# Effects of aquaculture practices on Vibrio population dynamics and oyster microbiome

## TL;DR

This study examines how different oyster farming methods affect Vibrio bacteria and the oyster microbiome, with implications for food safety and public health.

## Contribution

The study reveals how aquaculture practices influence Vibrio populations and oyster microbiome diversity using metagenomic sequencing and MPN-qPCR.

## Key findings

- Floating cages showed higher Vibrio genetic representation in oyster samples compared to bottom cages.
- Aquaculture practices significantly affect phage distribution, antibiotic resistance, and virulence genes in oyster microbiomes.
- MPN-qPCR results varied with aquaculture methods and temperature abuse, highlighting methodological and environmental influences.

## Abstract

Oyster aquaculture is essential for ensuring a sustainable food source. Despite stringent controls, cases of oyster-related illnesses linked to pathogenic Vibrio parahaemolyticus (Vp) and Vibrio vulnificus (Vv) persist. This study investigated the impact of aquaculture practices on the oyster microbiome and pathogen levels, focusing on two common systems: on-bottom and floating cages. From June to November 2019, monthly samples were collected from the Chesapeake Bay, including oysters and water from each aquaculture system. Oyster samples included both fresh and temperature-abused oysters. The study utilized the most probable number and real-time PCR (MPN-qPCR) method to quantify total and pathogenic Vp and Vv in water and oyster samples. DNA was extracted from oyster homogenates and filtered water samples for shotgun metagenomic sequencing. The results revealed significant impacts of aquaculture practices on the diversity of the oyster microbiome, particularly affecting the distribution of phages, antibiotic resistance, and virulence factor genes. Shotgun metagenomic sequencing consistently showed higher genetic representation of Vibrio in floating cages for both fresh and temperature-abused oyster samples. MPN-qPCR results differed between practices, showing higher Vibrio levels in bottom cages for fresh oysters and higher levels in floating cages under temperature abuse. These discrepancies are likely explained by the stable conditions in bottom cages, the effects of temperature abuse, and the growth bias inherent to the MPN method. These results underscore the need for a holistic, time-sensitive approach, taking into account microbial states and the dynamic aspects of the oyster environment to understand the complex relationship between aquaculture practices and the oyster microbiome.

This study holds great importance for food safety, antibiotic resistance surveillance, aquaculture management, and environmental health. Unraveling the population dynamics of microbial communities in oysters and their responses to different aquaculture practices enhances our ability to ensure safer seafood, monitor antibiotic resistance, optimize aquaculture methods, and mitigate potential public health challenges. Moreover, it demonstrates the applicability of advanced metagenomic tools for future research. Furthermore, this research addresses critical aspects of food safety, food security, public health, and sustainable aquaculture practices, making it highly relevant in today’s context.