2019 ASHS Annual Conference

Aquaponics, a growing trend in food production, integrates aquaculture and hydroponics into one system. In aquaponics, bacteria function as biofilter to convert ammonia into nitrite and nitrate, plants absorb mineral nutrients from aquaculture wastewater and then the purified water returns to the fish tank. Aquaponics offer a promising solution for sustainable food production by reducing the usage of water and chemical fertilizers and has great potential to be one of the most promising food production systems, particularly for rapidly growing urban population. However, our results showed that crops grown in aquaponics had consistently lower yield and quality compared to those grown in hydroponics. Many studies on aquaponics have focused on improving nitrifying bacterial activities for faster conversion of harmful ammonia to nitrate, for which the suggested pH for aquaponics is 7. However, we found that plants can better perform and have higher yield in the range of pH 6 to 6.5. These results indicate that nitrifying bacteria may not be the key microbes in aquaponics, but there are other bacterial groups playing a key role affecting crop growth and yield in aquaponics. The largest bacterial phylum in aquaponic solution is reported to be Proteobateria, which consists of many different plant growth-promoting bacteria (PGPB). In this study, we hypothesized that plant growth-promoting bacteria (PGPB) are the key players in aquaponics by protecting them from abiotic stress such as high salinity and ammonia and nitrite stress and pH ranges of 6 to 6.5 may encourage their growth. As an initial step, we used different Psudomonas spp. isolates to identify which isolate enhances root elongation and salinity tolerance of Arabidopsis. As a second step, we inoculated potential PGPB on roots of lettuce seedlings and transplanted lettuce into aquaponic systems to compare crop performance in comparison to control plants. Key outcomes are expected to identify the role of PGPB in aquaponics systems. Our research will provide critical information to increase aquaponic crop production in the large-scale commercial operation.