The microbiome plays a key role in animal health, and is an important aspect of any natural or farmed ecosystem. Here we present the first environmental microbiome study of Ostrea edulis, as well as the first of a natural wild spawning event of any oyster species. Larval abundance was hypothesised to be correlated with specific microbial signatures. Water samples were collected throughout a natural spawning event of O. edulis at Loch Ryan, Scotland, UK. Samples were collected on 4 different dates from June to September 2019, across 8 different sampling sites on the loch at mid, bottom and surface levels within the water column to remove effects of salinity and tidal fluctuations. Larval count data was obtained from these samples before full-length sequencing of the 16S rRNA gene using Oxford Nanopore Technologies. Significant microbial differences were only found between samples collected on different dates, and not at different sites or water column depths. Differences in the microbiome throughout the spawning season were driven by changes in the abundance of certain taxa, most notably those belonging to the Rhodobacteraceae family. Inverse abundance profiles of Rhodobacteraceae and Vibrio over time are also discussed. This study provides important microbial baseline data about the spawning environment of O. edulis.