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Modern Environments and Calibration Studies

Calibration studies of benthic foraminiferal shell composition

The isotopic and elemental composition of the calcium carbonate shells of fossil benthic foraminifera are widely used to estimate deep-ocean chemistry and temperature at the time of calcification, but these estimates are only as good as our understanding of the controls on foraminiferal shell chemistry. Global field calibrations, based on core-top specimens collected along environmental gradients, form the foundation of most benthic foraminiferal paleoenvironmental proxies. To complement ongoing field studies, we are developing laboratory culturing methods to isolate and manipulate individual environmental factors that influence benthic foraminiferal shell composition.

 

Calibration studies of living corals in their natural environment

Behind many coral-based paleoclimate records is an extensive calibration study designed to establish the relationship between skeletal composition and known (recorded) environmental variables such as temperature and salinity. Often, temperature loggers are attached to the living coral colony so that we know exactly what temperatures the coral experienced over a certain period of growth. In addition, we use Alizarin Red S, a pink CaCO3 stain, to place visible markers within the skeleton. Later, when the coral is sampled, the location of those stainlines tell us about rate and seasonality of skeletal growth.  Our current field sites include Bermuda and St Croix, USVI. We are also working on corals from the Great Barrier Reef, Mocambique and Sodwana Bay (southern Indian Ocean), Barbados, Bahamas, Tahiti, North Carolina and Woods Hole, Massachusetts!