Corroborating ecological depth preferences of planktonic foraminifera in the tropical Atlantic with the stable oxygen isotope ratios of core top specimens

Abstract

[1] Past variability in upper ocean thermocline depth is commonly estimated from the abundance of different species of planktonic organisms or the difference in oxygen isotopic composition between two species of planktonic foraminifera, one that lives in the mixed layer and one that lives in or near the thermocline. To test the latter relationships, we measured the oxygen isotopic composition of eight species of planktonic foraminifera (pink and white varieties of Globigerinoides ruber, Globigerinoides sacculifer without the final chamber, Orbulina universa, Pulleniatina obliquiloculata, Globorotalia menardii, Neogloborotalia dutertrei, and Globorotalia tumida) in surface sediment samples from 31 tropical Atlantic deep-sea sediment cores. Bayesian analysis was used to compare measured oxygen isotopic compositions with their predictions based on modern data sets of annual temperatures and oxygen isotopic composition of ocean water in the upper 500 m at the core sites. Posterior probability densities for predictive model parameters were computed. Probability distributions of calcification depth for analyzed species corroborated their ecological preferences inferred from net tow and sediment trap data. Robustness of the habitat signals in core top specimens suggests that reconstructions of the entire upper ocean temperature profiles, not just their thermocline depth or temperature, might be possible.Citation: Farmer, E. C., A. Kaplan, P. B. de Menocal, and J. Lynch-Stieglitz (2007), Corroborating ecological depth preferences of planktonic foraminifera in the tropical Atlantic with the stable oxygen isotope ratios of core top specimens, Paleoceanography, 22, PA3205,

Anti-cyclonic eddy imprint on calcite geochemistry of several planktonic foraminiferal species in the Mozambique Channel

“…Anand et al, 2003;Field, 2004;Fallet et al, 2010), calcifying in the top 50 m (e.g. Dekens et al, 2002;Mohtadi et al, 2006;Farmer et al, 2007;Fallet et al, 2010;Birch et al, 2013).…”

“…Fairbanks et al, 1982;Curry et al, 1983;Eguchi et al, 2003;Farmer et al, 2007), where maximum abundances may coincide with a deep chlorophyll maximum (Fairbanks et al, 1980;Ravelo et al, 1990). Overall living depth is likely within the upper 200 m (Kroon and Darling, 1995;Farmer et al, 2007).…”

Planktic foraminifers as recorders of seawater Ba/Ca

“…Lea and Boyle (1991) argued that this may be attributed to a different calcification mechanism but their data are too variable to permit estimation of a coherent D Ba for the Globorotaliids. One parameter that the Globorotaliids have in common is that they all live in the subsurface, at water depths N70-300 m (Farmer et al, 2007), except for G. truncatulinoides which has been reported to live as deep as 700 m (Mulitza et al, 1999;Steph et al, 2009). Although the seawater Ba concentration increases with depth and may explain higher Ba/Ca ratios in deep living G. truncatulinoides, the seawater Ba concentration in the upper 300 m of the water column is similar to the surface layer, and accordingly we need to consider how [Ba] could be increased in the microenvironment of this particular group of foraminifer species.…”

Change in the intensity of low-salinity water inflow from the Bay of Bengal into the Eastern Arabian Sea from the Last Glacial Maximum to the Holocene: Implications for monsoon variations

“…The G. sacculifer is a spinose mixed-layer dwelling planktic foraminifer (Hembleben et al, 1989) calcifying in a narrow depth range of 25-40 m (Farmer et al, 2007), which is relatively more resistant to dissolution compared to other planktic foraminifera (Dekens et al, 2002;Delaney et al, 1985), having nearly uniform inter-chamber distribution of Mg and Ca (Eggins et al, 2003). Previously published δ 18 O data for both the sediment cores (Banakar et al, 2005;Chodankar et al, 2005) and paired Mg/Ca SST for the northern location core (Banakar et al, 2010) were available for the present study.…”