DOI
https://doi.org/10.25772/RRJJ-FZ19
Defense Date
2025
Document Type
Thesis
Degree Name
Master of Science
Department
Environmental Studies
First Advisor
Paul Bukaveckas
Abstract
Water clarity in aquatic ecosystems is crucial for submerged vegetation and algal dynamics. We investigated the factors influencing light attenuation (kd) by measuring total suspended solids (TSS), chlorophyll-a (CHLa), and chromophoric dissolved organic matter (CDOM) across thirteen stations located in seven reservoirs. Average kd was 1.69 m-1 (range: 0.37-3.99 m-1), with photic depths averaging 3.27 m (range: 1.15-12.43 m). TSS was the primary predictor of light attenuation (R² = 0.57, P = 0.003, SE = 0.053). Average TSS values for each site were multiplied by the slope of the kd-TSS relationship to find the proportion of kd attributed to TSS. A similar analysis was performed for CDOM by relating residual kd (i.e., kd after accounting for the effects of TSS) to determine the rate of change in light attenuation per unit of CDOM. Using this method, TSS was estimated to account for 57% ± 1% of attenuation, while CDOM explained 27% ± 1%. CHLa had minimal impact on kd across most sites, except Lake Anna, where it was the primary driver. This difference is likely due to Lake Anna’s larger size, which leads to longer water residence times. These longer times allow more opportunity for algal growth and provide a greater capacity for upstream sedimentation, which reduces the impact of particulates on water clarity. The negligible impacts of CHLa on kd in the remainder of sites are consistent with the analysis of particulate organic carbon, which showed that organic matter is a relatively minor component of TSS (32% on average). Regional differences also emerged: Piedmont reservoirs showed TSS dominance of light attenuation (61% of kd), while light attenuation of Southeastern Plains sites were more CDOM-influenced (51% of kd). Secchi depth exhibited a moderate relationship with kd when using site average data (R² = 0.45, P = 0.012, SE = 0.31), though it was insignificant at individual stations, suggesting limited predictive power at finer spatial scales.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
5-9-2025