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Noise derived from human activities at sea harms marine invertebrates and ocean ecosystems. This is demonstrated by an international scientific study led by the Laboratory of Bioacoustic Applications (LAB) of the Universitat Politècnica de Catalunya – Barcelona Tech (UPC), which indicates that noise pollution in the sea can even cause the death of some marine species.
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 have hearing organs. Recent studies have revealed that a wide diversity of invertebrates are also sensitive to sounds, especially through sensory organs, a function that allows them to maintain balance in the water column and perceive gravity. Not only do marine invertebrates represent the largest proportion of marine biomass and indicators of ocean health, but many of these species also have important socioeconomic values.
The team of scientists, made up of researchers from the Laboratory of Bioacoustic Applications (LAB) and 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, mollusks, squid, shrimp 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, researcher at the LAB, linked to the Polytechnic School of Vilanova i la Geltrú (EPSEVG). .
Solé specifies that, just as “light does not travel easily underwater, sound does, and invertebrates use sound for their vital activities (interspecific communication, detection of predators, reproduction…) Human activities, “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 the wide range of other activities, such as drilling, dredging and sonar, also cause noise and this affects the natural balance of the oceans.
Anomalies and mortality
The multiple impacts of this noise pollution on invertebrates are the delay in hatching and development of eggs, the significant increase in abnormalities and the mortality rate among larvae of crustaceans, bivalves (e.g. mussels and oysters), gastropods (such as snails) and cephalopods (such as cuttlefish and squid).
Likewise, low-frequency sounds such as those caused, for example, by underwater explosions, can cause injury and even death in blue crabs. In addition, the long-term exposure of these species to noise also affects their behavior: boat sounds limit the ability of shore crabs to change color to camouflage themselves, according to the team of scientists.
It has also been discovered that, due to exposure to sound, the Mediterranean cuttlefish changes its protein content, especially affecting structural and stress-related proteins. The same study includes works that demonstrate physiological changes in some species, such as a significant reduction in the growth and reproduction rate, 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 that have the function of allowing them to maintain balance in the water column and perceive the 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 greater and it also attenuates less over the same distance. Invertebrates can detect underwater sound through three types of sensory systems: ciliated receptors on the body surface, statocysts, and various 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 made by lobsters, crayfish, shrimp and crabs when they rub their body parts (as if they were ropes). a violin) and which they possibly serve to ward off predators. The study, titled Marine invertebrates and noise, has been published in the scientific journal Frontiers in Marine Science and includes all these forms of sound production and perception typical of invertebrates, as well as the different techniques used for their analysis. In addition, it identifies scientific gaps regarding the noise tolerance of marine ecosystems, concluding that more research is necessary in this area.
