New research shows that noise from human activities harms ocean invertebrates and ecosystems.
Scientists reviewed hundreds of studies on the impact of noise on marine invertebrates (such as crabs, molluscs, squids, prawns, and worms).
They concluded that noise caused by humans harms invertebrates in many ways, from the cellular level to entire ecosystems.
The international team, including Universitat Politècnica de Catalunya – BarcelonaTech (UPC) and the University of Exeter, is calling for urgent research to investigate and mitigate these effects.
“Many people are surprised to find out that invertebrates can even perceive sounds, but in fact sound is fundamental to their survival,” said first author Dr. Marta Soule, of the UPC.
“Light doesn’t travel well in water but sound does, and invertebrates use sound in a number of ways.
“Human activities – particularly marine transport – are rapidly changing the ocean acoustic landscape, and our study gathers the latest evidence on the effects of this.”
The study highlights the multiple effects of (human) human noise on invertebrates:
- It can delay the hatching and development of eggs in crustaceans, and significantly increase malformations and mortality rates among larvae of crustaceans, bivalves (such as mussels and oysters) and gastropods (such as snails).
- Low frequency sounds can cause injury and even death. For example, research has shown that the sound from underwater explosions can kill blue crabs. After an increase of cephalopods (such as squid and octopuses) washed up on beaches in Spain, research showed that the noise damaged their hemipods (the hearing organs that help them navigate).
- Effects on behavior include many species displaying a “startle” reaction in response to loud sounds. Long-term exposure to noise also affects behavior. For example, the sounds of ships limit the ability of shore crabs to change color to camouflage themselves
- Physiological changes were also detected. For example, Mediterranean squid showed changes in protein content due to exposure to sound – with some affected proteins linked to stress. In another study, permanent high-level exposure to sound resulted in a significant decrease in growth and reproduction rate, increased aggressiveness and mortality rate, and a decrease in the intake of forage shrimp.
- By altering the behavior and health of predators and prey in complex food webs, noise can affect entire ecosystems — and the researchers say more research is needed to investigate this.
Recent studies have revealed that a wide range of invertebrates are sensitive to sounds, particularly via sensory organs whose original function is to allow the maintenance of balance in the water column and to sense gravity.
Invertebrates can detect sound underwater through three types of sensory systems: “surface” receptors on the surface of their bodies, internal “statocyst” receptors (equivalent to ears), and flexible “chord” appendages that sense vibrations.
They can also produce sounds – ranging from the “cough” of scallops to the squeaks of lobsters, crayfish, shrimp and crabs, possibly to ward off predators.
“Our study confirms that these animals exist in a rich underwater acoustic environment,” said Dr Sophie Nedlec, from the University of Exeter.
“We urgently need to know more about the effects of noise pollution on these animals and ecosystems.
“Given that noise can affect invertebrates from the cellular level down to the ecosystem level, we need to bring together multidisciplinary expertise to embrace a holistic view of the problem.
“Given the many pressures caused by humans – including from climate change and fisheries – we must do everything we can to reduce 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, and a recent study by Exeter researchers has raised concerns about the effects of noise on wildlife.
