Fossil Oysters and Environmental Productivity

Crassostrea gigantissima

This summer I’ll be working on my thesis for the geology department. My primary interest is paleontology and most of my research is on extinct oysters. My thesis focuses on one species of oyster, Crassostrea gigantissima. C. gigantissima lived about 30 million years ago along the coast of the southeast United States. Its known for being one of the largest species of oyster, living or extinct. A large modern oyster may grow 10 centimeters in length. A typical C. gigantissima grew 25-30 centimeters long, with a remarkably thick shell. I’m interested in understanding why C. gigantissima grew so large, and hopefully applying that knowledge to help modern oysters.

Modern Oysters

Modern Chesapeake Bay oysters are in a state of decline, which is manifested in a reduction of body size. In 1994 the average length of oysters taken from the bay was around 8 centimeters less than just a century earlier (Rothschild et al., 1994).  Oysters play a vital role in shaping and maintaining marine ecosystems. They filter the water surrounding them, improving its quality. Their reefs provide structures and habitats, as well as protect coastal areas from incoming storms.

Proposed Work

It’s important to understand why modern oysters are failing because their decline would have lasting negative impacts on marine ecosystems. However, rather than studying why modern oysters are growing smaller I will study why the extinct C. gigantissima was so large. The main hypothesis I’ll be testing is that C. gigantissima lived during a time when there were higher levels of nutrients available, allowing them to grow large very quickly.
gigantissimaFigure: Partial C. gigantissima shell, roughly 35 centimeters in length. Unfortunately its difficult to find complete shells. This oyster was likely even longer in real life!


Rothschild, B.J., Ault, J., Goulletquer, P., and Heral, M., 1994, Decline of the Chesapeake Bay oyster population: a century of habitat destruction and overfishing: Marine Ecology Progress Series, v. 111, p. 29-39.


  1. egeichenberger says:

    What nutrients do you expect to find caused the increased growth rates of oysters in the past? Additionally, if you had the opportunity to eat an ancient oyster, do you think you could swallow it in one bite? I look forward to your enlightening response!

  2. mqgaetano says:

    Thanks for your interest! In a few weeks I’ll be posting about the geochemistry behind this project, but for now the two main nutrients I’m measuring are nitrogen and phosphorus.