Navegando por Assunto "Palynology"

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dinâmica da vegetação durante o quaternário tardio no limite continental da península bragantina, litoral amazônico
(Universidade Federal do Pará, 2022-11-25) MACIEL, Giordana Leticia Monteiro; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994; https://orcid.org/0000-0002-6468-6158; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790; https://orcid.org/0000-0002-3784-7702
The eastern Amazonian region is dominated and shaped by a macrotidal regime, harboring environments such as muddy plains colonized by mangroves, estuaries associated with tidal channels, floodplains, and macrotidal beaches, among others. To understand the vegetation dynamics and carry out the paleoenvironmental reconstitution in an Amazonian floodplain, palynological, sedimentary, and C-14 dating data were integrated based on a subsurface sedimentary profile collected in the region of the Taperaçu’s herbaceous fields, in the Bragança peninsula (PA), on the Amazon coast. The present study identified three fácies associations and four pollen zones that occurred during the Late Pleistocene and Holocene. The first facies association is defined as an alluvial deposit, which presented pelite facies, flaser heterolithic bedding with a coarsening upward sequence. The vegetation was predominantly typical of trees and shrubs, marked by the presence of Rubiaceae, Agavaceae, and Annonaceae families and with low herbaceous vegetation dominated by the Araceae family developed around 41,200- 39,975 cal years BP. The second facies association identified showed typical characteristics of a tidal channel, with a well-delimited erosive surface, which marks a transition in the processes operating over this environment; it comprises gravel, massive sand, and wavy-marked mud facies. Toward the Taperaçu’s tidal channel, herbaceous vegetation was developed, represented by Cyperaceae and Ulmaceae, and the presence of trees and shrubs, such as Arecaceae, Malphighiaceae, and Rubiaceae. During the early and mid-Holocene (6000-5915 cal years BP), at a depth of 6.45 m from the surface, the results revealed the formation of a tidal flat. The main pollen result during this phase was the establishment of mangroves, colonized by Rhizophora and Avicennia, in addition to the presence of herbaceous vegetation, which currently occupies the studied region, marking the late Holocene.
Acesso aberto (Open Access)
Efeitos das mudanças climáticas nos limites austral e boreal dos manguezais americanos durante o Holoceno e Antropoceno
(Universidade Federal do Pará, 2021-09-08) RODRIGUES, Érika do Socorro Ferreira; KAM, Biu Liu; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
During the Holocene, mangrove distributions were primarily controlled by climate change and sea level fluctuations. In particular, low winter temperatures in the subtropical coastal areas limited these ecosystems to expand beyond 30°N and 28°S in the North and South Hemisphere. Therefore, under the continuous warming trend during the Anthropocene, mangroves are expected to migrate to more temperate regions previously occupied by saltmarshes (e.g., Spartina sp.). The purpose of this Thesis is evaluate the effects of climate changes and SLR fluctuations on the distribution of American mangroves along the Holocene and Anthropocene, based on satellite and drone images, sedimentary facies, diatoms, pollen, geochemistry (LOI, XRF, TOC , TN, TS, C: N, C: S, δ13C and δ15N) as well 210Pb and 14C datings .To achieve the aforementioned objectives, studies were conducted on the tropical coast of southeastern Brazil - south of the Espírito Santo State (20°41'S), the subtropical coastal regions located on the north (26°6'S) and south (28°29’ S) coast of Santa Catarina, and Louisiana littoral (29° 09' N). The results of this research are presented in four scientific papers. The first one (see, chapter II) deals with the effects of global warming on the establishment of mangroves in the Louisiana littoral (29° 09’ N) during the Holocene. The second scientific paper (see, chapter III) shows southward migration of the austral limit mangroves in South America, according to the increase in minimum winter temperatures in the Anthropocene (southern Santa Catarina coast, 28°29' S). The third manuscript (see, chapter IV) assesses the impacts of sea level rise on tropical mangroves in southeastern Brazil (southern Espírito Santo coast, 20°41'S) during the Holocene and Anthropocene, using a multi-proxy approach. The fourth scientific paper (see, chapter V) addresses the establishment of mangroves in the São Francisco do Sul Bay (north Santa Catarina coast , 26° 6'S), in response to global warming in the last 1000 years. The results indicated