Role of Increased Marine Silica Input on Paleo-pCO2 Levels

http://www.agu.org/journals/pa/v015/i003/1999PA000427/

PALEOCEANOGRAPHY, VOL. 15, NO. 3, PAGES 292–298, 2000

Role of Increased Marine Silica Input on Paleo-pCO2 Levels

Kevin G. Harrison
Geology and Geophysics Department, Boston College, Chestnut Hill, Massachusetts

Abstract

Changing the supply of silica to the ocean may alter pCO2 levels. The increase in dust delivered to the ocean during glacial times increased the availability of silica for biological uptake. The increased silica levels shifted species composition: Diatom populations increased and coccolith populations decreased. Decreasing the population of coccoliths decreased the flux of calcite to the sediments, which, in turn, lowered pCO2 levels enough to explain the glacial-interglacial pCO2 transition. Furthermore, the contemporary increase in dust delivered to the ocean’s mixed layer may be removing significant amounts of carbon dioxide from the atmosphere at present. To set the stage, this silica hypothesis is compared with the iron fertilization and nitrogen fixation hypotheses.

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Silica flow into oceans has decreased in 20th Century and has not increased, this is one of the causes of Dead Zones in estuaries and coastal waters and for fish kills and harmful algal blooms in lakes and rivers.

The reduction is silica is both actual and in proportion to N and P flow.
Dams reduce the amount of silt flowing down rivers and higher agricultural activity results in higher N and P flow down rivers.

Its well documented that in River Mississippi Si : N ratio was 3 : 1 fifty years ago and not its < 1 : 1. This has resulted in the Gulf of Mexico Dead Zone.