Honors Theses
Date of Award
Spring 4-24-2026
Document Type
Undergraduate Thesis
Department
Biology
First Advisor
Colin R Jackson
Second Advisor
Bradley Jones
Third Advisor
Jannell Clampitt
Relational Format
Dissertation/thesis
Abstract
Microbial communities are essential to the function of coastal ecosystems; however, few studies have examined their response to short-term reductions in salinity. This study used a microcosm approach to examine how decreased salinity over five days affected seawater bacterial community composition, diversity, and richness. Microcosms were assigned to three treatments: unmanipulated seawater (control) collected from the Mississippi coast, seawater amended with natural freshwater, and seawater amended with sterilized freshwater. Length of time bacteria spent in the microcosms was found to have the strongest effect on bacterial community composition, while salinity effects were weaker but still statistically significant. All treatments shifted in bacterial community structure over time, with an increase in the relative abundance of Gammaproteobacteria and smaller changes in other bacterial phyla. This was followed by a partial recovery to initial conditions by days 3 and 5. Bacterial species diversity decreased initially but then increased, while species richness started lower then increased on days 3 and 5. While a microcosm ‘bottle effect’ was important, these results indicate that lowering salinity caused short-term changes in seawater bacterial communities, allowing for opportunistic taxa to emerge. Understanding how the composition and type of bacterial phyla change under lowered salinity conditions gives insight into how coastal ecosystems may respond to environmental changes.
Recommended Citation
Sues, Jackson C., "Mississippi Coastal Bacterial Community Response to Lowered Salinty" (2026). Honors Theses. 3440.
https://egrove.olemiss.edu/hon_thesis/3440