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Dissertações em Geologia e Geoquímica (Mestrado) - PPGG/IG

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2604

O Mestrado Acadêmico pertence ao Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).

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Acesso aberto (Open Access)
Análise espaço-temporal dos manguezais degradados de Bragança, com base em imagens de satélite e modelos de elevação digital
(Universidade Federal do Pará, 2022-02-22) MOLANO CÁRDENAS, Sergio Mauricio; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The Bragança Peninsula occurs at the northern littoral of Brazil, in the state of Pará. It is characterized by the largest continuous mangrove belt in the world. The construction of the PA- 458 road in the ‘70s changed the hydrodynamics of the peninsula, causing the degradation of a considerable portion of the mangroves in the central region of the peninsula. Recently, degraded areas are being colonized by mangrove trees, mainly by the Avicennia germinans specie. This study intends to identify changes in the degraded areas of the tidal flats in topographically higher sectors during the last 35 years. To reach that objective, we used the following techniques: a) manual mapping of the degraded areas with mid spatial resolution satellite imagery; b) object-based classification of the degraded areas and mangrove species, using high spatial resolution satellite imagery; c) photogrammetry of drone imagery; d) digital elevation models; and e) topographic validation with theodolite and GNSS GPS “Antenna Catalyst”. From 1986 to 2019, there was a reduction in the degraded areas of 247.96 ha according to the mid-resolution “dataset” quantification. However, high-resolution data showed a reduction in the degraded areas of 211.65 ha between 2003 and 2019. The degraded areas quantification presents fluctuations in the regeneration trend; it is related to significant climatic phenomena such as “El Niño” and “La Niña”, accompanied by periods of drought and high rainfall, respectively. Overall accuracy and Kappa index values for the high-resolution data generally exhibited values above 0.9. Producers’ and users’ accuracy and Kappa per class values showed the difficulties separating mangrove species due to the lack of radiometric resolution of the analyzed images. The digital terrain model representing the tidal flat showed two topographically differentiated regions in the degraded areas, separated by the PA-458 road, which are mainly influenced by the Caeté’s and Taperaçú’s characteristics. This same difference was found in the vegetation height model, where the largest trees are located toward the SE side of the road, reaching 25 m, while at the NW side of the road, the tree heights oscillated mainly between 5 and 15 m. The sea-level rise specifically controls regeneration rates. This relocated the intertidal zone to topographically higher areas, increasing tidal flushing processes, essential for the mangrove forests development.
Acesso aberto (Open Access)
Análise integrada da paisagem para avaliação da vulnerabilidade à perda de solo das margens da Baía de Marajó, estado do Pará
(Universidade Federal do Pará, 2011-11-30) GUIMARÃES, Ulisses Silva; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Marajó Bay is part of the Coastal Zone in the Amazon estuary, and it constitutes a form of "V" with intensive processes of erosion and progradation. The bay shores are the object of this study, from the west coast, represented by the west coast by Salvaterra and Soure municipalities, to the east coast of Mosqueiro Island. The purpose is to analyze the coastal environments adjacent to the Marajó Bay, with a systemic and integrated approach using thematic databases (geology, geomorphology, pedology, climatology and Use and Land Cover) and remote sensing images (Landsat TM 5 and MDE SRTM) to prepare maps syntheses of landscape units and vulnerability to loss of soil as a subsidy to coastal management. The main steps of this methodology are: i) atmospheric correction by dark-object subtraction, geometric correction by orthorectification, with supervised classification algorithm Spectral Angle Mapper (SAM) through training samples to map the Use and Land Cover; ii) compilation, adaptation and classification to improve data of morphology; iii) development of derivatives geomorphometric; and, iv) integration of the thematic basis for map algebra, with an overlap equation for synthesis of the landscape units maps and another equation for the preparation of the arithmetic average map of vulnerability to loss of soil. The Marajo Bay shores have mostly the unit of Fields with 17.61% of the study area (50,483.16 ha), maximum altimetry of 58 m, the topography is flat and smooth, the relief were overwhelmingly straight and planar. The integrated data indicate that the pedogenetic processes prevail in only 3.58% (10,231.38 ha) of the study area. The areas in balance between morphogenic and pedogenetic processes correspond to 3.75% (10,737.63 ha), while morphogenesis is prevalent in 42.40% (121,317.39 ha). The superiority of morphogenic units shows the hazard of coastal environments per surface mechanisms, how substrate desegregation and erosion by processes of runoff and mass displacement.
Acesso aberto (Open Access)
O aumento do nível do mar pós-glacial afetou a dinâmica das florestas de várzea da Amazônia durante os últimos 5000 anos?
