21 Insights from Microfossils and Their Modern Analogs: From Traditional to Emerging Approaches

Traditional applications of microfossils are central to many studies, while novel approaches (especially geochemistry) utilizing microfossils have expanded recently. This session highlights traditional and innovative microfossil applications in terrestrial and marine environments, including modern analogs.

Sunday, 19 October 2025
8:00 AM - 12:00 PM
HBGCC, 303C

Tracking Sharks’ Responses to Coral Reef Degradation Over Millennia in the Panamanian Pacific Using Fossil Dermal Denticles

Paper number: 21-14
Program: Technical Sessions
Time: 11:25 AM – 11:40 AM

Authors

Abstract

Climate change threatens the persistence of coral reefs, which in turn has affected reef-associated predators such as sharks. However, the relationship between reef health and shark abundance remains uncertain, and we know little about how it might shift under future environmental change. This is particularly true in the Tropical Eastern Pacific, where reefs experience large climatic variability. Here, we leverage a past climatic episode in the Panamanian Pacific—a climate-driven slowdown of reef accretion and loss of coral habitat—to assess how shark communities respond to reef degradation following climate stress. The reef collapse, which lasted over 2,500 years (~4.2–1.5 ka), has been well-documented through estimates of reef accretion and analyses of coral community composition in reef matrix cores collected throughout the region. We quantified the accumulation of shark scales (dermal denticles) in cores spanning the last ~6,000 years to reconstruct shark communities before, during, and after the reef collapse at two locations within the Gulf of Panama (Las Perlas Archipelago and Isla Iguana). Dermal denticles were also measured and classified by morphotype to track changes in the functional structure of shark communities through time. Finally, ratios of shark dermal denticles to fish otoliths (ear stones) accumulating in the same samples were used as a proxy of relative trophic structure. Our preliminary data suggest that 1) shark abundances might have decreased during the reef collapse but were able to recover and 2) both the functional structure of shark communities and relative trophic structure remained fairly stable across the event. These results evidence the historical resilience of shark communities during past environmental disturbances along Panama’s Pacific coast, enabling predictions of how different ecological groups of sharks might fare under intensifying fishing and climate impacts in the region.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413130

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.