Stable isotope geochemistry of corals from Costa Rica as proxy indicator of the El Nino/Southern Oscillation (ENSO)
- McMaster Univ., Hamilton, Ontario (Canada)
The authors analyzed the [delta][sup 18]O and [delta][sup 13]C time-series contained in coral skeletons collected from Isla de Cano, Costa Rica, that survived the 1982-1983 El Nino warming event. Coral [delta][sup 18]O give a record of thermal histories with a precision of [approximately]0.5[degrees]C. For this locality, the authors have determined that the average [Delta][delta][sub w] effect in the coral skeletons is equivalent to 33% of the skeletal [delta][sup 18]O range. Therefore, if [delta][sub w] effects are not compensated for, the annual skeletal-[delta][sup 18]O range displays a temperature range of 1[degrees]C lower than actual values. The isotopic record of Porites lobata skeletons shows simultaneous depletions in [sup 18]O and [sup 13]C at skeletal levels corresponding to 1983, coincident with the El Nino/Southern Oscillation (ENSO) event. Therefore, the El Nino event is not only recorded as negative [delta][sup 18]O anomalies in the skeleton, suggesting the warming of ambient waters, but also in the [delta][sup 13]C signal as negative anomalies, indicating coral bleaching. Contrary to the predictions of the [open quotes][sup 13]C-insolation model[close quotes] that the annual carbon isotope variation should be attenuated with depth in proportion to the decrease in light-intensity variation with depth, the authors found a clear trend where [Delta][delta][minus][sup 13]C increases with depth. Coral bioenergetics, which depends on both coral physiology and ecology, may adequately explain the unexpected increase in [delta][sup 13]C range with depth, without contradicting the seasonal character of [delta][sup 13]C variability with the solar irradiance cycle. Although some authors have determined the presence of hiatuses in the skeletal record due to severe stress and growth cessation, in this study it has been found that skeletal growth was not seriously diminished during the El Nino year of 1983.
- OSTI ID:
- 5148022
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Vol. 58:1; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBON 13
ISOTOPE RATIO
CLIMATIC CHANGE
GEOLOGIC HISTORY
CORALS
QUANTITATIVE CHEMICAL ANALYSIS
OXYGEN 18
SOUTHERN OSCILLATION
BIOLOGICAL INDICATORS
COSTA RICA
TIME-SERIES ANALYSIS
ANIMALS
CARBON ISOTOPES
CENTRAL AMERICA
CHEMICAL ANALYSIS
CNIDARIA
COELENTERATA
DEVELOPING COUNTRIES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
INVERTEBRATES
ISOTOPES
LATIN AMERICA
LIGHT NUCLEI
MATHEMATICS
NUCLEI
OXYGEN ISOTOPES
STABLE ISOTOPES
540310* - Environment
Aquatic- Basic Studies- (1990-)
540110