The oyster fishery in the Gulf of Mexico has been a global leader in oyster production. Declining water quality, storm events, and human impacts (e.g., oil spills, flood control) have diminished wild oyster populations. Aquaculture can support restoration efforts, commercial oyster aquaculture, and wild harvests. The commercial oyster aquaculture industry relies on hatchery production of single-set oyster seed, the supply of which can be unreliable due to variability in 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. Seawater, whether artificial or natural, contains complex communities of microorganisms that play critical roles in maintaining conditions that affect oyster larvae development, growth, and survival. Therefore, understanding the dynamics of microbiomes in recirculating systems may provide information about the state of the system that connects to larval production outcomes.
Water samples were collected from recirculating ASW production systems at the University of Southern Mississippi’s Thad Cochran Marine Aquaculture Center, in Ocean Springs, Mississippi, USA during the 2020-2023 hatchery seasons. Water samples were filtered through 0.22uM filters, genomic DNA was extracted, and 16S rRNA gene amplification and sequencing targeting the V6–V8 variable regions was performed on the Illumina MiSeq platform. Bioinformatics analyses were performed using Quantitative Insights into Microbial Ecology with DADA2. Water quality parameters were collected simultaneously with water samples. Larval survival data, including assessments of fecundity, percent of larvae reaching day two (D-stage), and percent of larvae reaching pediveliger stage also were collected to calculate brood outcome indices.
Preliminary data show that the location within the system and transition between brood introductions and removals (stocking and harvesting) were key factors shaping microbiome composition. Across the four-year study period, water quality became more stable, concomitant with a more uniform microbiome in different system compartments. Brood outcome indices improved across the study period. This work may provide information that can support improved larval survival and tools to monitor whole system (biotic and abiotic) conditions.