An exploration of nematode assemblages in the hydroponic media beds of a commercial aquaponics system

Nematodes perform important ecosystem services in soils and are well studied in traditional farming, but their role in newer soil-less food production systems is unstudied. We determined the nematode assemblages from substrates within the hydroponic media beds of a commercial aquaponics system. Three substrates were studied: coir, compost and lightweight expanded clay aggregate (LECA), with the nematode assemblages ascertained via traditional morphological analysis. All substrates were suitable for nematodes but abundance was lower compared with traditional compost. Compost from within the hydroponic media beds had nematode assemblages with similar maturity indices (MI) to compost external to the system, and both composts housed nematodes with a high proportion of bacterivores, a high degree of enrichment and no structure. LECA that were regularly disturbed and had little organic build up resembled compost – highly enriched and lacking structure. LECA that had been left undisturbed for longer and allowed to accumulate more organic matter had highly structured assemblages and showed less enrichment than the other substrates. Nematode assemblages within the coir showed very little enrichment but had higher MI and were more structured than compost. Problematic plant-parasitic nematodes were not found in any of the samples. We present the first glimpse into the role of nematodes in aquaponics systems and encourage future studies to explore how nematodes in these systems affect yield and plant health.