Selenium and Neem oil accumulation in aquaponics systems

Abstract

By Zach Fyan, Biochemistry; Aline Pereira de Oliveira, University of Cincinnati

Advisor: Julio Landero

Abstract: Aquaponics is a horticulture technique that has been increasing in popularity for industry and household use. It converts the ammonia fish waste to nitrites and nitrates through nitrifying bacteria, Nitrosomonas and Nitrobacter. The treated water is used to fertilize plants on a hydroponic bed. Recirculation and treatment conserves water but can lead to an accumulation of various toxins. This project focuses on the effects and accumulation of dosing systems with selenium and neem oil. Selenium is an essential nutrient for humans with a narrow daily intake range of 40-400_g. Selenoproteins mediate oxidative stress through use of the encoded amino acid selenocysteine (SeCys), while selenium-containing proteins accumulate selenomethionine SeMet. Neem oil is an effective organic pesticide that is used widely throughout the agriculture industry. It's effective against insects, but the effects on nitrifying bacteria in aquaponics are not known. Selenium was dossed to the water and later quantified in various foodstuffs and water collected from the systems. Samples were analyzed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The accumulation of Se in water was more pronounced from inorganic species; compared with organics that showed more accumulation in foodstuff. The active molecule of neem oil, azadirachtin, and its degraded form were detected via Reverse-Phase High Performance Liquid Chromatography (RP-HPLC) in foodstuff. Chlorophyll content in leaves was determined with UV spectroscopy and used to determine the health of the systems metabolism. The nitrification was not affected by any treatment and no toxic levels of Se or neem oil were found in edible parts.