New Publication: Complexity of Nearshore Strontium-to-Calcium Ratio Variability in a Core Sample of the Massive Coral Siderastrea siderea Obtained in Coral Bay, St. John, U.S. Virgin Islands
This study shows that a colony of the massive starlet coral, Siderastrea siderea, from the Island of St. John, U.S. Virgin Islands, does not show clear annual patterns in skeletal density or in the ratio of strontium to calcium. Since both annual density banding and Sr/Ca are used to deduce ocean temperature in the past, other proxies may need to be used to reconstruct sea surface temperature at this location. While the study does reveal problems for the Sr/Ca proxy on the island of St. John, preliminary analyses on corals of the same species from St. Thomas are showing usable records.
From the Abstract:
Strontium-to-calcium ratios (Sr/Ca) were measured on the skeletal matrix of a core sample from a colony of the massive coral Siderastrea siderea collected in Coral Bay, St. John, U.S. Virgin Islands. Strontium and calcium are incorporated into the coral skeleton during the precipitation of aragonite by the coral polyps and their ratio is highly temperature dependent. The robustness of this temperature dependence makes Sr/Ca a reliable proxy for sea surface temperature (SST). Details presented from the St. John S. siderea core indicate that terrestrial inputs of sediment and freshwater can disrupt the chemical balance and subsequently complicate the utility of Sr/Ca in reconstructing historical SST. An approximately 44-year-long record of Sr/Ca shows that an annual SST signal is recorded but with an increasing Sr/Ca trend from 1980 to present, which is likely the result of runoff from the mountainous terrain of St. John. The overwhelming influence of the terrestrial fingerprint on local seawater chemistry makes utilizing Sr/Ca as a SST proxy in nearshore environments very difficult.
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Citation: Reich, C.D., Kuffner, I.B., Hickey, T.D., Morrison, J.M., and Flannery, J.A., 2013, Complexity of nearshore strontium-to-calcium ratio variability in a core sample of the massive coral Siderastrea siderea obtained in Coral Bay, St. John, U.S. Virgin Islands: U.S. Geological Survey Open-File Report 2013–1092, 12 p.
From the Abstract:
Strontium-to-calcium ratios (Sr/Ca) were measured on the skeletal matrix of a core sample from a colony of the massive coral Siderastrea siderea collected in Coral Bay, St. John, U.S. Virgin Islands. Strontium and calcium are incorporated into the coral skeleton during the precipitation of aragonite by the coral polyps and their ratio is highly temperature dependent. The robustness of this temperature dependence makes Sr/Ca a reliable proxy for sea surface temperature (SST). Details presented from the St. John S. siderea core indicate that terrestrial inputs of sediment and freshwater can disrupt the chemical balance and subsequently complicate the utility of Sr/Ca in reconstructing historical SST. An approximately 44-year-long record of Sr/Ca shows that an annual SST signal is recorded but with an increasing Sr/Ca trend from 1980 to present, which is likely the result of runoff from the mountainous terrain of St. John. The overwhelming influence of the terrestrial fingerprint on local seawater chemistry makes utilizing Sr/Ca as a SST proxy in nearshore environments very difficult.
Click here to view the full article.
Citation: Reich, C.D., Kuffner, I.B., Hickey, T.D., Morrison, J.M., and Flannery, J.A., 2013, Complexity of nearshore strontium-to-calcium ratio variability in a core sample of the massive coral Siderastrea siderea obtained in Coral Bay, St. John, U.S. Virgin Islands: U.S. Geological Survey Open-File Report 2013–1092, 12 p.