros realizam partição de recursos na coluna de água. Os nossos dados suportam a ideia de que a camada de transição na base da camada de mistura superior é um hábitat importante para os eufausídeos na área de estudo. Este estudo revelou que espécies e estágios de desenvolvimento possuem padrões específicos de distribuição vertical para este táxon–chave nos oceanos tropicais oligotróficos. / This study describes the vertical distribution of euphausiid in the presence of a permanent thermocline in the oligotrophic waters of the Tropical Atlantic (00º 55 'N, 29º 21' W). Sampling was conducted from June 2010 to October 2011, from 100 to zero m in vertically stratified hauls during day and the night. Densities were analyzed regarding their relation to depth, temporal variability and station. Mean total euphausiids density was 2.65 ind. m-³ with values up to 30.4 ind. m-³. This community was mainly composed of larvae (80%). Larvae of the Euphausia were most abundant, with 56.4% of all individuals. Euphausiids were always most abundant during the night. The ontogenetic vertical distribution of euphausiids presented three patterns: (i) calyptopis larvae were most abundant in the transition layer (ii) furcilia larvae in the upper mixed layer. (iii) and for adults, patterns varied according to species. Distinct distribution patterns could be described three species of Euphausia (E. americana, E. tenera and E. similis) and two species of Stylocheiron (S. carinatum and S. suhmii), suggesting that congeneric species of these two genera perform resource partition in the water column. Our data support the idea that the transition layer at the base of the upper mixed layer is an important habitat for euphausiids in the study area. This study revealed species- and stage- specific patterns of vertical distribution for these key taxa in the oligotrophic tropical oceans.

Submitted by Caroline Falcao (caroline.rfalcao@ufpe.br) on 2017-05-25T17:32:09Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Correia, 2014. Migração vertical do microzooplâncton do Arqu.pdf: 826813 bytes, checksum: 00687ea39607e8dbd933fd417ff647dc (MD5) / Made available in DSpace on 2017-05-25T17:32:09Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Correia, 2014. Migração vertical do microzooplâncton do Arqu.pdf: 826813 bytes, checksum: 00687ea39607e8dbd933fd417ff647dc (MD5) Previous issue date: 2014 / A presente dissertação é composta por dois manuscritos. O primeiro foi elaborado com o intuito de responder ao objetivo principal da dissertação: caracterizar a migração vertical do microzooplâncton do Arquipélago de São Pedro e São Paulo (ASPSP). A partir das amostras analisadas, ainda foi possível obter um manuscrito adicional, registrando a primeira ocorrência de Aetideus australis para o Brasil e Aetideus giesbrechti para o ASPSP. Para isto, foram realizadas coletas diurnas e noturnas em três campanhas (C1: junho de 2010; C2: setembro de 2011; C3: outubro de 2011), em duas estações fixas, uma a leste (E1) e outra a oeste (E2) do ASPSP. Foram feitos arrastos verticais com rede de plâncton com sistema de fechamento tipo Nansen e malha com abertura de 64 μm, em cinco camadas pré-determinadas de 20 metros, até 100 m de profundidade (L1: 0-20 m, L2: 20-40 m, L3: 40-60 m, L4: 60-80 m e L5: 80-100 m). Adicionalmente, para caracterizar a estrutura termohalina, foram obtidos perfis com um CTD da superfície até 100 m; ainda, foram realizados perfis verticais através de sonda perfiladora SCAMP para obtenção de dados de clorofila-a em C1. Para obter os dados de clorofila-a em C2 e C3, foi coletada água com auxílio de uma garrafa de Niskin. Foi observado um pico subsuperficial deste parâmetro aproximadamente a 70 m de profundidade. A diversidade de espécies foi muito alta (3,60 ± 0,36 bits.ind-1 ), sendo identificados 102 taxa, considerando a menor unidade taxonômica possível de se identificar. Estes taxa estiveram representados por 9 Filos (Dinophyta, Ciliophora, Protozoa, Cnidaria, Annelida, Mollusca, Arthropoda, Chaetognatha, Chordata), com predomínio de organismos pertencentes ao protozooplâncton (dinoflagelados, foraminíferos, radiolários e tintinídeos) e à classe dos Copepoda (náuplios, juvenis e adultos). Copepoda destacou-se com cerca de 60 espécies, dentre as quais Aetideus australis e Aetideus giesbrechti foram registradas pela primeira vez para o Brasil e o ASPSP, respectivamente. Foi observada uma estratificação na coluna d’água em duas camadas (acima e abaixo da termoclina) diferentes significativamente uma da outra: superfície (L1, L2 e L3) e subsuperfície (L4 e L5). Os organismos puderam