Date of Award

Spring 5-10-2025

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Biology

College

College of Science

First Advisor

Vladislav Gulis

Abstract/Description

Dissolved oxygen concentration in freshwater ecosystems may affect larger organisms and also modulate microbial activity. Bacteria and fungi are important drivers of ecosystem-level processes such as plant litter decomposition, and control nutrient and energy transfer to higher trophic levels in streams and wetlands. Switch cane (Arundinaria tecta) and red maple (Acer rubrum) are common in the riparian zones and wetlands in the Southeastern U.S. However, little is known about switch cane decomposition and associated microbial processes. We conducted a decomposition experiment at 16 largely undisturbed sites in Lewis Ocean Bay Heritage Preserve, Waccamaw National Wildlife Refuge, and CCU campus that varied in dissolved oxygen from < 1 to ~8 mg/L mainly due to water velocity (stagnant to flowing). Leaf litter was incubated in submerged mesh bags for ~10 weeks and associated parameters measured on three sampling dates. For switch cane, dissolved oxygen availability increased microbial respiration rates, while the effects on fungal growth rate, production, and decomposition rates were only marginally significant. In contrast, all parameters of microbial activity and decomposition were stimulated by oxygen availability for maple leaf litter. These effects were most pronounced early in the experiment. Microbial parameters at early stages of decomposition (day 18) also correlated with decomposition rates of both types of leaf litter by the end of experiment, suggesting that fungi control decomposition in these freshwater ecosystems. This study provides first insight into submerged decomposition and microbial activity on switch cane, a wetland plant that has lost 98% of its former area in the U.S.

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