A taxonomic revision of 29 species distributed in 12 vetigastropod families collected in a 60-260 m depth range at Canopus Bank, a seamount off NE Brazil, is performed based on detailed shell morphology. Their distribution and bathymetric ranges are re-examined based on specimens from Canopus and the MZSP collection. Three possibly new species are revealed and tentatively described: Arene aff. brareus can be distinguished by a large shell for the genus; sculpture consisting of spiral cords ornamented by large, semi-hollow, scale-like spines; cords separated by equally wide, deep interspaces and thin axial growth lines more visible in the interspaces; protoconch sculptured by small, subsutural axial lamellae; and color ranging from white to intense reddish, darker on spiral cords, and lighter at the base, with a yellow apex. Parviturbo aff. tuberculosus can be told apart from local congeners by its slightly taller than wide shell, which is profusely sculptured by a reticulate pattern of equally strong axial ribs and spiral cords, with angular nodules at the intersections. Calliostoma sp.1 shows no close affinities with any other local congener and is characterized by a small shells with convex whorls and a large, rounded apex; ivory white ground color with honey yellow apex and spiral cords; sculpture consisting of 4-6 narrow, nodulous spiral cords per whorl; suture marked by a suprasutural cord; inflated and mostly smooth base; narrow, shallow, and axially sculptured umbilicus. Moreover, three species have their distributions expanded northward from SE to NE Brazilian waters: Emarginula suspira Simone & Cunha, 2014, Hemimarginula hemitoma Simone & Cunha, 2014, and Homalopoma boffi Marini, 1975. Three species have their northern range limit expanded from Bahia state to Ceará state: Arene flexispina Leal & Coelho, 1985 and Turbo heisei Prado, 1999; a single NE Brazilian species is newly reported from northern waters: Haplocochlias risoneideneryae Barros, Santos, Santos, Cabral & Acioli, 2002; and another species, previously known only from Pernambuco state, is newly reported from Ceará state, also in NE Brazil: Solariella quinni Barros & Pereira, 2008. Two Caribbean species are firstly reported in the SW Atlantic: Dentistyla dentifera (Dall, 1889) and Gaza cf. fischeri (Dall, 1889); and a species previously reported from the Venezuelan shelf is firstly recorded in Brazilian waters: Parviturbo annejoffeae Rubio, Rolán & Lee, 2015. The bathymetric ranges of 11 species are expanded. High-resolution photographs of the type specimens, SEM images, and comparisons with local congeners are also provided / Uma revisão taxonômica de 29 espécies distribuídas em 12 famílias de vetigastrópodes coletadas a 60-260 m de profundidade no Banco de Canopus, uma montanha submarina do Nordeste do Brasil, é fornecida com base na morfologia detalhada da concha. Sua distribuição e intervalos batimétricos são reexaminados com base em espécimes de Canopus e da coleção do MZSP. Três espécies possivelmente novas são reveladas e tentativamente descritas: Arene aff. briareus pode ser distinguido por uma concha grande para o gênero; escultura constituída por cordas espirais ornamentadas por espinhos grandes, semi-ocos e escalares; cordas separadas por intervalos igualmente amplos e profundos e linhas de crescimento axiais finas mais visíveis nos inter-espaços; protoconcha esculturada por pequenas lamelas axiais subsuturais; e cor variando de branco a avermelhado intenso, mais escura nas costelas espirais, e mais clara na base, com um ápice amarelo. Parviturbo aff. tuberculosus pode ser distinguida dos congéneres locais pela sua concha mais alta do que larga, profusamente esculturada por um padrão reticulado de costelas axiais igualmente fortes e cordas espirais, com nódulos angulares nas intersecções. Calliostoma sp.1 não apresenta estreitas afinidades com qualquer outro congênere local e é caracterizado por uma concha pequena com voltas convexas e um grande ápice arredondado; cor branco-marfim com ápice e cordas espirais amarelo mel; escultura de 4-6 cordas espirais estreitas e nodulosas por volta; sutura marcada por um cordão suprasutural; base inflada e lisa; umbílico estreito, raso e axialmente esculturado. Três espécies têm suas distribuições expandidas para o norte, de águas do SE para o NE do Brasil: Emarginula suspira Simone & Cunha, 2014, Hemimarginula hemitoma Simone & Cunha, 2014, e Homalopoma boffi Marini, 1975. Três espécies têm seu limite de extensão norte expandido da Bahia para o Ceará: Arene flexispina Leal & Coelho, 1985 e Turbo heisei Prado, 1999; Uma única espécie