Date of Award

Spring 2025

Project Type

Thesis

Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Brittany Jellison

Second Advisor

Michelle Fournet

Third Advisor

Elizabeth Harvey

Abstract

Anthropogenic noise pollution is increasing in the world’s oceans, particularly along urbanized coastlines and global shipping routes. Many human activities, such as vessel traffic, pile driving, drilling, and other construction projects, produce loud low-frequency noise (Duarte et al. 2021). Marine invertebrates, including the blue mussel Mytilus edulis, sense sound through particle motion and may use acoustic signals as informational cues. While excessive noise has been shown to have negative physiological effects on adult and larval shellfish, Mytilidae larvae have also demonstrated a positive settlement response to some types of low-frequency anthropogenic noise (Solé et al. 2023). During the summer of 2023, two floating docks in Portsmouth Harbor, NH, were equipped with ST-500 hydrophones and settlement plates to compare sound pressure levels (SPLs) with mussel settlement, growth, and performance. Ambient noise levels were quantified using root mean square (RMS) SPL in the 10–5000 Hz frequency band, which was primarily comprised of sounds from large to mid-size vessels. At the end of the season, mussel recruits were removed from the plates for group comparisons of population counts and physiological metrics, including respiration and condition index (defined as the ratio of wet weight to shell length). Our results show that during peak settlement, settlement rates of M. edulis were generally higher at louder SPLs, but end-of-season recruitment measurements were similar across all groups. We also found that recruits exposed to higher SPL environments during the first four weeks of growth had decreased condition indices. Potential explanations for the positive settlement response to low-frequency ambient noise, including both direct and indirect effects, are discussed in the context of the observed ecological conditions.

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