Temporary noise-induced underwater hearing loss in an aquatic turtle (Trachemys scripta elegans)

Area of Science:

• Aquatic toxicology
• Bioacoustics
• Sensory ecology

Background:

• Aquatic noise pollution poses a threat to marine life, potentially causing hearing impairment.
• Understanding the auditory sensitivity of aquatic species is crucial for assessing noise impacts.

Purpose of the Study:

• To investigate the effects of continuous underwater white noise on the auditory sensitivity of the red-eared slider turtle (Trachemys scripta elegans).
• To determine the sound exposure levels (SELs) that induce temporary threshold shifts (TTS) in turtles.

Main Methods:

• Exposure of turtles to underwater white noise across 16 conditions varying in duration and amplitude (155–193 dB re 1 μPa²s).
• Measurement of auditory sensitivity at 400 Hz using auditory evoked potential methods before and after noise exposure.
• Analysis of the relationship between TTS magnitude and exposure parameters (duration, amplitude, SEL).

Main Results:

• All tested turtles exhibited TTS, with shifts up to 40 dB observed at most tested SELs.
• Significant positive correlations were found between TTS magnitude and exposure duration, amplitude, and SEL.
• The mean predicted TTS onset level was 160 dB re 1 μPa²s, suggesting turtles are sensitive to relatively low noise levels.

Conclusions:

• Aquatic turtles demonstrate sensitivity to underwater noise pollution, experiencing hearing loss at comparatively low sound levels.
• Individual variation exists in TTS susceptibility, magnitude, and recovery, with recovery rates generally higher after larger shifts.
• These findings highlight the potential vulnerability of aquatic turtles to anthropogenic noise in their habitats.