What, if anything, are mass extinctions?

1989 ◽  
Vol 325 (1228) ◽  
pp. 253-261 ◽  
Keyword(s):  
Organic Matter ◽  
Mass Extinction ◽  
Atmospheric Oxygen ◽  
World Ocean ◽  
Nutrient Deficiency ◽  
Late Eocene ◽  
Global Ocean ◽  
Mass Extinctions ◽  
Geological Time ◽  
Sea Bottom

Many phenomena that have traditionally been called ‘mass extinctions’ are in fact clusters of extinction episodes roughly associated in geological time. This is the case with the latest Ordovician, late Devonian, mid-Cretaceous, latest Cretaceous and Late Eocene-Oligocene extinctions. Several of these clusters are caused, each episode by a different causal factor. Such mass extinctions are then due to the coincidence of various processes in the environment, and they can hardly be considered as individual events. The latest Permian mass extinction, however, is caused by a single process that affected the global ocean-atmosphere system. In the late Permian, the world ocean was full of deposits rich in organic matter, which enhanced nutrient recycling. After oxygen was brought to the sea floor (by whatever process), nutrients began to sink to the sea-bottom, and the resulting nutrient deficiency must have caused mass extinction in the sea. Oxidation of huge amounts of organic matter and associated sediments at the sea bottom must have drawn oxygen from the atmosphere, and the resulting fall in atmospheric oxygen must have contributed to extinctions on land.

The biology of mass extinction: a palaeontological view

1989 ◽  
Vol 325 (1228) ◽  
pp. 357-368 ◽  
Keyword(s):  
Mass Extinction ◽  
Large Scale ◽  
Individual Species ◽  
Ecological Groups ◽  
Mass Extinctions ◽  
Geological Time ◽  
Evolutionary Patterns ◽  
Data Set ◽  
High Species Richness ◽  
Extinction Events

Extinctions are not biologically random: certain taxa or functional/ecological groups are more extinction-prone than others. Analysis of molluscan survivorship patterns for the end-Cretaceous mass extinctions suggests that some traits that tend to confer extinction resistance during times of normal (‘background’) levels of extinction are ineffectual during mass extinction. For genera, high species-richness and possession of widespread individual species imparted extinction-resistance during background times but not during the mass extinction, when overall distribution of the genus was an important factor. Reanalysis of Hoffman’s (1986) data ( Neues Jb. Geol. Palaont. Abh. 172, 219) on European bivalves, and preliminary analysis of a new northern European data set, reveals a similar change in survivorship rules, as do data scattered among other taxa and extinction events. Thus taxa and adaptations can be lost not because they were poorly adapted by the standards of the background processes that constitute the bulk of geological time, but because they lacked - or were not linked to - the organismic, species-level or clade-level traits favoured under mass-extinction conditions. Mass extinctions can break the hegemony of species-rich, well-adapted clades and thereby permit radiation of taxa that had previously been minor faunal elements; no net increase in the adaptation of the biota need ensue. Although some large-scale evolutionary trends transcend mass extinctions, post-extinction evolutionary pathways are often channelled in directions not predictable from evolutionary patterns during background times.

scholarly journals Revisiting the disappearance of terrestrial dissolved organic matter in the ocean: a <i>δ</i><sup>13</sup>C study

2014 ◽  
Vol 11 (13) ◽  
pp. 3707-3719 ◽  
Author(s):  
K. Lalonde ◽  
A. V. Vähätalo ◽  
Y. Gélinas
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Solar Radiation ◽  
World Ocean ◽  
Photochemical Reactions ◽  
Global Ocean ◽  
Terrestrial Organic Matter ◽  
The World ◽  
Radiation Induced ◽  
Simulated Solar Radiation

