scholarly journals Coincidence of photic zone euxinia and impoverishment of arthropods in the aftermath of the Frasnian-Famennian biotic crisis

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Krzysztof Broda ◽  
Leszek Marynowski ◽  
Michał Rakociński ◽  
Michał Zatoń
Keyword(s):  
Bottom Water ◽  
Geochemical Data ◽  
Photic Zone ◽  
Diversity Patterns ◽  
Bottom Waters ◽  
Phosphorous Content ◽  
Abundance And Diversity ◽  
Fossil Preservation ◽  
First Time ◽  
Palaeoenvironmental Changes

AbstractThe lowermost Famennian deposits of the Kowala quarry (Holy Cross Mountains, Poland) are becoming famous for their rich fossil content such as their abundant phosphatized arthropod remains (mostly thylacocephalans). Here, for the first time, palaeontological and geochemical data were integrated to document abundance and diversity patterns in the context of palaeoenvironmental changes. During deposition, the generally oxic to suboxic conditions were interrupted at least twice by the onset of photic zone euxinia (PZE). Previously, PZE was considered as essential in preserving phosphatised fossils from, e.g., the famous Gogo Formation, Australia. Here, we show, however, that during PZE, the abundance of arthropods drastically dropped. The phosphorous content during PZE was also very low in comparison to that from oxic-suboxic intervals where arthropods are the most abundant. As phosphorous is essential for phosphatisation but also tends to flux off the sediment during bottom water anoxia, we propose that the PZE in such a case does not promote the fossilisation of the arthropods but instead leads to their impoverishment and non-preservation. Thus, the PZE conditions with anoxic bottom waters cannot be presumed as universal for exceptional fossil preservation by phosphatisation, and caution must be paid when interpreting the fossil abundance on the background of redox conditions.

Aalenian–Lower Bajocian Foraminiferal Fauna from the Ammonitico Rosso Series of Bakonycsernye (Hungary). Part 2: Palaeoecological and Palaeobiogeographical Aspects

2020 ◽  
Vol 50 (1) ◽  
pp. 73-88 ◽  
Author(s):  
Gábor Zsiborás ◽  
Ágnes Görög
Keyword(s):  
Acetic Acid ◽  
Sea Level ◽  
Glacial Acetic Acid ◽  
Marine Snow ◽  
Photic Zone ◽  
Upper Bajocian ◽  
Abundance And Diversity ◽  
Palaeoenvironmental Changes

Abstract This paper provides the first assessment of the paleoecology and biogeography of foraminiferal assemblages from the continuous Aalenian–lower Bajocian succession from the pelagic region of the Neotethys. Foraminiferal assemblages were extracted by glacial acetic acid from the Tűzkövesárok section B of Bakonycsernye (Hungary), which is well dated by ammonites and consists of Ammonitico Rosso type limestones. Palaeoenvironmental changes were evaluated based on microfacies studies, taxonomic and palaeoecological analyses (abundance, diversity, morphogroups, and ecozones) of the 49 benthic and one planktic taxa. The grazer-dominated foraminiferal assemblages indicated normal marine salinity and well-oxygenated conditions in a pelagic swell-graben environment below the photic zone. The majority of the foraminifera likely grazed on a biofilm or mat produced by microbes and/or fungi and also may have fed on marine snow. At the Aalenian–Bajocian transition, the decrease in abundance and diversity was linked with a sea-level fall event (JBj1). In the upper Bajocian, dissolution due to deepening resulted in the gradual and selective impoverishment of the fauna. In addition, two biomes, Boreal-Atlantic and Mediterranean, were distinguished within the area of the Boreal-Atlantic-Caucasian Province, based on the review of the coeval faunas.

scholarly journals Spider crabs of the Western Atlantic with special reference to fossil and some modern Mithracidae

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1301 ◽  
Author(s):  
Adiël A. Klompmaker ◽  
Roger W. Portell ◽  
Aaron T. Klier ◽  
Vanessa Prueter ◽  
Alyssa L. Tucker
Keyword(s):  
Fossil Record ◽  
Early Pleistocene ◽  
Caribbean Region ◽  
Deep Time ◽  
Western Atlantic ◽  
Extant Species ◽  
Length Width ◽  
The Caribbean ◽  
Abundance And Diversity ◽  
First Time

