scholarly journals Tracking Organomineralization Processes from Living Microbial Mats to Fossil Microbialites

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 605 ◽  
Author(s):  
Inès Eymard ◽  
María Alvarez ◽  
Andrés Bilmes ◽  
Crisogono Vasconcelos ◽  
Daniel Ariztegui
Keyword(s):  
Organic Matter ◽  
South America ◽  
Fossil Record ◽  
Microbial Mats ◽  
High Density ◽  
Rich Phase ◽  
Physicochemical Processes ◽  
Carbonate Matrix ◽  
Photosynthetic Microorganisms ◽  
Mixed Carbonate

Geneses of microbialites and, more precisely, lithification of microbial mats have been studied in different settings to improve the recognition of biogenicity in the fossil record. Living microbial mats and fossil microbialites associated with older paleoshorelines have been studied in the continental Maquinchao Basin in southernmost South America. Here, we investigate carbonate crusts from a former pond where active mineralizing microbial mats have been previously studied. Petrographic observations revealed the presence of abundant erect and nonerect microfilaments and molds with diameters varying from 6 to 8 micrometers. Additionally, smaller pores and organic matter (OM) remains have been identified in areas containing less filaments and being dominated by carbonate. A Mg, Al and Si-rich phase has also been identified in the carbonate matrix associated with the dominant micritic calcite. Moreover, mineralized sheaths contain mixed carbonate (calcite) with Mg, Al and Si, where the latter elements are associated with authigenic clays. The presence of mineralized sheaths further attests to biologically induced processes during the uptake of CO2 by photosynthetic microorganisms. Additionally, the high density of the micritic phase supports the subsequent mineralization by nonphotosynthetic microorganisms and/or physicochemical processes, such as evaporation. Since the micritic filament microstructure of these recent crusts is very similar to that observed in fossil microbialites, they can be used to bridge the gap between living mats and fossil buildups.

Eucalyptus grandis Response to Calcium Fertilization in Colombia

2021 ◽  
Author(s):  
Zach S Grover ◽  
Rachel L Cook ◽  
Marcela Zapata ◽  
J Byron Urrego ◽  
Timothy J Albaugh ◽  
...  
Keyword(s):  
Organic Matter ◽  
South America ◽  
Eucalyptus Grandis ◽  
Application Rate ◽  
Soil Conditions ◽  
Nutrient Deficiencies ◽  
Site Specific ◽  
Application Rates ◽  
Eucalyptus Plantations ◽  
Calcium Source

Abstract Calcium (Ca) is a critical plant nutrient typically applied at the time of planting in intensive Eucalyptus plantations in South America. At two sites in Colombia, we examined (1) calcium source by comparing growth after application of 100 kg ha−1 elemental Ca as lime or as pelletized highly reactive calcium fertilizer (HRCF) compared to a no application control, and (2) Ca rate by applying 0, 100, 200, and 400 kg ha−1 elemental Ca as HRCF with the addition of nitrogen, phosphorus, potassium, sulfur, and boron (NPKSB). We assessed height, diameter, and volume after 12 and 24 months. There were no growth differences from Ca source at the 100 kg ha−1 rate. We found increased volume after 24 months at the “Popayan” site with 200 and 400 kg ha−1 Ca HRCF+NPKSB treatments (112 and 113 m3 ha−1, respectively) compared to control (92 m3 ha−1), a 22% increase. In contrast, volume did not differ after 24 months at the “Darien” site, ranging from 114 m3 ha−1 in the 0 kg ha−1 Ca HRCF+NPKSB treatment to 98 m3 ha−1 in the control. Differences in response are likely due to soil characteristics, such as organic matter, emphasizing the importance of identifying site-specific nutrient deficiencies. Study Implications: Operational applications may be over- or under-applying calcium carbonate in Eucalyptus plantations in South America. In the first two years of a seven-year rotation located in volcanic soils in Colombia, we found that one site with more organic matter at a greater depth did not need Ca additions, whereas the other site required greater than current operational applications to optimize productivity. Ca application rate trials across a gradient of soil conditions could establish critical values and improve recommendations of appropriate Ca application rates and emphasize the importance of understanding site-specific soil conditions to produce effective fertilization regimes.

scholarly journals Late Pleistocene echimyid rodents (Rodentia, Hystricognathi) from northern Brazil

2016 ◽  
Vol 88 (2) ◽  
pp. 829-845 ◽  
Author(s):  
THAIS M.F. FERREIRA ◽  
ADRIANA ITATI OLIVARES ◽  
LEONARDO KERBER ◽  
RODRIGO P. DUTRA ◽  
LEONARDO S. AVILLA
Keyword(s):  
South America ◽  
Tropical Forests ◽  
Late Pleistocene ◽  
Fossil Record ◽  
South American ◽  
Squamate Reptiles ◽  
Northern Brazil ◽  
Northern South America ◽  
First Time