Abstract. Organic carbon (OC) depleted in 13C is a widely used tracer for terrestrial organic matter (OM) in aquatic systems. Photochemical reactions can, however, change δ13C of dissolved organic carbon (DOC) when chromophoric, aromatic-rich terrestrial OC is selectively mineralized. We assessed the robustness of the δ13C signature of DOC (δ13CDOC) as a tracer for terrestrial OM by estimating its change during the photobleaching of chromophoric DOM (CDOM) from 10 large rivers. These rivers cumulatively account for approximately one-third of the world's freshwater discharge to the global ocean. Photobleaching of CDOM by simulated solar radiation was associated with the photochemical mineralization of 16 to 43% of the DOC and, by preferentially removing compounds depleted in 13C, caused a 1 to 2.9‰ enrichment in δ13C in the residual DOC. Such solar-radiation-induced photochemical isotopic shift could bias the calculations of terrestrial OM discharge in coastal oceans towards the marine end-member. Shifts in terrestrial δ13CDOC should be taken into account when constraining the terrestrial end-member in global calculation of terrestrially derived DOM in the world ocean.

Fire, Flowers, and Dinosaurs

2018 ◽  
Author(s):  
Andrew C. Scott
Keyword(s):  
Atmospheric Oxygen ◽  
Time Interval ◽  
Mass Extinctions ◽  
Fossil Plants ◽  
Geological Time ◽  
Ecosystem Recovery ◽  
Deep Time ◽  
The World ◽  
The University ◽  
Lateral Thinking

The Mesozoic Era is the geological interval comprising the Triassic, Jurassic, and Cretaceous Periods, and it is best known for the rise and fall of the dinosaurs. The Mesozoic began around 250 million years ago and continued to around 66 million years ago—a not inconsiderable chunk of geological time, and framed by mass extinctions at its beginning and end. Fifty years ago there were very few published papers on fire in deep time, but the most important one, which I’ve touched on before, was ‘Forest fire in the Mesozoic’, by Tom Harris of the University of Reading. Tom was an important scientist, one of the leading palaeobotanists in the world. Energetic and passionate about his fossil plants, he was a scientist with broad interests, and given to experimentation and lateral thinking. The evidence that Tom used in his paper on fires in the Mesozoic was limited to only a couple of charcoal occurrences in these rocks. The Permian Period ended with the biggest known mass extinction in Earth history, when life was almost wiped out. Whole ecosystems collapsed. So what would the world have looked like at the start of the Triassic? Among whole groups of plants that had become extinct were the giant club mosses that had been the major coal-forming plants of the late Paleozoic, and the glossopterids that had dominated southern continental vegetation. In the first few million years after the extinctions, plant diversity appears to have been low, but some new plants became prominent, including the pole-like spore-bearing lycopod called Pleuromeia, and the scrambling seedplant called Dicroidium, which had fern-like foliage. The first 10 million years of the Triassic are thought to have been a time of ecosystem recovery. According to Berner’s model, the Triassic started with very low levels of oxygen in the atmosphere. Researchers had noticed that there were no coals found at the beginning of the Triassic, and this interval was called the ‘coal gap’. The problem, therefore, was that charcoal in coal could not be used as a proxy for atmospheric oxygen for this time interval.

The paradox of the first tier: an agenda for paleobiology

Paleobiology ◽  
1985 ◽  
Vol 11 (1) ◽  
pp. 2-12 ◽  
Author(s):  
Stephen Jay Gould
Keyword(s):  
Evolutionary Theory ◽  
Mass Extinction ◽  
Time Trends ◽  
Mass Extinctions ◽  
Conventional Theory ◽  
Geological Time ◽  
The Third ◽  
Hierarchical Structuring ◽  
Simple Extrapolation ◽  
Second Tier

Nature's discontinuities occur both in the hierarchical structuring of genealogical individuals and in the distinct processes operating at different scales of time, here called tiers. Conventional evolutionary theory denies this structuring and attempts to render the larger scales as simple extrapolation from (or reduction to) the familiar and immediate—the struggle among organisms at ecological moments (conventional individuals at the first tier). I propose that we consider distinct processes at three separable tiers of time: ecological moments, normal geological time (trends during millions of years), and periodic mass extinctions.I designate as “the paradox of the first tier” our failure to find progress in life's history, when conventional theory (first tier processes acting on organisms) expects it as a consequence of competition under Darwin's metaphor of the wedge. I suggest a resolution of the paradox: whatever accumulates at the first tier is sufficiently reversed, undone, or overriden by processes of the higher tiers. In particular, punctuated equilibrium at the second tier produces trends for suites of reasons unrelated to the adaptive benefits of organisms (conventional progress). Mass extinction at the third tier, a recurring process now recognized as more frequent, more rapid, more intense, and more different than we had imagined, works by different rules and may undo whatever the lower tiers had accumulated.

