Research paper
Regional versus physiographic effects on morphologic variability withinBulimina aculeata andB. marginata

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Abstract

Ecophenotypic trends within living species of benthic foraminifera offer a novel paleoenvironmental tool for distinguishing regional water masses or physiographic trends within large areas. Twenty-nine Recent samples ofBulimina aculeata andB. marginata from the coasts of the Northeastern U.S., Gulf of Mexico and West Africa were analyzed morphometrically in relation to their distributions within and among regions. Northeast Coast and Gulf of Mexico specimens were compared further to temperature, oxygen and salinity measurements to determine bottom water characteristics having the greatest influence on interspecific morphologic variation.

Morphologies are influenced most strongly by regional differences, showing a potential for use as water mass indicators. However, the degree of chamber inflation can be used to distinguish depth and physiographic locale across the Northeast Coast and Gulf of Mexico regions, at a scale finer than many interpretations based on species assemblages. For Northeast and Gulf Coast samples, measures of the proportional size of individuals ofB. aculeata are correlated most strongly with minimum temperature and a combination of minimum temperature and salinity strongly influence prolocular size inB. marginata. These morphologic trends show potential as indicators of paleobathymetry and paleotemperature.

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Present address: Museum of Paleontology, University of Michigan, Ann Arbor, MI 48109-1079, U.S.A.