2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 270-6
Presentation Time: 9:15 AM


ELDER, Leanne E., HULL, Pincelli M., HSIANG, Allison Y. and KAHANAMOKU, Sara, Geology and Geophysics, Yale University, New Haven, CT 06511, leanne.elder@yale.edu

Taxon-free morphological trait analysis, referred to as ecometrics, can be used as a common currency to examine and compare ecological dynamics between communities with entirely different species compositions. As such, it provides a powerful means of comparing community dynamics over geological time. Here, we take the first step towards developing ecometric approaches for open ocean microfossil communities with a calibration study of community shape in recent sediments.

To date, ecometric studies have only rarely been applied to address population level trends because of the time intensive nature of traditional morphometric measurements. To overcome this problem, we have developed a high-throughput set of methods to collect assemblage-scale data, with methods tuned to foraminiferal samples (e.g., light objects on a dark background). Methods include serial focused dark-field microscopy, custom software (Automorph) to batch process these images, extract 2D and 3D shape parameters and frames (Hsiang et. al 2015), and implement landmark-free geometric morphometric analyses.

We will present a first overview of the ‘shape’ of modern planktonic foraminiferal communities from 25 Atlantic core top samples (23 sites in the North and Equatorial Atlantic; 2 sites in the South Atlantic). At four of the localities depth transects (3-depths each) are used to assess the effect of preservation on results. In total, more than 100,000 microfossils and fragments were imaged from these sites’ sediment cores, an unprecedented morphometric sample set. These microfossils are primarily planktonic foraminifera, but also include benthic foraminifera, ostracods, pteropods, and spicules. Correlates of community shape, including diversity, temperature, and latitude, will be discussed.