Fire and the Coming of the Modern World

2018 ◽  
Author(s):  
Andrew C. Scott
Keyword(s):  
Mass Extinction ◽  
Atmospheric Oxygen ◽  
Late Eocene ◽  
Modern World ◽  
Early Eocene ◽  
Earth System ◽  
Fundamental Change ◽  
Oxygen Level ◽  
The Usa ◽  
Permian Mass Extinction

What kind of world dawned after the K/P boundary? We know from studies across localities in the USA that there is evidence of frequent wildfires continuing into the earliest Paleogene. But what happened to the atmospheric oxygen level after recovery from the K/P mass extinction—did it remain above modern levels? Were we still in a high-fire world? If there were fires, what is the evidence in the charcoal record, and do we know anything about the vegetation that was burning? When the charcoal in the coal database was originally compiled, one of the important issues was how we recorded and represented our data. Early to mid-Paleocene Epoch coals (from around 65 to 55 million years ago) are often recorded as ‘earliest Tertiary’ in coal literature. (The Tertiary was the name we used to use for what we now call the Paleogene and Neogene Periods, stretching from around 65 to 1 million years ago.) However, coals that are nearer to the start of the Eocene Epoch, just older than 55 million years ago, are notoriously difficult to date. This is a problem we have with many coal sequences, as they are deposited on land, and most of the fossils used to give ages are found in marine waters. Many coals of this age are often simply recorded as coming from the late Paleocene or early Eocene. Where we have good dating information, Paleocene coals all tend to have high inertinite (charcoal) contents, well above 19 per cent. By the mid to late Eocene (50–40 million years ago), however, worldwide the charcoal contents are low, around 5 per cent or even less. There must, therefore, have been a fundamental change in the Earth system at this time. Another problem is the way in which we chose to represent our data and show the calculated oxygen curve. In order to get sufficient data to plot the curves we decided to use 10-millionyear bins. This was not a problem for the Paleozoic–Mesozoic transition, covering the great Permian mass extinction, which took place 250 million years ago.

Evidence for catastrophic organic changes in the geological record

2004 ◽  
Author(s):  
Tony Hallam
Keyword(s):  
Mass Extinction ◽  
Sedimentary Rocks ◽  
Significant Proportion ◽  
Natural World ◽  
European Population ◽  
Mass Extinctions ◽  
Geological Time ◽  
Geological Record ◽  
Coastal Cliffs ◽  
Definition Of

If asked what they understood by the word ‘catastrophe’, most people would probably agree that it was something big, bad, and sudden, and involved damage to organisms. In the natural world today, perhaps the most striking catastrophes result from major earthquakes, in which thousands of people can be killed within minutes. Going back through human history, we allow for greater stretches of time. Thus, in the middle of the fourteenth century, over a period of five years, an estimated one-third of the European population died directly as a result of catching the plague: the ‘Black Death’. By any reckoning this ranks as a catastrophe. It had a dramatic effect on European society for many years. When we extend our consideration to geological time, in which it is routine to deal with changes taking place over millions of years, events lasting only a few thousand years may be regarded as catastrophic if the contrast with the ‘background’ is sharp enough. Various definitions have been proposed for a mass extinction. A conveniently concise if imprecise one that I favour is that it is the extinction of a significant proportion of the world’s living animal and plant life (the biota) in a geologically insignificant period of time. The imprecision about the extent of an extinction can be dealt with fairly satisfactorily in particular instances by giving percentages of fossil families, genera, or species, but the imprecision about time is more difficult to deal with. An important question about mass extinctions is to assess how catastrophic they were, so we also require a definition of ‘catastrophe’ in this context. One thought-provoking attempt at such a definition is that a catastrophe is a perturbation of the biosphere that appears to be instantaneous when viewed at the level of detail that can be resolved in the geological record. At this point more needs to be said about the nature of the geological record. The material that geologists and palaeontologists deal with occurs in the layered successions of sedimentary rocks, mainly sandstones, shales, and limestones, that can clearly be observed in good rock exposures, either natural ones, as in coastal cliffs or mountains, or artificial ones, as in quarries or borehole cores.