brasileira do NE é relatada para águas do Norte: Haplocochlias risoneideneryae Barros, Santos, Santos, Cabral & Acioli, 2002; E uma outra espécie, anteriormente conhecida apenas do estado de Pernambuco, é reportada para o estado do Ceará: Solariella quinni Barros & Pereira, 2008. Duas espécies caribenhas são registradas pela primeira vez no Atlântico sudoeste: Dentistyla dentifera (Dall, 1889) e Gaza cf. fischeri (Dall, 1889); e uma espécie reportada previamente para a plataforma venezuelana é registrada pela primeira vez no Brasil: Parviturbo annejoffeae Rubio, Rolán & Lee, 2015. As distribuições batimétricas de 11 espécies são expandidas. Fotografias dos espécimes tipo, imagens MEV e comparações com congêneres locais são fornecidas

The use of geophysical techniques to image the interiors of active volcanoes can provide a better understanding of their structure and plumbing. The need for such information is especially critical for undersea volcanoes, whose environment makes them difficult to investigate. Because undersea volcanoes are made up of highly magnetic basaltic rock, it is possible to use variations in the magnetic field to explore the internal structure of such edifices. This study combines magnetic survey data from 12 research cruises to make a magnetic anomaly map of volcanically active Loihi, located in the Hawaiian Island chain. NRM intensities and susceptibility measurements were measured from recovered rock samples and suggest that magnetic properties of Loihi are widely varied (NRM intensities range from 1-157 A/m and susceptibilities from 1.26 x 10-3 to 3.62 x 10-2 S.I.). The average NRM intensity is 26 A/m. The size and strength of magnetic source bodies were determined by using various modeling techniques. A strongly magnetized shield can explain most of the anomaly with a large nonmagnetic zone inside, beneath the summit. Prominent magnetic highs are located along Loihi's north and south rift zone dikes and modeling solutions suggest strongly magnetized source bodies in these areas as well as a thin, magnetic layer atop the nonmagnetic zone. The strong magnetic anomalies found along the volcano's rift zones cannot be readily attributed to recent lava flows at the surface. Instead, the source bodies must continue several kilometers in depth to give reasonable magnetization values and are interpreted as dike intrusions. Nonmagnetic anomalies at the summit and south of the summit suggest the presence of a magma system. The model solution suggests Loihi is an inhomogeneously magnetized seamount with highly magnetic dike intrusions along the rift zones with a nonmagnetic body at its center overlain with a magnetic layer.

The use of geophysical techniques to image the interiors of active volcanoes can provide a better understanding of their structure and plumbing. The need for such information is especially critical for undersea volcanoes, whose environment makes them difficult to investigate. Because undersea volcanoes are made up of highly magnetic basaltic rock, it is possible to use variations in the magnetic field to explore the internal structure of such edifices. This study combines magnetic survey data from 12 research cruises to make a magnetic anomaly map of volcanically active Loihi, located in the Hawaiian Island chain. NRM intensities and susceptibility measurements were measured from recovered rock samples and suggest that magnetic properties of Loihi are widely varied (NRM intensities range from 1-157 A/m and susceptibilities from 1.26 x 10-3 to 3.62 x 10-2 S.I.). The average NRM intensity is 26 A/m. The size and strength of magnetic source bodies were determined by using various modeling techniques. A strongly magnetized shield can explain most of the anomaly with a large nonmagnetic zone inside, beneath the summit. Prominent magnetic highs are located along Loihi's north and south rift zone dikes and modeling solutions suggest strongly magnetized source bodies in these areas as well as a thin, magnetic layer atop the nonmagnetic zone. The strong magnetic anomalies found along the volcano's rift zones cannot be readily attributed to recent lava flows at the surface. Instead, the source bodies must continue several kilometers in depth to give reasonable magnetization values and are interpreted as dike intrusions. Nonmagnetic anomalies at the summit and south of the summit suggest the presence of a magma system. The model solution suggests Loihi is an inhomogeneously magnetized seamount with highly magnetic dike intrusions along the rift zones with a nonmagnetic body at its center overlain with a magnetic layer.

