The core microbiome of cultured Pacific oyster spat develops with age but not mortality

The Pacific oyster (Magallana gigas, also known as Crassostrea gigas) is the most widely cultivated shellfish and is important to the economy of many coastal communities. However, high mortality of spat during the first few days following metamorphosis can affect the seed supply to oyster growers. Here, we show that the microbiome composition of recently settled oyster spat experiencing low or high mortality were not significantly different. Instead, development of the core microbiome were associated with spat aging and was partially driven by dispersal through the water. These findings imply the importance of early stage rearing conditons for spat microbiome development in aquaculture facilities. Furthermore, shellfish growers could gain information about the developmental state of the oyster spat microbiome by assessing key taxa. Additionally, the study provides a baseline micriobiome for future hypothesis testing on developing spat.