ser separados em três grupos: os que se distribuíram por toda coluna d’água (Dinoflagelados, Copepoda (Náuplio), Oithona spp., Oncaea spp.), os que ocorreram em águas superficiais (Clausocalanus furcatus, Farranula gracilis, Appendicularia) e os que parecem evitar águas acima da termoclina média (Ostracoda, Aetideus spp., Haloptilus spp.). Através do uso da WMD (Weighted Mean Depth), não foi identificado um padrão típico de migração vertical diária em nenhum taxa no presente estudo, fato já mencionado para organismos de classes de tamanho menores, sendo geralmente o padrão de migração vertical atribuído a organismos zooplanctônicos de classes de tamanho maior. Não foram observadas diferenças significativas entre os períodos diurno e noturno bem como não foi observada uma variação temporal nem a curto (C2 ≠ C3) nem a longo prazo (C1 ≠ C2 e C3). Deste modo, esta dissertação descreve, pela primeira vez, padrões de distribuição vertical dos principais taxa e constata a ausência de padrões de MVD em organismos microzooplanctônicos no ASPSP. Além disso, mostra a alta diversidade destes organismos neste ambiente oceânico tropical, destacando a necessidade do desenvolvimento de mais estudos envolvendo a estrutura básica desta comunidade. / This dissertation consists of two manuscripts. The first was designed with the intuite of answer the main objective of the dissertation: characterize the vertical migration of microzooplankton of Saint Peter and Saint Paul Archipelago (SPSPA). From the samples analised, it was still possible to obtain an additional manuscript, recording the firt occurrence of Aetideus australis to Brazil e Aetideus giesbrechti to SPSPA. For this, diurnal and nocturnal sampling were carried out in three campaigns (C1: June/2010; C2: September/2011; C3: October/2011), in two fixed stations, one in the East (S1) and another to the West (S2) from SPSPA. Vertical hauls with plankton net with a closing system Nansen type and mesh size of 64 μm were made, considering five predetermined layers of 20 m. (L1: 0-20 m, L2: 20-40 m, L3: 40-60 m, L4: 60-80 m and L5: 80-100 m). Additionally, to characterize the thermohaline structure, CTD profiles were obtained from surface to 100 m depth; and vertical profiles were carried out using a Self Contained Autonomous MicroProfiler SCAMP in C1 to obtain data of chlorophyll-a. To obtain data of chlorophyll-a in C2 and C3, water was collected with the support of a Niskin bottle. A chlorophyll-a subsurface peak of this parameter was observed at approximately at 70 m depth. Species diversity was very high (3.60 ± 0.36 bits.ind-1 ), being identified 102 taxa, considering the smallest taxonomic unit possible to be identified. These taxa have been represented by 9 Phyla (Dinophyta, Ciliophora, Protozoa, Cnidaria, Annelida, Mollusca, Arthropoda, Chaetognatha, Chordata). Among these, predominated organisms belonging to protozooplankton (dinoflagellates, foraminiferans, radiolarians and tintinnids) and to Copepoda (nauplii, juveniles and adults). Copepoda showed highest richness with 60 species, among which Aetideus australis e Aetideus giesbrechti was register for the first time to Brazil and SPSPA, respectively. A stratification was observed in the water column separing in two layers (above and below the thermocline) significantly different from each other: surface (L1, L2 and L3) and subsurface (L4 and L5). The organisms presented three groups: those who was distributed throughout the water column (Dinoflagellates, Copepoda – nauplius –, Oithona spp., Oncaea spp.), those who occurred in superficial waters (Clausocalanus furcatus, Farranula gracilis, Appendicularia) and those that seem to avoid water above the medium thermocline (Ostracoda, Aetideus spp., Haloptilus spp.). Through the use of WMD (Weighted Mean Depth), it was not identified a typical pattern of daily vertical migration (DVM) to none taxa in the present study. This fact was already mentioned to organisms of smaller size classes, as vertical migration pattern being generally attributed to zooplanktonic organisms of larger size. No significant differences were observed between day and night periods and it was not observed a temporal variation nor at short (C2 ≠ C3) or long term (C1 ≠ C2 e C3). Thus, this work describes, for the first time, patterns of vertical distribution of the main taxa and notes the lack of patterns of DVM in microzooplanktonic organisms in the SPSPA. Furthermore, it shows the high diversity of these organisms in this tropical ocean environment, highlighting the need to develop more studies involving the basic structure of this community.