We sought to examine the influence of exogenous organic matter substrate addition and suboxic conditions on viral replication in the giant Pacific sea cucumber Apostichopus californicus. This economically and ecologically valuable species undergoes occasional mortality due to a wasting-like condition. We recovered an aquatic flavivirus from wasting specimens in 2016. To examine the influence of microbial activity on flavivirus dynamics, peptone, glucose, n-acetylglucosamine and fucose+rhamnose were added to observe impacts on microbial composition.