title: Globigerinoides ruber morphotypes in the Gulf of Mexico: a test of null hypothesis.
abstract: 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 δ(18)O, and δ(13)C. 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.
authors.affiliation: 1] Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, J. J. Pickle Research Campus, Building 196, 10100 Burnet Road (R2200), Austin, Texas 78758-4445, USA [2] Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, 1 University Station C9000, Austin, Texas 78712-1722, USA.
authors.forename: Kaustubh
authors.initials: K
authors.lastname: Thirumalai
authors.affiliation: United States Geological Survey, St. Petersburg Coastal and Marine Science Center, 600, Fourth Street South, St. Petersburg, FL 33701-4846.
authors.forename: Julie N
authors.initials: JN
authors.lastname: Richey
authors.affiliation: 1] Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, J. J. Pickle Research Campus, Building 196, 10100 Burnet Road (R2200), Austin, Texas 78758-4445, USA [2] Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, 1 University Station C9000, Austin, Texas 78712-1722, USA.
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Quinn
authors.affiliation: United States Geological Survey, St. Petersburg Coastal and Marine Science Center, 600, Fourth Street South, St. Petersburg, FL 33701-4846.
authors.forename: Richard Z
authors.initials: RZ
authors.lastname: Poore
mesh_terms: D044822:Biodiversity; D002247:Carbon Isotopes / Q000378:metabolism; D017753:Ecosystem; D056908:Foraminifera / Q000254:growth & development* / Q000502:physiology; D060851:Gulf of America; D008954:Models, Biological; D010103:Oxygen Isotopes / Q000378:metabolism; D011157:Population Dynamics
chemical_list: D002247:Carbon Isotopes; D010103:Oxygen Isotopes
references.citation: Biometrika. 1947;34(1-2):28-35
references.pmid: 20287819
references.citation: Nature. 2014 May 1;509(7498):76-80
references.pmid: 24784218