THE INFLUENCE OF GROWTH RATES ON FORAMINIFERAL STABLE ISOTOPES

Cibicidoides wuellerstorfi collected from elevated substrates on the seafloor examined with MicroCT scanning has produced new insights into morphologic variations based on the mode of reproduction. Megalospheric forms begin the formation of their tests with a large initial chamber (proloculus) and produce fewer, but larger, chambers compared to their microspheric counterparts with small proloculi and smaller and more numerous chambers. Once the total test diameter has reached the second whorl and is generally >500um, megalo- and microspheric forms are indiscernible without the use of x-rays to penetrate overgrowth obscuring the proloculus. It is therefore assumed that various growth rates and ultimately, metabolisms, may influence stable isotopic and trace metal incorporation into test materials. To test this possibility, stable isotopes will be compared across significant populations of foraminifera (C. wuellerstorfi) of different sphericities collected from six sets of elevated materials from 4,000 to 600m water depth. Comparisons are also made between populations colonizing substrates deployed for 6mo, 1yr, 2yrs, 3yrs, and naturally occurring materials. By comparing these populations we will gain insights into population sphericities and how they change with time, and document metabolic variations, if any, between new and established populations. These results are essential in the use of SEA³s (Seafloor Epibenthic Attachment Cubes) and accurate interpretations of geochemically based proxies.