Variability of stable isotopes and maximum linear extension in reef-coral skeletons at Kaneohe Bay, Hawaii |
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Authors: | A G Grottoli |
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Institution: | (1) Department of Biology, University of Houston, Houston, Texas 77204-5513, USA, US |
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Abstract: | Stable-isotope and growth records of coral skeletons are often used to reconstruct tropical paleoclimate, yet few surveys
have systematically examined the natural variability in coral skeletal 13C, 18O and maximum linear skeletal extension (MLSE) across depth. Here, interspecific, intraspecific, and geographical variations
in coral skeletal 13C, 18O, and MLSE were examined in the corals Porites compressa, P. lobata, and Montipora verrucosa grown at 1.7, 5.0, and 8.3 m depth from August 1996 to March 1997 at The Point Reef and Patch Reef #41 field sites in Kaneohe
Bay, Hawaii. Coral skeletal 13C values significantly decreased with depth and differed between species, but did not vary between field sites. 18O values were not significantly different across depth within a species, but did differ among species and field sites. High-resolution
analysis of the intra-annual variation in skeletal 13C and 18O in P. compressa at 2.0 m depth confirms that these isotopes reflect changes in solar irradiance and temperature, respectively. Changes in
MLSE across depth were consistent within, but highly variable among, species. Peak MLSE occurred at 1.7, 5.0, and 8.3 m for
P. lobata, P. compressa, and M. verrucosa, respectively. Such interspecific variation in MLSE patterns may be attributable to one or more of the following: increases
in zooplankton in the diet, changes in metabolic processes, or changes in growth form with depth. Overall, these results imply
that natural inter- and intraspecific variability in coral skeletal 13C, 18O, and MLSE should be considered when interpreting and comparing coral-based tropical paleoclimate data from various coral
species, depths, and field sites.
Received: 6 October 1998 / Accepted: 8 July 1999 |
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