Many marine organisms use a variety of sounds for echolocation, navigation, or communication, creating rich soundscapes in the world’s oceans. Recently though, increasingly more sounds from human activities are permeating the waters. A new study led by the Alfred Wegener Institute for Polar and Marine Research (AWI) has found that such sounds affect some invertebrates that live on the seafloor in such a way that the important functions they provide for their ecosystems may be impacted.
Marine invertebrates such as mussels, crustaceans, or worms are major ecosystem engineers, continually changing the sediment they live in by burrowing, feeding, aerating, and fertilizing it. Such activities contribute to nutrient cycling in the ocean and allow for more carbon from dead organic matter to be stored in the seafloor.
Besides pollution, ocean warming, and acidification, noises caused by human activities are also placing marine organisms under increased stress recently. Experts from AWI have now shown that such noises – coming from resource extraction operations, cargo ships, or recreational boats – stress not only marine mammals, but also invertebrates.
“We investigated how crustaceans, mussels, and worms on the seafloor respond to low-frequency noise and how frequently and intensively they are able to transform and break down sediment during noise exposure,” said study lead author Sheng Wang, a biologist at AWI.
The researchers studied in the laboratory how sound waves with frequencies between 100 and 200 hertz are affecting a variety of amphipods, lugworms, and Baltic clams.
“After six days, we could clearly see that all three species responded to the noise even though they belong to very different groups of animals that lack actual organs for hearing,” reported study senior author Jan Beermann, an AWI ecologist.
While the amphipods burrowed less and not as deep in the sediment following exposure to such sounds, no clear response was observed in the case of lugworms, although they seemed to behave more inconsistently. Potential stress responses in need of investigation have also been noticed for the Baltic clams. According to the scientists, more field studies should be conducted, since experimental setups under laboratory conditions may fail to capture the full complexity of natural settings.
The experts concluded that human-made noises could inhibit seafloor invertebrates from cultivating and restructuring sediments, thus impacting important functions of marine ecosystems, such as nutrient supply and food availability for organisms higher up on the trophic chain, such as fish.
“Things could get even ‘noisier’ on the seafloor due to human activities. We are just beginning to understand how exactly noise processes work here. Understanding this, however, is crucial for the sustainable use of our oceans,” Professor Beermann concluded.
The study is published in the journal Environmental Pollution.