Commercial production of Florida pompano (Trachinotus carolinus) larvae at low salinity induces variable changes in whole-larvae microbial diversity, gene expression and gill histopathology

Authors: BRADSHAW, DAVID - Harbor Branch Oceanographic Institute; PERRICONE, CARLIE - Harbor Branch Oceanographic Institute; KING, LAURA - Harbor Branch Oceanographic Institute; ALLMON, ELIZABETH - Purdue University; SEPULVEDA SOLEDAD, MARIA - Purdue University; WILLIS, PAUL - Harbor Branch Oceanographic Institute; RICHE, MARTY - Harbor Branch Oceanographic Institute; KIRCHOFF, NICOLE - Live Advantage Bait, Llc; MEJRI, SAHAR - Harbor Branch Oceanographic Institute

Submitted to: Frontiers in Marine Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2023
Publication Date: 4/6/2023
Citation: Bradshaw, D., Perricone, C.S., King, L., Allmon, E.B., Sepulveda Soledad, M., Willis, P.S., Riche, M., Kirchoff, N., Mejri, S. 2023. Commercial production of Florida pompano (Trachinotus carolinus) larvae at low salinity induces variable changes in whole-larvae microbial diversity, gene expression and gill histopathology. Frontiers in Marine Science. 10:1158446. https://doi.org/10.3389/fmars.2023.1158446.
DOI: https://doi.org/10.3389/fmars.2023.1158446

Interpretive Summary: One of the greatest costs associated with land-based aquaculture is maintaining an appropriate salinity for raising their fish. Florida pompano (Trachinotus carolinus) is a promising new aquaculture species that can tolerate a wide range of salinities, but few studies exist regarding its potential larviculture in lower salinities. In partnership with local farmers, we explored the effects of different salinities on raising larvae in a commercial setting on their gill health, bacterial communities, and gene expression. Genes related to turning on the immune system due to detection of potential pathogens showed little response to different salinities and over the life of the larvae. This occurred despite the greater presence of potentially infectious organisms at lower salinities. There expression associated with decreasing the effects of oxidative stress increased during the second half of the study, which corresponded with the fish’s loss of larval physical characteristics. This is an energy-demanding time which indicates that farmers could improve their survival by providing antioxidants in their feed. These results demonstrate that Florida pompano larvae can be grown at salinities as low as 10 ppt in a commercial setting potentially saving the farmers time and resources.

Technical Abstract: Salinity presents economic and technical challenges in land-based recirculating aquaculture systems (RAS) in the U.S. warm water marine finfish aquaculture industry. In addition to osmoregulation and osmotic stress in fish larvae, changes in salinity can affect the larvae microbiome and innate immune system. Florida pompano (Trachinotus carolinus) is a popular sportfish that inhabits marine and estuarine waters along the Atlantic Coasts of the United States and Brazil along with the Gulf of Mexico. This species has been targeted for land-based RAS due to its impressive market value and euryhaline capacity. An on-farm study aimed to improve hatchery production of Florida pompano larvae by determining lower salinities for larviculture. Larvae were cultured at 10, 20, and 30 ppt in triplicates, and larvae samples were collected for histopathology, microbiome, and whole transcriptomics analysis every three days from hatching until the time of weaning (24 days post hatch [DPH]). Water samples were also taken for microbiome analysis on larval sampling days. Histopathology of the larval gills indicated epithelial lifting at lower salinities (i.e., 10 ppt). High-throughput 16S DNA sequencing identified changes in the microbial taxonomic composition of Florida Pompano larvae and tank water in response to salinity treatments (i.e., higher Flavobacterium and Pseudomonas in lower salinities) and diet (increase in Vibrio with addition of Artemia during 12-20 DPH). RNA sequencing revealed few changes in immune-related genes in the larvae between salinities (nod1) but revealed a greater effect on genes across DPH. These changes were driven more by metamorphosis, causing an increase in expression of antioxidant genes (cat, gss, gsto1, and scara3) than by the presence of potentially pathogenic genera, which failed to induce an immune response (low or unchanged expression of downstream elements of the NOD1 or TLR5 pathways). These findings provide baseline information on Florida pompano low salinity tolerance in larviculture during early developmental stages. This study shows minimal effects on the immune system at salinities as low as 10 ppt. This work has important implications for larval health management and can be used to refine and direct future research regarding improving commercial production of warm water marine species.