Spider crabs (Majoidea) are well-known from modern oceans and are also common in the western part of the Atlantic Ocean. When spider crabs appeared in the Western Atlantic in deep time, and when they became diverse, hinges on their fossil record. By reviewing their fossil record, we show that (1) spider crabs first appeared in the Western Atlantic in the Late Cretaceous, (2) they became common since the Miocene, and (3) most species and genera are found in the Caribbean region from the Miocene onwards. Furthermore, taxonomic work on some modern and fossil Mithracidae, a family that might have originated in the Western Atlantic, was conducted. Specifically,Maguimithraxgen. nov. is erected to accommodate the extant speciesDamithrax spinosissimus, whileDamithraxcf.pleuracanthusis recognized for the first time from the fossil record (late Pliocene–early Pleistocene, Florida, USA). Furthermore, two new species are described from the lower Miocene coral-associated limestones of Jamaica (Mithrax arawakumsp. nov. andNemausa windsoraesp. nov.). Spurred by a recent revision of the subfamily, two known species from the same deposits are refigured and transferred to new genera:Mithrax donovanitoNemausa, andMithrax unguistoDamithrax. The diverse assemblage of decapods from these coral-associated limestones underlines the importance of reefs for the abundance and diversity of decapods in deep time. Finally, we quantitatively show that these crabs possess allometric growth in that length/width ratios drop as specimens grow, a factor that is not always taken into account while describing and comparing among taxa.

scholarly journals Reversal of freshening trend of Antarctic Bottom Water in the Australian-Antarctic Basin during 2010s

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
S. Aoki ◽  
K. Yamazaki ◽  
D. Hirano ◽  
K. Katsumata ◽  
K. Shimada ◽  
...  
Keyword(s):  
Continental Slope ◽  
Bottom Water ◽  
Ross Sea ◽  
Bottom Layer ◽  
Ice Shelves ◽  
West Antarctic ◽  
Sea Bottom ◽  
Salinity Increase ◽  
Bottom Waters ◽  
Late Twentieth

Abstract The Antarctic continental margin supplies the densest bottom water to the global abyss. From the late twentieth century, an acceleration in the long-term freshening of Antarctic Bottom Waters (AABW) has been detected in the Australian-Antarctic Basin. Our latest hydrographic observations reveal that, in the late 2010s, the freshening trend has reversed broadly over the continental slope. Near-bottom salinities in 2018–2019 were higher than during 2011–2015. Along 170° E, the salinity increase between 2011 and 2018 was greater than that observed in the west. The layer thickness of the densest AABW increased during the 2010s, suggesting that the Ross Sea Bottom Water intensification was a major source of the salinity increase. Freshwater content on the continental slope decreased at a rate of 58 ± 37 Gt/a in the near-bottom layer. The decadal change is very likely due to changes in Ross Sea shelf water attributable to a decrease in meltwater from West Antarctic ice shelves for the corresponding period.

scholarly journals Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

2016 ◽  
Vol 13 (1) ◽  
pp. 77-94 ◽  
Author(s):  
A. Laurent ◽  
K. Fennel ◽  
R. Wilson ◽  
J. Lehrter ◽  
R. Devereux
Keyword(s):  
Water Column ◽  
Bottom Water ◽  
In Situ Measurements ◽  
Nutrient Loads ◽  
Water Fluxes ◽  
Overlying Water ◽  
Louisiana Shelf ◽  
Biogeochemical Models ◽  
Bottom Waters

Abstract. Diagenetic processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be a significant contributor to oxygen depletion in hypoxic systems, and sediment–water nutrient fluxes support primary productivity in the overlying water column. Moreover, nonlinearities develop between bottom water conditions and sediment–water fluxes due to loss of oxygen-dependent processes in the sediment as oxygen becomes depleted in bottom waters. Yet, sediment–water fluxes of chemical species are often parameterized crudely in coupled physical–biogeochemical models, using simple linear parameterizations that are only poorly constrained by observations. Diagenetic models that represent sediment biogeochemistry are available, but rarely are coupled to water column biogeochemical models because they are computationally expensive. Here, we apply a method that efficiently parameterizes sediment–water fluxes of oxygen, nitrate and ammonium by combining in situ measurements, a diagenetic model and a parameter optimization method. As a proof of concept, we apply this method to the Louisiana Shelf where high primary production, stimulated by excessive nutrient loads from the Mississippi–Atchafalaya River system, promotes the development of hypoxic bottom waters in summer. The parameterized sediment–water fluxes represent nonlinear feedbacks between water column and sediment processes at low bottom water oxygen concentrations, which may persist for long periods (weeks to months) in hypoxic systems such as the Louisiana Shelf. This method can be applied to other systems and is particularly relevant for shallow coastal and estuarine waters where the interaction between sediment and water column is strong and hypoxia is prone to occur due to land-based nutrient loads.

