A study based on mathematical modelling has found that the temperature and acidity of water affect how sound travels through the ocean. Emissions of greenhouse gasses are increasing seawater acidity, and this added to the rise in seawater temperature, led researchers to anticipate that underwater sound will travel further in the future in most parts of the oceans. They predict that changes in currents caused by temperature changes could lead to noise levels increasing by 7 decibels by the end of the century. This corresponds to nearly five times as much noise energy under water. Therefore, sounds generated by shipping and sources like air guns used for seismic surveys, will increase. Louder human noise will affect marine life. Researcher Luca Possenti of the Royal Netherlands Institute for Sea Research (NIOZ) said: "In the absence of good visibility underwater, fish and also marine mammals communicate mainly through sounds. If fish can no longer hear their predators, or if whales have a harder time communicating with each other, this will affect the entire ecosystem."
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