Characterization of nitrogen dynamics in an aquaponic system

Abstract

The rapid environmental change during the last years has emphasized the need for new global solutions for food production. However, a substantial increase in food production with a concomitant reduction of its environmental footprint presents a significant challenge and requires the development of nutrient efficient and sustainable strategies. Here, multi-trophic aquaponic systems, which reduce nutrient loss to the environment through the co-cultivation of plants and aquatic animals, may present a solution. These systems consist of various compartments, with each compartment having its own specific function as part of the total system. This compartmentalization of functions creates a range of unique microenvironments, each of which supports the development of a unique microbial community. This high microbial diversity makes aquaponics an attractive soilless model system for the study of nutrient transformation processes. In particular, the nitrogen cycle is of importance, as its disruption is not only detrimental to plant and animal growth but has environment-wide consequences. This dissertation deepens the understanding of aquaponic system-specific nitrogen transformation processes through the characterization of individual interactions in the aquaponic compartments on both a chemical and a microbial level. To this end, next-generation DNA sequencing was used to characterize localized microbial community composition and diversity and was combined with chemical analyses to determine nutrient content and abiotic parameter values. Significant differences in nitrogen composition and abiotic parameters were observed between the individual compartments of the aquaponic system. These differences could be responsible for the unique microenvironments that, in turn, give rise to specific microbial communities and, thus, foster further specialization of compartment function. Notable differences were especially observed between the aerobic and anaerobic compartments regarding archaeal and bacterial composition. While this work investigated both the presence and composition of bacterial and archaeal communities, it also points to the importance of determining their active role in the nitrogen cycle.