Mesozooplankton community in a seasonally hypoxic and highly eutrophic bay

2015 ◽  
Vol 66 (8) ◽  
pp. 719 ◽  
Author(s):  
Min-Chul Jang ◽  
Kyoungsoon Shin ◽  
Pung-Guk Jang ◽  
Woo-Jin Lee ◽  
Keun-Hyung Choi
Keyword(s):  
High Temperature ◽  
Bottom Water ◽  
Oxygen Solubility ◽  
Low Oxygen ◽  
Negative Effects ◽  
Mesozooplankton Community ◽  
Seawater Chemistry ◽  
Hypoxic Conditions ◽  
Bottom Waters ◽  
Major Factors

A 2-year survey of seawater chemistry and mesozooplankton abundance was carried out in Masan Bay, South Korea, one of the most eutrophic coastal ecosystems known. The study aimed to identify the major factors contributing to the seasonally persistent hypoxia in the bay, to characterise the Bay’s mesozooplankton community and to examine the effects of low oxygen on the distribution of mesozooplankton. Hypoxia (<2mgO2L–1) was present only in summer, with ultrahypoxia (<0.2mg O2 L–1) in the bottom waters of the inner bay in both years. Low summer oxygen can be attributed to high summer phytoplankton stocks, together with reduced oxygen solubility at high temperature and stratification of the water column that limits downward diffusion of oxygen. A seasonally and spatially distinct mesozooplankton community was identified in summer when there was greater influence of freshwater discharge in the inner bay. Marine cladocerans were very abundant, with a population outburst of Penilia avirostris in the inner bay (>4000 individuals m–3) during summer. During hypoxic events, the abundance of Penilia avirostris was positively related to oxygen levels in the bottom water, suggesting that hypoxic conditions may cause mortality or have sublethal negative effects on population growth of this filter-feeding cladoceran.

Regional thermal‐inertia mapping from an experimental satellite

Geophysics ◽  
1982 ◽  
Vol 47 (12) ◽  
pp. 1681-1687 ◽  
Author(s):  
Kenneth Watson
Keyword(s):  
Satellite Data ◽  
Thermal Model ◽  
Thermal Inertia ◽  
Powder River Basin ◽  
Geochemical Data ◽  
Preliminary Assessment ◽  
Geologic Materials ◽  
Thermal Data ◽  
Resource Exploration ◽  
First Time

A new experimental satellite has provided, for the first time, thermal data that should be useful in reconnaissance geologic exploration. Thermal inertia, a property of geologic materials, can be mapped from these data by applying an algorithm that has been developed using a new thermal model. A simple registration procedure was used on a pair of day and night images of the Powder River basin, Wyoming, to illustrate the method. Preliminary assessment of these satellite data suggests that they will be of significant use for resource exploration when used in conjunction with other geologic, geophysical, and geochemical data.

Circular RNA profiling reveals abundant and diverse circRNAs of SARS-CoV-2, SARS-CoV and MERS-CoV origin

2020 ◽  
Author(s):  
Shaomin Yang ◽  
Hong Zhou ◽  
Ruth Cruz-Cosme ◽  
Mingde Liu ◽  
Jiayu Xu ◽  
...  
Keyword(s):  
De Novo ◽  
Splice Junction ◽  
Circular Rna ◽  
Circular Rnas ◽  
Sequencing Data ◽  
Rna Profiling ◽  
Systematic Strategy ◽  
Coronavirus Infection ◽  
Abundance And Diversity ◽  
First Time

