Quantitative determination of nitrogen cycling functional genes in an aquaponic system : master thesis

Jamšek, Jena (author), Griessler Bulc, Tjaša (mentor), Smits, T. (co-mentor), Schmautz, Zala (co-mentor), Ovca, Andrej (reviewer)

Nitrogen is one of the main nutrients required for the maintenance of the dynamic equilibrium between fish, plants and microorganisms in an aquaponic system. Integrating hydroponic plant production and recirculating aquaculture technology promises to enhance nitrogen use efficiency and overall environmental sustainability. The present study was carried out to quantify nitrogen functional genes involved in the nitrogen cycle by hydroponic lettuce integrated with tilapia aquaculture. We sampled different compartments of the aquaponic system, including biofilter, fish tank, hydroponic sump, hydroponic table, fish feces, fresh sludge, digested sludge and roots. The abundances of nitrogen functional genes were analyzed by comparison to 16S rRNA gene using quantitative polymerase chain reaction affiliated with nitrification and COMAMMOX (bacterial and archaeal amoA, hao, nxrB), denitrification (narG, napA, nirS, nirK, norB, nosZ), DNRA (nrfA), N-fixation (nifH) and ANAMMOX (hzs, hzo). The potential nitrogen cycling genes of bacteria and archaea varied between samples. Targeting these genes revealed high diversity and dominance of bacterial communities. Based on correlation analysis, nitrification was best explained by bacterial and archaeal amoA gene abundance followed by NH4+-N content, whereas denitrification was best explained directly by nirS, nirK, nosZ and norB abundances and NO3--N. Overall, identified functional genes involved in the nitrogen cycle could explain beneficial N processes linking with the microbial communities and operating parameters involved in aquaponics, but a deeper analysis would be required to predict environmental contamination and maintain a functioning aquaponic system.

• Language: English
• Keywords: master's theses, sanitary engineering, aquaponics, nitrogen cycle, gene abundance, 16S rRNA gene, quantitative PCR
• Work type: Master's thesis/paper
• Organization: ZF - Faculty of Health Sciences
• Place of publishing: Ljubljana
• Publisher: [J. Jamšek]
• Year: 2020
• Number of pages: 89 str., [14] str. pril.
• PID: 20.500.12556/RUL-119933
• COBISS.SI-ID: 28339459
• Publication date in RUL: 13.09.2020

Secondary language

• Language: Slovenian
• Title: Kvantitativno določanje izražanja genov v krogotoku dušika akvaponičnega sistema : magistrsko delo

Abstract

Dušik spada med glavna hranila, ki so potrebna za vzdrževanje dinamičnega ravnovesja med ribami, rastlinami in mikroorganizmi v akvaponičnem sistemu. Po vsem svetu narašča zaskrbljenost zaradi morebitnega onesnaženja okolja z odpadnimi vodami akvaponičnega in drugih sistemov, ki vsebujejo povečano vsebnost dušika. Povezovanje pridelave hidroponskih rastlin in recirkulacijske tehnologije za gojenje rib lahko poveča učinkovitost uporabe dušika in okoljsko trajnost. Študijo smo izvedli, da bi kvantitativno opredelili dušikove funkcionalne gene, ki sodelujejo pri kroženju dušika v sistemu s solato ter tilapijo. Vzorčili smo različne dele akvaponičnega sistema, vključno z biofiltrom, bazenom za ribe, hidroponskim zbiralnikom, hidroponsko mizo, ribjimi iztrebki, svežim blatom, odpadnim blatom ter koreninami. Številčnost genov dušika smo analizirali s kvantifikacijo gena 16S rRNA z uporabo molekularne tehnike kvantitativne verižne reakcije s polimerazo. Analizirani procesi so bili nitrifikacija in komamoks (geni bakterij in arhej amoA, hao, nxrB), denitrifikacija (narG, napA, nirS, nirK, norB, nosZ), DNRA (nrfA), fiksacija dušika (nifH) in anamoks (hzs, hzo). Potencialni geni dušikovih bakterij in arhej so se med vzorci razlikovali. Analiza dušikovih genov je razkrila veliko raznolikost in prevlado bakterijskih združb. Na osnovi korelacijske analize je nitrifikacijo najbolje razložiti s številčnostjo gena amoA bakterij in arhej ter NH4+-N, medtem ko denitrifikacijo neposredno z geni nirS, nirK, nosZ in norB ter NO3--N. Z identifikacijo funkcionalnih genov, ki sodelujejo pri kroženju dušika lahko razložimo procese mikrobnih združb s povezanimi okoljskimi parametri v akvaponiki, vendar pa bi bila potrebna podrobna analiza napovedi ravni onesnaženosti okolja ter delovanja akvaponičnega sistema.

• Keywords: magistrska dela, sanitarno inženirstvo, akvaponika, kroženje dušika, številčnost genov, gen 16S rRNA, kvantitativna PCR