Author ORCID Identifier

https://orcid.org/0000-0003-0241-8024

Date of Award

2024

Document Type

Thesis (Master's)

Department or Program

Earth Sciences

First Advisor

Mukul Sharma

Second Advisor

George A. O'Toole

Third Advisor

William D Leavitt, Erik R Zinser

Abstract

Atmospheric dust deposition plays a crucial role in marine biogeochemical cycles, yet mechanisms underlying its impact on particle dynamics remain unclear. This study investigates the synergistic interactions between marine heterotrophic bacteria and clay minerals in seawater, focusing on their effect on Transparent Exopolymer Particles (TEP) production and organoclay aggregation. Field experiments in the Gulf of Maine and laboratory roller tank studies were conducted using natural microbial communities and model heterotrophic bacterial strains (Alteromonas sp. EZ55, Marinobacter adhaerens HP15, and Sulfitobacter sp. NAS-14.1). Results demonstrate that clay exposure significantly enhances TEP production by bloom-associated heterotrophic bacteria, with increases up to 13-fold observed in the field experiment, and laboratory studies corroborating these findings, with bacteria-clay interaction showing rapid TEP synthesis within 2 hours of exposure for all tested strains. In abiotic controls, TEP synthesis occurred when clay mineral was added to seawater. The enhanced TEP production facilitated faster and larger organoclay aggregate formation compared to abiotic controls. Additionally, the dissolved organic matter (DOM) content was found to influence the TEP production and thereby the aggregation efficiency. These findings reveal a novel mechanism whereby addition of clay minerals to seawater results in enhanced TEP production and heterotrophic bacteria respond to clay mineral exposure by increasing TEP production, and enhancing particle aggregation efficiency. This study provides new temporal insights into the complex interactions between clay mineral, bacteria, and organic matter, having implications on understanding marine particle dynamics, and establishing baseline for potential negative emission technologies that leverage clay minerals to increase particulate organic matter flux in the oceans.

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