Keywords

Algal Toxin, Microcystin-LR, Water Quality, Freshwater, Estuarine

Abstract

Cyanobacterial toxins, particularly microcystin-LR (MC-LR), present persistent risks in freshwater and estuarine environments, especially under flow-regulated system where hydrodynamics and biology interact complexly. This study investigates the occurrence of MC-LR across a lake–estuary water matrixes, sampling 13 sites from Lake Okeechobee through Caloosahatchee canal, river, and estuarine zones from March to September. Water quality parameters including conductivity, temperature, dissolved oxygen, chlorophyll-a, and phycocyanin were measured in situ. The concentration of MC-LR, and nutrients (ammonium, orthophosphate, and nitrite concentrations) were measured in the laboratory. Multivariate correlation, principal component analysis, and multiple regression were employed to determine dominant drivers of toxin occurrence. The mean MC-LR concentration was 0.588 µg/L (SD 0.503), with peaks up to 2.34 µg/L, and show a notable spatial and temporal heterogeneity. Positive correlations of MC-LR with chlorophyll-a, temperature, and pressure were observed, while discharge and rainfall showed strong inverse relationships (r2 = –0.79 and –0.87, respectively). These results highlight that MC-LR accumulation is not strictly governed by nutrient levels alone but is substantially influenced by hydrologic regime and mixing dynamics along the continuum. This study enhances the understanding of cyanotoxin behavior in flow-influenced systems and supports integrative approaches for water quality monitoring, predictive modeling, and management in a freshwater–estuarine environment.

Completion Date

2025

Semester

Fall

Committee Chair

A H M Anwar Sadmani

Degree

Master of Science in Environmental Engineering (M.S.Env.E.)

College

College of Engineering and Computer Science

Department

Civil Environmental and Construction Engineering

Format

PDF

Identifier

DP0029803

Document Type

Thesis

Campus Location

Orlando (Main) Campus

Download

Share

COinS