Date of Award

Fall 2021

Project Type

Thesis

Program or Major

Animal and Nutritional Sciences

Degree Name

Master of Science

First Advisor

Stephen Jones

Second Advisor

Todd Guerdat

Third Advisor

Peter Konjoian

Abstract

To meet global nutritional needs, humans need to produce an ever-increasing amount of food with dwindling natural resources. Demand for nutritious foods, particularly lean meat, fruits, and vegetables, is rapidly accelerating. To increase the intensity of production and utilize non-arable land, many growers are turning to controlled environment agriculture systems like hydroponic crop production and aquaculture (fish farming), but these are inherently inefficient in terms of water and nutrient utilization. Aquaponics is a relatively novel agricultural method that combines hydroponic and aquacultural production models to mitigate many of the costs—both realized and implicit, environmental and economic—associated with either production model on its own. Fundamental research is needed to determine optimal system designs, water quality conditions, and potential food safety considerations specific to aquaponics. Here we demonstrate the operation of replicated, greenhouse-scale aquaponic systems with a novel design growing tilapia (Oreochromis spp.) and lettuce (Lactuca sativa L.) in continuous production. Nitrification efficiency in these systems was greater than in previous studies, and water quality conditions suggested a relationship between the system design, dissolved carbon/nitrogen ratio, nitrogen use efficiency, and environmental impact through emission of N oxides. Food safety risk was evaluated in these aquaponic systems through culture-based screening of production water for E. coli, Salmonella spp., and Listeria spp. None of these indicator organisms were detected, in accordance with most of the aquaponic food safety research to date. However, taxa containing less-common zoonotic and opportunistic human pathogens were observed, including Aeromonas hydrophila, Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia marcescens, Citrobacter freundii, and Providencia spp. Pathogenicity of the observed strains was not determined, but the persistent presence of these taxa suggests that aquaponics presents a unique environment in terms of potential food safety hazards. With increasing regulation of food production environments in the United States, European Union, and United Kingdom, understanding the hazards in aquaponics will be necessary to ensure fair and effective water quality standard enforcement. Our results provide baseline physicochemical and microbial water quality data for a novel aquaponic system design with the potential to improve efficiency and food safety risk. This information will help to inform future research and commercial system designs and the development and enforcement of regulatory microbial water quality standards.

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