(Universidade Federal do Pará, 2015-04-10) ARAUJO, Mayra Nina; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Four sediment cores, between three and ten meters depth, were sampled from fluvial plains and abandoned channels along the Rio Branco-Roraima. The stratigraphic analyses were based on grain size, structures and pollen content. In addition, the age of events were determined by seven radiocarbon dating. The data show cycles of channel abandonment, resulting in formation of lakes and, latter, its reactivation. The lake phases permitted the accumulation of mud sediments in different time intervals, suitable for pollen preservation. Pollen analyze indicated a combination of at least seventy taxa, the most representative are: Moraceae, Euphorbiaceae, Caesalpiniaceae, Fabaceae, Rubiaceae, Melastomataceae, Combretaceae, Sapindaceae, Poaceae, Cyperaceae, Aizoaceae and Apiaceae. They characterize arboreal and herbaceous vegetation, similar to modern vegetation of the study, since the middle Holocene. Considering the dry period occurred in the Amazon region during the early and middle Holocene, followed by a wet period in the late Holocene, the data presented in this work do not suggest significant changes in vegetation as a consequence of that climatic changes. Therefore, climatic and hydrologic conditions have favored the stability of vegetation in the study site for at least the last 5500 years. Three hypotheses are presented to justify this stability: 1) the early and middle Holocene dry period did not affect vegetation pattern; 2) a dry climatic phase was never present; or 3) the stabilization of the relative sea level about 6000 cal yr BP along the northern Brazilian littoral may have influenced the water table, and favored the establishment and maintenance of Amazonian lowland forest during the mid and late Holocene. In addition, this process may have attenuated the impact of that dry period in areas under most fluvial influence.
Acesso aberto (Open Access)
Dinâmica da vegetação da região de Humaitá - AM durante o Pleistoceno tardio e o Holoceno
(Universidade Federal do Pará, 2013-01-30) FRIAES, Yuri Souza; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Vegetation dynamics of Western Amazonia during the past 42000 cal yr BP was studied by pollen, sedimentary facies, 14C dating δ13C and C/N. Two sediment cores were sampled from Humaitá in southern Amazonas state, and Porto Velho, northern Rondônia. These sites, located in western Brazilian Amazonia, are covered by grassland and tropical rainforest vegetation, respectively. The sedimentary deposits are predominantly composed of massive sand, heterolithic mud/sand, and laminated or massive mud representative of sediment accumulation in floodplain, active channel, abandoned channel, and oxbow lake sedimentary environments. In these settings, reducing and low energy subaqueous conditions were developed, locally favoring preservation of a pollen community of herbaceous vegetation and glacial forest represented mainly by Alnus, Drymis, Hedyosmum, Podocarpus, and Weinmannia trees at least between > 42,033 – 43,168 cal yr BP and <34,804 – 35,584 cal yr BP. The herbaceous and arboreal vegetation ecotone persisted from the early to mid-Holocene, whilst the cold pollen assemblage became extinct. In this work, we record a significant plant population, at present restricted to Andean areas located at altitudes higher than 2000 - 3000 m, in areas of the Amazonia lowland toward the onset of the Last Glacial Maximum. This suggests that this time interval might have seen temperatures lower than previously proposed for this region.
Acesso aberto (Open Access)
A dinâmica das florestas alagadas durante o holoceno no litoral de Calçoene, Amapá
(Universidade Federal do Pará, 2008-02-25) GUIMARÃES, José Tasso Felix; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The integration of palynological and spectrophometric data with radiocarbon dating of sediment cores has allowed to propose developing model and vegetation dynamic according to climatic and relative sea-level changes during the Late Holocene in the Calçoene Coastal Plain- Amapá. Thus, this work suggests three periods characterized by marine influence between 2000- 800, 500-300, e 80 years BP - modern, as well as, two fluvial periods between 800-500 years BP and 300-80 years BP. The analysis of current patterns of geobotanical units distribution and palaeovegetation indicate a mangrove (311 Km 2 ) and várzea forest (684 Km 2 ) migration on inundated field (1.021 Km 2 ) positioned in elevated topographically areas of this coastal plain, which may be related to a local relative sea-level rise.
Acesso aberto (Open Access)
Dinâmica dos manguezais do litoral de Natal-RN de acordo com as mudanças no clima e nível do mar desde o Holoceno médio
(Universidade Federal do Pará, 2017-08-05) RIBEIRO, Samuel Rodrigues; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The factors behind the Holocene mangrove dynamics have long been a theme of great interest for research. Among all hypotheses, the establishment, expansion, and contraction of mangrove areas have been mainly attributed to sea level and climate changes. However, other driving forces of limited occurrence in time may be significantly affecting this system. Along the valley of the Ceará Mirim river, near the Natal city, Rio Grande do Norte littoral, northeastern Brazilian the integrate geomorphological, sedimentological, and palynological data with radiocarbon dating, as well as δ13C, δ15N and C/N from sedimentary organic matter from four sediment cores reveal an estuarine influence with mangrove development since 6950 cal yr BP after the post-glacial sea level rise, and it has been stable during the middle and late Holocene. The mangrove expansion along this fluvial valley since the middle Holocene was caused by the sea-level stabilization. The multi-proxies indicate a wetland dynamic was mainly controlled by autogenic factors, relating to tidal channel migrations on the muddy tidal flats formed after the channel abandonment provide suitable conditions for expansion of vegetation surrounding, instead of allogenic process, associated to sea level and/or climate change. Probably, some influence of sea-level and climate changes on mangrove dynamics along in this valley of the Ceará Mirim river have been weakened by the intense tidal channels activities since middle Holoceno.
