Bacterial decontamination of on-grown Artemia

Abstract

The bacterial load of on-grown Artemia was manipulated using a variety of commercially available enrichment DHA boosters, selected algal species (Skeletonema costatum; Nannochloropsis oculata; Tetraselmis suecica; Chaetoceros muelleri), and ozone to decontaminate enteric and external surfaces, respectively. Enrichment in C. muelleri over a 6-h period, with an additional algal exchange mid-enrichment, provided the most efficient method for enteric decontamination as measured by total viable counts. Direct exposure to ozone at 4 ppm for 5 min provided further bacterial reduction, resulting in a combined bacterial load reduction of 99.5% without compromising Artemia viability. The commercial enrichment A1 DHA Selco™, containing antibacterial compounds, provides an alternative to algal-based enrichments, however, its decontaminating properties were inferior. Fluorescence in situ hybridisation (FISH) was used on occasions to verify total bacterial abundance estimates obtained by standard plating procedures. In all except one case, Johnson's Marine Agar (JMA) provided results comparable to direct counts by FISH. This indicates that the bacterial community present in on-grown Artemia cultures is dominated by several fast-growing r-strategists amenable to culture on conventional plates. Underestimation of bacterial abundance using marine agar was therefore unlikely.