ABSTRACT Echimyidae (spiny rats, tree rats and the coypu) is the most diverse family of extant South American hystricognath rodents (caviomorphs). Today, they live in tropical forests (Amazonian, coastal and Andean forests), occasionally in more open xeric habitats in the Cerrado and Caatinga of northern South America, and open areas across the southern portion of the continent (Myocastor). The Quaternary fossil record of this family remains poorly studied. Here, we describe the fossil echimyids found in karst deposits from southern Tocantins, northern Brazil. The analyzed specimens are assigned to Thrichomys sp., Makalata cf. didelphoides and Proechimys sp. This is the first time that a fossil of Makalata is reported. The Pleistocene record of echimyids from this area is represented by fragmentary remains, which hinders their determination at specific levels. The data reported here contributes to the understanding of the ancient diversity of rodents of this region, evidenced until now in other groups, such as the artiodactyls, cingulates, carnivores, marsupials, and squamate reptiles.

scholarly journals Ferrihydrite Reduction by Photosynthetic Synechocystis sp. PCC 6803 and Its Correlation With Electricity Generation

2021 ◽  
Vol 12 ◽  
Author(s):  
Kenya Tanaka ◽  
Ginga Shimakawa ◽  
Shoko Kusama ◽  
Takashi Harada ◽  
Souichiro Kato ◽  
...  
Keyword(s):  
Electricity Generation ◽  
Microbial Mats ◽  
Microbial Reduction ◽  
Extracellular Electron Transfer ◽  
Solid State Electron ◽  
Exogenous Glucose ◽  
Photosynthetic Microorganisms ◽  
Dark Conditions ◽  
Reducing Bacteria ◽  
Pcc 6803

Microbial extracellular electron transfer (EET) to solid-state electron acceptors such as anodes and metal oxides, which was originally identified in dissimilatory metal-reducing bacteria, is a key process in microbial electricity generation and the biogeochemical cycling of metals. Although it is now known that photosynthetic microorganisms can also generate (photo)currents via EET, which has attracted much interest in the field of biophotovoltaics, little is known about the reduction of metal (hydr)oxides via photosynthetic microbial EET. The present work quantitatively assessed the reduction of ferrihydrite in conjunction with the EET of the photosynthetic microbe Synechocystis sp. PCC 6803. Microbial reduction of ferrihydrite was found to be initiated in response to light but proceeded at higher rates when exogenous glucose was added, even under dark conditions. These results indicate that current generation from Synechocystis cells does not always need light irradiation. The qualitative trends exhibited by the ferrihydrite reduction rates under various conditions showed significant correlation with those of the microbial currents. Notably, the maximum concentration of Fe(II) generated by the cyanobacterial cells under dark conditions in the presence of glucose was comparable to the levels observed in the photic layers of Fe-rich microbial mats.

Spatiotemporal palaeodiversity patterns of modern crocodiles (Crocodyliformes: Eusuchia)

2019 ◽  
Vol 189 (2) ◽  
pp. 635-656 ◽  
Author(s):  
Ane De Celis ◽  
Iván Narváez ◽  
Francisco Ortega
Keyword(s):  
South America ◽  
Least Squares ◽  
Late Miocene ◽  
North American ◽  
Fossil Record ◽  
Generalized Least Squares ◽  
Global Scale ◽  
Biotic Factors ◽  
Species Dynamics ◽  
Over Time

Abstract Eusuchia is a crocodyliform clade with a rich and diverse fossil record dating back to the Mesozoic. There are several recent studies that analyse crocodyliform palaeodiversity over time, but none of them focuses exclusively on eusuchians. Thus, we estimated subsampled eusuchian palaeodiversity species dynamics over time not only at a global scale, but also by continents and main crocodylian lineages (Alligatoroidea, Crocodyloidea and Gavialoidea). These estimates reveal complex spatiotemporal palaeodiversity patterns, in which two maxima can be detected: the first during the Palaeocene and the second, which is also the biggest, in the middle-late Miocene. The Palaeocene shift is related to a North American alligatoroid diversification, whereas the middle–late Miocene maximum is related to a diversification of the three main Crocodylia lineages in Gondwanan land masses, but especially in South America. Additionally, a model-based study using generalized least squares was carried out to analyse the relationships between different abiotic and sampling proxies and eusuchian palaeodiversity. The results show that palaeotemperature is the most important factor amongst the analysed proxies, in accordance with previous studies. However, the results suggest that, along with palaeotemperature, other abiotic and/or biotic factors might also be driving eusuchian palaeodiversity dynamics.

