Local and global perspectives on carbon and nitrogen cycling during the Hirnantian glaciation

LaPorte, D.F.; Holmden, Chris; Patterson, William P.; Loxton, Jason; Melchin, Michael J.; Mitchell, Charles E.; Finney, Stanley C.; Sheets, H. David

doi:10.1016/j.palaeo.2009.03.009

Cited by 143 publications

(89 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1) exhibit peak values of Shannon information (H) and evenness (E) in the Dicellograptus ornatus to mid-Paraorthograptus pacificus zones (see also Datasets S4 and S5), during the interval of the O4 relative water depth cycle (34). The highest recorded H and E values occur in the early P. pacificus Zone interval (O4b) when abundant black shales were deposited beneath a strongly developed denitrification zone at the site (21,22). Biomarkers (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…After death, all these graptolites settled to form mixed assemblages on the sea floor, with epipelagic graptolites present at relatively onshore as well as at more offshore localities, whereas mesopelagic species occur only in strata deposited near the shelf margin and beyond. Changes in deep-ocean circulation and oxygenation driven by climate change contributed to the Ordovician mass extinction (12,13,15,21,22), which suggests that the mesopelagic biotope may have been the most vulnerable and should exhibit disproportional extinction.…”

mentioning

confidence: 99%

“…Hirnantian (latest Ordovician) glaciation lowered sea levels by some 70-100 m (26,27), reduced tropical sea surface temperatures by ∼6°C (22,26), and increased oxygenation of the deep oceans (22,28,29). In combination, these changes appear to have reduced the supply of nutrientrich, denitrified waters, which led to changes in the composition of the phytoplankton community at most sites formerly occupied by the diverse shelf-edge graptolite communities (21,22,30).…”

mentioning

confidence: 99%

“…The Blackstone River site (Ogilvie Mountains, Yukon, Canada; hereafter BR) was a shallower site located ∼3,000 km away, on the continental shelf, north of the paleoequator (32,33). Additionally, paleoenvironmental proxy data are available at these sites (21,22,30,34) that permit independent characterization of paleooceanographic changes. These data include e Nd values ( Fig.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Graptolite community responses to global climate change and the Late Ordovician mass extinction

Sheets

Mitchell

Melchin

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Mass extinctions disrupt ecological communities. Although climate changes produce stress in ecological communities, few paleobiological studies have systematically addressed the impact of global climate changes on the fine details of community structure with a view to understanding how changes in community structure presage, or even cause, biodiversity decline during mass extinctions. Based on a novel Bayesian approach to biotope assessment, we present a study of changes in species abundance distribution patterns of macroplanktonic graptolite faunas (∼447-444 Ma) leading into the Late Ordovician mass extinction. Communities at two contrasting sites exhibit significant decreases in complexity and evenness as a consequence of the preferential decline in abundance of dysaerobic zone specialist species. The observed changes in community complexity and evenness commenced well before the dramatic population depletions that mark the tipping point of the extinction event. Initially, community changes tracked changes in the oceanic water masses, but these relations broke down during the onset of mass extinction. Environmental isotope and biomarker data suggest that sea surface temperature and nutrient cycling in the paleotropical oceans changed sharply during the latest Katian time, with consequent changes in the extent of the oxygen minimum zone and phytoplankton community composition. Although many impacted species persisted in ephemeral populations, increased extinction risk selectively depleted the diversity of paleotropical graptolite species during the latest Katian and early Hirnantian. The effects of long-term climate change on habitats can thus degrade populations in ways that cascade through communities, with effects that culminate in mass extinction.abundance | climate change | extinction | macroevolution | selection M ass extinctions affect communities over a range of hierar-

show abstract

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Graptolite community responses to global climate change and the Late Ordovician mass extinction

Sheets

Mitchell

Melchin

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…With this possibility remaining open, more detailed basinal analyses of Paleozoic nitrogen isotopes (e.g. LaPorte et al, 2009;Luo et al, 2015) are required to parse out the differential influence of sea-level-and redox-driven variations in Phanerozoic nitrogen cycling.…”

