25 research outputs found
The composition and new records of micro- and mesophytoplankton near the VitĂłria-Trindade Seamount Chain
LHS 1815b: The First Thick-disk Planet Detected by TESS
We report the first discovery of a thick-disk planet, LHS 1815b (TOI-704b, TIC 260004324), detected in the Transiting Exoplanet Survey Satellite (TESS) survey. LHS 1815b transits a bright (V = 12.19 mag, K = 7.99 mag) and quiet M dwarf located 29.87 ± 0.02 pc away with a mass of 0.502 ± 0.015 M o˙ and a radius of 0.501 ± 0.030 R o˙. We validate the planet by combining space- and ground-based photometry, spectroscopy, and imaging. The planet has a radius of 1.088 ± 0.064 R â with a 3Ï mass upper limit of 8.7 M â. We analyze the galactic kinematics and orbit of the host star LHS 1815 and find that it has a large probability (P thick/P thin = 6482) to be in the thick disk with a much higher expected maximal height (Z max = 1.8 kpc) above the Galactic plane compared with other TESS planet host stars. Future studies of the interior structure and atmospheric properties of planets in such systems using, for example, the upcoming James Webb Space Telescope, can investigate the differences in formation efficiency and evolution for planetary systems between different Galactic components (thick disks, thin disks, and halo)
A comunidade microfitoplanctÎnica do Arquipélago de São Pedro e São Paulo (Atlùntico Norte-Equatorial): variação diurna e espacial
Dinoflagelados (Peridiniales, Prorocentrales) do microplĂąncton na plataforma continental e talude do extremo sul do Brasil (inverno 2005, verĂŁo 2007)
PLANKTONIC SYSTEM OF GUANABARA BAY: A REVIEW
A baĂa de Guanabara Ă© um dos ecossistemas tropicais mais eutrofizados do mundo. Sua hidrobiologia varia segundo um tutor temporal definido pelo verĂŁo chuvoso e um duplo gradiente espacial, vertical e horizontal condicionado pela influĂȘncia da marĂ© e dos e efluentes continentais. O impacto antrĂłpico manifesta-se nas ĂĄreas internas por elevados teores em amĂŽnia (? 650 mM) e fĂłsforo (? 308 mM ) e baixa transparĂȘncia (< 1 m). O fitoplĂąncton, representado por diversos grupos taxonĂŽmicos, Ă© dominado pelo nanoplĂąncton (flagelados e diatomĂĄceas) e cianofĂceas, especialmente em superfĂcie e no verĂŁo. O aumento da biomassa primaria no canal principal de circulação da baĂa nos Ășltimos 20 anos indica um comprometiĂÂmento progressivo da capacidade de diluição dos despejos domĂ©sticos e industriais. O zooplĂąncton Ă© bom indicador do grau de deteriorização ambiental, diminuindo (copĂ©podes, quetognatos, cladĂłceros, apendiculĂĄrias) ou desaparecendo (sifonĂłforos e taliaceos), nas ĂĄreas internas mais impactadas. As densidades de ovos e larvas de peixes sĂŁo maiores na entrada da baĂa e no canal central do que na ĂĄrea noroeste interna onde a baixa qualidade de ĂĄgua constitui um fator prejudicial Ă desova e recrutamento. Pesquisas em curso visam quantificar os elementos da teia microbiana (bacterioplĂąncton, picoplĂąncton e protozooplĂąncton) essenciais para a compreenĂÂsĂŁo dos mecanismos que regem a transferĂȘncia da energia neste sistema.Guanabara Bay, one of the most eutrophic tropical systems in tire world, receives large loads of urban and industrial wastes. Its hydrobiology shows temporal trends according to seasonal variations determined by the rainny summer and spatial trends associated to a tidally induced current pattern that create horizontal and vertical gradients. Human impact is strongest along the shores in the inner reaches of the Bay that present high ammonia and phosphorus concentrations (? 650 ?M and ? 