Acesso aberto (Open Access)
Os efeitos da subida do nível do mar sobre os manguezais do litoral sul da Bahia durante o Holoceno
(Universidade Federal do Pará, 2015-03-25) FONTES, Neuza Araújo; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
This work integrates the palinological, sedimentological and geomorphological data with radiocarbon dating, as well as δ13C and C/N from the sedimentary organic matter to identify the impact of changes in sea level and climate during the Holocene in Jucuruçu River’s mangroves, near the city of Prado, South Bahia. A sediment core with 4.5 m depth was sampled from a fluvial valley, 23 km away from the modern coastline. The base of sediment core presents age of 7450 cal yrs BP. The data reveal two important phases characterized by 1) an estuarine system with tidal flats colonized by mangroves. Its sedimentary organic matter is mainly sourced from estuarine algae during the early and middle Holocene; and 2) in the second phase, the mangroves shrank and herbaceous vegetation expanded. The δ13C and C/N values show an increase in contribution of terrestrial C3 plants. These phases identified in this study are in agreement with the relative sea-level (RSL) rise during the early and middle Holocene, and its subsequent fall during the late Holocene. In addition, the influence of weather patterns proposed for Holocene may be identified throughout the studied sediment core. Probably, changes in depositional environment and dominant vegetation at the study site were caused by the combined action of changes in RSL and fluvial discharge. According to the model proposed in this work, during the early and middle Holocene occurred a RSL rise that caused a marine incursion along the studied fluvial valley. The dry period occurred during the early and middle Holocene produced a decrease in the fluvial discharge and contributed to this marine transgression. However, during the late Holocene occurred a RSL fall and a wet period. It favored the marine regression and consequently, the mangroves migrated to tidal flats attached to the edge of lagoons near the modern coastline. The geomorphologic and vegetation evolution is in agreement with the mid-Holocene RSL maximum above present RSL and subsequent fall to the present time. Keywords: climate; Holocene; relative sea-level; South of Bahia; vegetation.
Acesso aberto (Open Access)
Os efeitos dos manguezais e das intervenções humanas na dinâmica sedimentar das praias de SalinópoliS, PA
(Universidade Federal do Pará, 2025-03-07) PÉREZ MARTINEZ, Julián David; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Salinópolis, on the coast of Pará, has become an important tourist hub, expanding its infrastructure along the coastal zone. This area is considered sensitive to sea-level rise. Therefore, identifying the area most vulnerable to coastal erosion is extremely important, especially due to the growth of coastal urban areas, which can interfere with sediment balance, intensifying erosion processes. This master's thesis aims to identify the effects of mangroves and coastal urban expansion on sediment balance along the beaches of Salinópolis. This study was carried out through a spatio-temporal analysis based on satellite (2003 – 2023) and drone data (2019-2024). The data revealed that the urban area expanded (627 ha), while the mangrove area fluctuated, increasing from 3630 ha to 3889 ha between 2003 and 2023. Erosion was identified along the beaches, particularly at Praia do Farol Velho (erosion = 432,625 m³, sedimentation = 217,259 m³). Praia do Atalaia (erosion = 115,415 m³, sedimentation = 462,630 m³) and the Maçarico/Corvina beaches (erosion = 640,389 m³, sedimentation = 801,670 m³) showed a trend of sediment accumulation. Erosion has predominantly occurred in the lower intertidal zone, while sedimentation has occurred in the supratidal zone and the upper intertidal zone. Residences, particularly in Farol Velho, may accentuate this process and Praia do Atalaia, which are currently located in the intertidal and supratidal zones in front of the mangroves. The walls built to protect these residences from waves and current action have also functioned as a barrier to retain sediments at the upper intertidal/supratidal transition. In much of Praia do Farol Velho, without these walls, there has been erosion in the intertidal zone, with a retreat of the coastline by about 100 meters between 2009 and 2023. However, the Maçarico/Corvina beaches have mangroves in front of the urban infrastructure, with sediment accumulation predominantly in the supratidal zone and the upper part of the intertidal zone. Human interventions on these beaches have not impacted the sedimentary dynamics until 2023. This beach provides a good example of how coastal infrastructure projects should be planned, using mangroves as protection against the action of waves and currents. However, the construction of beach access walkways in 2024 altered the hydrodynamic flow of a tidal channel, trapping tidal waters and creating muddy intertidal zones with porewater salinities close to 70 ‰. This process has already killed approximately 7 ha of mangrove. These data provide valuable insights to guide more efficient public and private investments, avoiding construction in high-risk areas or those that harm the mangroves, offering crucial information about coastal erosion and its impacts on urban infrastructure in the beaches of Salinópolis, especially in the face of sea-level rise.
Acesso aberto (Open Access)
Estabelecimento e expansão dos manguezais de Laguna-SC: efeito do aquecimento global ou resultado de processos sedimentares?
