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81-13 Rapid sulfurization and biomarker preservation in a transient euxinic environment: insights from Trunk River Lagoon, Cape Cod.

Session: New Advances in Geomicrobiology

Presenting Author:

Diana Dumit

Authors:

Dumit, Diana¹, Moynihan, Molly A², Husain, Fatima³, Vanderscheuren, Hannah ⁴, Liu, Xiaolei⁵, Ruff, S. Emil⁶, Summons, Roger E.⁷r> (1) Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA, (2) Department of Geosciences, Florida Atlantic University, Boca Raton, Florida, USA, (3) Department of Earth, Atmospheric an Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA, (4) Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, USA, (5) School of Geosciences, The University of Oklahoma, Norman, OK, USA, (6) Biology/Chemistry, Universität Bremen, Bremen, Germany; Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, USA, (7) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA,

Abstract:

Lipid biomarkers derived from anoxygenic phototrophic bacteria are widely used as indicators of ancient photic zone euxinia (PZE) and ocean anoxia. Here, we present a biomarker study of the Trunk River Lagoon (Falmouth, MA), a shallow, oxygenated estuary that transiently turns euxinic and hosts blooms of blooms of anoxygenic phototrophs. Although these microorganisms are considered strict anaerobes and are typically restricted to permanently euxinic settings, they colonize an initially oxygenated water column in this particular case. The Trunk River Lagoon thus represents a valuable modern system for investigating PZE biomarker signatures that are formed transiently in shallow water.

We sampled the water column during an active bloom across a vertical profile spanning the lagoon’s surface water, the water-bloom interface, the bloom core, and the bloom-sediment interface. Using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF) and gas chromatography-tandem mass spectrometry (GC-MS/MS), we conducted a comparative analysis of carotenoids of three lipid pools: functionalized (intact) lipids, sulfur-bound lipids, and geolipids (fossil biomarkers). Our results reveal distinct carotenoid distributions among these pools. Notably, the sulfur-bound lipid pool contains biomarkers including steroids, hopanoids, and carotenoids, and demonstrates that sulfurization occurs rapidly within the water column.

These findings challenge the assumption that euxinic biomarker signatures are markers of persistent anoxia, and they highlight the sulfur-bound lipid pool as an essential and underexplored archive for reconstructing modern ancient euxinic environments. The Trunk River Lagoon demonstrates the utility of transient phototrophic bacterial ecosystems for calibrating the formation, transformation, and preservation of geobiological signals.

Rapid sulfurization and biomarker preservation in a transient euxinic environment: insights from Trunk River Lagoon, Cape Cod.

Description

Session Format: Oral

Presentation Date: 10/11/2026

Presentation Start Time: 04:45 PM

Presentation Room: CCC, 105

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