Ecological Study of Aquaponics Bacterial Microbiota over the Course of a Lettuce Growth Cycle

Mathilde Eck,Sébastien Massart,M Haïssam Jijakli,Iris Szekely

doi:10.3390/w13152089

Abstract

The study of microorganisms in aquaponics is an important topic which requires more research before exploiting the full potential of beneficial microorganisms. In this experiment, we focused on the evolution over time of the bacterial communities in four compartments of an aquaponic system i.e., the sump, the biofilter, the lettuce rhizoplane and lettuce root. We studied these communities over the course of a lettuce growth cycle via regular sampling and sequencing of the 16S rRNA gene of the collected bacteria. We also followed the physicochemical parameters of the aquaponic water throughout the experiment. Results show that a different community could be found in each compartment and that all four communities were stable throughout time and resilient to naturally occurring water parameter changes which characterize functioning aquaponic systems. Furthermore, the communities of the sump and biofilter also seem stable over the years as the predominant taxa (Luteolibacter, Flavobacterium, Nitrospira) observed in our study are similar to the ones previously reported for this aquaponic system. Finally, our results provide proof for similarities between aquaponic and soil borne lettuce root communities (gammaproteobacteria, Flavobacterium, Pseudomonadaceae, Sphingomonadaceae) thus showing that aquaponics can be similar to soil production in terms of microbial life.

Highlights

Aquaponics is a combination of hydroponics and recirculating aquaculture, i.e., of plants and fish rearing [1]
The Permanova pseudo-F test, which was conducted to compare the bacterial communities between physicochemical groups, was performed on the whole system while, when we look at compartments separately, we can notice that in the biofilter, for example, the diversity of the community is still correlated with the water temperature, the EC and the NO3 concentration
The plainest answer it can offer is that, throughout a full lettuce growth cycle, no major modifications of the bacterial communities could be observed in the sump, biofilter and root compartments of the aquaponic system

Summary

Introduction

Aquaponics is a combination of hydroponics and recirculating aquaculture, i.e., of plants and fish rearing [1]. Microorganisms in aquaponics are assumed to have other beneficial effects on plants such as those observed in soils [3,4], but precise knowledge is currently scarce. To soil borne plants [5,6,7,8], the phytobiome of aquaponic crops is barely known while it could prove highly beneficial for plant health and yields in aquaponics. Recent studies are focusing their efforts on the characterization and understanding of the complex microbial communities present in the different compartments of an aquaponic system and the relationships between those communities and plant health and care

Objectives

Methods

Results

Discussion

Conclusion