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Wizemann, Andre; Meyer, Friedrich Wilhelm; Hofmann, Laurie C; Wild, Christian; Westphal, Hildegard (2015): Ocean acidification alters the calcareous microstructure of the green macro-alga Halimeda opuntia. PANGAEA, https://doi.org/10.1594/PANGAEA.846939, Supplement to: Wizemann, A et al. (2015): Ocean acidification alters the calcareous microstructure of the green macro-alga Halimeda opuntia. Coral Reefs, https://doi.org/10.1007/s00338-015-1288-9

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Abstract:
Decreases in seawater pH and carbonate saturation state (Omega) following the continuous increase in atmospheric CO2 represent a process termed ocean acidification, which is predicted to become a main threat to marine calcifiers in the near future. Segmented, tropical, marine green macro-algae of the genus Halimeda form a calcareous skeleton that involves biotically initiated and induced calcification processes influenced by cell physiology. As Halimeda is an important habitat provider and major carbonate sediment producer in tropical shallow areas, alterations of these processes due to ocean acidification may cause changes in the skeletal microstructure that have major consequences for the alga and its environment, but related knowledge is scarce. This study used scanning electron microscopy to examine changes of the CaCO3 segment microstructure of Halimedaopuntia specimens that had been exposed to artificially elevated seawater pCO2 of 650 µatm for 45 d. In spite of elevated seawater pCO2, the calcification of needles, located at the former utricle walls, was not reduced as frequent initiation of new needle-shaped crystals was observed. Abundance of the needles was 22 %/µm**2 higher and needle crystal dimensions 14 % longer. However, those needles were 42 % thinner compared with the control treatment. Moreover, lifetime cementation of the segments decreased under elevated seawater pCO2 due to a loss in micro-anhedral carbonate as indicated by significantly thinner calcified rims of central utricles (35-173 % compared with the control treatment). Decreased micro-anhedral carbonate suggests that seawater within the inter-utricular space becomes CaCO3 undersaturated (Omega < 1) during nighttime under conditions of elevated seawater pCO2, thereby favoring CaCO3 dissolution over micro-anhedral carbonate accretion. Less-cemented segments of H. opuntia may impair the environmental success of the alga, its carbonate sediment contribution, and the temporal storage of atmospheric CO2 within Halimeda-derived sediments.
Keyword(s):
Benthos; Chlorophyta; Coast and continental shelf; Containers and aquaria (20-1000 L or < 1 m**2); Growth/Morphology; Halimeda opuntia; Laboratory experiment; Macroalgae; Plantae; Single species; South Pacific; Tropical
Further details:
Gattuso, Jean-Pierre; Epitalon, Jean-Marie; Lavigne, Héloise (2015): seacarb: seawater carbonate chemistry with R. R package version 3.0.6. https://cran.r-project.org/package=seacarb
Comment:
In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2015) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2015-06-01.
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1SpeciesSpeciesWizemann, Andre
2TreatmentTreatWizemann, Andre
3Image number/nameImageWizemann, Andre
4NeedlesNeedlesWizemann, Andre
5LengthlµmWizemann, Andre
6WidthwµmWizemann, Andre
7Duration, number of daysDurationdaysWizemann, Andre
8TreatmentTreatWizemann, Andre
9LengthlµmWizemann, Andremedullary utricles
10IdentificationIDWizemann, Andrequadrate
11IdentificationIDWizemann, Andre
12NeedlesNeedles#Wizemann, Andre
13Alkalinity, totalATµmol/kgWizemann, AndrePotentiometric titration
14SalinitySalWizemann, Andre
15Temperature, waterTemp°CWizemann, Andre
16pHpHWizemann, AndrePotentiometricNBS scale
17Carbonate system computation flagCSC flagYang, YanCalculated using seacarb after Nisumaa et al. (2010)
18pHpHYang, YanCalculated using seacarb after Nisumaa et al. (2010)total scale
19Carbon dioxideCO2µmol/kgYang, YanCalculated using seacarb after Nisumaa et al. (2010)
20Fugacity of carbon dioxide (water) at sea surface temperature (wet air)fCO2water_SST_wetµatmYang, YanCalculated using seacarb after Nisumaa et al. (2010)
21Partial pressure of carbon dioxide (water) at sea surface temperature (wet air)pCO2water_SST_wetµatmYang, YanCalculated using seacarb after Nisumaa et al. (2010)
22Bicarbonate ion[HCO3]-µmol/kgYang, YanCalculated using seacarb after Nisumaa et al. (2010)
23Carbonate ion[CO3]2-µmol/kgYang, YanCalculated using seacarb after Nisumaa et al. (2010)
24Carbon, inorganic, dissolvedDICµmol/kgYang, YanCalculated using seacarb after Nisumaa et al. (2010)
25Aragonite saturation stateOmega ArgYang, YanCalculated using seacarb after Nisumaa et al. (2010)
26Calcite saturation stateOmega CalYang, YanCalculated using seacarb after Nisumaa et al. (2010)
Size:
6772 data points

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