# Microbiome as a Tool to Monitor Aquarium Systems

## TL;DR

This study tracks bacterial communities in zoo aquariums to understand how they respond to changes and maintain system stability.

## Contribution

The study introduces using DNA sequencing to monitor aquarium microbiomes, revealing their dynamic nature and stable ammonia-processing function.

## Key findings

- Bacterial numbers increased steadily before stabilizing in aquarium systems.
- Each aquarium developed a unique and frequently changing bacterial community.
- Freshwater and saltwater systems showed significantly different microbial compositions.

## Abstract

This study tracked bacterial communities in seven zoo aquarium systems during their first year to understand how they respond to environmental changes. Researchers collected water and surface samples monthly from one saltwater and six freshwater filtration systems, analyzing bacterial populations through both cultivation and DNA sequencing. Key findings showed that bacterial numbers grew steadily before stabilizing. Each aquarium developed its own unique bacterial community that changed frequently over time. Freshwater and saltwater systems had significantly different microbial compositions. Despite various disturbances resulting from maintenance activities and environmental conditions, the systems maintained their ability to process ammonia—a critical function for removing toxic waste. The research demonstrates that while aquarium microbiomes are dynamic and respond to external influences, their core nitrogen-processing capability remains stable. The authors suggest that advanced DNA sequencing methods could help develop better aquarium management protocols by monitoring these bacterial communities, ultimately benefiting fish health and welfare. This represents an important step toward understanding how to maintain stable, healthy aquatic environments in captive settings.

The bacterial microbiome in aquaria plays an essential role in system stability by metabolizing toxic compounds like ammonia. This study monitored microbiome changes in seven zoo aquatic systems during their first year to assess responses to external influences. Over one year (October 2021–October 2022), water and swab samples were collected from one seawater tank and six filtration systems at regular intervals. Bacterial cultivation included total bacterial counts. Metagenomic analysis was performed on samples corresponding to environmental events using Oxford Nanopore sequencing. Taxonomical analysis at the phylum and genus levels used EPI2ME software. Diversity analyses and statistical tests were performed using R. Total bacterial counts increased steadily after inoculation and stabilized by the end of the collection period. Diversity analysis revealed significant differences within and between freshwater and saltwater tanks. Each aquarium exhibited a distinct bacterial community with frequent compositional changes. Despite environmental conditions and maintenance interventions and resulting disturbances that affected the microbiome, the overall nitrifying capacity remained unaffected. Nitrifying taxa emerged as potential indicators for environmental effects. Combined with investigations of ecological function, next-generation sequencing could facilitate the development of aquarium management protocols, ultimately improving fish welfare.