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Effects of Water Filtration and Temperature on Microbial Colonization and Survival of Lake Sturgeon Eggs

Physical and biotic factors that affect development and survival during the embryonic period of fish are major concerns in aquaculture, particularly when individuals are produced using natural surface water sources. We quantified the effects of bacterial community taxonomic composition and abundance, water filtration treatment, and incubation temperature on the development and survival of embryos from Lake Sturgeon Acipenser fulvescens, a threatened Great Lakes fish species. Eggs were fertilized and incubated using a two-by-two treatment design by manipulating water treatments (treated [filtered and UV treated] and untreated stream water) and temperature (12°C and 18°C) during incubation. Egg samples from five full-sibling families were exposed to each rearing treatment. At different stages during development, eggs were analyzed for egg surface microbial community composition and abundance using terminal restriction fragment length polymorphism methods based on the 16S rRNA gene and quantitative PCR, respectively. Sanger sequencing identified egg-associated microbial taxa. Microbial community composition derived from terminal restriction fragment length polymorphism was visualized using principal component analysis. Permutational multivariate analysis of variance revealed that the composition of microbial communities that developed on egg surfaces varied as a function of water filtration and temperature. Quantitative PCR analysis revealed that significantly higher microbial abundance was present on surfaces of eggs reared in untreated stream water than on those reared in treated stream water. Temperature did not affect egg surface microbial abundance. Significantly higher egg mortality was documented for eggs reared in unfiltered stream water (mean± SD = 77.4± 17.6%) than for eggs reared in treated stream water (50.3± 14.7%). Temperature during incubation did not affect levels of egg mortality. Sequence analysis revealed that certain microbial taxa were associated with eggs characterized by higher survival, including Acidovorax spp. and Massilia spp., suggesting that they may be candidates for natural probiotics. Filtration and UV treatment of surface water was an effective method for modification of egg microbial community composition and quantity and significantly reduced egg mortality. Microbial communities immediately develop on fish egg surfaces upon deposition into water during reproduction (Fujimoto et al. 2013, 2018; Llewellyn et al. 2014). Microbial community composition and abundance on fish egg surfaces change over time across the incubation period (Fujimoto et al. 2018) and are also influenced by abiotic *Corresponding author: scribne3@msu.edu Present address: Soil and Water Sciences Department, University of Florida, 1692 McCarty Drive, Room 2181, Building A, Gainesville, Florida 32611-0290, USA. Received September 17, 2019; accepted September 9, 2020 North American Journal of Aquaculture © 2020 American Fisheries Society ISSN: 1522-2055 print / 1548-8454 online DOI: 10.1002/naaq.10169