Friday, August 10, 2018
ESA Exhibit Hall, New Orleans Ernest N. Morial Convention Center
Background/Question/Methods
Growing non-native plants, such as crops, in desert ecosystems is a challenge due to insufficient natural water sources, desert soils that are organic matter poor, and high temperatures in the summer. Using treated wastewater in an indoor hydroponics system is a feasible alternative to overcome those challenges, as it both reduces our carbon footprint and need for fertilizer application. However, in addition to high nutrient loads, treated wastewater also contains low levels of pharmaceuticals, known as contaminants of emerging concern (CECs), including antibiotics and antidepressants. Treated wastewater could impact plant growth, as well as influence the ability of the microbial communities within the rhizosphere of the roots to perform previously demonstrated functions such as bioremediation, biofertilization, and biocontrol of plant pathogens. Furthermore, CECs could be absorbed by plants and bioaccumulate in the edible plant tissues. We tested these factors by growing cherry tomatoes in an aeroponics system irrigated with treated, ultra-filtered(UF) wastewater, and we compared both growth and the rhizosphere community composition against a control group irrigated with tap water. Plant growth characteristics such as time to germination, number of stems, stalk diameter, plant height, and root length were measured bi-monthly. Water and tissue samples were collected for CECs, as well as determination of microbial community composition of the rhizosphere using high-throughput sequencing.
Results/Conclusions
Phosphate and nitrate levels were not significantly different between the two water sources, while conductivity was nearly double in the UF water as compared to the tap water, due to urban inputs. The pH between control (tap water) and UF treatment was not significantly different, but the growth and density of plant roots and stems was significantly greater in the UF water than the tap water. Fruiting occurred earlier with UF treated plants, but root health declined substantially after fruit ripened in the UF treatment. CEC concentrations in plant leaves were measurable for seven of the 13 compounds evaluated, with higher concentrations for compounds with a higher transpiration stem concentration factor. Microbial community composition was evaluated over a 10 week period in the control and treatment plants, with different successioinal trajectories depending on the water source. The dataset was evaluated for the presence of key organisms contributing to plant health, including plant pathogens, nitrogen cycling organisms, and microbes capable of secreting plant hormones.These preliminary findings will help determine how treated wastewater will be used in urban agriculture, as well as its possible threat to human health.