Section: Phanerozoic (Since ~05 Gyr)mentioning

confidence: 99%

The evolution of Earth's biogeochemical nitrogen cycle

Stüeken

Kipp

Koehler

et al. 2016

Earth-Science Reviews

290

287

View full text Add to dashboard Cite

Nitrogen is an essential nutrient for all life on Earth and it acts as a major control on biological productivity in the modern ocean. Accurate reconstructions of the evolution of life over the course of the last four billion years therefore demand a better understanding of nitrogen bioavailability and speciation through time. The biogeochemical nitrogen cycle has evidently been closely tied to the redox state of the ocean and atmosphere. Multiple lines of evidence indicate that the Earth"s surface has passed in a non-linear fashion from an anoxic state in the Hadean to an oxic state in the later Phanerozoic. It is therefore likely that the nitrogen cycle has changed markedly over time, with potentially severe implications for the productivity and evolution of the biosphere. Here we compile nitrogen isotope data from the literature and review our current understanding of the evolution of the nitrogen cycle, with particular emphasis on the Precambrian. Combined with recent work on redox conditions, trace metal availability, sulfur and iron cycling on the early Earth, we then use the nitrogen isotope record as a platform to test existing and new hypotheses about biogeochemical pathways that may have controlled nitrogen availability through time. Among other things, we conclude that (a) abiotic nitrogen sources were likely insufficient to sustain a large biosphere, thus favoring an early origin of biological N 2 fixation, (b) evidence of nitrate in the Neoarchean and Paleoproterozoic confirm current views of increasing surface oxygen levels at those times, (c) abundant ferrous iron and sulfide in the midPrecambrian ocean may have affected the speciation and size of the fixed nitrogen reservoir, and (d) nitrate availability alone was not a major driver of eukaryotic evolution.

show abstract

Why are the δ¹³C_org values in Phanerozoic black shales more negative than in modern marine organic matter?

Meyers

2014

Geochem Geophys Geosyst

View full text Add to dashboard Cite

The d13 C org values of Phanerozoic black shales average 227&, whereas those of modern marine organic matter average 220&. The black shale isotopic values mimic those of continental organic matter, yet their organic geochemical properties mandate that they contain predominantly marine organic matter. Hypotheses that proposed to explain the low d13 C values of black shales include diagenetic losses of isotopically heavier organic matter components, releases of isotopically light carbon from methane clathrates or extensive magmatic events, greater photosynthetic discrimination against 13 C during times of higher atmospheric pCO 2 , and greenhouse climate stratification of the surface ocean that magnified photic zone recycling of isotopically light organic matter. Although the last possibility seems contrary to the vertical mixing that leads to the high productivity of modern oceanic upwelling systems, it is consistent with the strongly stratified conditions that accompanied deposition of the organic carbon-rich Pliocene-Pleistocene sapropels of the Mediterranean Sea. Because most Phanerozoic black shales contain evidence of photic zone anoxia similar to the sapropels, well-developed surface stratification of the oceans was likely involved in their formation. Existence of isotopically light land plant organic matter during several episodes of extensive magmatism that accompanied black shale deposition implies massive release of mantle CO 2 that added to the greenhouse conditions that favored oceanic stratification. The 13 C depletion common to most Phanerozoic black shales apparently resulted from a greenhouse climate associated with elevated atmospheric pCO 2 that led to a strongly stratified ocean and photic zone recycling of organic matter in, augmented by magmatic CO 2 releases.

show abstract

Local and global perspectives on carbon and nitrogen cycling during the Hirnantian glaciation

Cited by 143 publications

References 75 publications

Graptolite community responses to global climate change and the Late Ordovician mass extinction

Graptolite community responses to global climate change and the Late Ordovician mass extinction

The evolution of Earth's biogeochemical nitrogen cycle

Why are the δ¹³C_org values in Phanerozoic black shales more negative than in modern marine organic matter?

Contact Info

Product

Resources

About

Local and global perspectives on carbon and nitrogen cycling during the Hirnantian glaciation

Cited by 143 publications

References 75 publications

Graptolite community responses to global climate change and the Late Ordovician mass extinction

Graptolite community responses to global climate change and the Late Ordovician mass extinction

The evolution of Earth's biogeochemical nitrogen cycle

Why are the δ13Corg values in Phanerozoic black shales more negative than in modern marine organic matter?

Contact Info

Product

Resources

About

Why are the δ¹³C_org values in Phanerozoic black shales more negative than in modern marine organic matter?