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

scholarly journals MAREDAT: towards a World Ocean Atlas of MARine Ecosystem DATa

2012 ◽  
Vol 5 (2) ◽  
pp. 1077-1106 ◽  
Author(s):  
E. T. Buitenhuis ◽  
M. Vogt ◽  
R. Moriarty ◽  
N. Bednaršek ◽  
S. C. Doney ◽  
...  
Keyword(s):  
Marine Ecosystem ◽  
World Ocean ◽  
Zooplankton Biomass ◽  
Global Ocean ◽  
Special Issue ◽  
Biomass Distribution ◽  
Phytoplankton Pigment ◽  
Autotrophic Biomass ◽  
Ocean Ecosystem ◽  
World Ocean Atlas

Abstract. We present a summary of biomass data for 11 Plankton Functional Types (PFTs) plus phytoplankton pigment data, compiled as part of the MARine Ecosystem biomass DATa (MAREDAT) initiative. The goal of the MAREDAT initiative is to provide global gridded data products with coverage of all biological components of the global ocean ecosystem. This special issue is the first step towards achieving this. The PFTs presented here include picophytoplankton, diazotrophs, coccolithophores, Phaeocystis, diatoms, picoheterotrophs, microzooplankton, foraminifers, mesozooplankton, pteropods and macrozooplankton. All variables have been gridded onto a World Ocean Atlas (WOA) grid (1° × 1° × 33 vertical levels × monthly climatologies). The data show that (1) the global total heterotrophic biomass (2.0–6.4 Pg C) is at least as high as the total autotrophic biomass (0.5–2.6 Pg C excluding nanophytoplankton and autotrophic dinoflagellates), (2) the biomass of zooplankton calcifiers (0.9–2.3 Pg C) is substantially higher than that of coccolithophores (0.01–0.14 Pg C), (3) patchiness of biomass distribution increases with organism size, and (4) although zooplankton biomass measurements below 200 m are rare, the limited measurements available suggest that Bacteria and Archaea are not the only heterotrophs in the deep sea. More data will be needed to characterize ocean ecosystem functioning and associated biogeochemistry in the Southern Hemisphere and below 200 m. Microzooplankton database: doi:10.1594/PANGAEA.779970.

Biogeochemical disruptions across the Cretaceous-Paleogene boundary : insights from sulfur isotopes

2021 ◽  
Author(s):  
Arbia Jouini
Keyword(s):  
Mass Extinction ◽  
Environmental Changes ◽  
Sea Water ◽  
Sulfur Isotopes ◽  
Deep Understanding ◽  
Sulfur Cycle ◽  
Mass Extinctions ◽  
Deccan Volcanism ◽  
Organic Carbon Burial ◽  
Early Paleocene