308 ?M), and low, transparence (< 1m). All major phytoplankton groups are present, but cyanobacteria and the nanoplankton fraction (flagellates and diotoms < 20 ?m) are dominant, especially in the inner reaches and during summer. Increasing phytoplankton biomass in the main circulation channel for the past two decades indicate a progressive deterioration in water quality. Tire presence/absence of zooplankton populations are good water quality indicator, according to their specific levels of sensitivity to pollution: not very sensitive (appendicularians), sensitive copepods, chaetognats, cladocerans) and very sensitive (siphonophores and thaliaceans). The highest concentrations of fish eggs and larvae are detected closer to the entrance to lhe Bay and along its main circulation channel, in contrast to the lowest concentrations found in the Northwestern region. Water quality is considered an important fator for accurrence of spawning and recruitment. Present research focuses on the components of the microbial web (bacterioplankton, picoplankton and protozooplankton), considered essential for the understanding of energy flow in this system
Dinophysiales (Dinophyceae) no extremo sul do Brasil (inverno de 2005, verĂŁo de 2007)
The dinoflagellates of the Dinophysiales order are a morphologically diverse and ecologically heterogeneous group that includes autotrophic, mixotrophic and heterotrophic species and others containing endosymbionts or phycotoxin producers. In this research Dinophysis, Ornithocercus, Histioneis and Amphisolenia species have been identified in both coastal and oceanic waters of the Southern region of Brazil next to Santa Marta Grande Cape, SC and AlbardĂŁo-ChuĂ, RS. Vertical hauls were performed with plankton nets (20 ÎŒm) on board of the R. V. AtlĂąntico Sul at 33 oceanographic stations sampled in August/September 2005 (Winter) and February 2007 (Summer). The plankton was fixed with formaldehyde (4%) and analyzed with the help of an inverted microscope. A total of 43 Dinophysiales species were identified, most of them widely distributed in the coastal, continental and oceanic areas such as Dinophysis acuminata, D. exigua, D. ovata and Histioneis hyalina in the Summer of 2007 and D. acuminata, D. caudata, D. fortii e D. schroederi in the Winter of 2005. The distribution of some species was restricted to the oceanic region under the influence of the Brazil Current as it was observed for Dinophysis dubia, D. exigua, D. schuetti, Histioneis para, Ornithocercus thumii and O. splendidus in the Winter of 2005 and D. similis, D. rapa, H. megalocopa, H. milneri, O. heteroporus and O. splendidus in the Summer of 2007. Six potentially toxic species were registered, Dinophysis acuminata, D. caudata, D. fortii, D. mitra, D. tripos and D. rotundata.Os dinoflagelados da ordem Dinophysiales representam um grupo morfologicamente diverso e ecologicamente heterogĂȘneo, incluindo espĂ©cies autotrĂłficas, mixotrĂłficas e heterotrĂłficas, outras contendo endossimbiontes ou ainda produtoras de ficotoxinas. No presente trabalho, foram identificadas as espĂ©cies de Dinophysis, Ornithocercus, Histioneis e Amphisolenia em ĂĄguas costeira e oceĂąnica na regiĂŁo Sul do Brasil, ao largo do Cabo de Santa Marta Grande, SC e AlbardĂŁo-ChuĂ, RS. Arrastos verticais foram realizados com rede de plĂąncton (20 ÎŒm) Ă bordo do N. O. AtlĂąntico Sul em 33 estaçÔes oceanogrĂĄficas visitadas em agosto/setembro de 2005 (inverno) e fevereiro de 2007 (verĂŁo). As amostras de plĂąncton foram fixadas com formol (4%) e analisadas com o auxĂlio de microscĂłpio invertido. Ao todo, 43 espĂ©cies de Dinophysiales foram identificadas, a maioria com ampla distribuição nas regiĂ”es costeira, de plataforma continental e oceĂąnica, como Dinophysis acuminata, D. exigua, D. ovata e Histioneis hyalina no verĂŁo de 2007, e D. acuminata, D. caudata, D. fortii e D. schroederi no inverno de 2005. Algumas espĂ©cies apresentaram distribuição restrita Ă regiĂŁo oceĂąnica, sob influĂȘncia da Corrente do Brasil, como Dinophysis dubia, D. exigua, D. schuetti, Histioneis para, Ornithocercus thumii e O. splendidus no inverno de 2005, e D. similis, D. rapa, H. megalocopa, H. milneri, O. heteroporus e O. splendidus no verĂŁo de 2007. Seis espĂ©cies potencialmente tĂłxicas foram encontradas, Dinophysis acuminata, D. caudata, D. fortii, D. mitra, D. tripos e D. rotundata