Influences Of Aquaculture Water Additives On The Larval Sablefish (Anoplopoma fimbria) Skin Microbiome

The skin microbiome of marine fish aids in their health and survival and is thought to come from bacteria in the surrounding water, particularly during the larval stages. However, it’s not clear how shifting the microbial communities in the rearing water can alter the composition and development of the larval skin microbiome. In aquaculture, water additives are often added to larval rearing tanks to increase water turbidity. Algae-based water additives, or “greenwater”, are commonly used but are expensive and may promote growth of Vibrio spp. Clay-based additives, or “claywater”, are cheaper, but have yielded mixed results on fish health and survival. The effects of these water additives on microbial communities in rearing water and on larval sablefish skin were explored in this study using 16S rRNA gene sequencing. Three treatments were used: greenwater, claywater, and greenwater with a switch to claywater after one week. The additives differentially altered the microbial communities in the rearing water over the course of two weeks, but the larval skin communities were minimally affected and retained many of the bacterial families present in the water of the hatching silos in which they were held before being transferred into experimental tanks. However, on the final day of the experiment, larval skin communities from the greenwater-claywater treatment shared more operational taxonomic units (OTUs) with those in the greenwater treatment than in the claywater treatment, indicating a possible lasting effect of the initial exposure to greenwater. Larval skin and claywater were dominated by Alteromonadaceae, Colwelliaceae, Oceanospirillaceae, Pseudoalteromonadaceae, and Rhodobacteraceae, while Vibrionaceae was more abundant in greenwater tanks than larval skin, claywater, or water from hatching silos. Three days after addition of larvae and rotifer feed into the tanks, there was a significant loss in diversity in greenwater tanks and increase in OTUs in tank water communities from all treatments. The skin microbiome of larval sablefish appears to be mostly resilient to changes in the surrounding microbial communities but may be more sensitive in the first week post-first-feed than in the later stages of development.