Ocean acidification reduces hardness and stiffness of the Portuguese oyster shell with impaired microstructure: a hierarchical analysis
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Published:2018-11-16
Issue:22
Volume:15
Page:6833-6846
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Meng Yuan, Guo Zhenbin, Fitzer Susan C.ORCID, Upadhyay Abhishek, Chan Vera B. S.ORCID, Li Chaoyi, Cusack Maggie, Yao Haimin, Yeung Kelvin W. K., Thiyagarajan Vengatesen
Abstract
Abstract. The rapidly intensifying process of ocean acidification (OA) due to
anthropogenic CO2 is not only depleting carbonate ions necessary
for calcification but also causing acidosis and disrupting internal pH
homeostasis in several marine organisms. These negative consequences of OA on
marine calcifiers, i.e. oyster species, have been very well documented in
recent studies; however, the consequences of reduced or impaired
calcification on the end-product, shells or skeletons, still remain one of
the major research gaps. Shells produced by marine organisms under OA are
expected to show signs of dissolution, disorganized microstructure and
reduced mechanical properties. To bridge this knowledge gap and to test the
above hypothesis, we investigated the effect of OA on juvenile shells of the
commercially important oyster species, Magallana angulata,
at ecologically and climatically relevant OA levels (using pH 8.1, 7.8, 7.5,
7.2). In lower pH conditions, a drop of shell hardness and stiffness was
revealed by nanoindentation tests, while an evident porous internal
microstructure was detected by scanning electron microscopy. Crystallographic
orientation, on the other hand, showed no significant difference with
decreasing pH using electron back-scattered diffraction (EBSD). These results
indicate the porous internal microstructure may be the cause of the reduction
in shell hardness and stiffness. The overall decrease of shell density observed
from micro-computed tomography analysis indicates the porous internal
microstructure may run through the shell, thus inevitably limiting the
effectiveness of the shell's defensive function. This study shows the potential
deterioration of oyster shells induced by OA, especially in their early life
stage. This knowledge is critical to estimate the survival and production of
edible oysters in the future ocean.
Funder
Research Grants Council, University Grants Committee
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
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