Many marine organisms use different sounds for echolocation, navigation or communication, creating rich soundscapes in the oceans. Recently, however, more and more sounds from human activity have penetrated into the waters. A new study led by the Alfred Wegener Institute for Polar and Marine Research (AWI) has shown that such sounds affect some seafloor invertebrates in a way that can disrupt important functions they provide to their ecosystems.
Marine invertebrates such as mussels, crustaceans or worms are the main engineers of ecosystems, constantly changing the sediment they live in, burrowing into, feeding on, aerating and fertilizing it. Such activities facilitate ocean nutrient cycling and allow more carbon to accumulate on the seafloor from dead organic matter.
In addition to pollution, ocean warming and acidification, recent human-induced noise has also put marine organisms under increased stress. Experts from AWI have shown that such noises, whether from resource extraction, cargo ships or recreational boats, stress not only marine mammals but also invertebrates.
“We studied how crustaceans, mussels and worms on the seafloor respond to low-frequency noise, and how often and how intensely they are able to transform and break down sediment during noise exposure,” said lead author Sheng Wang, a biologist at AWI.
The researchers studied in the laboratory how sound waves of 100 to 200 hertz affect a variety of amphipods, egg-pods and Baltic molluscs.
“After six days, we clearly saw that all three species responded to noise, despite the fact that they belong to completely different groups of animals that do not have hearing organs,” said Jan Beermann, AWI ecologist, senior author of the study.
If the amphipods, after exposure to such sounds, burrowed into the sediment less and not so deeply, then in the case of worms there was no clear reaction, although they behaved more inconsistently. Potential stress responses that need to be investigated have also been observed in Baltic molluscs. According to scientists, more field research is needed, since experimental setups in the laboratory may not reflect the full complexity of natural conditions.
The experts concluded that anthropogenic noise could prevent seafloor invertebrates from cultivating and restructuring sediments, thereby affecting important marine ecosystem functions such as nutrient supply and food availability for higher up the food chain organisms such as fish.
Due to human activities, the seabed can become even more “noisy”. We are just beginning to understand exactly how noise processes work. However, understanding this is critical to the sustainable use of our oceans,” Prof Biermann concluded.
The study was published in the journal Environmental Pollution.