10-8 Diversity and Abundance of Molluscan Assemblages from North and Central Florida across the Plio-Pleistocene

Session: Undergraduate and Graduate Geoscience Student Showcase (Posters)

Poster Booth No.: 65

Presenting Author:

Yahlena Brodhead

Authors:

Brodhead, Yahlena C.¹, Nguyen, Kiet V.², Little, Sawyer³, Weinstein, Sofia R. Y.⁴, Horvath, Shannon M.⁵, Visaggi, Christy C.⁶, Portell, Roger W.⁷

(1) Biology, Georgia State University, Atlanta, GA, USA, (2) Environmental Science, Georgia State University, Atlanta, GA, USA, (3) Geosciences, Georgia State University, Atlanta, GA, USA, (4) Geosciences, Georgia State University, Atlanta, GA, USA, (5) Biology, Georgia State University, Atlanta, GA, USA, (6) Geosciences, Georgia State University, Atlanta, GA, USA; Center for Excellence in Teaching, Learning, and Online Education, Georgia State University, Atlanta, GA, USA, (7) Florida Museum of Natural History, Gainesville, FL, USA,

Abstract:

Human interference has caused severe damage to marine ecosystems globally. Determining the ecological impact of environmental disturbances on marine communities is key to understanding how best to address conservation efforts. The fossil record functions as a vital baseline for assessing changes to marine communities prior to human influence. This study focuses on examining shifts in molluscan communities across extinction episodes over the last few million years and adds new data to an understudied part of the coastline in north and central Florida. Existing data from this research comes from float samples of the Nashua Formation at East Coast Aggregates (Hastings, FL) as well as in-situ samples collected from Buck Hammock Materials (Deer Park, FL). In-situ samples of the younger Anastasia Formation from World Golf Village (St. Augustine, FL) were also previously analyzed. Here we add new data from a sample of the Nashua Formation collected in-situ at Dickerson Rucks Pit from Okeechobee County, Florida. All samples studied were sieved to remove finer sediments and only specimens larger than 5mm were retained. Specimens with an umbo (bivalves) or apex (gastropods) were picked from the remaining matrix and separated as either whole (>85% intact) or fragmented shells. Shells were then identified to genus level from which richness, diversity, and evenness were evaluated. Analytic Rarefaction was used to compare rarefied richness across samples from all localities. Preliminary findings from the new sample collected at Dickerson Rucks Pit revealed diverse and abundant bivalves with Mulinia being dominant. Glycymeris, Anadara, and Anomia are other bivalves well-represented in this sample. Gastropods were less abundant but included Crepidula, Neverita, and Olivella, among others. Ongoing sample processing will lead to more detailed analysis and comparison of the new sample with existing data from the other localities listed. This research helps to fill a biogeographic gap in knowledge regarding molluscan communities in north and central Florida near the boundary between the Carolinian and Gulf faunal provinces across the Plio-Pleistocene.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

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