Underwater noise also harms marine invertebrates | Polarjournal
Zooplankton, including krill, and numerous other marine invertebrates are harmed in a variety of ways by underwater noise. Photo: Wikipedia/Uwe Kils

The dangerous effects of underwater noise are known, especially from marine mammals. However, they are by no means the only marine animals harmed by ship noise, seismic exploration, deep-sea mining or sonar. A new review study shows that noise is also dangerous to a wide range of invertebrates and even affects ecosystems.

In the new study, published in the journal Frontiers in Marine Science, the international team of authors analyzed hundreds of studies on the effects of underwater noise on marine invertebrates such as mussels, snails, sea urchins, starfish, shrimp, jellyfish, crabs, lobsters, worms, squid, octopuses and more.

The results show that human-induced underwater noise has multiple negative effects on invertebrates, from the cellular level to entire ecosystems. “Many people are surprised to discover that invertebrates can even perceive sounds, but in fact sound is fundamental to their survival,” says Dr. Marta Solé of the Universitat Politècnica de Catalunya – Barcelona Tech, first author of the study. “Light doesn’t travel very well in water but sound does, and invertebrates use sound in a variety of ways.”

“Human activities – especially shipping – are changing the ocean soundscape rapidly, and our study brings together the latest evidence on the impacts of this,” Dr. Solé added.

Larvae of the snow crab Chionocetes opilio often do not survive the noise caused by seismic airguns. Photo: Wikipedia/Totti, CC BY-SA 4.0

Among the many effects of anthropogenic noise on marine invertebrates are:

  • Hatching and egg development in crustaceans can be delayed.
  • Larvae of crustaceans, mollusks, and snails may have more frequent malformations after airgun explosions, and mortality rates may increase significantly. This is true, for example, for the larvae of snow crabs (Chionocetes opilio), which are also found in the Arctic Ocean and the Bering Sea. Furthermore, their development is slower when exposed to noise.
  • Low-frequency noise, for example caused by seismic exploration, can cause injury and even death, e.g. in crabs or cephalopods (squid, octopuses). The latter washed up on beaches after noise damaged their hearing organs that help with navigation (statocysts).
  • Seismic exploration also harms zooplankton. One study showed that immediately after airgun explosions, all krill larvae died. Other zooplankton were also affected.
  • Many species show a startle response to loud noises. Long-term noise exposure also affects behavior.
  • Physiological responses include change in protein levels in squid, with some of the proteins related to stress.
  • Sustained high noise exposure caused shrimp to have reduced growth and reproductive rates, increased aggressiveness and mortality, and decreased food intake.
  • Even entire marine ecosystems can be affected by noise, as it alters the health and behavior of predators and prey in complex food webs.
Deep-sea mining and preceding seismic exploration are among the loudest sources of noise in the ocean. They pose a threat to a wide range of marine life. Graphic: Deep-Sea Mining: A noisy affair, OceanCare

Recent studies showed that the animals respond particularly through sensory organs, whose original function is to maintain balance in the water column and sense gravity.

The various invertebrate phyla evolved three types of sensory systems with which they perceive sounds: Receptors on the body surface, internal receptors in the statocyst (equivalent to ears), and so-called chordotonal organs on the limbs, which only crustaceans possess. Some of the animals can also make their own sounds, such as scallops, lobsters, crabs, shrimp and crabs.

“Our study underlines that these animals exist in a rich underwater soundscape,” said Dr. Sophie Nedelec of the University of Exeter, co-author of the study. “We urgently need to know more about the impacts of noise pollution on these animals and ecosystems. Considering that noise can affect invertebrates from cellular to ecosystems level, we need to bring together interdisciplinary expertise to embrace a holistic vision of the problem.”

Underwater noise is primarily caused by ships, drilling, seismic exploration, deep-sea mining, dredging, and sonar.

For the invertebrate inhabitants of Arctic waters, as well as for marine mammals, it is feared that underwater noise will increase in the future with diminishing sea ice and subsequent growth in shipping traffic and expanding resource exploration.

Antarctica is likely to be quieter underwater, as any activities aimed at exploring mineral resources are prohibited, scientific research excepted. However, there are seismic explorations on a huge scale there as well, e.g. by Russia. Whether these serve exclusively scientific purposes is questionable. In addition, there is shipping traffic in the Southern Ocean, consisting mainly of fishing vessels and cruise ships, with the latter concentrated particularly along the western side of the Antarctic Peninsula.

“Given the many pressures being caused by humans – including from climate change and fisheries – we must do everything we can to limit underwater noise,” concludes Dr. Nedelec.

Julia Hager, PolarJournal

Link to the study: Marta Solé, Kenzo Kaifu, T. Aran Mooney et al. Marine invertebrates and noise. Frontiers in Marine Science, 2023; 10 DOI: 10.3389/fmars.2023.1129057.

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