An 11,000-year record of depositional environmental change based upon particulate organic matter and stable isotopes (C and N) in a lake sediment in southeastern Brazil

The aim of this paper is to reconstruct an 11,000-year history of depositional environmental change in southeastern Brazil, based upon the integration of particulate organic matter and stable isotope (C and N) data from a 136-cm sediment core from Lake Canto Grande. These proxies are used to explore the evolution of terrestrial and marine influence on the lake. Isotopic (δ13C: -7.8‰ to -31.9‰; δ15N: -0.07‰ to 4.9‰) and elemental (total organic carbon - TOC: 0.58% to 37.19%; total nitrogen - TN: 0.08% to 1.73%; C/N: 0.3 to 54.7) values recorded in Lake Canto Grande suggest that the sedimentary organic matter was derived from mostly C3 land plants and freshwater phytoplankton. Particulate organic matter and cluster analyses distinguished four associations characterized by the predominance of amorphous organic matter, followed by phytoclasts and palynomorphs. These results indicate two different phases of lake evolution. The first phase (136 - 65 cm; ~10,943 cal yr. B.P. to ~8,529 cal yr. B.P.) is recorded by sand layers interbedded with mud, which contain amorphous organic matter (AOM, 45-59%) and phytoclasts (opaques - OP: 6-18%; non-opaques – NOP: 17-23%) which indicate a floodplain area. The second phase (65 – 0 cm; ~8,529 cal yr. B.P. to ~662 cal yr. B.P.) comprises mud, AOM (68-86%) and palynomorphs (PAL, 8-16%) related to lake establishment comparable to modern conditions. Thus, characterizing particulate organic matter, in combination with stable isotopes, proved to be invaluable proxies for lacustrine paleoenvironmental change through the Holocene

Fitólitos como indicadores de mudanças ambientais durante o Holoceno na costa norte do estado do Espírito Santo (Brasil)

Um testemunho de 12 metros de profundidade e idade de ~47260 anos cal AP na sua base foi coletado na planície deltaica do litoral norte do estado do Espírito Santo. Esse trabalho teve como principal objetivo a caracterização do conjunto de fitólitos, auxiliado pelas fácies sedimentares, dados isotópicos (C e N) e datações 14C para reconstituir o paleoambiente. Os valores de carbono orgânico total - COT (0,16% a 3,28%), nitrogênio total - N total (0,01% a 0,09%), δ13C (-4,25‰ a -28,06‰), δ15N (-6,19‰ a 15,75‰) e da razão C/N (7,8 a 99) mostraram em linhas gerais que a matéria orgânica sedimentar foi originada a partir de fitoplâncton, e da mistura de plantas C3 e C4. A análise de fitólitos foi efetuada ao longo de 1,50 metros do perfil, e a partir dos agrupamentos por similaridade foi possível o estabelecimento de três intervalos que refletem mudanças na vegetação e provavelmente no clima a partir de ~7589 anos cal AP. No intervalo 1 (~7589 anos cal AP a ~5441 anos AP – idade interpolada), a assembléia fitolítica e os índices estatísticos de fitólitos calculados refletem uma vegetação composta pela mistura de árvores e gramíneas C3 e C4, semelhante e/ou comparável à vegetação de restinga, provavelmente sob clima quente e úmido. A análise de fitólitos do intervalo 2 (~5441 anos AP – idade interpolada a ~143 anos cal AP) sugeriu a presença de uma vegetação em mosaico provavelmente constituída por diferentes formações da restinga, sob influência de clima quente e sazonal, com períodos de estresse hídrico. A diminuição da densidade arbórea, assinalada pelo índice D/P, e a formação da vegetação semelhante à atual, herbácea e com sinais de antropização, ocorreu nos últimos ~200 anos (Intervalo 3), sob clima quente e úmido. Os dados de fitólitos são inéditos para a costa do Espírito Santo e mostram o potencial destes bioindicadores em estudos de reconstituição paleoambiental

White sand vegetation in an Amazonian lowland under the perspective of a young geological history

What controls the formation of patchy substrates of white sand vegetation in the Amazonian lowlands is still unclear. This research integrated the geological history and plant inventories of a white sand vegetation patch confined to one large fan-shaped sandy substrate of northern Amazonia, which is related to a megafan environment. We examined floristic patterns to determine whether abundant species are more often generalists than the rarer one, by comparing the megafan environments and older basement rocks. We also investigated the pattern of species accumulation as a function of increasing sampling effort. All plant groups recorded a high proportion of generalist species on the megafan sediments compared to older basement rocks. The vegetation structure is controlled by topographic gradients resulting from the smooth slope of the megafan morphology and microreliefs imposed by various megafan subenvironments. Late Pleistocene-Holocene environmental disturbances caused by megafan sedimentary processes controlled the distribution of white sand vegetation over a large area of the Amazonian lowlands, and may have also been an important factor in species diversification during this period. The integration of geological and biological data may shed new light on the existence of many patches of white sand vegetation from the plains of northern Amazonia. © 2019, Academia Brasileira de Ciencias. All rights reserved

Cold and humid Atlantic forest during the late glacial, northern Espírito Santo state, southeastern Brazil

