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Degradation of Internal Organic Matter is the Main Control on Pteropod Shell Dissolution After Death
Author(s) -
Oakes R. L.,
Peck V. L.,
Manno C.,
Bralower T. J.
Publication year - 2019
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2019gb006223
Subject(s) - aragonite , dissolution , carbonate , seawater , organic matter , calcite , geology , ocean acidification , saturation (graph theory) , mineralogy , sediment , pyrite , environmental chemistry , oceanography , chemistry , materials science , paleontology , metallurgy , mathematics , organic chemistry , combinatorics
The potential for preservation of thecosome pteropods is thought to be largely governed by the chemical stability of their delicate aragonitic shells in seawater. However, sediment trap studies have found that significant carbonate dissolution can occur above the carbonate saturation horizon. Here we present the results from experiments conducted on two cruises to the Scotia Sea to directly test whether the breakdown of the organic pteropod body influences shell dissolution. We find that on the timescales of 3 to 13 days, the oxidation of organic matter within the shells of dead pteropods is a stronger driver of shell dissolution than the aragonite saturation state of seawater. Three to four days after death, shells became milky white and nano scanning electron microscope images reveal smoothing of internal surface features and increased shell porosity, both indicative of aragonite dissolution. These findings have implications for the interpretation of the condition of pteropod shells from sediment traps and the fossil record, as well as for understanding the processes controlling particulate carbonate export from the surface ocean.