# Effects of Underwater Noise Exposure on Early Development in Zebrafish

## TL;DR

Exposure to underwater noise, especially at night, harms zebrafish embryo development and increases stress, suggesting the need for time-specific noise control in aquatic environments.

## Contribution

This study reveals the differential effects of daytime and nighttime underwater noise on zebrafish embryonic development and oxidative stress.

## Key findings

- Noise exposure delays embryo hatching and reduces larval heart rates, with nighttime noise causing more severe effects.
- Nighttime noise increases larval deformity rates and impairs otolith development.
- Noise exposure elevates oxidative stress markers and alters the expression of genes related to hair cell and otolith development.

## Abstract

Underwater noise pollution poses a growing threat to fish populations, yet its developmental impacts on fish remain poorly understood. As a well-established model organism in environmental and developmental research, zebrafish (Danio rerio) provides an ideal model to investigate these effects. This study examined the effects of daytime and nighttime underwater noise exposure on zebrafish using an embryo model. The results showed that noise exposure delayed embryo hatching and reduced larval heart rates, with nighttime noise causing more severe developmental issues. Furthermore, noise exposure induced oxidative stress, impaired otolith development, and altered the expression of hair cell-related genes. These findings underscore the significance of noise pollution timing and offer valuable insights for implementing time-specific noise control measures to protect aquatic biodiversity.

Anthropogenic noise pollution is a significant global environmental issue that adversely affects the behavior, physiology, and auditory functions of aquatic species. However, studies on the effects of underwater noise on early developmental stages of fish remain scarce, particularly regarding the differential impacts of daytime versus nighttime noise exposure. In this study, zebrafish (Danio rerio) embryos were exposed to control group (no additional noise), daytime noise (100–1000 Hz, 130 dB, from 08:00 to 20:00) or nighttime noise (100–1000 Hz, 130 dB, from 20:00 to 08:00) for 5 days, and their embryonic development and oxidative stress levels were analyzed. Compared to the control group, the results indicated that exposure to both daytime and nighttime noise led to delays in embryo hatching time and a significant decrease in larval heart rate. Notably, exposure to nighttime noise significantly increased the larval deformity rate. Noise exposure, particularly at night, elevated the activities of catalase (CAT) and glutathione peroxidase (GPX), as well as the concentration of malondialdehyde (MDA), accompanied by upregulation of antioxidant-related gene expression levels. Nighttime noise exposure significantly increased the abnormality rate of otolith development in larvae and markedly downregulated the expression levels of otop1 related to otolith development regulation, while daytime noise exposure only induced a slight increase in the otolith abnormality rate. After noise exposure, the number of lateral neuromasts in larvae decreased slightly, yet genes (slc17a8 and capgb) related to hair cell development were significantly upregulated. Overall, this study demonstrates that both daytime and nighttime noise can induce oxidative stress and impair embryonic development of zebrafish, with nighttime noise causing more severe damage.