Thesis (Ph. D.)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / The mechanisms of faunal dispersal across ocean basins are key unknowns toward understanding of the modern biogeography and biodiversity of deep-sea fauna. Seamounts are considered to play a defining role in faunal evolution, acting as regional centers of speciation, "stepping-stones" for dispersal, and/or refugia for deep-sea populations. The overarching goal of this dissertation was to examine the role of seamounts in structuring marine biodiversity and biogeography. This study focused on North Atlantic seamounts, specifically the New England seamount chain, the Corner Rise seamounts, and Muir seamount, areas damaged and threatened by deep-sea fisheries and currently a focus of conservation efforts. Videographic analyses of biological community structure revealed distinct faunal assemblages, dominated by the Porifera, Cnidaria, and Echinodermata and structured by geographic region, depth regions (with apparent taxonomic breaks at 1300 m, 2300 m, and 2600 m), and substrate type (including natural/anthropogenic and abiotic substrates and biotic substrates). Amongst these assemblages, seven highly specific coral host- invertebrate associate relationships were identified. To investigate whether or not these broad community patterns were discernible at a genetic level, the 16S mtDNA gene was utilized as a genetic "barcode" within the Class Ophiuroidea, through which 22 putative species were identified, including four target species (Asteroschema clavigera, Ophiocreas oedipus, Ophioplinthaca abyssalis, and Ophioplinthaca chelys) for subsequent population genetic studies. Analyses of mitochondrial 16S and COI gene sequences revealed evidence for recent population expansion and estimates of recent high gene flow across all four species throughout the North Atlantic seamount region. / (cont.) However, genetic differentiation within populations of A. clavigera and 0. chelys within seamount regions was significant, suggesting that historical diversification has been mediated by a long-distance dispersal mechanism that homogenizes this genetic signal on a regional scale. In addition, comparisons of all ophiuroid populations revealed no congruent pattern of historical migration amongst seamounts, which may also be attributed to the varying levels of host specificity and reproductive strategy of each ophiuroid species. These results will guide future studies and conservation efforts to protect seamount communities vulnerable to deep-sea fishery activities. / by Walter W. Cho. / Ph.D.

As the largest and most poorly environment on Earth, the deep-sea is facing global threats from climate change and anthropogenic disturbance further compounded by the lack of critical baseline data on seafloor species composition and community structure. Many data-deficient regions include those in geographically-isolated offshore environments, like low-latitude seamounts, where sampling and surveys have been limited, resulting in critical knowledge gaps that do not allow for effective conservation measures to be realized. This work seeks to characterize the coral fauna of tropical seamount environments greater than 150 m depth and understand the environmental controls on species distribution and community assembly for long-lived, ecologically-important species, primarily from the Octocorallia, Antipatharia, Stylasteridae, and Scleractinia. Methodologies for accomplishing this research have included analysis of remotely operated vehicle (ROV) video surveys and identification of collected voucher specimens to understand biogeographic patterns within coral communities on seamounts and other rugged seafloor features in 3 different regions: the tropical western Atlantic (Anegada Passage), the equatorial central Pacific (Phoenix Islands), and the tropical eastern Pacific (Costa Rica). These regions represent vastly different oceanographic regimes in terms of biological productivity and water column structure resulting in differential effects on deep-sea coral communities. Evidence from these three regions has shown significant effects of the role that oceanic water masses have on structuring deep-water coral biodiversity and suggests that these features, along with other abiotic environmental variables, are important indicators for understanding species distribution patterns, community structure, and global biogeographic patterns. More broadly, the results of this work have demonstrated the capabilities of exploratory ROV surveys, across multiple platforms, to add practical knowledge to coral species inventories and identify bathyal biogeographic patterns in remote regions of the deep sea. The results of this work, serving as baseline coral biodiversity surveys for each area, are also germane to evaluating the effects of human-mediated disturbance and global climate change in the deep ocean. These disturbances also include ocean acidification, ocean deoxygenation, deep-sea mining, and bottom-contact fishing, all of which have been identified as threats to the seamount benthos. / Biology

L’objectif de cette étude est de contraindre les déformations au cours du Pléistocène d'une marge active à partir de l’analyse sismo-stratigraphique des sédiments conservés sur la plate-forme et la pente supérieure, le long de la marge centrale d’Equateur. A partir les données de sismique haute résolution et de carottage collectées pendant l'expédition Atacames (2012), plusieurs bassins ont été identifiés. La répartition latérale et de la succession des séquences T-R dans ces bassins montrent une distribution complexe des sédiments dans le temps et l'espace. Ce travail montre que, le long des marges actives, l’analyse sismo-stratigraphique de l’enregistrement des séquences liées aux cycles eustatiques du Pléistocène est un outil très puissant. A l'échelle locale, la subduction de seamounts perturbe et renforce l'effet de déformation régionale de la ride de Carnegie. / The aim of this study is to constrain recent deformation and stratigraphic evolution of an active margin, using sismo-stratigraphic analysis of Pleistocene sediment preserved on the margin shelf and upper slope along of the Central Ecuadorian margin. From the extensive geophysical and sedimentological investigations carried out during the ATACAMES expedition (2012), we are identified serveral basins in the Ecuadorian margin. A detailed analysis of the thickness, the lateral distribution and stacking patterns in these basins show a complex distribution of sediments in time and space. The seismic-sequence stratigraphy analysis related to eustatic cycles of the Pleistocene shows a regional regional unconformity at the base (1782-Ka as minimum age), which can correspond to the signature of the beginning of the Carnegie ridge collision.

