Joan M. Bernhard

Culturing studies of environmental controls on benthic foraminiferal shell chemistry

Tom Chandler (University of South Carolina); Tim Shaw (University of South Carolina); Dan McCorkle (WHOI G&G); Christopher Hintz (USC postdoc); Jessica Blanks (USC MS student); Helena Filipsson (Goteborg University, Sweden); Sara Lincoln (MIT PhD student)

Colleagues and I culture deep-water calcareous benthic foraminifera. Culturing methods provide ways to study environmental and physiological (?vital?) influences on the foraminifer?s shell chemistry. Our recent efforts resulted in growth and reproduction of Bulimina aculeata, an infaunal species common on the NW Atlantic continental margin, under controlled conditions in artificial-sediment culture chambers. The stable isotopic and trace element compositions of these cultured B. aculeata were determined, and the foraminiferal *13C, *18O, Cd/Ca, and Ba/Ca values were compared with the water chemistry of the culture system, and with the shell chemistry of ?free-range? B. aculeata (see Hintz et al. 2004 Limnology & Oceanography Methods; Hintz et al. in press Geochimica et Cosmochimica Acta for more detailed discussion of results). This study demonstrated that foraminiferal cultures that reproduce and calcify can be maintained under tightly constrained carbonate chemistry and trace element concentrations and that the cultured foraminifera show reproducible, interpretable compositional patterns that are consistent with field-based understanding of foraminiferal ecology and shell chemistry. Presently, we are conducting experimental studies designed to isolate the influence of single factors (e.g., carbonate ion concentration; trace element composition; temperature) that influence benthic foraminiferal shell chemistry. In addition to these culturing studies, related field-based studies of in situ foraminiferal life positions and shell composition are also being conducted. This material is based upon work supported by the National Science Foundation under Grant No. 0437366. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Aside from the trace metal and carbonate ion work funded by NSF Marine Geology & Geophysics; initial temperature experiments were funded by WHOI's Ocean & Climate Change Institute, which led to additional (ongoing) funding from NSF Marine Geology & Geophysics. These temperature experiments are being done in collaboration with Helena Filipsson (Goteborg University, Sweden) and Sara Lincoln (MIT). See a recent article from Oceanus magazine about this project: Cell-sized Thermometers.

Last updated: December 18, 2013