Ocean Noise And Invertebrates

Many people are aware of the detrimental effects of pollutants such as oil, plastic, toxic chemicals, and sewage on marine ecosystems. Marine invertebrates may also be susceptible to another, less frequently discussed form of pollution: noise pollution. This study, published in Scientific Reports, sought to investigate how repeated exposure to human-produced noise might impact the early-life development and survival of marine invertebrates.

Specifically, the authors investigated the effect of boat noise on the embryonic development and survival of the sea hare (Stylocheilus striatus), a species of mollusk. They conducted a field experiment with strategically placed sea hare eggs in a lagoon in French Polynesia. Using underwater loud speakers, the authors exposed half of the eggs to recordings of boat noise mixed with ambient noise. They exposed the other half to recordings of ambient noise only. After five days, the authors collected the samples and counted the number of eggs that developed and hatched. They also counted the number of veligers (the final stage of larvae) that survived or died shortly after birth.

The results showed the following:

• Of the 29,416 eggs counted, 7,497 failed to develop. Sound treatment seemed to significantly affect the percentage that failed to develop. A mean of 21.3 fewer eggs per mother developed when exposed to boat-noise playback compared to ambient-noise playback.
• Of the 21,919 eggs that developed successfully, 13,257 had not hatched after five days. Sound treatment did not seem to significantly affect the percentage of developing eggs that remained un-hatched.
• Of the 8,662 eggs that successfully hatched, 3,514 veligers died before the researchers could count them. Sound treatment seemed to significantly affect the percentage of dead veligers. There was a median of 21.6 more larvae dying after exposure to boat-noise playback than after ambient-noise playback.

In summary, the authors state that “boat-noise playback significantly increased the likelihood of sea hares suffering developmental failure at the embryonic stage and mortality at the free-swimming veliger stage, but had no discernible impact on the rate of embryo development.” They suggest that the death of embryos might be the result of stronger molecular vibrations produced by boat-noise recordings. These stronger vibrations may lead to disrupted tissue formation or altered gene expression. They suggest that the death of veligers might be the result of stress caused from detecting high levels of noise.

The authors note that their findings should be taken with care. This is because the findings were based on recordings played on loud speakers rather than actual boat noise. But, the authors believe that the findings could have far-reaching implications. These include that “anthropogenic noise has the potential to impact gastropod molluscs,” a large class of invertebrates that play a key role in the equilibrium between corals and algae. It also includes that anthropogenic noise can have “detrimental fitness consequences early in life.” This could have a fundamental influence on population dynamics and resilience in marine ecosystems. The authors recommend that boat noise is “considered in the management of fisheries and protected areas” at both local and international levels.

For advocates, the paper offers evidence of the significant harmful effects that anthropogenic noise can have on marine ecosystems. More specifically, it provides additional evidence of the detrimental impacts of boats. And boats are also significant sources of other means of pollution such as oil spills and fuel leaks. As the authors note, these findings may be particularly relevant for shaping policies regarding marine protected areas, as well as threatened and endangered species. Finally, the paper indicates that noise from human activities impacts the development and early survival of members of one particular species. This could be further explored with other animal species.