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Globigerinoides ruber morphotypes in the Gulf of Mexico: a test of null hypothesis

August 11, 2014

Planktic foraminifer Globigerinoides ruber (G. ruber), due to its abundance and ubiquity in the tropical/subtropical mixed layer, has been the workhorse of paleoceanographic studies investigating past sea-surface conditions on a range of timescales. Recent geochemical work on the two principal white G. ruber (W) morphotypes, sensu stricto (ss) and sensu lato (sl), has hypothesized differences in seasonal preferences or calcification depths, implying that reconstructions using a non-selective mixture of morphotypes could potentially be biased. Here, we test these hypotheses by performing stable isotope and abundance measurements on the two morphotypes in sediment trap, core-top, and downcore samples from the northern Gulf of Mexico. As a test of null hypothesis, we perform the same analyses on couplets of G. ruber (W) specimens with attributes intermediate to the holotypic ss and sl morphologies. We find no systematic or significant offsets in coeval ss-sl δ18O, and δ13C. These offsets are no larger than those in the intermediate pairs. Coupling our results with foraminiferal statistical model INFAUNAL, we find that contrary to previous work elsewhere, there is no evidence for discrepancies in ss-sl calcifying depth habitat or seasonality in the Gulf of Mexico.

Publication Year 2014
Title Globigerinoides ruber morphotypes in the Gulf of Mexico: a test of null hypothesis
DOI 10.1038/srep06018
Authors Kaustubh Thirumalai, Julie N. Richey, Terrence M. Quinn, Richard Z. Poore
Publication Type Article
Publication Subtype Journal Article
Series Title Scientific Reports
Index ID 70129883
Record Source USGS Publications Warehouse
USGS Organization St. Petersburg Coastal and Marine Science Center