Geologic controls on phytoplankton elemental composition

Planktonic organic matter forms the base of the marine food web, and its nutrient content (C:N:Porg) governs material and energy fluxes in the ocean. Over Earth history, C:N:Porg had a crucial role in marine metazoan evolution and global biogeochemical dynamics, but the geologic history of C:N:Porg is unknown, and it is often regarded constant at the “Redfield” ratio of ∼106:16:1. We calculated C:N:Porg through Phanerozoic time by including nutrient- and temperature-dependent C:N:Porg parameterizations in a model of the long-timescale biogeochemical cycles. We infer a decrease from high Paleozoic C:Porg and N:Porg to present-day ratios, which stems from a decrease in the global average temperature and an increase in seawater phosphate availability. These changes in the phytoplankton’s growth environment were driven by various Phanerozoic events: specifically, the middle to late Paleozoic expansion of land plants and the Triassic breakup of the supercontinent Pangaea, which increased continental weatherability and the fluxes of weathering-derived phosphate to the oceans. The resulting increase in the nutrient content of planktonic organic matter likely impacted the evolution of marine fauna and global biogeochemistry.

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Geologic controls on phytoplankton elemental composition

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2113263119 ◽

2021 ◽

Vol 119 (1) ◽

pp. e2113263119

Author(s):

Shlomit Sharoni ◽

Itay Halevy

Keyword(s):

Organic Matter ◽

Nutrient Content ◽

Geologic History ◽

Temperature Dependent ◽

Marine Fauna ◽

Growth Environment ◽

Marine Food Web ◽

Average Temperature ◽

Phosphate Availability ◽

History Of

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Geologic controls on phytoplankton elemental composition

10.21203/rs.3.rs-763415/v1 ◽

2021 ◽

Author(s):

Shlomit Sharoni ◽

Itay Halevy

Keyword(s):

Organic Matter ◽

Nutrient Enrichment ◽

Nutrient Content ◽

Geologic History ◽

Marine Fauna ◽

Average Temperature ◽

Marine Organic Matter ◽

Phosphate Availability ◽

Redfield Ratios

Abstract Although the nutrient content of planktonic organic matter (C:N:Porg) plays a crucial role in marine metazoan evolution and global biogeochemistry (1–3), its geologic history is poorly constrained, and it is often regarded as a constant “Redfield” ratio of C:N:Porg~106:16:1. We calculate C:N:Porg through the Phanerozoic by including nutrient- and temperature-dependent C:N:Porg parameterizations (4–6) in a model of long-term biogeochemical cycles (7). We infer a decrease from high Paleozoic C:Porg and N:Porg to present-day Redfield ratios. This gradual nutrient enrichment of marine organic matter stems from a decrease in the global average temperature and an increase in seawater phosphate availability, which are driven by various Phanerozoic events, mainly the middle to late Paleozoic emergence and expansion of land plants and the Triassic breakup of the supercontinent Pangaea. The nutrient enrichment of planktonic organic matter likely impacted the evolution of marine fauna and global biogeochemistry.

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The geologic history of seawater oxygen isotopes from marine iron oxides

Science ◽

10.1126/science.aaw9247 ◽

2019 ◽

Vol 365 (6452) ◽

pp. 469-473 ◽

Cited By ~ 24

Author(s):

Nir Galili ◽

Aldo Shemesh ◽

Ruth Yam ◽

Irena Brailovsky ◽

Michal Sela-Adler ◽

...

Keyword(s):

Iron Oxide ◽

Oxygen Isotope ◽

Iron Oxides ◽

Isotope Composition ◽

Geologic History ◽

Temperature Dependent ◽

Oxygen Isotope Fractionation ◽

History Of ◽

Sediment Cover

The oxygen isotope composition (δ18O) of marine sedimentary rocks has increased by 10 to 15 per mil since Archean time. Interpretation of this trend is hindered by the dual control of temperature and fluid δ18O on the rocks’ isotopic composition. A new δ18O record in marine iron oxides covering the past ~2000 million years shows a similar secular rise. Iron oxide precipitation experiments reveal a weakly temperature-dependent iron oxide–water oxygen isotope fractionation, suggesting that increasing seawater δ18O over time was the primary cause of the long-term rise in δ18O values of marine precipitates. The18O enrichment may have been driven by an increase in terrestrial sediment cover, a change in the proportion of high- and low-temperature crustal alteration, or a combination of these and other factors.

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Elements for a General Organology

Derrida Today ◽

10.3366/drt.2020.0220 ◽

2020 ◽

Vol 13 (1) ◽

pp. 72-94

Author(s):

Bernard Stiegler

Keyword(s):

Organic Matter ◽

Planetary Scale ◽

General Account ◽

Inorganic Matter ◽

History Of

These lectures outline the project of a general organology, which is to say an account of life when it is no longer just biological but technical, or when it involves not just organic matter but organized inorganic matter. This organology is also shown to require a modified Simondonian account of the shift from vital individuation to a three-stranded process of psychic, collective and technical individuation. Furthermore, such an approach involves extending the Derridean reading of Socrates's discussion of writing as a pharmakon, so that it becomes a more general account of the pharmacological character of retention and protention. By going back to Leroi-Gourhan, we can recognize that this also means pursuing the history of retentional modifications unfolding in the course of the history of what, with Lotka, can also be called exosomatization. It is thus a question of how exteriorization can, today, in an epoch when it becomes digital, and in an epoch that produces vast amounts of entropy at the thermodynamic, biological and noetic levels, still possibly produce new forms of interiorization, that is, new forms of thought, care and desire, amounting to so many chances to struggle against the planetary-scale pharmacological crisis with which we are currently afflicted.

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