a marine transgression off the southern coast of Santa Catarina (28°29’ S) and the Louisiana littoral (29°09’ N) during early Holocene. This natural process converted a lake into lagoons colonized by herbs adapted to an estuarine environment. On the Brazilian tropical coast, the middle Holocene high sea-level stand (2-5 m above the current level) was decisive for the establishment of mangroves. This comportment was observed in an estuary located on the south coast of Espírito Santo (20°41'S) where a herbaceous plain was gradually replaced by a lagoon surrounded by mangroves between ~6300 cal yr BP and ~4650 cal yr BP. However, between ~ 4650 cal yr BP and 2700 cal yr BP the lagoon colonized by mangroves on its margins was converted to a tidal flat occupied by herbs, palms and trees/shrubs reflecting the reduction of estuarine influence in the late Holocene, according to with the fall and/or stabilization of the RSL. From the last thousand years there has been a significant decrease in the occurrence of mangrove pollen in the sediments of the tidal flats of southern Espirito Santo (390 cal yr BP (1560 AD) and 77 cal yr BP (1873 AD), probably caused by a RSL fall associated with Little Ice Age (LIA). Paleoclimatic studies have indicated temperature fluctuations during LIA (380 to 50 cal yr BP) and MCA – Medieval Warm Period (950 to 750 cal yr BP) in the late Holocene and consequent change in the Brazil southern vegetation. These climatic events probably influenced the appearance of the mangrove genera succession in the São Francisco do Sul Bay (north Santa Catarina coast, 26°6' S). The effects of the sea level fall and/or stabilization during late Holocene were recorded on the southern coast of Santa Catarina (Laguna, 28° 29 ′ S) through changes in coastal geomorphology. In this same period at the Louisiana coastline (29°09 ′ N), sandy sediments (overwash sediments) were deposited in these estuaries reflecting the gradual migration of these sediments towards land likely a result of storm events. The position of RSL on the southern Brazilian coast (Laguna, 28° 29 ′ S) and north american (Louisiana coast, 29° 09 ′ N) from the middle Holocene were the same presenting suitable physicochemical conditions for mangrove development, as occurred on the coast of Espírito Santo (~6300 cal yr BP) and São Francisco do Sul Bay (~1500 cal yr BP). However, no mangrove pollen grains were recorded in the sediments of the current austral (Laguna, 28° 29 ′ S) and boreal (Louisiana coast, 29° 09 ′ N) limit of American mangroves during the Holocene. During this time interval, there was a significant contribution of organic matter of estuarine source in tidal flats occupied by Spartina sp. Regarding to global warming and RSL rise during Anthropocene an increase mangrove pollen of Espírito Santo sedimentary cores (20° 40' S) reflected mangrove migration to topographically higher sandy plains previously dominated by herbaceous vegetation. Regarding Laguna mangroves (current southern limit of the American mangroves, 28° 29 ′ S), pollen analyzes, 14C and 210Pb datings indicated that the mangroves were established under estuarine influence between ~1957 and 1986 AD, represented by Laguncularia sp. trees. Spatio-temporal analyzes based on satellite and drone images indicated that mangroves have been expanding in recent decades with the introduction of new mangrove genera. In our study area in São Francisco do Sul Bay (north coast of Santa Catarina, 26°6' S), palynological analyzes and 14C dating revealed that mangroves were established around ~ 1500 cal yr BP represented by Laguncularia sp. followed by Avicennia sp. (~500 cal yr BP) and Rhizophora sp. in the last century. This mangrove succession genera were likely caused by a warming trend in South America during the late Holocene and Rhizophora sp. by warming during the Anthropocene. In relation to the mangroves located on the Louisiana littoral, historical records indicated the presence of small shrubs of Avicennia sp. at the beginning of the 20th century. Currently, remote sensing studies coordinated by Cohen (2021) indicate a latitudinal expansion of Avicennia sp. colonizing areas that were previously occupied by Spartina sp. after two decades of warm winters. Therefore, mangroves migrated from the tropics to temperate zones as winter minimum temperatures increased during the Holocene. The Laguna and Louisiana mangroves (currently South and North American mangroves limit) were only established in the early and mid-21st century, respectively. Such dynamics were likely caused by the natural global warming of the Holocene and intensified during the Anthropocene. This process also caused a RSL rise which resulted in the migration of mangrove from lowlands to new higher tidal flats.
