Diversity of Microbiomes Across a 13,000-Year-Old Amazon Sediment.

The microbiome is fundamental for understanding bacterial activities in sediments. However, only a limited number of studies have addressed the microbial diversity of Amazonian sediments. Here, we studied the microbiome of sediments from a 13,000-year BP core retrieved in a floodplain lake in Amazonia using metagenomics and biogeochemistry. Our aim was to evaluate the possible environmental influence over a river to a lake transition using a core sample. To this end, we sampled a core in the Airo Lake, a floodplain lake in the Negro River basin. The Negro River is the largest tributary of the Amazon River. The obtained core was divided into three strata: (i) surface, almost complete separation of the Airo Lake from the Negro River when the environment becomes more lentic with greater deposition of organic matter (black-colored sediment); (ii) transitional environment (reddish brown); and (iii) deep, environment with a tendency for greater past influence of the Negro River (brown color). The deepest sample possibly had the greatest influence of the Negro River as it represented the bottom of this river in the past, while the surface sample is the current Airo Lake bottom. In total, six metagenomes were obtained from the three different depth strata (total number of reads: 10.560.701; sequence length: 538 ± 24, mean ± standard deviation). The older (deeper) sediment strata contained a higher abundance of Burkholderia, Chitinophaga, Mucilaginibacter, and Geobacter, which represented ~ 25% of the metagenomic sequences. On the other hand, the more recent sediment strata had mainly Thermococcus, Termophilum, Sulfolobus, Archaeoglobus, and Methanosarcina (in total 11% of the metagenomic sequences). The sequence data were binned into metagenome-assembled genomes (MAGs). The majority of the obtained MAGs (n = 16) corresponded to unknown taxa, suggesting they may belong to new species. The older strata sediment microbiome was enriched with sulfur cycle genes, TCA cycle, YgfZ, and ATP-dependent proteolysis in bacteria. Meanwhile, serine-glyoxylate cycle, stress response genes, bacterial cell division, cell division-ribosomal stress protein cluster, and oxidative stress increased in the younger strata. Metal resistance and antimicrobial resistance genes were found across the entire core, including genes coding for fluoroquinolones, polymyxin, vancomycin, and multidrug resistance transporters. These findings depict the possible microbial diversity during the depositional past events and provided clues of the past microbial metabolism throughout time.

New bacterial and archaeal lineages discovered in organic rich sediments of a large tropical Bay.

The nutrient and oxygen gradient present in marine sediments promotes high levels of microbial diversity. We applied metagenomics and biogeochemical tools to analyze microbial communities in different sediment depths (0-4 m below sea floor, mbsf) from Guanabara Bay, Brazil, a brackish tropical ecosystem with a history of massive anthropogenic impacts, and a largely unknown sediment microbial diversity. Methanogens (e.g. Methanosarcinales, Methanomicrobiales) were more abundant at 1 mbsf, while sulphate-reducing microbes (Desulfurococcales, Thermoprotales, and Sulfolobales) were more abundant at deeper layers (4 mbsf; corresponding to 3 K Radiocarbon years before present, Holocene Epoch). Taxonomic analyzes and functional gene identification associated with anaerobic methane oxidation (e.g. monomethylamine methyltransferase (mtmB), trimethylamine methyltransferase (mttB) and CO dehydrogenase/acetyl-CoA synthase delta subunit) and sulfate reduction indicated the dominance of Campylobacteria (Sulfurimonas) at deeper sediment layers. Gene sequences related to assimilation of inorganic sulfur increased with depth, while organic sulfur related sequences decrease, accompanying the clear reduction in the concentration of sulfur, organic carbon and chla torwards deeper layers. Analyzes of metagenome assembled genomes also led to the discovery of a novel order within the phylum Acidobacteriota, named Guanabacteria. This novel order had several in silico phenotyping features that differentiate it from closely related phylogenetic neighbors (e.g. Acidobacteria, Aminicenantes, and Thermoanaerobaculum), including several genes (carbon monoxide dehydrogenase, CO dehydrogenase/CO-methylating acetyl-CoA synthase complex subunit beta, heterodisulfide reductase, sulfite exporter TauE/SafE family protein, sulfurtransferase) that relevant for the S and C cycles. Furthermore, the recovered Bathyarchaeota genome SS9 illustrates the methanogenic potential in deeper sediment layer.

Interdisciplinary paleovegetation study in the Fernando de Noronha Island (Pernambuco State), northeastern Brazil

The aim of this research was to reconstruct vegetation changes (with climate inferences) that occurred during the Holocene in the Fernando de Noronha Island, Pernambuco State, northeastern Brazil. The research approach included the use of geochemical (mineralogy, elemental), carbon isotopes (δ13C, 14C) and pollen analyses in soil organic matter (SOM) and sediments collected in Lagoa da Viração and Manguezal do Sueste. The carbon isotopes data of SOM indicated that there was no significant vegetation changes during the last 7400 BP, suggesting that the climate was not the determinant factor for the vegetation dynamics. The pollen analysis of the sediment of a core collected in the Lagoa da Viração showed the absence of Quaternary material in the period between 720 BP and 90 BP. The mineralogical analysis of deeper layer showed the presence of diopside indicating this material was developed "in situ". Only in the shallow part of the core were found pollen of similar plant species of the modern vegetation. The geochemistry and isotope results, in association with the sediment type and pollen analyses of sediment samples of Manguezal do Sueste, indicated variations in the vegetation and in its location since the middle Holocene. Such variations can be associated with climatic events and sea level oscillations and also with anthropogenic events considering the last five hundred years.