The waters of the open ocean constitute the largest living space on Earth but despite its obvious significance to the biosphere, the open ocean remains an unexplored frontier. With a regional focus on the Indian Ocean, this thesis investigates (i) the distribution of pelagic biota on basin scales, (ii) the effect of abrupt topography on pelagic biota and their predator-prey relationships, and (iii) the use of genetic techniques to elucidate population connectivity and dispersal of pelagic taxa. (i) Pelagic scattering layers (SLs) were surveyed with scientific echosounders across the southwest (SWIO) and central Indian Ocean to investigate their vertical and geographical distribution. Structurally distinct SL regimes were found across the Subantarctic Front, and may explain recently observed foraging behaviours of southern elephant seals. Regression models indicated a close relationship between sea surface temperature and mean volume backscatter, with significantly elevated backscatter in the subtropical convergence zone. The heterogeneous distribution of scattering layer biota may have implications for predator foraging and carbon cycling in the Indian Ocean. (ii) Acoustic surveys revealed diverse interactions between SLs, aggregations and topography around islands as well as shallow ( < 200m) and intermediate (200-800m) seamounts at spatial scales from 1 to 100 km. Epi-and mesopelagic backscatter was increased around reefs and banks of the Chagos archipelago, indicating connectivity between oceanic and neritic systems. SWIO seamounts harboured summit-associated aggregations, but the distributions of surrounding SLs did not follow a general pattern. Downstream SL depletion was observed in one location and combined with stomach content analyses, provides an insight into the mechanics of prey flux between open-ocean and seamount ecosystems. (iii) A mitochondrial marker was used to assess the population structure and demography of the hatchetfish Argyropelecus aculeatus in the SWIO. The results are suggestive of a single, well-connected population and indicate a recent population expansion around 0.14 million years ago. This highlights that even highly abundant mesopelagic populations are vulnerable to global climatic changes. Dispersal and recruitment are key ecological processes structuring seamount communities and are directly relevant for the management of exploited populations. Genetic barcoding was evaluated as a means to identify cryptic larval specimens of eels (leptocephali) and spiny lobsters (phyllosomata). Identification success was limited, but indicated the presence of 3-4 phyllosoma clades and 5-6 leptocephalus clades along the SWIR.

Nearly all deep-sea cephalopod life history studies have been completed by examination of specimens collected in the wild. Much of this work is like piecing together a puzzle; knowledge of the life history of many species remains fragmented and hence, taxonomically and phylogenetically confused. Molecular approaches and sequencing technologies are powerful tools for deciphering wild-type cephalopod life history and population dynamics. Use of molecular markers offers additional certainty for identifying specimens damaged during deep-sea collections and can elucidate often cryptic, intra- and interspecific diversity. The research presented in this study assessed broad genetic patterns of biodiversity in deep-sea cephalopods from the Gulf of Mexico and northwestern Atlantic Ocean. This study has two key objectives: [1] to examine intraspecies variation among regionally disjunct subpopulations, comparing collections separated by the Florida Peninsula, and [2] to examine intraspecies variation within deep-sea cephalopods in the Gulf of Mexico. Through Sanger sequencing marker genes COI, 16S rRNA, and 28S rRNA, this study has generated a genetic baseline characterization of deep-sea cephalopods in the Gulf of Mexico, assessed intraspecies genetic variation, and linked morphological identification with DNA barcodes, testing morphological hypotheses of species identification and naming. Results of investigating intraspecies variation within regionally disjunct subpopulations reveal there is no regional distinction between the Gulf of Mexico subpopulations of Vampyroteuthis infernalis, Pyroteuthis margaritifera, and Cranchia scabra, and the Bear Seamount subpopulations in the northwestern Atlantic Ocean. Results of investigating intraspecies variation within the Gulf of Mexico displayed potential for cryptic species, novel sequence records, and large expansions to sequence records for species known to inhabit the Gulf of Mexico. Analysis of intraspecies variation within the Gulf of Mexico facilitated identification of damaged specimens used for this study, but also revealed GenBank database issues of misidentified records, and outdated nomenclature in accession records. Because cephalopods play a central role in most oceanic ecosystems, characteristics like a short average life span and a rapid growth rate mean that cephalopod populations have the potential to serve as an invaluable reflection of ecosystem change.