Meta-analysis of the effects of organic matter on polychaetes of the east coast of South America

2019 ◽  
Vol 149 ◽  
pp. 148-156
Author(s):  
Vanessa Fernández-Rodríguez ◽  
Cinthya S.G. Santos ◽  
Aliny P.F. Pires
Keyword(s):  
Organic Matter ◽  
South America ◽  
East Coast ◽  
Meta Analysis

Paleometry as a key tool to deal with paleobiological and astrobiological issues: some contributions and reflections on the Brazilian fossil record

2019 ◽  
Vol 18 (6) ◽  
pp. 575-589 ◽  
Author(s):  
Amanda L. S. Gomes ◽  
Bruno Becker-Kerber ◽  
Gabriel L. Osés ◽  
Gustavo Prado ◽  
Pedro Becker Kerber ◽  
...  
Keyword(s):  
Fossil Record ◽  
Microbial Mats ◽  
Fish Bone ◽  
Common Interest ◽  
Cross Point ◽  
Origin And Evolution ◽  
Evolution Of Life ◽  
Bone Preservation ◽  
Fossil Preservation ◽  
Non Destructive

AbstractInvestigations into the existence of life in other parts of the cosmos find strong parallels with studies of the origin and evolution of life on our own planet. In this way, astrobiology and paleobiology are married by their common interest in disentangling the interconnections between life and the surrounding environment. In this way, a cross-point of both sciences is paleometry, which involves a myriad of imaging and geochemical techniques, usually non-destructive, applied to the investigation of the fossil record. In the last decades, paleometry has benefited from an unprecedented technological improvement, thus solving old questions and raising new ones. This advance has been paralleled by conceptual approaches and discoveries fuelled by technological evolution in astrobiological research. In this context, we present some new data and review recent advances on the employment of paleometry to investigations on paleobiology and astrobiology in Brazil in areas such biosignatures in Ediacaran microbial mats, biogenicity tests on enigmatic Ediacaran structures, research on Ediacaran metazoan biomineralization, fossil preservation in Cretaceous insects and fish, and finally the experimental study on the decay of fish to test the effect of distinct types of sediment on soft-tissue preservation, as well as the effects of early diagenesis on fish bone preservation.

Taxonomic review of two fossil crocodylians from the Cenozoic of South America and its implications for the crocodylian fauna of the continent

Zootaxa ◽  
2019 ◽  
Vol 4656 (3) ◽  
pp. 475-486
Author(s):  
GIOVANNE M. CIDADE ◽  
DANIEL FORTIER ◽  
ASCANIO DANIEL RINCÓN ◽  
ANNIE SCHMALTZ HSIOU
Keyword(s):  
South America ◽  
Fossil Record ◽  
Middle Miocene ◽  
Taxonomic Status ◽  
Junior Synonym ◽  
Diverse Group ◽  
Taxonomic Review ◽  
Nomen Dubium ◽  
Extant Species ◽  
The World

The crocodylomorph fauna of the Cenozoic of South America is one of the richest and most diverse in the world. The most diverse group within that fauna is Alligatoroidea, with nearly all of its species belonging to the Caimaninae clade. Many of the fossil alligatoroid species from the Cenozoic of South America were proposed based on very incomplete remains, and as a result their validity requires revision. Two such species are Balanerodus logimus Langston, 1965, from the middle Miocene of Colombia and Peru, and Caiman venezuelensis Fortier & Rincón, 2012, from the Pliocene-Pleistocene of Venezuela. This study has performed a thorough review of the taxonomic status of these two alligatoroid species, concluding that B. logimus is a nomen dubium and that Ca. venezuelensis is a junior synonym of the extant species Ca. crocodilus. This review offers a significantly more accurate scenario for alligatoroid diversity in the Cenozoic of South America in different epochs such as the Miocene and Pleistocene. Additionally, the record of Ca. crocodilus from the Pleistocene of Venezuela is the first fossil record that can be assigned to this species. 

scholarly journals Fungi and viruses as important players in microbial mats

2020 ◽  
Vol 96 (11) ◽  
Author(s):  
Cátia Carreira ◽  
Christian Lønborg ◽  
Michael Kühl ◽  
Ana I Lillebø ◽  
Ruth-Anne Sandaa ◽  
...  
Keyword(s):  
Organic Matter ◽  
Aquatic Ecosystems ◽  
Microbial Mats ◽  
Freshwater Ecosystems ◽  
Food Web Structure ◽  
Element Cycling ◽  
Functional Roles ◽  
Web Structure ◽  
Experimental Approaches ◽  
And Function

ABSTRACT Microbial mats are compacted, surface-associated microbial ecosystems reminiscent of the first living communities on early Earth. While often considered predominantly prokaryotic, recent findings show that both fungi and viruses are ubiquitous in microbial mats, albeit their functional roles remain unknown. Fungal research has mostly focused on terrestrial and freshwater ecosystems where fungi are known as important recyclers of organic matter, whereas viruses are exceptionally abundant and important in aquatic ecosystems. Here, viruses have shown to affect organic matter cycling and the diversity of microbial communities by facilitating horizontal gene transfer and cell lysis. We hypothesise fungi and viruses to have similar roles in microbial mats. Based on the analysis of previous research in terrestrial and aquatic ecosystems, we outline novel hypotheses proposing strong impacts of fungi and viruses on element cycling, food web structure and function in microbial mats, and outline experimental approaches for studies needed to understand these interactions.

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