Acesso aberto (Open Access)
A evolução dos manguezais nos litorais Nordeste e Sul brasileiros durante o Holoceno
(Universidade Federal do Pará, 2020-09-30) FREIRE, Neuza Araújo Fontes; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
It is possible that climate changes and sea level fluctuations (allogenic processes) are and will cause major changes in mangrove dynamics. However, other driving forces may be significantly affecting this system. Distinguishing allogenic and autogenic influence on mangroves is a challenging question, because mechanisms related to the natural dynamics of depositional environments (autogenic processes) have strong influences on the establishment and degradation of mangroves. Thus, impacts on mangroves caused by autogenic processes may be erroneously attributed to allogenic mechanisms. Therefore, it is imperative to identify the ‘fingerprint’ of global changes in modern mangrove dynamics. This thesis integrates palynological, geochemical, sedimentological data, 14C dating of sedimentary organic matter, geomorphological and vegetation data in order to evaluate the influence of autogenic and allogeneic processes on Brazilian mangroves during the Holocene. Tropical estuaries from Rio Grande do Norte and southern Bahia, and subtropical estuaries in northern and southern Santa Catarina estates with different climatic, geomorphological and oceanographic characteristics were studied. The Relative Sea-Level (RSL) along the Rio Grande do Norte reached modern level and stabilized at about 7,000 cal yr BP, allowing the mangrove establishment at the edges of the Ceará-Mirim River estuary until the nowadays. However, changes in the spatial distribution of mangroves have occurred since then due to channels dynamics in the region (autogenic processes). Considering the mangroves of the Jucuruçu River in southern Bahia, their horizontal and vertical distribution were controlled by the interactions of the changes in the RSL and fluvial discharge. Therefore, the dynamics of these estuarine mangroves during the Holocene was mainly controlled by changes in sea level and precipitation that affected fluvial discharge. These allogeneic mechanisms were the main drivers of the dynamics of these mangroves. However, during the last 600 years, factors intrinsic to the depositional system gained relevance by controlling the establishment and migration of mangroves by deposition and erosion of muddy tidal flats, abandonment and reactivation of channels (autogenic processes). In the case of Santa Catarina mangroves, the RSL rise up to the middle Holocene was decisive for the establishment of tidal flats appropriate for the expansion of saltmarshes. However, mangroves did not tolerate the Holocene low temperatures in the southern littoral of Santa Catarina. The pollen data indicate the establishment of mangroves with Laguncularia around 1,700 cal yr BP, followed by Avicennia and lastly Rhizophora trees, a cold less tolerant genus, around 650 cal yr BP in São Francisco do Sul, north of Santa Catarina. The mangroves of Laguna, south of Santa Catarina, composed of Laguncularia and Avicennia, were established in the current southern limit of the South American mangroves only in the last decades. No evidence was found for the presence of mangroves in Laguna during the Holocene. The establishment of these mangroves in the region probably started during the Anthropocene, as a consequence of the increase in minimum winter temperatures in southern Brazil. Considering changes in precipitation rates over drainage basins that feed mangrove estuaries, as well as trends in RSL rise and temperatures until the end of the 21st century, tropical estuarine mangroves will likely migrate to higher topographically sectors in the interior of the river valleys, where its extension will depend on the volume of river discharge interacting with the RSL rise. Subtropical mangroves are expected to expand to more temperate zones as minimum winter temperatures increase. This process should cause an increase in the diversity of mangrove species, such as the introduction of the Rhizophora genus in the current southern limit of the mangroves, positioned in Laguna-SC. However, in the case of high rates of RSL rise, the relatively new subtropical mangroves are also expected to migrate to topographically higher sectors of the coast.
Acesso aberto (Open Access)
Holocene history of a lake filling and vegetation dynamics of the Serra Sul dos Carajás, southeast Amazonia
(Academia Brasileira de Ciências, 2017-08-24) GUIMARÃES, José Tasso Felix; SAHOO, Prafulla Kumar; SOUZA FILHO, Pedro Walfir Martins e; FIGUEIREDO, Mariana Maha Jana Costa de; REIS, Luiza Santos; RODRIGUES, Tarcísio Magevski; SILVA, Marcio da Silva
Down-core changes in sedimentary facies, elemental geochemistry, pollen, spore, δ13C, δ15N and radiocarbon records from a filled lake, named R4, of the Serra Sul dos Carajás were used to study the relationship between the paleomorphological and paleoecological processes and their significance for Holocene paleoclimatology of the southeast Amazonia. The sediment deposition of the R4 lake started around 9500 cal yr BP. Increase of detrital components from 9500 to 7000 cal yr BP suggests high weathering of surrounding catchment rocks and soils, and deposition into the lake basin under mudflows. At that time, montane savanna and forest formation were already established suggesting predominance of wet climate. However, from 7000 to 3000 cal yr BP, a decline of detrital input occurred. Also, forest formation and pteridophytes were declined, while palms and macrophytes were remained relatively stable, indicating that water levels of the lake is likely dropped allowing the development of plants adapted to subaerial condition under drier climate conditions. After 3000 cal yr BP, eutrophication and low accommodation space lead to high lake productivity and the final stage of the lake filling respectively, and forest formation may has acquired its current structure, which suggests return of wetter climate conditions.