The hydrothermal vent environment, in its extreme spatial and temporal variability, offers the opportunity to study habitats that are naturally fragmented and unstable. The vestimentiferan tubeworm Ridgeia piscesae is a foundation species inhabiting hydrothermal vent habitat in the Northeast Pacific Ocean. R. piscesae is a phenotypically plastic species and is arranged in a metapopulation spatial structure, with each local population displaying one of a range of morphotypes. Ridgeia piscesae participates in an obligate symbiosis that is dependent on hydrogen sulphide in the hydrothermal vent fluid that supplies each local population. Hydrothermal fluid flow is highly variable in the hydrothermal vent environment and hydrogen sulphide flux is a limiting nutrient for R. piscesae; this variability may create differences in habitat quality. The objective of this study is to determine whether local populations of R. piscesae centered on high and low flux hydrothermal fluid outputs are similar in body condition, reproductive condition, and juvenile recruitment. Using the submersibles ROPOS and Alvin, I collected high flux and low flux sample pairs from within meters of each other at multiple sample sites on Axial Seamount and the Endeavour segment of the Juan de Fuca Ridge. I used morphological measurements, histology and lipid analysis to assess physiological and reproductive condition. I also determined the relative abundances of new and older recruits in high and low flux local populations. I found that low flux habitat was inferior in its ability to support Ridgeia piscesae at all stages in the tubeworm’s life cycle. In terms of body condition, local populations in low flux habitat had lower body weight, greater body length, smaller anterior tube diameter, lower trophosome volume, lower total lipid volume, and lower branchial plume condition. With respect to reproductive condition, local populations in low flux habitat had lower proportions of reproductive individuals, less sperm transfer, lower gonad volume, and fewer mature oocytes; there was no difference in sperm development stages between high and low flux habitat. From the perspective of the individual, low flux tubeworms live longer, and lifetime reproductive output may be comparable to high flux tubeworms. However, turnover is higher in the high flux habitat, so reproductive output of high flux populations is greater than that of low flux populations. Juvenile recruitment was biased toward high flux habitat, although this trend was not significant and recruitment to low flux habitat was still notable. The differences between reproductive output and juvenile recruitment between these habitats support a source-sink model of population dynamics. From the perspective of the metapopulation, low flux habitat is inferior in its ability to support Ridgeia piscesae at all stages in the tubeworm’s life cycle. This distribution of relative contributions to the overall population of a key species in a Marine Protected Area (MPA) should factor into management decisions affecting MPA boundaries and use. / Graduate

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-15T14:57:52Z No. of bitstreams: 1 Tese Maria das Neves M Braid.pdf: 4130892 bytes, checksum: 7043780010dce74a0b8f41d220998c5f (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-15T15:38:40Z (GMT) No. of bitstreams: 1 Tese Maria das Neves M Braid.pdf: 4130892 bytes, checksum: 7043780010dce74a0b8f41d220998c5f (MD5) / Made available in DSpace on 2016-09-15T15:38:40Z (GMT). No. of bitstreams: 1 Tese Maria das Neves M Braid.pdf: 4130892 bytes, checksum: 7043780010dce74a0b8f41d220998c5f (MD5) / Em área oceânica do Atlântico Sul (20°15'- 21°10'S; 28°49'- 35°55'W), ao longo da Cadeia Vitória-Trindade (CVT), ocorreram dois cruzeiros de pesquisa, no navio Astro Garoupa, em 1998 (verão) e 2000 (outono). Na coluna d’água, da superfície aos 200 m de profundidade, foram coletas amostras em 23 estações, localizadas em perfis paralelos à costa. O estudo visou caracterizar a região da CVT, por meio da avaliação da distribuição, espacial e temporal, dos principais parâmetros físico-químicos: temperatura, salinidade, pH, alcalinidade, oxigênio dissolvido (OD) e nutrientes inorgânicos (fosfato, silicato, nitrito e nitrato). Os valores médios, no verão e outono, respectivamente, apresentaram temperatura (23,82 e 25,25°C) e salinidade (36,69 e 37,01 USP) com variações típicas de regiões tropicais; oxigênio dissolvido (99,8 % e 92,0 %) com taxas próximas da saturação, indicando pouca demanda biológica e influência de processos físicos; pH alcalino (8,283 e 8,374), dentro da faixa própria de águas oceânicas; alcalinidade total (2,170 e 2,524 meq.L-1) regulada, principalmente, pelo sistema carbonato; concentrações dos nutrientes (µmol.L-1), fosfato-P (0,172 e 0,389), silicato (0,733 e 1,186), nitrito-N (0,033 e 0,019) e nitrato-N (0,743 e 0,878), conforme ambientes com baixa produtividade primária. A estrutura termohalina provocou a estratificação da coluna d’água, apresentando termoclina mais rasa em 1998 (verão) que em 2000 (outono). Para avaliar as relações mais relevantes entre os parâmetros estudados, foram empregados procedimentos quimiométricos, com a análise de componentes principais (PCA) mostrando a separação da coluna d’água em duas zonas contíguas, eufótica e disfótica. Em geral, na zona eufótica, as concentrações foram muito baixas para os nutrientes, indicando taxa de captação rápida e baixos níveis de remineralização da matéria orgânica, predominando águas quentes, salinas e pobres em nutrientes; na zona disfótica, ocupada por águas frias e produtivas, o fosfato e nitrato apresentaram correlações significativas e seus teores mostraram a tendência de aumentar com a profundidade, de acordo com perfis encontrados no Atlântico Sul. Evidência de ressurgência nas imediações do banco Jaseur, mais próximo da costa, foi associada ao Giro de Vitória, que ocorre na região por causa do desvio da Corrente do Brasil. O estudo das massas d’água indicou a presença da Água Tropical (AT) na camada superficial e, aos 200 m, da Água Central do Atlântico Sul (ACAS). O domínio da AT, com águas quentes e pobres em nutrientes, permitiram caracterizar a CVT como uma região oligotrófica, influenciada pela sazonalidade, condizente com áreas oceânicas tropicais. / Two research cruises were made in the South Atlantic Ocean area (20°15'- 21°10'S; 28°49'- 35°55'W) along the Vitória-Trindade Seamount chain (VTC) on the Astro Garoupa ship, one in the summer of 1998 and another in the Autumn of 2000. Water column samples were collected at 200 m deep at 23 stations located in profiles parallel to the coast. This study aimed to characterize the VTC region by evaluation of the distribution, in space and time, of the main physical-chemical parameters: Temperature, salinity, pH, alkalinity, dissolved oxygen, and inorganic nutrients (phosphate, silicate, nitrite and nitrate). The mean summer and autumn values were as follows: Temperature (23,82 and 25.25°C) and salinity (36.69 and 37.01 USP), a typical variation of tropical regions; dissolved oxygen (99.8 % and 92.0 %), a rate close to saturation, which indicates low biological demand and the influence of physical processes; alkaline pH (8.283 and 8.374), in the range of ocean waters; alkalinity (2.170 and 2.524 meq.L-1) regulated mainly by the carbonate system; nutrients concentrations (µmol.L-1), phosphate-P (0.172 and 0.389), silicate (0.733 and 1.186), nitrite-N (0.033 and 0.019) and nitrate-N (0.743 and 0.878), in agreement with values of environments with low biological productivity. The thermohaline structure provoked the stratification of the water column, with shallower thermocline in 1998 (summer) than in 2000 (autumn). To evaluate the most relevant relations between the parameters studied, it was used Chemometrics procedures such as principal component analysis (PCA), which indicated the separation of the water column between the two contiguous zones, euphotic and dysphotic. In general, the euphotic zone presented very low concentrations of nutrients, indicating a faster capture rate and low remineralization levels of organic matter; warm, saline and nutrient-poor waters predominate. In the cold and productive waters of the dysphotic zone, phosphate and nitrate had important correlations and their contents tended to increase with depth, in agreement with the profiles found in the South Atlantic. Evidences of upwelling were observed close to Jaseur bank, closer to the coast, associated to the Vitoria Eddy, which occurs in the region due to the Brazil Current deviation. The study of water masses indicated the presence of Tropical Water (TW) on the top layer and of South Atlantic Central Water (SACW) at 200 m. The prevalence of TW with warm nutrient-poor waters allowed characterizing the VTC as an oligotrophic region, influenced by seasonality, in agreement with tropical ocean areas.