The influence of salinity on Mg/Ca in planktic foraminifers - evidence from cultures, core-top sediments and complementary δ18O
Allen, Katherine A.
Lea, David W.
Spero, Howard J.
Eggins, Stephen M.
deMenocal, Peter B.
Russell, Ann D.
MetadataShow full item record
The Mg/Ca ratio in foraminiferal calcite is one of the principal proxies used for paleoceanographic temperature reconstructions, but recent core-top sediment observations suggest that salinity may exert a significant secondary control on planktic foraminifers. This study compiles new and published laboratory culture experiment data from the planktic foraminifers Orbulina universa, Globigerinoides sacculifer and Globigerinoides ruber, in which salinity was varied but temperature, pH and light were held constant. Combining new data with results from previous culture studies yields a Mg/Ca-sensitivity to salinity of 4.4±2.3%, 4.7±1.2%, and 3.3±1.7% per salinity unit (95% confidence), respectively, for the three foraminifer species studied here. Comparison of these sensitivities with core-top data suggests that the much larger sensitivity (27±4% per salinity unit) derived from Atlantic core-top sediments in previous studies is not a direct effect of salinity. Rather, we suggest that the dissolution correction often applied to Mg/Ca data can lead to significant overestimation of temperatures. We are able to reconcile culture calibrations with core-top observations by combining evidence for seasonal occurrence and latitude-specific habitat depth preferences with corresponding variations in physico-chemical environmental parameters. Although both Mg/Ca and δ18O yield temperature estimates that fall within the bounds of hydrographic observations, discrepancies between the two proxies highlight unresolved challenges with the use of paired Mg/Ca and δ18O analyses to reconstruct paleo-salinity patterns across ocean basins. The first step towards resolving these challenges requires a better spatially and seasonally resolved δ18Osw archive than is currently available. Nonetheless, site-specific reconstructions of salinity change through time may be valid.
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 121 (2013):196-213, doi:10.1016/j.gca.2013.07.028.
Showing items related by title, author, creator and subject.
Reconstructing the thermal structure of the upper ocean : insights from planktic foraminifera shell chemistry and alkenones in modern sediments of the tropical eastern Indian Ocean Mohtadi, Mahyar; Oppo, Delia W.; Luckge, Andreas; De Pol-Holz, Ricardo; Steinke, Stephan; Groeneveld, Jeroen; Hemme, Nils; Hebbeln, Dierk (American Geophysical Union, 2011-09-10)Shell chemistry of planktic foraminifera and the alkenone unsaturation index in 69 surface sediment samples in the tropical eastern Indian Ocean off West and South Indonesia were studied. Results were compared to modern ...
Abrupt climate change in the Atlantic Ocean during the last 20,000 years : insights from multi-element analysis of benthic and planktic foraminifera and a coupled OA-GCM Came, Rosemarie E. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2005-09)Minor and trace element records from planktic and benthic foraminifera from Atlantic sediment cores, as well as outputfrom a coupled OA·GCM, were used to investigate the magnitude and distribution of the oceanic response ...
Mercury-pollution induction of intracellular lipid accumulation and lysosomal compartment amplification in the benthic foraminifer Ammonia parkinsoniana Frontalini, Fabrizio; Curzi, Davide; Canonico, Barbara; Giordano, Francesco M.; De Matteis, Rita; Bernhard, Joan M.; Pieretti, Nadia; Gu, Baohua; Eskelsen, Jeremy; Jubb, Aaron; Zhao, Linduo; Pierce, Eric M.; Gobbi, Pietro; Papa, Stefano; Coccioni, Rodolfo (Public Library of Science, 2016-09-07)Heavy metals such as mercury (Hg) pose a significant health hazard through bioaccumulation and biomagnification. By penetrating cell membranes, heavy metal ions may lead to pathological conditions. Here we examined the ...