Abstract

Viruses have been found to be the most abundant biological life forms on earth with high abundance, particularly in the ocean (10⁷ ml^-1) where they have been associated with marine biomass destruction at an approximate rate of 10 to 20% per day.^1,2 Although native aquatic environments have been the focus of recent viral metagenomics (Virome) studies,^2,5 there is a need to understand the role of viruses in regulating their host population in the built and controlled aquatic environment. The goals of this study were to apply metagenomics approaches to (i) characterize viral and bacterial communities of cold and warm marine, and freshwater human-contact aquaria habitats and (ii) examine the role of water treatment components, nutrients, and physicochemical factors in shaping viral and bacterial populations of these habitats. A total of 75 physicochemical (n=25), bacterial (n=25), and viral (n=25) water samples were collected from three aquarium systems: Oceanarium (cold marine), Wild Reef (warm marine), and Sturgeon Touch (freshwater), and their water treatment components: sand filter, ozone tower, foam fractionators, and UV water disinfection at Shedd Aquarium in Chicago. Twenty-three physicochemical tests were run, while bacterial water samples were collected by Sterivex™ filters, DNA extracted, and amplicon-sequenced (16S rRNA, V3-V4) by Illumina Miseq™. Viral water samples were concentrated, enriched, purified and DNA/RNA extracted, reverse transcribed, randomly amplified, and sequenced by Illumina HigSeq™ 4000. Bacterial community composition significantly varied by sampled habitats (p=0.001) but not by water treatment components, and had the highest diversity in Sturgeon Touch water storage. Archaeal community composition varied with both sampled habitat (p=0.001) and water treatment components (p=0.031), and was abundant in Wild Reef. Seven of 23 physicochemical parameters - pH, Alkalinity, NO3, Salinity, PO4, Temperature, and N02-N - correlated with bacterial and archaeal community compositions (R=0.4, p=0.001) and explained high variation (ranged from 9 to 22.0%, p=0.001) in both community compositions of sampled habitats. Viral composition varied with sampled habitats (p=0.002), but not with water treatment components and moderately correlated with physicochemical parameters (R=0.38, p=0.001) of which temperature and pH explained a variation in viral composition of 16.4% and 10%, respectively. The top five abundant viral family taxa included those infecting bacteria or archaea (Siphoviridae and Myoviridae), eukaryotes or protozoa (Phycodnaviridae and Miniviridae), and only bacteria (Podoviridae). Seven human-associated viral family taxa were identified in Sturgeon Touch exhibit, which is exposed to frequent human contact and in the Oceanarium. Wild Reef exhibit did not show any presence of human-associated viral family taxa. Nodaviridae and Dicistroviridae viral family taxa associated with fish diseases were solely identified in sand filter backwash. Most of these potential disease causing viral taxa identified in sampled exhibits were not detected in effluents of UV disinfection, suggesting efficient removal of viruses. We demonstrated that metagenomics profiling of bacterial, archaeal, and viral compositions in aquatic built environments may shed light on ecosystem microbial stability in studied aquaria and improve operational and water treatment management.

Acknowledgements

This research is supported by Alfred P. Sloan Foundation and Michigan State University.

The authors wish to thank Prof. Joan B. Rose Laboratory team, Shedd Aquarium Microbiome Project team and members of the Animal Health and Facilities departments who provided notable assistance.

* Presenting author

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