(Universidade Federal do Pará, 2018-03-19) SOARES, Jaine Freitas; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The integration of pollen, isotopes (δ13C, δ15N, C/N), sedimentary features, 14C and 210Pb dating from four sediment cores (LAG-3, LAG-4,LAG-5 e LAG-6). Sampled from a sandbar at Santo Antônio Lagoon, Laguna City, Santa Catarina, allowed the paleoenviromental reconstruction of the last 900 years BP. The dates reveal two facies associations along these cores: (A) Sandbar, represented by massive sand (facies Sm), and (B) tidal flat, represented by lenticular heterolithic bedding (Hl) and wavy heterolithic bedding (Hw). The deposits of sand bar was accumulated between >940 e ~431 cal years BP, probably under influence of a stable relative sea level (RSL) or rise of RSL during the last 1000 years. The pollen data preserved along the sandbar phase indicate a predominance of trees, shrubs herbs and some palms originating from vegetation units surrounding the lagoon. The relation δ13C (-24‰ - 15‰) and C/N (6-30) of this facies association reveals a strong contribution of organic matter from marine algae and terrestrial plants C3 and C4. During the accumulation of tidal flat deposits, occurred during the last 60 years, there was the establishment mainly of Spartina with some spaced Laguncularias shurbs. The relation δ13C (-24‰ - 16‰) and C/N (7-22) reveals an origin of sedimentary organic matter similar to the period of sandbar deposits. Based on this data and distribution gradient of Spartina and on mangrove’s trees genus along the Santa Catarina coast, is reasonable to propose that the recent colonization of Laguncularia at region of Laguna has been caused by gradual increase in minimum winter temperatures observed during last 50 years. Whether the climatic trend is the main force driving the expansion of Laguncularia trees to southern Brazil, the surface of the sandybars and tidal flats of the lagoon margin of southern Brazil, now largely occupied by Spartina, will be gradually colonized and/or replaced not only by Laguncularia, but also by Avicennia, followed during the next years, by Rhizophora.
Acesso aberto (Open Access)
Estudo comparativo dos índices de reflectância da vegetação de manguezal e várzea-de-maré do litoral paraense através de sensoriamento remoto e técnicas espectrofotométricas
(Universidade Federal do Pará, 2009-10-08) SILVA, Jadson Queiroz da; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The present work delimited the main littoral vegetations of the Pará State through the differences in the reflectance levels obtained by Landsat images and in situ by a spectrophotometer. This study indicated that the mangrove leaves present lower values of reflectance than others vegetations, mainly in the visible interval of the electromagnetic spectrum.This may be related to the strong absorption developed by the photosynthesis pigments of the mangrove trees. Among its leaves, the Avicennia presented higher reflectance values than Rhizophora. Besides, the reflectance of mangrove leaves changed between the studied areas, mainly the Rhizophora that in Curuçá presented higher values. This can be associated to the stress conditions found in the Bragança and Mosqueiro, since the environmental changes affects the spectral reflectance of leaves. In the case of the mangrove, adverse salinity conditions may hinder the plants development. The tidal water salinity in Mosqueiro presents low values. This factor allows a wider ecological competition between the mangrove species and others vegetations that together with the sediment type, may produce an increase in the stress to the mangrove. It may justify the low height of the trees, and the relatively high reflectance values. Thus, the relationship between the tree height and spectral values of the Rhizophora and Avicennia indicates an inverse relation. This may be attributed to the development of chlorophyll in the initial periods of vegetation growth that allows a elevated amount of energy reflected in the visible interval until the leaves reach its typical green color with relatively lower reflectance. Based on the reflectance data was possible to elaborate maps with the following vegetation units: mangrove, terra firme vegetation, tidal varzea, transition zones mangrove/varzea and herbaceous field.
Acesso aberto (Open Access)
Estudo dos manguezais degradados da costa oeste da Flórida durante os últimos 20 anos baseado em imagens de satélite e dados Lidar.
(Universidade Federal do Pará, 2024-05-31) CARDENAS RUIZ, Diana Paola; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The Gulf of Mexico presents one of the longest mangrove belts in southern Florida. This continuous mangrove strip has an approximate area of 2200 km2. Natural stressors such as hurricanes, storms, and other anthropogenic factors such as oil spills or pollution can trigger the dieback of the mangrove on the southwest coast of Florida. The dieback of the mangrove refers to the phenomenon where the mangrove forests experience a loss in the canopy that can lead to the decline or death of the trees. The effects of the dieback occasionally leave a scar of degradation in the mangrove forest. In the last century, with urban development in southwest Florida, the adverse effects of dieback seem to be gaining permanence. The present study identified the possible causes of the permanence of mangrove degradation associated with dieback over the last two decades. To identify these causes, the following methodology was used: a) classification of vegetation cover along the west coast of Florida, b) identification of dieback points in high-resolution satellite images, c) spatiotemporal analysis of dieback areas, and d) digital models of surface elevation and vegetation height. 86 dieback points (PD) were found grouped into 6 regions: Crawl Key, Key West, Marco Island, Pine Island, Charlotte, and Terra Ceia. 75% of the PD appeared between 2004 and 2007, coinciding with hurricane activity. In 2020, the total dieback area in southwest Florida was 119,69 ha. For the periods of 2014-2016 and 2009-2011, the areas of dieback recorded values of 116,47 and 127,89 ha, respectively, evidencing a dynamic of regeneration and degradation. The digital terrain models for Pine Island and Marco Island showed changes in the height of the tidal flat with variations between -2 to 45 cm. These variations may be linked to sedimentation processes, dissolution of carbonates in the tidal flat, or peat collapse associated with the mangrove soil. The mangrove trees reduced their height after the passage of hurricanes, particularly in the PD. Even though the PD showed regeneration, this process was slow, leaving a scar exposed to the tidal flat. This study revealed a direct relationship between hurricanes and the appearance of dieback.