The Atlantic Rainforest, covering the area from the northern Espirito Santo to Southern Bahia states, has been considered as a stable forest during Pleistocene Glacial times. Despite the modelling and phylogenetic studies, this hypothesis has never been tested with empirical paleo-data and vegetation reconstruction. By using palynology, radiocarbon dating, carbon and nitrogen elemental and isotope of organic matter, we reconstructed the vegetation dynamics and inferred climatic changes since Late Pleistocene in the centre of this global biodiversity hotspot. Our results show that the forest biome was resilient to Last Glacial Maximum - LGM conditions, but floristics has changed when compared to nowadays. Since late glacial, the dense forest changed from cold to warm specimens. Major vegetation changes also occurred during early and mid-Holocene less humid conditions, with an opening of the forest, suggesting that future drought may have negative impacts and highlighting the importance of forest conservation to keep the Atlantic Rainforest biodiversity

Past and current mangrove dynamics on the Bragança Peninsula, Northern Brazil

A wide mangrove belt of about 350 km occurs along the coast between the Amazon estuary and the Gurupi River (North Brazil). The main objective of this work was to identify and analyze the present effect of inundation frequency on system structure and of past changes in relative sea-level and climate, using tools such as palynology, radiocarbon dating, remote sensing and the Geographic Information Systems (GIS).The combination of topography and tidal regime data allowed, together with GIS tools, to determine frequencies and the extent of flooded areas. This allowed the association between the topographical characteristics of the peninsula and the main vegetation types. The current mangrove dynamics, specially gain and lost of vegetation coverage at the coastline, suggest a relative sea-level (RSL) rise.The examined sediment cores from Bragança recorded at least two transgressive events, which defined the spatial distribution of the mangroves on that area during the Holocene. The study area was flooded by a rapidly rising sea-level during the postglacial. The stabilization of sea-level near modern level was found around 5100 14C yr BP. Probably, between 1800 and 1400 14C yr BP occurred a maximum decrease of about 1 m below the modern RSL, following a gradual RSL rise until 1000 14C yr BP, when the RSL was re-established close to the current RSL. The integration of stratigraphic and palynological data indicate two dry periods with relatively low inundation frequency during the last 1000 years. The first event probably extended over a period of 500 years and took place between 860 and 370 14C yr BP. The second one started 200 14C yr BP and probably finished about 100 years ago. These two dry events occurred during the so called Little Ice Age period, characterized by dry periods in South America and glacier advances

Nutrientes e outros fatores relacionados à produção primária na águas do manguezal de Bragança-PA

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Pollen data obtained along the core MD-3 in florida mangrove diebacks

Sediments (1-cm3) were subsampled at 2 cm and 5 cm intervals along the 0 - 32 cm and 32 – 59 cm depth, respectively. Pollen and spore classification, with at least 300 pollen grains identified for each sample, was based on reference collections of the LSU Global Paleoecology Laboratory and Laboratory of Coastal Dynamics – UFPA, 14C Laboratory of the Center for Nuclear Energy in Agriculture (CENA/USP)

Ground Control Points of tidal flats at Port Fourchon-Louisiana, USA

Ground Control Points (GCPs) of tidal flats at Port Fourchon-Louisiana-USA with longitude, latitude, elevation and differences (m) between latitudes longitudes and elevation obtained in Oct/2017, Mar/2018, Nov/2018, Nov/2019, Nov/2021 and Jul/2022 by aerophotogrammetry from a DJI Phantom 4 Advanced and RTK drone and those obtained in the field by a Trimble Catalyst receiver, supported by a differential Global Navigation Satellite System with a millimetric correction (precision ± 2 cm) and an electronic Self Leveling Horizontal Rotary Laser (precision ± 2 cm). These data were used to evaluate the digital elevation model (DEM) acquired by photogrammetry. The vertical differences between GCPs and the DEM were evaluated by equation Zdif = ZDEM - Zgrd, where Zdif = the vertical differences, ZDEM = the Z value of the DEM, and Zgrd = the Z value of the GCPs

Vergangene und heutige Dynamik von Mangroven auf der Braganca Halbinsel, Nordbrasilien

A wide mangrove belt of about 350 km occurs along the coast between the Amazon estuary and the Gurupi River (North Brazil). The main objective of this work was to identify and analyze the present effect of inundation frequency on system structure and of past changes in relative sea-level and climate, using tools such as palynology, radiocarbon dating, remote sensing and the Geographic Information Systems (GIS).The combination of topography and tidal regime data allowed, together with GIS tools, to determine frequencies and the extent of flooded areas. This allowed the association between the topographical characteristics of the peninsula and the main vegetation types. The current mangrove dynamics, specially gain and lost of vegetation coverage at the coastline, suggest a relative sea-level (RSL) rise.The examined sediment cores from Bragança recorded at least two transgressive events, which defined the spatial distribution of the mangroves on that area during the Holocene. The study area was flooded by a rapidly rising sea-level during the postglacial. The stabilization of sea-level near modern level was found around 5100 14C yr BP. Probably, between 1800 and 1400 14C yr BP occurred a maximum decrease of about 1 m below the modern RSL, following a gradual RSL rise until 1000 14C yr BP, when the RSL was re-established close to the current RSL. The integration of stratigraphic and palynological data indicate two dry periods with relatively low inundation frequency during the last 1000 years. The first event probably extended over a period of 500 years and took place between 860 and 370 14C yr BP. The second one started 200 14C yr BP and probably finished about 100 years ago. These two dry events occurred during the so called Little Ice Age period, characterized by dry periods in South America and glacier advances