Date of Graduation

Summer 2025

Degree

Master of Science in Biology

Department

Biology

Committee Chair

La Toya Kissoon-Charles

Abstract

Spring-fed aquatic ecosystems in the Ozark Highlands are characterized by stable water depths, clear water, and diverse aquatic vegetation (filamentous algae, submerged, floating, and emergent plants). Sudden changes in water depth can impact aquatic vegetation dynamics but the impacts of prolonged changes are poorly understood. I investigated seasonal and annual changes to aquatic vegetation abundance in a spring impoundment during and after a two-year period of low water depth that was caused by a broken outlet below an artificial dam. Water depth was significantly lower in 2020 and 2021 (low water years), compared to 2022 and 2023 (high water years). Vegetation abundances differed between years in certain seasons. In winter and spring, filamentous algae cover was lower in high water years than low water years, while in fall, cover was greater in high water years than low water years. In winter, submerged aquatic vegetation (SAV) cover decreased in the low water year just prior to outlet replacement and then increased in the high water year just after outlet replacement. Floating vegetation did not change. Redundancy Analysis (RDA) indicated that water temperature, phosphate, dissolved oxygen, and chlorophyll-a concentrations were significant predictors of aquatic vegetation cover, while water depth was a significant predictor of vegetation frequency. After water depth increased, invasive Potamogeton crispus became the dominant submerged species, with cover 3.5–4.5 times higher in high water than in low water years. Increased P. crispus cover corresponded with decreased native SAV cover. RDA indicated that water temperature, conductivity, and chlorophyll-a were significant predictors of P. crispus biomass and elemental composition. Seasonal variation likely influenced water temperature and quality, which subsequently impacted aquatic vegetation dynamics, while changes in water depth impacted vegetation distribution. Temperature was a key driver of P. crispus biomass, while competition for nutrients and seasonal variation influenced its elemental composition.

Keywords

spring-fed ponds, aquatic vegetation, water depth, nutrients, element concentration, Potamogeton crispus, submerged plants, algae

Subject Categories

Biology | Botany | Plant Biology | Plant Sciences | Terrestrial and Aquatic Ecology

Copyright

© Daphne Miles

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