Acesso aberto (Open Access)
Forçantes naturais e antrópicas sobre os manguezais de Salinópolis - Pará.
(Universidade Federal do Pará, 2023-10-05) SERRÃO, Izabelle Caroline Goes; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Mangroves stand out for their resilience and important role in environmental balance. Still, globally, mangrove areas have suffered losses of around 35% between 1980 and 2000, caused by changes in salinity gradients, wave and current action, relative sea level changes and urban expansion. The Brazilian coastal zone is distributed in 395 municipalities, among them Salinópolis, located on the Paraense coast, with a wide occurrence of mangroves that have also presented degradation. A spatial-temporal analysis based on Landsat, Quickbird and drone images was used to investigate the main forces driving the natural and anthropogenic mangrove dynamics in Salinópolis. These data allowed for individualizing the vegetation and geomorphology units between 2009 and 2019. An aerial photogrammetric survey based on drone data between Feb / 2019 and Sep / 2019 enabled the identification of changes in the topography of the tidal flats and cliffs. These data indicated an increase in mangrove areas of around 104 ha between 2009 and 2017 in the study area. However, there was a loss of this forest of approximately 52.3 ha between 2017 and 2019, when there was an increase in unregulated urbanization of coastal areas. The area comprising the so-called “Praia do Maçarico” presented losses of mangroves of around 15.2 and 28.8 ha in 2010 - 2017 and 2017 – 2019 periods, respectively. In the Atalaia area, there was a loss of about 23.5 ha between 2017 and 2019. The expansion of the mangroves occurred over higher coastal plains (~2.8 m above mean sea level), distant from human intervention, and probably caused by a relative sea level rise. However, the retraction of mangrove areas occurred mainly due to unregulated urban expansion over the higher tidal flats. In addition, the spatio-temporal analysis indicated erosion on the Maçarico cliff, with a retreat from the top of the cliff of up to 20 m between Feb / 2019 and Sep / 2019. In the year 2022 there were urban infrastructure works in this area with new sediment input to try to stabilize the cliff. It should be highlighted that the eroded material from the cliff caused an increase of up to 1 m on the tidal flat near the base of the cliff, where some mangroves occur, causing the burial of their roots and the death of these trees. The data showed that interventions on the coast with mangroves have caused losses in these forest areas that tend to migrate to topographically higher sectors due to the relative sea level rise, characterizing a conflict between the current expansion trend of this ecosystem and anthropogenic interventions on the coast. The coast of Salinópolis, with a vulnerability degree between very high (4,6) and high (3,6) requires the inclusion of projects with a quali-quantitative analysis of the interaction of the main coastal characteristics (e.g. geomorphology, topographic gradients of the coast, tidal range, vegetation, angle and speed of currents and surface runoff) before implementing works on the Salinópolis coast.
Acesso aberto (Open Access)
Impacto do último máximo glacial pleistocênico na vegetação de Humaitá, Amazonas
(Universidade Federal do Pará, 2016-09-27) LIMA JÚNIOR, Walmir de Jesus Sousa; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The amount of pollen data recovered from the sedimentary record of western Amazonia is still far from adequate to fully approach climate changes in this region over the Last Glacial period. In the present work, vegetation dynamics of western Amazonia during the past 42000 cal yr BP is analyzed in the context of previous and new pollen data. Two sediment cores were sampled from fluvial terraces of the Madeira River, a major southern Amazonian tributary. The study sites are covered by tropical rainforest vegetation. The sedimentary deposits consist mostly of massive sand, heterolithic bedded sand/mud as well as either laminated or massive mud. These deposits were formed under reducing and low energy conditions in an abandoned fluvial channel/lake environment. Such depositional setting favored the preservation of a pollen community suggestive of arboreous taxa common to the modern Amazonian rainforest mixed with herbaceous vegetation. Pollen analysis also recorded a significant proportion of cold-adapted Andean tree species, represented by Alnus (0-20%), Hedyosmum (1-15%), Podocarpus (0-5%), Illex (1-11%) and Weinmannia (0-1%) at least between > 42,000 cal yr BP and 10,300 cal yr BP. During the Holocene, only pollen representative of herbs and modern Amazon vegetation persisted. This new pollen record confirm previous multiple proxies analyzes of two sediment cores sampled also from Humaitá region, where a significant plant population, at present restricted to Andean areas located at altitudes higher than 2000 - 3000 m, in areas of the Amazonia lowland toward the onset, and probably, during the Last Glacial Maximum.