&lt;p&gt;&lt;strong&gt;Biogeochemical disruptions across the Cretaceous-Paleogene boundary : insights from sulfur isotopes&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Arbia JOUINI&lt;sup&gt;1*&lt;/sup&gt;, Guillaume PARIS&lt;sup&gt;1&lt;/sup&gt;, Guillaume CARO&lt;sup&gt;1&lt;/sup&gt;, Annachiara BARTOLINI&lt;sup&gt;2&lt;/sup&gt;&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1 &lt;/sup&gt;Centre de Recherches P&amp;#233;trographiques et G&amp;#233;ochimiques, CRPG-CNRS, UMR7358, ,15 rue Notre Dame des Pauvres, BP20, 54501Vandoeuvre-l&amp;#232;s-Nancy, France, email:[email protected]&lt;/p&gt;&lt;p&gt;&lt;sup&gt;2&lt;/sup&gt; Mus&amp;#233;um National D&amp;#8217;Histoire Naturelle, D&amp;#233;partement Origines &amp; Evolution, CR2P MNHN, CNRS, Sorbonne Universit&amp;#233;, 8 rue Buffon CP38, 75005 Paris, France&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The Cretaceous&amp;#8211;Paleogene (KPg) mass extinction event 66 million years ago witnessed one of the &amp;#8216;Big Five&amp;#8217; mass extinctions of the Phanerozoic. Two major catastrophic events, the Chicxulub asteroid impact and the Deccan trap eruptions, were involved in complex climatic and environmental changes that culminated in the mass extinction including oceanic biogenic carbonate crisis, sea water chemistry and ocean oxygen level changes. Deep understanding of the coeval sulfur biogeochemical cycle may help to better constrain and quantify these parameters.&lt;/p&gt;&lt;p&gt;Here we present the first stratigraphic high resolution isotopic compositions of carbonate associated sulfate (CAS) based on monospecific planktic and benthic foraminifers' samples during the Maastrichtian-Danian transition from IODP pacific site 1209C. Primary &amp;#948;34SCAS data suggests that there was a major perturbation of sulfur cycle around the KPg transition with rapid fluctuations (100-200kyr) of about 2-4&amp;#8240; (&amp;#177;0.54&amp;#8240;, 2SD) during the late Maastrichtian followed by a negative excursion in &amp;#948;34SCAS of 2-3&amp;#8240; during the early Paleocene.&lt;/p&gt;&lt;p&gt;An increase in oxygen levels associated with a decline in organic carbon burial, related to a collapse in primary productivity, may have led to the early Paleocene &amp;#948;34SCAS negative shift via a significant drop in microbial sulfate reduction. Alternatively, Deccan volcanism could also have played a role and impacted the sulfur cycle via direct input of isotopically light sulfur to the ocean. A revised correlation between &amp;#948;34SCAS data reported in this study and a precise dating of the Deccan volcanism phases would allow us to explore this hypothesis.&lt;/p&gt;&lt;p&gt;Keywords : KPg boundary, Sulphur cycle, cycle du calcium, Planktic and benthic foraminifera&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Mass extinctions alter extinction and origination dynamics with respect to body size

2021 ◽  
Vol 288 (1960) ◽  
Author(s):  
Pedro M. Monarrez ◽  
Noel A. Heim ◽  
Jonathan L. Payne
Keyword(s):  
Body Size ◽  
Mass Extinction ◽  
Evolutionary Biology ◽  
Marine Animal ◽  
Mass Extinctions ◽  
Extinction Selectivity ◽  
Extinction Events ◽  
Mass Extinction Events ◽  
Marine Biosphere

Whether mass extinctions and their associated recoveries represent an intensification of background extinction and origination dynamics versus a separate macroevolutionary regime remains a central debate in evolutionary biology. The previous focus has been on extinction, but origination dynamics may be equally or more important for long-term evolutionary outcomes. The evolution of animal body size is an ideal process to test for differences in macroevolutionary regimes, as body size is easily determined, comparable across distantly related taxa and scales with organismal traits. Here, we test for shifts in selectivity between background intervals and the ‘Big Five’ mass extinction events using capture–mark–recapture models. Our body-size data cover 10 203 fossil marine animal genera spanning 10 Linnaean classes with occurrences ranging from Early Ordovician to Late Pleistocene (485–1 Ma). Most classes exhibit differences in both origination and extinction selectivity between background intervals and mass extinctions, with the direction of selectivity varying among classes and overall exhibiting stronger selectivity during origination after mass extinction than extinction during the mass extinction. Thus, not only do mass extinction events shift the marine biosphere into a new macroevolutionary regime, the dynamics of recovery from mass extinction also appear to play an underappreciated role in shaping the biosphere in their aftermath.

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