176-11 Live-Dead Agreement in Benthic Foraminiferal Assemblages Reflect Timescales of Ecological Stressors Across Environments

Session: Laws of the Grave: Advances in Taphonomy Across the Paleontologic Record

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Abstract:

The faithful recording of living assemblages of organisms by the accumulation of their dead remains underlies our ability to use fossil records to reconstruct past ecosystems. However, the discordance between living assemblages (LAs) and dead assemblages (DAs) in surficial sediments also reflects real ecological changes that occur at timescales shorter than the time interval that the DA represents. Here, we take advantage of the ubiquity of benthic foraminifera in marine and marginal marine environments, and their long history of collection as both LAs and DAs, to test for environmental differences in live-dead agreement. We examine the fidelity of >3,000 DAs to their co-collected LAs (Rose-Bengal stained) using correlational metrics (Spearman rank order), similarity metrics (Bray-Curtis similarity), and ecological metrics (richness and evenness). On average, live-dead (LD) agreement is positive for benthic foraminiferal assemblages and richness is similar between LAs and DAs across the dataset. When the data is subset by environmental types, we find that environments prone to episodic disturbances, such as sea-floor canyons, hydrothermal systems, or highly seasonal shelf environments, have the lowest LD agreement whereas environments with more persistent stressors, such as oxygen minimum zones, methane seeps, and estuarine environments have the highest LD agreement. LD agreement remains positive for less unique oceanic environments and, on average, declines with water depth such that assemblages from <50 m water depth have greater LD agreement than outershelf to abyssal environments. Areas with recent natural disturbances (ex. volcanic ashfall, turbidite deposition) tend to have similar LD agreement as oceanic environments of similar water depth, however, areas with noted anthropogenic impacts have LD agreements more similar to episodically disturbed environments. This analysis of LD pairs across a diversity of environments highlights the utility of LD comparisons to ecological studies in environments where real-time monitoring is difficult and demonstrates which environments the fossil record is most likely to faithfully preserve.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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