Acesso aberto (Open Access)
Impactos das mudanças do nível do mar nos manguezais do sudeste do brasil durante o holoceno e antropoceno usando uma abordagem multi-proxy
(Universidade Federal do Pará, 2020-12-28) BOZI, Bettina Silva; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Mangroves are intertidal forests, susceptible to changes in tidal flooding frequency. Then, its dynamics along the topographic gradients of a coastal plain may be used as an indicator of sea-level changes. This work aims to identify the mangrove dynamics during the Holocene and Anthropocene and infer relative sea-level (RSL) changes based on satellite/drone images and pollen, isotopes (δ13C, δ15N), elemental (C\N), X-ray fluorescence (XRF), and sedimentary data, as well as C-14 dating along three cores sampled along a mangrove and a transition mangrove/herbaceous zone following a topographical gradient of a coastal plain in the southeastern Brazilian coast. These multi-proxy data indicated a change from a flat occupied by herbs, palms, tree/shrubs to a lagoon surrounded by mangroves with an increase of sedimentary organic matter sourced from estuarine waters between ~6300 and ~4650 cal yr BP. The RSL rise caused a landward mangrove migration during the early-middle Holocene, widely recorded along the Brazilian coast. The RSL fall converted that lagoon with mangroves into a flat occupied by herbs, palms, and trees/shrubs during the middle-late Holocene. The last thousand years were characterized by a significant decrease in the mangrove pollen occurrence on highest tidal flats occupied by modern mangroves between 390 cal yr BP (1560 AD) and 77 cal yr BP (1873 AD), probably caused by a RSL fall associated with the Little Ice Age (LIA). The core G-4, sampled from the lowest tidal flats and mainly occupied by Rhizophora, revealed an increased trend in Rhizophora pollen percentage since 77 cal yr BP (1873 AD). However, cores sampled from the highest mangrove tidal flats, in the ecotone mangrove/ herbaceous vegetation, indicated an increase of pollen percentages of Rhizophora, Avicennia, and Laguncularia, suggesting a mangrove migration into the highest tidal flats previously occupied by herbs, palms, and trees/shrubs since 1958 (core G-3) and 1955 AD (core RBN-2). These trends must be related to the increase in estuarine influence by a RSL rise since the end of the Little Ice Age and intensified during the last decades.
Acesso aberto (Open Access)
Influências das flutuações do nível do mar e mudanças climáticas na dinâmica dos manguezais do litoral Sul de Santa Catarina durante o Holoceno.
(Universidade Federal do Pará, 2019-06-10) ROCHA, Denise Oliveira Souza; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The objective of this work was to identify the main factors controlling the mangrove dynamics in the southern limit of this ecosystem in the South American continent, in the Laguna - Santa Catarina region. This study was based on the integration of sedimentary facies, isotopes (δ13C and δ15N), elementary organic matter (C/N), and pollen data with 14C dates obtained from core RP4 (S 28°29'18.41 " and W 48°50'47.01) with 2 meters depth sampled from a tidal flat near the Santo Antônio Lagoon, 8 km away from the present coastline, west of the town of Laguna. Three facies associations were identified: facies Herbaceous Floodplain, Fluvial channel and tidal flat with Spartina. The Herbaceous Floodplain is characterized by massive mud with benthic tubes, fragments of shells and roots. The facies association of Fluvial Channel presents sand with crossed stratification and massive. The top of the studied core presents the facies association Tidal Flat with Spartina represented by mud silt with roots fragments. The integration of these data suggests an increase in the relative sea-level during the Holocene, when the low river courses were flooded and it favored the formation of lagoon systems that are well represented along the Santa Catarina littoral, especially in the study area. A gradual Holocene marine transgression would have favored the mangrove expansion on tidal flat flats. Considering the physicochemical and hydrodynamic, probably the sedimentary environment was favorable for the establishment and expansion of mangroves over the last centuries, when occurs a strong contribution of organic matter sourced from estuary in the study site and development of tidal flats. The absence of mangrove pollen grains along the studied core (<9000 years AP) indicates, besides the low relative sea-level stand, another factor must have prevented mangrove establishment in the study area. The presence of Laguncularia and Avicennia shrubs/trees nowadays in the study area and the absence of mangrove pollen grains in the studied stratigraphic profile indicates that these genus were established only during the last decades. Probably, the temperatures during the Holocene winters on the modern austral limit of the South American mangroves prevented the mangrove establishment during that period the sediments of the core RP4 were accumulated. Probably, the increase in minimum winter temperatures during the last decades has allowed the expansion of the southern limit of the southern American mangroves into temperate zones.
