| 1. |
- Fitzer, Susan C., et al.
(författare)
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Biomineral shell formation under ocean acidification : a shift from order to chaos
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Biomineral production in marine organisms employs transient phases of amorphous calcium carbonate (ACC) in the construction of crystalline shells. Increasing seawater pCO(2) leads to ocean acidification (OA) with a reduction in oceanic carbonate concentration which could have a negative impact on shell formation and therefore survival. We demonstrate significant changes in the hydrated and dehydrated forms of ACC in the aragonite and calcite layers of Mytilus edulis shells cultured under acidification conditions (1000 mu atm pCO(2)) compared to present day conditions (380 mu atm pCO(2)). In OA conditions, Mytilus edulis has more ACC at crystalisation sites. Here, we use the high-spatial resolution of synchrotron X-ray Photo Emission Electron Microscopy (XPEEM) combined with X-ray Absorption Spectroscopy (XAS) to investigate the influence of OA on the ACC formation in the shells of adult Mytilus edulis. Electron Backscatter Diffraction (EBSD) confirms that OA reduces crystallographic control of shell formation. The results demonstrate that OA induces more ACC formation and less crystallographic control in mussels suggesting that ACC is used as a repair mechanism to combat shell damage under OA. However, the resultant reduced crystallographic control in mussels raises concerns for shell protective function under predation and changing environments.
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| 2. |
- Fitzer, Susan C., et al.
(författare)
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Ocean acidification alters the material properties of Mytilus edulis shells
- 2015
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Ingår i: Journal of the Royal Society Interface. - : Royal Society Publishing. - 1742-5689 .- 1742-5662. ; 12:103
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Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis, was cultured at projected levels of pCO(2) (380, 550, 750, 1000 mu atm) and increased temperatures (ambient, ambient plus 2 degrees C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus (E), hardness (H) and toughness (K-IC) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more brittle in OA conditions while the inner shell (aragonite) is softer and less stiff in shells grown under OA conditions. Combining increasing ocean pCO(2) and temperatures as projected for future global ocean appears to reduce the impact of increasing pCO(2) on the material properties of the mussel shell. OA may cause changes in shell material properties that could prove problematic under predation scenarios for the mussels; however, this may be partially mitigated by increasing temperature.
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| 3. |
- Fitzer, Susan C., et al.
(författare)
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Ocean acidification and temperature increase impact mussel shell shape and thickness : problematic for protection?
- 2015
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 5:21, s. 4875-4884
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Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification threatens organisms that produce calcium carbonate shells by potentially generating an under-saturated carbonate environment. Resultant reduced calcification and growth, and subsequent dissolution of exoskeletons, would raise concerns over the ability of the shell to provide protection for the marine organism under ocean acidification and increased temperatures. We examined the impact of combined ocean acidification and temperature increase on shell formation of the economically important edible mussel Mytilus edulis. Shell growth and thickness along with a shell thickness index and shape analysis were determined. The ability of M.edulis to produce a functional protective shell after 9months of experimental culture under ocean acidification and increasing temperatures (380, 550, 750, 1000atm pCO(2), and 750, 1000atm pCO(2)+2 degrees C) was assessed. Mussel shells grown under ocean acidification conditions displayed significant reductions in shell aragonite thickness, shell thickness index, and changes to shell shape (750, 1000atm pCO(2)) compared to those shells grown under ambient conditions (380atm pCO(2)). Ocean acidification resulted in rounder, flatter mussel shells with thinner aragonite layers likely to be more vulnerable to fracture under changing environments and predation. The changes in shape presented here could present a compensatory mechanism to enhance protection against predators and changing environments under ocean acidification when mussels are unable to grow thicker shells. Here, we present the first assessment of mussel shell shape to determine implications for functional protection under ocean acidification.
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| 4. |
- Fitzer, Susan C., et al.
(författare)
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Ocean acidification impacts mussel control on biomineralisation
- 2014
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification is altering the oceanic carbonate saturation state and threatening the survival of marine calcifying organisms. Production of their calcium carbonate exoskeletons is dependent not only on the environmental seawater carbonate chemistry but also the ability to produce biominerals through proteins. We present shell growth and structural responses by the economically important marine calcifier Mytilus edulis to ocean acidification scenarios (380, 550, 750, 1000 mu atm pCO(2)). After six months of incubation at 750 matm pCO(2), reduced carbonic anhydrase protein activity and shell growth occurs in M. edulis. Beyond that, at 1000 matm pCO(2), biomineralisation continued but with compensated metabolism of proteins and increased calcite growth. Mussel growth occurs at a cost to the structural integrity of the shell due to structural disorientation of calcite crystals. This loss of structural integrity could impact mussel shell strength and reduce protection from predators and changing environments.
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| 5. |
- Fitzer, Susan C., et al.
(författare)
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Ocean acidification reduces the crystallographic control in juvenile mussel shells
- 2014
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Ingår i: Journal of Structural Biology. - : Elsevier. - 1047-8477 .- 1095-8657. ; 188:1, s. 39-45
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Tidskriftsartikel (refereegranskat)abstract
- Global climate change threatens the oceans as anthropogenic carbon dioxide causes ocean acidification and reduced carbonate saturation. Future projections indicate under saturation of aragonite, and potentially calcite, in the oceans by 2100. Calcifying organisms are those most at risk from such ocean acidification, as carbonate is vital in the biomineralisation of their calcium carbonate protective shells. This study highlights the importance of multi-generational studies to investigate how marine organisms can potentially adapt to future projected global climate change. Mytilus edulis is an economically important marine calcifier vulnerable to decreasing carbonate saturation as their shells comprise two calcium carbonate polymorphs: aragonite and calcite. M. edulis specimens were cultured under current and projected pCO(2) (380, 550, 750 and 1000 mu atm), following 6 months of experimental culture, adults produced second generation juvenile mussels. juvenile mussel shells were examined for structural and crystallographic orientation of aragonite and calcite. At 1000 mu atm pCO(2), juvenile mussels spawned and grown under this high pCO(2) do not produce aragonite which is more vulnerable to carbonate under-saturation than calcite. Calcite and aragonite were produced at 380, 550 and 750 mu atm pCO(2). Electron back scatter diffraction analyses reveal less constraint in crystallographic orientation with increased pCO(2). Shell formation is maintained, although the nacre crystals appear corroded and crystals are not so closely layered together. The differences in ultrastructure and crystallography in shells formed by juveniles spawned from adults in high pCO(2) conditions may prove instrumental in their ability to survive ocean acidification.
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