In recent decades, the sensitivity to noise of marine mammals -especially cetaceans and pinnipeds- and fish has been studied, because it is known that they possess hearing organs. Recent studies have revealed that a great diversity of invertebrates are also sensitive to sounds, especially through sensory organs whose function is to maintain balance in the water column and perceive gravity. Marine invertebrates not only account for the largest proportion of marine biomass and are indicators of ocean health, but many of these species also have important socioeconomic values.
A team of scientists, made up of researchers from the Bioacoustic Applications Laboratory (LAB) of the Polytechnic University of Catalonia – BarcelonaTech (UPC) and from other universities and research centers in Australia, Spain, the United States, France, Japan, Italy, New Zealand and the United Kingdom, has reviewed hundreds of studies on the impact of noise on marine invertebrates −such as crabs, molluscs, squid, shrimps and worms− and has concluded that anthropogenic noise (derived from human activity) is harming these species in many ways, from the cellular level to entire ecosystems.
“Many people are surprised to discover that invertebrates can even perceive sounds, but, in fact, sound is essential for their survival,” explains Marta Solé, a LAB researcher, linked to the Vilanova i la Geltrú Polytechnic School (EPSEVG). of the UPC.
Solé specifies that, just as “light does not travel easily under water, sound does, and invertebrates use sound for their vital activities (interspecific communication, predator detection, reproduction, etc.). Human activities, shipping, especially shipping, are changing the ocean soundscape very rapidly and this study brings together the latest evidence on these impacts.”
Ships are the main sources of marine noise, but a wide range of other activities, such as drilling, dredging and sonar, also cause noise and this affects the natural balance of the oceans.
multiple impacts
The study warns of the multiple impacts of this noise pollution on invertebrates. Some of them are delayed hatching and development of eggs, significant increase in anomalies and mortality rate among crustacean larvae, bivalves (for example, mussels and oysters), gastropods (such as snails) and cephalopods (such as cuttlefish and squid).
Cangrejo hermitaño (Hot Dardanus). (Photo: UPC)
Also, low frequency sounds such as those caused by underwater explosions, for example, can cause injury and even death to blue crabs. In addition, the long-term exposure of these species to noise also affects their behaviour: sounds from ships limit the ability of shore crabs to change color to camouflage themselves, according to the team of scientists.
It has also been found that due to sound exposure, common Mediterranean cuttlefish changes protein content, affecting mainly structural and stress-related proteins. The same review includes works that demonstrate physiological changes in some species, such as a significant reduction in the rate of growth and reproduction, an increase in the rate of aggression and mortality, and a reduction in food intake.
Other recent studies have revealed that a wide range of invertebrates are sensitive to sounds, especially through statocysts (internal receptors equivalent to ears), sensory organs whose function is to maintain balance in the water column and perceive gravity. .
How do invertebrates produce and detect sound?
Sound travels about five times faster in water (about 1,500 meters per second) than in air (about 340 meters per second) because the density of water is higher, and it also attenuates less at the same distance. Invertebrates can detect underwater sound through three types of sensory systems: ciliated receptors on their body surface, statocysts, and chordotonal organs, associated with the joints of the legs and antennae of crustaceans that detect vibrations.
These species can also produce sounds: from ‘coughing’ in the case of scallops, to stridulation, the sound that lobsters, langoustines, shrimps and crabs make when they rub against two parts of the body (as if they were the strings of a violin). rubbed with the bow) and possibly used to ward off predators. The study includes all these forms of sound production and perception typical of invertebrates, as well as the different techniques used for their analysis.
Effects of noise on marine ecosystems
By changing the behavior and health of predators and prey in complex food webs, noise can affect entire ecosystems. Invertebrates have important functions in marine ecosystems, such as water filtration, habitat creation, organic matter processing, carbon transfer through food webs, and nutrient recycling. For this reason, the researchers see the urgency of continuing research along these lines in order to mitigate these impacts.
“Our study underscores that these animals exist in a rich underwater soundscape,” explains Sophie Nedelec, from the University of Exeter in the UK. “We need to know more about the impacts of noise pollution on these animals and ecosystems. Given that noise can affect invertebrates from the cellular level to ecosystems, we need to bring together interdisciplinary expertise to take a holistic view of the problem. Given With the many pressures caused by human activity, including climate change and fishing, we must do everything we can to limit underwater noise.”
The study, which summarizes current scientific knowledge on invertebrate bioacoustics (sound production, reception, sensitivity) as well as on the acoustic impact of anthropogenic noises on marine invertebrates, also identifies scientific gaps on the noise tolerance of marine ecosystems, so it concludes that more research is necessary in this area.
The study is titled “Marine invertebrates and noise”. And it has been published in the academic journal Frontiers in Marine Science. (Source: UPC)