Acesso aberto (Open Access)
Morfologia polínica de espécies de Bonamia thouars, Evolvulus l. e Jacquemontia choisy (Convolvulaceae) ocorrentes numa região de ecótono no município de Caetité, BA, Brasil
(Instituto de Botânica, 2019-07) VASCONCELOS, Liziane Vilela; JUNQUEIRA, Maria Elizangela Ramos; BIANCHINI, Rosangela Simão; SABA, Marileide Dias
The pollen morphology of 17 taxa of Convolvulaceae [Bonamia agrostopolis, Evolvulus (nine species) - Tribe Cresseae), and Jacquemontia (seven species) - Tribe Jacquemontieae)] was described under light microscopy (LM) and scanning electron microscopy (SEM) with the objective of contributing to the palynology and the taxonomy of the group. The pollen material was collected from anthers and/or floral buds of herbarium exsicates, acetolyzed, analyzed quantitative and qualitatively under LM and SEM, described and illustrated. The data presented here on the pollen morphology of the studied Bonamia, Evolvulus and Jacquemontiaspecies, showed that B. agrostopolis has medium, isopolar, microechinate, granulated pollen grains with the 3-colpate apertural type, which is present in the majority of Jacquemontia species studied. On the other hand, Evolvulus species, J. gracillima and J. pentanthos have the same pollen type, characterized by being spheroidal, pantocolpate and microechinate. The other species of Jacquemontia were characterized by the subprolate to prolate-spheroidal shape, and the zonocolpate and microechinate exine in the pollen grains of all species, with granules, perforations, and micro-reticules in some species. We observed a lack of definition of the pollen types that delimit Cresseae and Jacquemontieae since there are palynological affinities between species of the two tribes. The species of Evolvulus form a stenopalynous group; however, the present study presents unpublished palynological descriptions for nine species, contributing to the expansion of pollen data and confirming the eurypalynous character of Convolvulaceae.
Acesso aberto (Open Access)
Reconstituição paleoambiental da vegetação costeira na foz dos rios Santa Maria da Vitória e Jucu durante o holoceno médio e tardio, Estado do Espírito Santo, Brasil
(Universidade Federal do Pará, 2025-03-13) PANTOJA, NISYA ROBELLY CARDOSO; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790; https://orcid.org/0000-0002-3784-7702
Climate and sea level changes may have caused significant alterations in coastal morphology and mangrove distribution on the central coast of Espírito Santo State, Brazil. Therefore, this study aims to identify the dynamics of coastal vegetation during the middle and late Holocene, in the Santa Maria da Vitória and Jucu rivers. For this purpose, 14C dates, sedimentary data and pollen data were used, obtained from two sedimentary cores, called RSMV (340 cm) and JUCU (190 cm). During the middle Holocene, around 7245-7368 cal years BP, the relative sea level (SSL) was above the current level, resulting in the development of mangroves in the RSMV core region. However, around 2699-2787 cal years BP, with the regression of the SSL, the mangrove area moved to topographically lower regions. Another determining factor for the reduction of these areas during this period to date was human intervention. In the JUCU core region, mangrove forests were identified between 2188-2332 cal yr BP, initially colonized by Laguncularia. Thus, in this context, the dynamics of vegetation and sediments are associated with fluctuations in relative sea level and climate change throughout the Holocene.
Acesso aberto (Open Access)
Sedimentação recente e palinologia do Talude Continental Superior Amazônico-Maranhão
(Universidade Federal do Pará, 2025-04-24) AZEVEDO, Gabriela Miranda de; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429; https://orcid.org/0000-0001-7850-1217
The continental slope off the Amazonas, coast of Pará is a geologically complex region, influenced by tectonic phenomena and sedimentary processes associated with the proximity of the Amazon River mouth. The Amazon River discharges approximately 5.7 × 10¹² m³ of water per year and 1.2 × 10³ m³·s⁻¹ of solid load. The continental slope displays a diverse sedimentary cover distribution, which varies regionally depending on the origin of the sediment sources. Few studies (in sedimentology, palynology, and paleontology) have been conducted on the continental slope of the northern region. The main objective of this study is to analyze the sedimentological characteristics (grain size distribution, calcium carbonate content/CaCO₃, organic matter/OM, and organic carbonate/OC) and investigate the occurrence of fertile sediments in the sediment cover of the upper continental slope off Pará, based on two core samples (T66 and T144). The methodology involved: (1) Bibliographic research on scientific databases; (2) Acquisition of sub-surface core samples using a piston corer; (3) Macroscopic description of cores (color, stratigraphic arrangement, and sediment analysis) and core subsampling; (4) Grain size analysis of the sampled layers, including separation of the silt/clay fraction; (5) Quantification of OM and CaCO₃ contents; (6) Selection of fertile samples for palynological analysis. The results indicate that the sediments are predominantly muddy, with a dominance of coarse silt fraction. They are mostly well-sorted, with approximately symmetrical skewness and platykurtic kurtosis. OM content in the cores ranged from 10.64% to 24.42%, with an average of 16.39% (T66) and 10.64% to 24.42% with an average of 16.39% (T144). Preliminary palynological investigation confirms the presence of pollen grains in the samples. The sediments from the continental slope off Pará consist of a mixture of allochthonous and autochthonous material, with the occurrence of palynomorphs.