Date of Conferral

2023

Degree

Ph.D.

School

Public Health

Advisor

Richard Jimenez

Abstract

Algal blooms result in the formation of cyanotoxic conditions in a freshwater lake causing severe detrimental impacts to community and public health. Nitrogen, phosphorous, and ammonia stimulate the growth of phytoplankton biomass and algae, as measured by chlorophyll. This retrospective quantitative research study, grounded in the socioecological model, examined the relationship between nutrient pollutants and chlorophyll-a (Chl-a) that forecast harmful algal blooms, a precursor to cyanotoxins. A former impaired lake, Machado Lake in California, provided an ideal setting to assess relationships among nutrient indicators and Chl-a post-lake rehabilitation. Correlation and multiple regression analyses were performed to determine if a relationship existed between total nitrogen (TN), total phosphorous (TP), ammonia (NH3), and the dependent variable Chl-a. The observational data total count was N = 102 for each variable. The data were transformed to approximate normality and NH3 was recoded as dichotomous. Results revealed a positive correlation of TN and TP; however, NH3 was negatively correlated. The regression model outcome resulted in approximately 63% of the variability of Chl-a concentration explained by the independent variables. A predictive model to forecast Chl-a was developed, potentially providing an early warning to harmful algal blooms and cyanotoxins. Implications for positive social change include protecting communities and public health by examining the precursors of harmful algal blooms and cyanotoxins to minimize risk of exposure to toxins that could potentially result in human illnesses and mortality.

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