Graduation Year


Document Type




Degree Name

Master of Science (M.S.)

Degree Granting Department

Marine Science

Major Professor

Heather L. Judkins, Ph.D.

Co-Major Professor

Brad A. Seibel, Ph.D.

Committee Member

Michael Vecchione, Ph.D.

Committee Member

Dale Griffin, Ph.D.


DEEPEND, ontogengy, pelagic snails, vertical migration


Large thecosome pteropods have a significant role in the pelagic ecosystem of the northern Gulf of Mexico (GoM). This research analyzed species abundances, vertical and horizontal distributions, and trends in shell thickness between 2011 and 2015. Pteropod samples were collected following the 2010 Deepwater Horizon oil spill by two midwater sampling programs: the Offshore Nekton Sampling and Analysis Program (ONSAP, 2011) and the Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND, 2015). All samples were collected using a 10-m2 Multiple Opening/Closing Net and Environmental Sensing System (MOC10) midwater trawl, with 3-mm mesh size. This gear sampled five discrete depths between 0–1500 m. To date over 13,000 pteropod specimens have been examined, and 25 species identified. Clio pyramidata was the most abundant species during both collection periods and five genera (Diacria, Clio, Styliola, Cuvierina, Cavolinia) demonstrated diel vertical migration from the meso- to epipelagic zone. Shell thickness comparisons between 2011 and 2015 were significantly different for several species, showing an increase in shell thickness in 2015. There was a slight positive correlation between shell length and thickness in several species.