213 Cushman Symposium: Microfossils of Extremophiles: Living in the Danger Zone

This session will assemble studies documenting microfossil presence and/or microfossil-generating taxa in extreme environments, widely defined present and past, and those elucidating adaptations employed by extremophiles, to inform interpretations of the geologic record.

Tuesday, 21 October 2025
1:30 PM - 5:30 PM
HBGCC, 303C

Living in the Margins: Benthic Foraminiferal Strategies Across Environmental Extremes, from Modern Oxygen-Depleted Waters to Paleogene Hyperthermals

Paper number: 213-1
Program: Technical Sessions
Time: 1:35 PM – 1:55 PM

Authors

Abstract

From plastic-littered abyssal plains to Paleogene oceans in upheaval, benthic foraminifera persist where few eukaryotes can. This study synthesizes morphologic, geochemical, and imaging data across modern and ancient extreme environments to examine how benthic foraminifera adapt to, and how their carbonate tests record, oxygen stress, chemical contamination, and ecological disruption.

At Station M (4000m water depth, NE Pacific), deployments of SEA³ experimental substrates reveal rapid colonization of plastics by Lobatula wuellerstorfi, with morphological shifts interpreted as environmentally driven ecophenotypic variation. The site also yielded a newly described arborescent monothalamid genus (Adhaerentella dendrocoronam), highlighting the continued discovery potential of remote deep-sea habitats. Along the Southern California margin, assemblage structure and morphometrics reflect gradients in oxygen and organic matter flux.

In deep-time, foraminiferal assemblages across the PETM and K/Pg boundaries reveal extinction, sluggish recolonization, and shifts in test morphology and wall thickness. MicroCT-derived Calcite Factor values and single-chamber geochemistry clarify preservation versus environmental signals. Preliminary data show that proloculus size varies with bottom-water oxygen availability, echoing patterns observed in SPORE (Surface Pore Opening REsponse; Rathburn et al., 2018), and supporting the  use of proloculus characteristics as a potential qualitative oxygenation proxy.

Together, these findings illustrate the resilience and adaptability of foraminifera across environmental extremes, while advancing new morphological tools for decoding the geologic record in the face of past, and future, ocean deoxygenation.

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

doi: 10.1130/abs/2025AM-413644

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