ABSTRACTCircular RNAs (circRNAs) encoded by DNA genomes have been identified across host and pathogen species as parts of the transcriptome. Accumulating evidences indicate that circRNAs play critical roles in autoimmune diseases and viral pathogenesis. Here we report that RNA viruses of the Betacoronavirus genus of Coronaviridae, SARS-CoV-2, SARS-CoV and MERS-CoV, encode a novel type of circRNAs. Through de novo circRNA analyses of publicly available coronavirus-infection related deep RNA-Sequencing data, we identified 351, 224 and 2,764 circRNAs derived from SARS-CoV-2, SARS-CoV and MERS-CoV, respectively, and characterized two major back-splice events shared by these viruses. Coronavirus-derived circRNAs are more abundant and longer compared to host genome-derived circRNAs. Using a systematic strategy to amplify and identify back-splice junction sequences, we experimentally identified over 100 viral circRNAs from SARS-CoV-2 infected Vero E6 cells. This collection of circRNAs provided the first line of evidence for the abundance and diversity of coronavirus-derived circRNAs and suggested possible mechanisms driving circRNA biogenesis from RNA genomes. Our findings highlight circRNAs as an important component of the coronavirus transcriptome.SummaryWe report for the first time that abundant and diverse circRNAs are generated by SARS-CoV-2, SARS-CoV and MERS-CoV and represent a novel type of circRNAs that differ from circRNAs encoded by DNA genomes.

Age and Origin of Deep Crustal Meta-igneous Xenoliths from the Scottish Midland Valley: Vestiges of an Early Palaeozoic Arc and ‘Newer Granite’ Magmatism

2019 ◽  
Vol 60 (8) ◽  
pp. 1543-1574 ◽  
Author(s):  
Eszter Badenszki ◽  
J Stephen Daly ◽  
Martin J Whitehouse ◽  
Andreas Kronz ◽  
Brian G J Upton ◽  
...  
Keyword(s):  
Late Ordovician ◽  
Geochemical Data ◽  
Arc Magmatism ◽  
Precambrian Basement ◽  
Zircon Dating ◽  
Magmatic Arc ◽  
Granite Magmatism ◽  
Early Palaeozoic ◽  
First Time ◽  
Rule Out

Abstract Deep crustal felsic xenoliths from classic Scottish Midland Valley localities, carried to the surface by Permo-Carboniferous magmatism, are shown for the first time to include metaigneous varieties with dioritic and tonalitic protoliths. Four hypotheses regarding their origin have been evaluated: (1) Precambrian basement; (2) Permo-Carboniferous underplating; (3) ‘Newer Granite’ magmatism; (4) Ordovician arc magmatism. U–Pb zircon dating results rule out the Precambrian basement and Permo-Carboniferous underplating hypotheses, but establish that the meta-igneous xenoliths represent both ‘Newer Granite’ and Ordovician (to possibly Silurian) arc magmatism. The metadiorite xenoliths are shown to have protolith ages of c. 415 Ma with εHft zircon values ranging from +0·1 to +11·1. These are interpreted to represent unexposed ‘Newer Granite’ plutons, based on age, mineralogical, isotopic and geochemical data. This shows that Devonian ‘Newer Granite’ magmatism had a greater impact on the Midland Valley and Southern Uplands crust than previously realized. Clinopyroxene–plagioclase–quartz barometry on the metadiorites from the east and west of the Midland Valley yielded a similar pressure range of c. 5–10 kbar, and a metadiorite from the east yielded a minimum two-feldspar temperature estimate of c. 793–816°C. These results indicate that the metadiorites once resided in the middle–lower crust. In contrast, two metatonalite xenoliths have a Late Ordovician protolith age (c. 453 Ma), with zircon εHft values of +7·8 to +9·0. These are interpreted as samples of a buried Late Ordovician magmatic arc situated within the Midland Valley. Inherited zircons with similar Late Ordovician ages and εHft=453 values (+1·6 to +10·8) are present in the metadiorites, suggesting that the Devonian ‘Newer Granites’ intruded within or through this Late Ordovician Midland Valley arc. A younger protolith age of c. 430 Ma from one of the metatonalites suggests that arc activity continued until Silurian times. This validates the long-standing ‘arc collision’ hypothesis for the development of the Caledonian Orogen. Based on U–Pb zircon dating, the metatonalite and metadiorite xenoliths have both experienced metamorphism between c. 400 and c. 391 Ma, probably linked to the Acadian Orogeny. An older phase of metamorphism at c. 411 Ma was possibly triggered by the combined effects of heating owing to the emplacement of the ‘Newer Granite’ plutons and the overthrusting of the Southern Uplands terrane onto the southern margin of the Midland Valley terrane.

