The oyster fishery in the Gulf of Mexico has been a global leader in oyster production . However, degrading water quality, storm events, the Deepwater Horizon oil spill, and extended opening of the Bonnet Carré Spillway, ha ve diminished wild oyster populations. Aquaculture has the potential to supplement wild populations and support a commercial oyster aquaculture industry. The industry relies on hatchery production of single-set oyster seed which can be unreliable due the variability of the natural seawater (NSW) used for hatchery production. The use of artificial seawater (ASW) has the potential to enhance aquaculture production for the Eastern oyster, Crassostrea virginica, by expanding production capability into inland areas, avoiding fluctuating environmental conditions, and reducing risks from anthropogenic pollutants. NSW , however, contains complex communities of microorganisms that play a critical role in maintaining ecological processes that affect oyster development, growth, and survival. Characterization of microbial communities in ASW through molecular sequencing will lead to improved aquaculture operations .
Samples were collected from recirculating ASW, oyster production systems located at the University of Southern Mississippi's Thad Cochran Marine Aquaculture Center, in Ocean Springs, Mississippi, USA during the 2018 - 2020 hatchery seasons. Samples were filtered through Sterivex-GP 0.22uM filter (Millipore-Sigma) and genomic DNA was extracted using the FastDNA ® SPIN kit (MP Biomedical Inc.), and ~2 ng/µL of sample was used at the Integrated Microbiome Resource (IMR) facility at Dalhousie University (Halifax, Nova Scotia, Canada) for 16S rRNA gene amplification and sequencing, targeting the V6-V8 variable regions. Samples were quantified, and analyzed on an Illumina MiSeq platform, generating 300 bp, paired-end sequences. For bioinformatics analyses, we have used Quantitative Insights into Microbial Ecology (QIIME2). QIIME2-DADA2 pipeline was used for quality control and the generation of amplicon sequence variants (ASV), which were clustered into OTUs and used for taxonomic identification and phylogenetic assignment against the ribosomal RNA database reference (SILVA). Bacterial plating , nutrient analysis and larval performance was examined to identify potential correlations between bacterial community composition and larval health and condition.
Preliminary data show differences in microbial diversity at different locations within the hatchery system and through time. Further analyses will determine how microbial communities change as water inventory ages and throughout larval culture cycles. This data will improve understanding of the role of microorganisms in artificial saltwater oyster hatchery systems and have potential to inform methods to establish bacterial communities to sustain oyster larval health and development.