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Tidal modulation of Sr/Ca ratios in a Pacific reef coral
Author(s) -
Cohen Anne L.,
Sohn Robert A.
Publication year - 2004
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2004gl020600
Subject(s) - coral , oceanography , reef , forcing (mathematics) , strontium , coral reef , porites , zooxanthellae , sea surface temperature , geology , photosynthesis , environmental science , atmospheric sciences , chemistry , biology , symbiosis , botany , paleontology , organic chemistry , bacteria
The strontium‐to‐calcium ratio (Sr/Ca) of reef coral skeleton is an important tool for reconstructing past sea surface temperatures (SSTs). However, the accuracy of paleoSSTs derived from fossil coral Sr/Ca is challenged by evidence that physiological processes influence skeletal chemistry. Here we show that water level variations from tidal forcing are correlated with changes in coral Sr/Ca that cannot be accounted for by changes in SST. Ion microprobe measurements of Sr/Ca ratios in a Pacific Porites lutea reveal high‐frequency variations at periods of ∼6, ∼10, and ∼25 days. The relationship between Sr/Ca and temperature on these short timescales does not follow trends observed at longer periods, indicating that an additional forcing is required to explain our observations. We demonstrate that Sr/Ca is correlated with both tidal water level variations and SST, and that their contributions to the Sr/Ca content of the skeleton vary as a function of period. We propose that water level influences Sr/Ca indirectly via modulation of photosynthetically‐active radiation (PAR) that drives large changes in zooxanthellate photosynthesis.