Recent Foraminifers and Stable Isotopes Records on a Bathymetric Transect off Portugal (Cruise JC089) and implications for the Palaeoxygenation proxy

2020 ◽  
Author(s):  
Maryline Mleneck-Vautravers ◽  
David Hodell
Keyword(s):  
Stable Isotopes ◽  
Pore Water ◽  
Bottom Water ◽  
Habitat Preferences ◽  
Sediment Cores ◽  
Geochemical Data ◽  
Major Influence ◽  
The One ◽  
Productive Systems ◽  
Iberian Margin

&lt;p&gt;The oceanographic cruise 89 (RRS James Cook) sailed in 2013 off the Iberian margin in support of an IODP proposal centred on IODP Site 1385. JC089 collected a range of hydrographic data and recovered a set of short sediment cores. We focus on 11 of the later, sampling the hydrography of the last c.400 years along a bathymetric gradient (600-4600 m). The stable isotopes (&amp;#948;&lt;sup&gt;18&lt;/sup&gt;O &amp; &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C) for: 8 common benthic foraminifer species with varied habitat preferences, the sediment pore-water and the bottom water above the sites were measured. The geochemical data is compared to various sedimentary and micropalaeontological data. The later comprises abundances of the main benthic foraminifera species &gt;212&amp;#956;m, checking for living position of the endo-fauna in Rose-Bengal stained samples and for the abundances of phytodetritus-loving species &lt;em&gt;E.exigua&lt;/em&gt; in the &gt;90&amp;#956;m for all the 0-1cm samples. The study of the planktonic foraminifer assemblages along a gradient stretching 170 km offshore confirms the major influence of the upwelling to the East. Except for the epi-benthic species &lt;em&gt;C.wuellestorfi&lt;/em&gt;, which records the bottom water &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C at equilibrium, all other species failed to record the &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C of the (pore) water at the depth of their living-position. We find that &lt;em&gt;G.affinis&lt;/em&gt; could record the &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;DIC&lt;/sub&gt; near equilibrium with the pore-water at a depth of c.-1cm; therefore above its living population peak. This could be explained by vertical migrations through the sediment column at sites where the supply of organic matter is pulsed. The later assumption seems supported by a reverse correlation between high relative abundances of &lt;em&gt;E.exigua&lt;/em&gt; and that of the planktonic upwelling indicator species &lt;em&gt;G.bulloides&lt;/em&gt; under productivity pulses corresponding to higher &amp;#916;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C(epi-&lt;em&gt;G.affinis&lt;/em&gt;).&lt;/p&gt;&lt;p&gt;The &amp;#916;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C varies from 1.7 to 4.9&amp;#8240; (n=6) across a decreasing but increasingly pulsed surface productivity gradient further away from the coast. Across this range, &lt;em&gt;G.affinis&lt;/em&gt; is observed living at increasing depths in the sediment but always peaks in oxic sediments. The absence of &lt;em&gt;G.affinis&lt;/em&gt; from water deeper than 3100 meters prevents &amp;#916;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C estimates at deeper water depths. For 6 of the 11 sites where &lt;em&gt;G.affinis&lt;/em&gt; was present &lt;em&gt;C.wuellestorfi&lt;/em&gt; occurred only twice. The &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C for &lt;em&gt;H.elegans&lt;/em&gt; and &lt;em&gt;C.mundulus&lt;/em&gt; adjusted by -1.08 and +0.25&amp;#8240; respectively (this study) were used instead for the shallower sites. Off the Iberian Margin the style of seasonally fluctuating food supply could be the main factor on &amp;#916;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C. The implication on future and long-ranging IODP-based palaeoclimatic studies is that the &amp;#916;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C could be used to estimate the type of productivity regime back in time. In the one hand the sites mostly influenced by the main upwelling cell exhibit &amp;#916;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C &lt; 3&amp;#8240; &amp; correspond to less than 10% of the time spent in an oligotrophic setting below 0.2mg (chla)/m&lt;sup&gt;3&lt;/sup&gt;. In the other hand &amp;#916;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C &gt;3&amp;#8240; trace offshore rare productive surface filaments in an environment otherwise corresponding to c.90% of the time under oligotrophic surface water. The absence &lt;em&gt;G.affinis&lt;/em&gt; (for the range of depths studied) could indicate a record sitting outside either of these productive systems' influence.&lt;/p&gt;

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