Microorganisms in aquaponics: insights on their functions and the potential modifications of their communities over the course of a full lettuce growth cycle
Mathilde Eck is a PhD student at Gembloux Agro-Bio Tech, University of Liège, Belgium, under the supervision of Prof. Haïssam Jijakli. Her thesis focuses on the study of microorganisms in aquaponics and their roles in nutrient cycles and plant growth promotion. Indeed, a better knowledge of the microbial processes in aquaponics could help foster the development of more sustainable and viable systems. Hence, she has decided to hinge her PhD around two main themes, each composed of two specific questions. The first theme tackles the description of the bacterial communities in aquaponics with a first question focused on what the aquaponics bacteria are and a second dealing with how they evolve throughout time in a given system. To answer that first question, she sampled ten different systems in northern Europe to compare their bacterial communities with the help of 16S rRNA sequencing. The main conclusions were that i) each system has its own community, and ii) despite this apparent diversity, a few common taxa could be observed in every system. These taxa belonged to families commonly found in freshwater but also in plant roots and surprisingly in soil. The second experiment was carried out on the closed-loop aquaponic system in Gembloux Agro-Bio Tech in which she followed the composition of the bacterial communities of the sump, the biofilter and the lettuce roots over the course of a lettuce growth cycle. It came out that each compartment harboured a specific community. Analysis of the evolution of each community is still going on. The second theme deals with the plant beneficial functions present in the aquaponic bacterial communities and how they can impact lettuce growth. Thirty-one bacterial strains were therefore collected from the sump of our aquaponic system and grown in vitro and were then submitted to biochemical tests to assess their ability to solubilize phosphorus and potassium and to produce ammonia, siderophores and IAA. In vivo tests were next conducted in a controlled growth chamber to evaluate the impact of three strains of interest (presenting a combination of potentially beneficial functions) on lettuce yields. The data thus obtained are still under analysis.
Mathilde Eck won the ISHS Young Minds Award for the best oral presentation at the III International Symposium on Soilless Culture and Hydroponics: Innovation and Advanced Technology for Circular Horticulture, which was held virtually in Cyprus in March 2021.
Mathilde Eck, Gembloux Agro-Bio Tech, University of Liège, Passage des Déportés 2, 5000 Gembloux, Belgium, e-mail: email@example.com
The article is available in Chronica Horticulturae