 |
| Titel |
CO₃²⁻ concentration and pCO₂ thresholds for calcification and dissolution on the Molokai reef flat, Hawaii |
| VerfasserIn |
K. K. Yates, R. B. Halley |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 3, no. 3 ; Nr. 3, no. 3 (2006-07-24), S.357-369 |
| Datensatznummer |
250001063
|
| Publikation (Nr.) |
 copernicus.org/bg-3-357-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
| The severity of the impact of elevated atmospheric pCO2 to coral reef
ecosystems depends, in part, on how seawater pCO2 affects the balance
between calcification and dissolution of carbonate sediments. Presently,
there are insufficient published data that relate concentrations of
pCO2 and CO32− to in situ rates of reef calcification in
natural settings to accurately predict the impact of elevated atmospheric
pCO2 on calcification and dissolution processes. Rates of net
calcification and dissolution, CO32− concentrations, and pCO2
were measured, in situ, on patch reefs, bare sand, and coral rubble on the
Molokai reef flat in Hawaii. Rates of calcification ranged from 0.03 to 2.30
mmol CaCO3 m−2 h−1 and dissolution ranged from –0.05 to –3.3
mmol CaCO3 m−2 h−1. Calcification and dissolution varied
diurnally with net calcification primarily occurring during the day and net
dissolution occurring at night. These data were used to calculate threshold
values for pCO2 and CO32− at which rates of calcification and
dissolution are equivalent. Results indicate that calcification and
dissolution are linearly correlated with both CO32− and pCO2.
Threshold pCO2 and CO32− values for individual substrate
types showed considerable variation. The average pCO2 threshold value
for all substrate types was 654±195 μatm and ranged from 467 to
1003 μatm. The average CO32− threshold value was 152±24 μmol
kg−1, ranging from 113 to 184 μmol kg−1. Ambient
seawater measurements of pCO2 and CO32− indicate that
CO32− and pCO2 threshold values for all substrate types were
both exceeded, simultaneously, 13% of the time at present day atmospheric
pCO2 concentrations. It is predicted that atmospheric pCO2 will
exceed the average pCO2 threshold value for calcification and
dissolution on the Molokai reef flat by the year 2100. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|