Eric Waters
Pronouns: he/him
Research Mentor(s): Sierra Petersen
Research Mentor School/College/Department: Earth and Environmental Sciences / LSA
Program: UROP
Session: Session 1 (9:00am – 9:50am)
Authors: Eric Waters, Lucas Gomes, Sierra Petersen
Abstract
The Pliocene-Pleistocene fossil record of Florida records a major mollusk mass extinction over the past 3-5 Ma. Understanding the causes of this extinction event involves analyzing changes in taxa that lived during that time. Chione sp. is a bivalve taxon that commonly occurred in both the past and present (different species) in Florida and the Caribbean. It is found in great abundance in Plio-Pleistocene deposits in central Florida and surrounding regions. As with other bivalves, growth rates are dependent on environmental factors (i.e. nutrient concentration, temperature, predation). Due to the overall abundance of Chione within the Florida region, robust statistics are possible with this taxon that are not possible with rarer taxa. We gathered over 1000 valves of Chione from bulk sediment samples collected every half meter through 9m of section at Punta Gorda, a Florida shell quarry, taken from the 3/8†to 1†sieved size fraction. With each valve we examined the number of boreholes, ornaments, and notches (indicator of age). Surface area data was measured with a computer program, ImageJ, which we used to convert an 8-bit, high-contrast photo into numerical area measurements of each valve. We have found changes in predation through the section indicated by variability in the prevelance of boreholes; the number of boreholes per valve decreased dramatically through the 3 – 4 m and 6.5-7 m portions of the section. As low as 2% of Chione valves exhibited boreholes in these intervals (compared to 27% in the 5.9 – 6.1 m interval). Size distributions of Chione also vary through the section. Studying changes in a single populous taxon can lead to understanding of the environmental conditions at play. Results from this study will be paired with grain size indicators and isotopic paleothermometry to describe a holistic picture of the past environment, and to reveal a backdrop on which the mass extinction took place.