Esta pesquisa teve o objetivo de reconstruir trocas de vegetação (com referências climáticas) que ocorreram durante o Holoceno na ilha de Fernando de Noronha, Estado de Pernambuco, nordeste do Brasil. Para o desenvolvimento da pesquisa utilizou-se de análises geoquímicas (minerais, elementar), isótopos do carbono (δ13C, 14C) e análises polínicas em solos e sedimentos coletados na Lagoa da Viração e no manguezal do Sueste. Os isótopos do carbono dos solos indicaram que não houve trocas significativas de vegetação durante os últimos 7400 anos AP, sugerindo que o clima não foi um fator determinante para a dinâmica da vegetação. A análise polínica dos sedimentos da Lagoa da Viração mostrou ausência de elementos quaternários no período entre 720 AP e 90 AP. A análise mineralógica das camadas mais profundas mostrou a presença de diopsídeo, indicando que este material foi desenvolvido"in situ". Somente na parte superficial do testemunho foram encontrados palinomorfos de plantas similares à vegetação moderna. Os resultados geoquímicos e isotópicos, em associação com o tipo de sedimento e as análises polínicas das amostras de sedimento do Manguezal do Sueste, indicaram variações na vegetação e na sua localização desde o Holoceno médio. Tais variações podem estar associadas a eventos climáticos e oscilações do nível do mar e também a eventos antrópicos considerando os últimos quinhentos anos.

Interdisciplinary paleovegetation study in the Fernando de Noronha Island (Pernambuco State), northeastern Brazil.

The aim of this research was to reconstruct vegetation changes (with climate inferences) that occurred during the Holocene in the Fernando de Noronha Island, Pernambuco State, northeastern Brazil. The research approach included the use of geochemical (mineralogy, elemental), carbon isotopes (delta13C, 14C) and pollen analyses in soil organic matter (SOM) and sediments collected in Lagoa da Viração and Manguezal do Sueste. The carbon isotopes data of SOM indicated that there was no significant vegetation changes during the last 7400 BP, suggesting that the climate was not the determinant factor for the vegetation dynamics. The pollen analysis of the sediment of a core collected in the Lagoa da Viração showed the absence of Quaternary material in the period between 720 BP and 90 BP. The mineralogical analysis of deeper layer showed the presence of diopside indicating this material was developed "in situ". Only in the shallow part of the core were found pollen of similar plant species of the modern vegetation. The geochemistry and isotope results, in association with the sediment type and pollen analyses of sediment samples of Manguezal do Sueste, indicated variations in the vegetation and in its location since the middle Holocene. Such variations can be associated with climatic events and sea level oscillations and also with anthropogenic events considering the last five hundred years.

Carbon storage in Amazonia during the last glacial maximum: secondary data and uncertainties.

The Amazonian forest is, due to its great size, carbon storage capacity and present-day variability in carbon uptake and release, an important component of the global carbon cycle. Paleo-environmental reconstruction is difficult for Amazonia due to the scarcity of primary palynological data and the mis-interpretation of some secondary data. Studies of lacustrine sediment records have shown that Amazonia has known periods in which the climate was drier than it is today. However, not all geomorphological features such as dunes, and slope erosion, which are thought to indicate rainforest regression, date from the time of the Late Glacial Maximum (LGM) and these features do not necessarily correspond to episodes of forest regression. There is also uncertainty concerning LGM carbon storage due to rainforest soils and biomass estimates. Soil carbon content may decrease moderately during the LGM, whereas rainforest biomass may change considerably in response to changes in the global environment. Biomass per unit area in Amazonia has probably been reduced by the cumulative effects of low CO2 concentration, a drier climate and lower temperatures. As few paleo-vegetation data are available, there is considerable uncertainty concerning the amount of carbon stored in Amazonia during the LGM, which may have corresponded to 44-94% of the carbon currently stored in biomass and soils.

Atmospheric mercury deposition over Brazil during the past 30.000 years

Atmospheric Hg deposition over Brazil is presented for the past 30,000 years as a tracer of the different natural and anthropogenic processes affecting the atmospheric environment of Brazil. During most of the prehistoric period, atmospheric deposition rates were rather constant with an average of about 2 mug m(-2) yr(-1). Peak deposition, ranging from 4 to 6 mug m2 y(-1), occurred at least during two periods between 3,300 and 3,600 BP and between 8,500 to 12,000 BP, and during the last glacial maximum (LGM), at about 18,000 years BP. These periods were characterized by drier, colder climates with high frequency of fores fires, as shoen by correlation with coal and pollen distribution data. During the colonial period Hg atmospheric deposition rates were much higher, about four times the prehistoric background and reached 6 to 8 mug m(-2) yr(-1). These increasing Hg deposition rates can only be explained by the large Hg emissions in South and Central America from Spanish silver mines, which emitted to the continent's environment about 200,000 tons of Hg from 1580 to 1820. During the present century, Hg deposition rates varied according to the region of the country. In the Amazon region, where gold mining is the major source of Hg emission to the atmosphere, deposition rates increased continuously during the last 40 years, reaching 8 to 10 mug m(-2) yr(-1). In the industrialized Southeast, Hg deposition was higher during the mild 1960s and 1970s, ranging from 80 to 130 mug m(-2) yr(-1), but decreased to 20 to 30 mug m(-2) yr(-1) in the 1990s, due to the enforcement of emission control policies. However, where Hg emissions are mostly from urban, nonpoint sources, such as along the high urbanized coastal area, Hg deposition, although smaller, increased steadily from the 1940s reaching a maximum at surface sediment layers of about 40.0 mug (-2) yr(-1). The results presented suggest Hg as a reliable tracer of natural (paleoclimatic changes) and anthropogenic (industrial and mining emissions) processes able to affect the atmosphere in Brazil.