Ocean acidification reduces hardness and stiffness of the Portuguese oyster shell with impaired microstructure: a hierarchical analysis
Type | Article | ||||||||||||||||
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Date | 2018-11 | ||||||||||||||||
Language | English | ||||||||||||||||
Author(s) | Meng Yuan1, 2, Guo Zhenbin3, Fitzer Susan C.4, Upadhyay Abhishek1, 2, Chan Bin San5, 6, Li Chaoyi1, 2, Cusack Maggie7, Yao Haimin3, Yeung Kelvin W. K.8, Thiyagarajan Vengatesen1, 2, 9 | ||||||||||||||||
Affiliation(s) | 1 : Univ Hong Kong, Swire Inst Marine Sci, Pokfulam, Hong Kong, Peoples R China. 2 : Univ Hong Kong, Sch Biol Sci, Pokfulam, Hong Kong, Peoples R China. 3 : Hong Kong Polytech Univ, Dept Mech Engn, Kowloon, Hong Kong, Peoples R China. 4 : Univ Stirling, Fac Nat Sci, Inst Aquaculture, Pathfoot Bldg, Stirling FK9 4LA, Scotland. 5 : Clemson Univ, Dept Biol Sci, Clemson, SC 29634 USA. 6 : IFREMER, Physiol Fonct Organismes Marins, UMR 6539, LEMAR,CNRS,UBO,IRD, CS 10070, F-29280 Plouzane, France. 7 : Univ Stirling, Fac Nat Sci, Div Biol & Environm Sci, Cottrell Bldg, Stirling FK9 4LA, Scotland. 8 : Univ Hong Kong, Queen Mary Hosp, Dept Orthopaed & Traumatol, Pokfulam, Hong Kong, Peoples R China. 9 : State Key Lab Marine Pollut, Hong Kong, Hong Kong, Peoples R China. |
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Source | Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2018-11 , Vol. 15 , N. 22 , P. 6833-6846 | ||||||||||||||||
DOI | 10.5194/bg-15-6833-2018 | ||||||||||||||||
WOS© Times Cited | 33 | ||||||||||||||||
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. |
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