Acesso aberto (Open Access)
Mudanças da vegetação na ilha de Marajó durante o Holoceno Superior
(Universidade Federal do Pará, 2009-06-15) RODRIGUES, Thanan Walesza Pequeno; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The vegetation dynamic around the Lake Arari – Marajo Island during the Late Holocene was studied. This research is based on pollen analysis, reflectance data, C/N relationship and AMS radiocarbon date of three sediment cores. The sampling sites are located in Santa Cruz do Arari, 6 meters height. A sediment core (65 cm) was sampled from the bottom of Lake Arari and the others (40 and 30 cm) were taken of herbaceous plain inside the lake drainage area. Probably, the herbaceous plain that dominates the eastern part of the Marajó Island began its development about 3800 cal years AP. Between 3800 and 3000 cal years A.P., the pollens diagram indicated a few mangrove pollens that suggests the final stage of an old expansion of a mangrove area. The C/N and _13C of organic matter accumulated during this period showed a marine influence. The low concentration of pollens between 3000 and 2000 cal years BP, probably due to change in flow energy, hinders the interpretation of the predominant vegetation type, but the C/N and _13C indicates a strong contribution of marine organic matter accumulated in studied sediments. This period of pollen absence may indicate an episode of difficult vegetation development due to, for example, the increase in marine influence. The last 2000 cal years A.P presented polinic content compatible with an herbaceous plain with a contribution trend of continental organic matter. The last 5 centimeters of the pollen diagram presented a predominance of Poaceae and Cyperaceae families which reflect the current predominant vegetation in the study area. The pollen diagram (PH1 and PH2) of the herbaceous plain, which colonizes the drainage basin of Lake Arari, describes a smaller spatial representation of vegetation, since they demonstrate only a constant predominance of Cyperaceae and Poaceae pollen that represents the main families of local sampling. The low depth of these profiles allowed to register the presence of herbs vegetation only from 460 and 590 cal years BP, respectively. Alternation between typical vegetation of freshwater and brackish water probably indicate changes in the porewater salinity that must be related to changes in freshwater discharge of rivers in the region and/or changes in sea level.
Acesso aberto (Open Access)
Mudanças na vegetação do litoral Leste da ilha de Marajó durante o Holoceno Superior
(Universidade Federal do Pará, 2010-07-13) FRANÇA, Marlon Carlos; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The integration of palynological, chemical, isotopic and stratigraphic data with radiocarbon dating, obtained from two cores, allowed the identification of two periods during the last millennium in the coastal plain of the Soure in Marajó Island. The first period, from 1275- 1165 cal yr BP to 760-480 cal years BP, indicates the expansion of herbaceous vegetation, characterized by the presence of the Cyperaceae, Poaceae and Fabaceae. During this period it was recorded the largest continental influence through the relationship δ 13C (-30 and -25 ‰) and C/N ratio (20-40). During the last 500 years the mangrove vegetation has expanded, being represented by the Rhizophora and Avicennia pollens. The C/N ratio decreased to values <20, indicating an increase in the contribution of aquatic organic matter (phytoplankton). This aquatic influence was observed on the lithology and sediment structure, indicated by the predominance of silt-clay sediments with parallel-laminated and some millimetrics lens of clay, which may have their origin associated to tidal flat. This trend during the last centuries on the Marajó Island may be associated to the eustatic sea-level rise, changes in the Amazon rivers discharge due to climatic changes or tectonic effects.
Acesso aberto (Open Access)
Processos autocíclicos e alocíclicos afetando os registros da paleoflora da foz do rio Jucuruçu, litoral sul da Bahia, durante os últimos 1000 anos
(Universidade Federal do Pará, 2016-06-07) MORAES, Caio Alves de; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The vegetation holocenic history along the southern Bahia littoral is characterized by establishment, expansion and contraction phases of mangroves. This vegetation dynamics is mainly associated to climate change and to relative sea level oscillations. However, punctually and in a smaller time scales, for example, during the last 1000 years, other processes inherent to the sedimentary dynamics of depositional environment, termed autocyclic processes, are controlling the pollen assembly along stratigraphic profiles formed by active channels followed by its abandonment. Based on sedimentary features, pollen grains, isotopes (δ13C, δ15N C/N) and radiocarbon dating of sedimentary organic matter from two cores (PR-11 and PR-12) sampled from an abandoned meander and a tidal flat in the mouth of the Jucuruçu river, is proposed a model for evolution of a tidal channel surrounded by wetlands. The core PR-11, with 1.48 meters depth, was sampled from a mangrove zone, with a maximum age of 678 cal yr BP. The PR-12 was collected from a várzea vegetation, approximately 2.7 km from the current shoreline with 1.92 meters depth and, maximum age of 680 cal yr BP. The data present two facies associations: (A) Tidal channel, represented by massive sand deposits (facies Sm); cross-stratified sand (Scs) and facies flaser heterolithic bedding (Hf) and (B) Tidal plain, represented by facies wavy heterolithic bedding (Hw), lenticular heterolithic bedding (Hl), massive mud (Mm) and massive sand (Sm). The pollen data reveals that the facies association (A) presents absence of pollen grains of mangroves. It may have been caused be an intense activity of sediments reworking of channel margins and sediment deposition with pollen grains sourced from vegetation units not necessarily from the study site. In the top of the studied succession, in association facies (B), is possible to