Did you know that many marine animals use sound for communication? That certain sounds travel for kilometers through water? Find out more about marine sounds and the way humanity interrupts the song of marine life.
Sound in seawater travels 4.4 times faster underwater than in the air; at an average speed of 1500 meters per second (m/s), and only 340 m/s in air. Seasonal fluctuations of temperature and salinity accelerate sound, for instance, in seawater each 1 °C rise increases sound speed by 4.5 m/s, a rise by one unit of salinity increases by 1.3 m/s. Recent studies suggest that in an acidified ocean, sound must travel twice as far to lose its intensity. The impacts of climate change – increases in temperature, salinity and acidity – may therefore change the way sound spreads in the ocean.
On average, marine ambient sound ranges from about 20 to 80 decibels (1 µPa) with occasionally louder sounds, underwater volcanoes, earth-quakes, sea ice movement etc. In the last decades, maritime traffic in certain areas has increased the ambient sound up to 12 dB above the natural level. Many other human activities, wherther commercial or military, are important sources of sounds capable of disturbing marine life by generating intensities ranging up to 250 dB a meter away from the source (1 µPa).
MEET INHABITANTS THAT PRODUCE SOUNDS:
Seahorse - 800Hz - 28kHz
Seahorses produce sound in association with feeding and courtship. Stridulation of the bony edges of the skull and coronet produce snaps and clicks which are possibly amplified by the swim bladder.
Chromis - 100 - 1000Hz
Chromis are well-known for the male courtship display known as the signal jump, in which a male rises in the water column and then swims down rapidly while producing a pulsed sound. Thanks to this specific method, females are able to determine male courtship rates by listening, without watching, leaving time for other activities like feeding. The courtship sounds vary in features such as pulse number.
Tub gurnard - 129 - 215Hz
Triglid fish are very active sound producers and emit typical swimbladder sounds during social interactions. The sounds of the tub gurnard include grunt or growling that differ in their temporal and frequency characteristics. Sounds are always produced in relation to agonistic behaviour or to alarm reactions.
European spiny lobster - 300Hz
Spiny lobsters rub a piece of soft tissue called the plectrum against a smooth, stiff file that is near their eye. The plectrum “sticks and slips” against the file and produces a rasping sound. This technique resembles a bow moving over the strings of a violin. The sound produced is maybe used for protection against predators.
Sea urchin - 800Hz - 28kHz
Grazing sea urchins produce underwater sounds that contribute to the surrounding soundscape. The calcified test of the sea urchin acts as a resonator. The scraping of the rocks by the teeth causes the fluid inside the urchin to resonate. This resonance causes crackling sounds.