New research shows that noise from human activities is harming ocean invertebrates and ecosystems.
Scientists analyzed hundreds of studies on the effects of noise on marine invertebrates (such as crabs, clams, squid, shrimp and worms).
They concluded that human-caused noise harms invertebrates in a variety of ways, from the cellular level to entire ecosystems.
An international team, including the Polytechnic University of Catalonia – BarcelonaTech (UPC) and the University of Exeter, are calling for urgent research to investigate and mitigate these effects.
“Many people are surprised to discover that invertebrates can even perceive sound, but in fact sound is fundamental to their survival,” said first author Dr. Marta Sole from UPC.
“Light doesn’t travel well in water, but sound does, and invertebrates use sound in a variety of ways.
“Human activities – especially shipping – are rapidly changing the ocean’s soundscape, and our study brings together the latest evidence on the impact of this.”
The study highlights the multiple impacts of anthropogenic (human) noise on invertebrates:
- It can delay hatching and egg development in crustaceans, and significantly increase abnormality and mortality rates among larval crustaceans, bivalves (such as mussels and oysters), and gastropods (such as snails).
- Low-frequency sounds can cause injury and even death. For example, studies have shown that sounds from underwater explosions can kill blue crabs. After an increase in the number of cephalopods (such as squid and octopus) washed up on Spanish beaches, studies have shown that the noise has damaged their statocysts (the organs of hearing that help them navigate).
- Behavioral effects include many species exhibiting a “startle” response in response to loud noises. Long-term exposure to noise also affects behavior. For example, ship noises limit the ability of shore crabs to change color to camouflage themselves
- Physiological changes were also detected. For example, in the common Mediterranean cuttlefish, protein content changed due to exposure to sound – some proteins were associated with stress. In another study, continuous exposure to high-level sound resulted in significantly reduced growth and reproductive rates, increased aggressiveness and mortality, and decreased feed consumption by shrimp.
- By changing the behavior and health of predators and prey in complex food webs, noise can affect entire ecosystems — and researchers say more research is needed to explore this.
Recent studies have shown that a wide range of invertebrates are sensitive to sound, particularly through sensory organs whose primary function is to maintain balance in the water column and sense gravity.
Invertebrates can detect underwater sound using three types of sensory systems: “surface” receptors on their body surface, internal “statocyst” receptors (equivalent to ears), and flexible “chordotonal” appendages that sense vibrations.
They can also make sounds, from the “coughing” of scallops to the squeaking of lobsters, crayfish, shrimp, and crabs, possibly to ward off predators.
“Our research highlights that these animals exist in a rich underwater soundscape,” said Dr Sophie Nedelek from the University of Exeter.
“We urgently need to learn more about the impact of noise pollution on these animals and ecosystems.
“Given that noise can affect invertebrates from the cellular to the ecosystem level, we need to bring together interdisciplinary expertise to take a holistic view of the problem.
“Given the many human pressures – including climate change and fishing – we must do everything we can to limit underwater noise.”
Ships and boats are the main sources of marine noise, but a wide range of other activities, including drilling, dredging and sonar, also cause noise.
Seabed mining in international waters could be allowed for the first time later this year, with a recent study by Exeter researchers raising concerns about the impact of the noise on wildlife.