identify the establishment and expansion of mangroves in the newly formed tidal flat (PR-11) or lake (PR-12). Regarding the core PR-12, it is marked by channel abandonment. The reduced interaction between fluvial discharge and tidal waves have caused the infilling of mud sediments, and a highest potential for organic matter preservation. It provided conditions for the mangrove development and pollen preservation. In the case of PR-11, the tidal channel migration have caused the development of a tidal flat, which have favored the mangrove expansion. These depositional environments, favorable to the formation of mangroves, can be partially or completely modified by the natural dynamics of tidal channels and estuarine channels, which are under the influence of changes of sedimentary fluvial contribution on the shore and littoral drift processes along the coast associated with tides, waves and currents. These results were compared with some data from one core sampled 23 km upstream of Jucuruçu River that also indicated the presence of mangroves on tidal flat with estuarine organic matter during the early and middle Holocene, followed by herbaceous vegetation on a fluvial plain with organic matter sourced from freshwater during the late Holocene (Fontes, 2015). In this case, the sea level fluctuations and climate change were the main driving forces controlling the wetlands dynamics at the mouth of this river during the Holocene, characterizing an allocyclic process. However, considering the stratigraphic sequences of the analyzed cores in this master's work (PR-11 and PR-12), such sedimentary sequences associated with changes in vegetation and sources of organic matter are related to the infilling processes of coastal depressions, mainly marked by active channels, abandoned channels and tidal flats. Therefore, in a small time scale of coastal vegetation changes are not necessarily directly associated with sea-level and climate change (allocyclic processes). On the other hand, processes associated to the sedimentary dynamics of the depositional environment (autocyclic processes) must have controlled pollen assembly along the studied stratigraphic profiles.
Acesso aberto (Open Access)
A resiliênca dos manguezais do estuário do rio Ceará Mirim-RN às intervenções humanas.
(Universidade Federal do Pará, 2024-09-23) AQUINO, Ronaldo Darlan Gaspar; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Mangroves are recognized for being extremely sensitive to changes in the physical and chemical environment and are widely used as indicators of changes in climate, sea level, and human interference. The study area comprises the mouth of the Ceará-Mirim/RN River, located on the coast of the state of Rio Grande do Norte (RN), in northeastern Brazil. This area has a history of mangrove deforestation for implementing shrimp farming. This study aims to analyze the mangrove dynamics from 1985 to 2020. The research uses orbital remote sensing and drone images to develop a spatial-temporal analysis. The data indicates that despite the expansion of aquaculture activity from 46 ha to 183.47 ha considering active and inactive tanks, there was an increase in mangrove areas from 351 to 489 ha. Over the 35 years, aquaculture activity has mainly occupied flooded fields and apicum regions and occasionally some areas have been converted from mangrove areas. However, the expansion in mangrove areas was mostly due to the abandonment of aquaculture, which before 1985 suppressed mangroves to construct ponds. Despite severe anthropogenic interference in this delicate ecosystem, these forests have shown great resilience by recolonizing their tidal flats.
Acesso aberto (Open Access)
A resposta dos manguezais de um estuário do sul da Bahia sob influência das mudanças do clima, flutuações do nível do mar e dinâmica dos canais durante o Holoceno
(Universidade Federal do Pará, 2017-06-09) OLIVEIRA, Nêdra Nunes; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
This work integrates palynology, sedimentology, geomorphology and radiocarbon dating, as well as δ13C, δ15N, and C/N from sedimentary organic matter obtained by the description of a core (5,20 m deep) sampled ~8 km from current coastline, 2m above sealevel at Jucuruçu River valley, near the city of Prado, south coast Bahia-Brazil. Based on this core and previously published works, the effects of climate and Relative Sea-level (RSL) changes on Jucuruçu’s mangroves during the Holocene were detailed. Along the studied core two phases were identified and correlated with others sediment cores. The first phase occurred in part of the middle Holocene (7200 - <6950 cal yr BP), developed on a tidal flat colonized by mangrove. It presents a transition from C3 terrestrial plants to marine organic matter upward this phase. On second phase, a fluvial plain developed followed by a mangrove shrinkage and, herbaceous and ferns expansion. At this phase, the biogeochemical data revealed an increased trend to organic matter sourced from freshwater. The integration of palaeoenvironmental data reveals an important RSL rise, which caused a marine incursion inside this river valley and allowed mangroves establishment under a strong estuarine influence, this incursion reached ~23 km upstream during the middle Holocene. The RSL fall at the middle and late Holocene caused a gradual mangrove replacement by mainly herbaceous vegetation associated to freshwater plankton predominance up river, while mangroves and marine algae migrated to the Jucuruçu river mouth. A decrease fluvial discharge during early and middle Holocene most likely favored this mangrove migration pattern and estuarine/marine organic matter spreading upstream. In contrast, probably the mangrove establishment at river mouth up present days was favored by an increase fluvial discharge at late Holocene. Noteworthy is the fact that tidal channels dynamics have controlled mangrove distribution last thousand years. Therefore, this study allowed to identify and to describe the effects of allogenic (caused by climate and RSL change) and autogenic processes (conducted, for example, by channels dynamic).