International scientists warn of the serious effects of noise pollution on marine invertebrates

An international scientific study, led by UPC’s Laboratory of Applied Bioacoustics (LAB), shows that noise from human activities at sea is harming marine invertebrates and ocean ecosystems. Posted in Frontiers in Marine Sciencethe paper points out that noise pollution at sea can even cause death in some marine species.

In recent decades, scientists have studied the noise sensitivity of marine mammals—especially cetaceans and fins—and fish because they are known to have hearing organs. Recent studies have revealed that a wide variety of invertebrates are also sensitive to sound, particularly through sensory organs whose function is to allow the maintenance of balance in the water column and to sense gravity. Not only do marine invertebrates represent the largest proportion of marine biomass and are indicators of ocean health, but many species also have important socio-economic values.

A team of scientists, consisting of researchers from the Laboratory of Applied Bioacoustics (LAB) from the Universitat Politècnica de Catalunya—BarcelonaTech (UPC) and other universities and research centers in Australia, Spain, the United States, France, Japan, Italy, New Zealand and the UK have reviewed hundreds of studies on the effect of noise on marine invertebrates such as crabs, molluscs, squid, shrimp and worms. They concluded that anthropogenic noise—noise from human operations—harms these species in many ways, from the cellular to the ecosystem level.

“Many people are surprised to discover that invertebrates can even perceive sound, but sound is actually necessary for their survival,” explains Marta Solé, UPC LAB researcher attached to the Polytechnic School of Engineering of Vilanova i la Geltrú (EPSEVG). “Light does not travel easily underwater, but sound does, and invertebrates use sound for their vital activities (interspecific communication, predator detection, reproduction, etc.). Human activities, especially shipping, change the ocean soundscape very quickly, and this study brings together the latest evidence on those effects.” Shipping is the main source of marine noise, but there are many others—drilling, dredging, sonar, etc.—and this affects the natural balance of the oceans.

Multiple effects

Entitled “Marine invertebrates and noise”, the paper was published in the journal Frontiers in Marine Science. It warns of the multiple effects of noise pollution on invertebrates, including delayed egg hatching and development, and significantly increased rates of larval malformation and mortality in crustaceans, bivalves (mussels and oysters), gastropods (snails) and cephalopods (cuttlefish) and .

Low-frequency sounds, such as those from underwater explosions, can cause injury and even death to blue crabs. Long-term exposure of these species to noise also affects their behavior. Ship noise limits the land crabs’ ability to change color for camouflage, according to the research team.

After sound exposure, Mediterranean common cuttlefish showed changes in protein content, mainly in structure- and stress-related proteins. The authors have also reviewed studies that show physiological changes in some species, such as a significant reduction in growth and reproduction rate, an increase in the level of aggression and mortality rate, and a decrease in food intake.

Recent studies have revealed that a wide range of invertebrates are sensitive to sound, especially through statocysts – analogous to the inner ear of vertebrates – whose original function is to allow balance to be maintained in the water column and to sense gravity.

How do invertebrates produce and detect sound?

Sound travels about five times faster in water (about 1,500 m/s) than in air (about 340 m/s) because water is more dense and also attenuates less over the same distance. Invertebrates detect underwater sound through three types of sensory systems: ciliated receptors on the body surface, statocysts, and chordotonic organs, connected to antennae or leg joints in crustaceans.

They can also make sounds: from the “coughing” of scallops to the screeching, in which lobsters, crayfish, shrimp and crabs rub certain body parts together — like bowing a violin — and make sounds that can scare away predators. . The study presents all these forms of sound production and perception that are specific to invertebrates, as well as the techniques used to analyze them.

Effects of noise on ecosystems

By changing the behavior and health of predators and prey in complex food webs, noise can thus affect entire ecosystems. Invertebrates provide important ecosystem functions such as filtering water, creating habitats, processing organic matter, transporting carbon through food webs, and recycling nutrients. Therefore, researchers consider it urgent to continue research in this area to mitigate the effects.

“Our study highlights that these animals exist in a rich underwater soundscape,” explains Dr Sophie Nedelec from the University of Exeter. “We need to learn more about the effects of noise pollution on these animals and ecosystems. Since noise can affect invertebrates from the cellular to the ecosystem level, we need to bring together interdisciplinary expertise to get a holistic view of the problem. Considering the many anthropogenic pressures, including climate change and fisheries, we must do everything possible to limit underwater noise.”

The study summarizes current scientific knowledge about invertebrate bioacoustics (sound production, reception, sensitivity) and how marine invertebrates are affected by anthropogenic noise. It also identifies gaps in scientific knowledge about the tolerance of marine ecosystems to noise, concluding that more research is needed.