User:Paul1204/Noise pollution

Wildlife
Sound is the primary way many marine organisms learn about their environment. For example, many species of marine mammals and fish use sound as their primary means of navigating, communicating, and foraging. Anthropogenic noise can have a detrimental effect on animals, increasing the risk of death by changing the delicate balance in predator or prey detection and avoidance, and interfering with the use of the sounds in communication, especially in relation to reproduction, and in navigation and echolocation. These effects then may alter more interactions within a community through indirect ("domino") effects. Acoustic overexposure can lead to temporary or permanent loss of hearing.

European robins living in urban environments are more likely to sing at night in places with high levels of noise pollution during the day, suggesting that they sing at night because it is quieter, and their message can propagate through the environment more clearly. The same study showed that daytime noise was a stronger predictor of nocturnal singing than night-time light pollution, to which the phenomenon often is attributed. Anthropogenic noise reduced the species richness of birds found in Neotropical urban parks.

Zebra finches become less faithful to their partners when exposed to traffic noise. This could alter a population's evolutionary trajectory by selecting traits, sapping resources normally devoted to other activities and thus leading to profound genetic and evolutionary consequences.

Underwater noise pollution due to human activities is also prevalent in the sea, and given that sound travels faster through water than through air, is a major source of disruption of marine ecosystems and does significant harm to sea life, including marine mammals, fish and invertebrates. The principal anthropogenic noise sources come from merchant ships, naval sonar operations, underwater explosions (nuclear), and seismic exploration by oil and gas industries. Cargo ships generate high levels of noise due to propellers and diesel engines. This noise pollution significantly raises the low-frequency ambient noise levels above those caused by wind. Animals such as whales that depend on sound for communication can be affected by this noise in various ways. Higher ambient noise levels also cause animals to vocalize more loudly, which is called the Lombard effect. Researchers have found that humpback whales' song lengths were longer when low-frequency sonar was active nearby.

Underwater noise pollution is not only limited to oceans, and can occur in freshwater environments as well. Noise pollution has been detected in the Yangzte River, and has resulted in the endangerment of Yangtze finless porpoises. A study conducted on noise pollution in the Yangzte River suggested that the elevated levels of noise pollution altered the temporal hearing threshold of the finless porpoises and posed a significant threat to their survival.

Noise pollution may have caused the death of certain species of whales that beached themselves after being exposed to the loud sound of military sonar. (see also Marine mammals and sonar) Even marine invertebrates, such as crabs (Carcinus maenas), have been shown to be negatively affected by ship noise. Larger crabs were noted to be negatively affected more by the sounds than smaller crabs. Repeated exposure to the sounds did lead to acclimatization.

Stress recorded in physiological and behavioral responses
Many of the studies that were conducted on invertebrate exposure to noise found that a physiological or behavioral response was triggered. Most of the time, this related to stress, and provided concrete evidence that marine invertebrates detect and respond to noise. Some of the most informative studies in this category focus on hermit crabs. In one study, it was found that the behavior of the hermit crab Pagurus bernhardus, when attempting to choose a shell, was modified when subjected to noise. Proper selection of hermit crab shells strongly contributes to their ability to survive. Shells offer protection against predators, high salinity and desiccation. However, researchers determined that approach to shell, investigation of shell, and habitation of shell, occurred over a shorter time duration with anthropogenic noise as a factor. This indicated that assessment and decision-making processes of the hermit crab were both altered, even though hermit crabs are not known to evaluate shells using any auditory or mechanoreception mechanisms. In another study that focused on Pagurus bernhardus and the blue mussel, (Mytilus edulis) physical behaviors exhibited a stress response to noise. When the hermit crab and mussel were exposed to different types of noise, significant variation in the valve gape occurred in the blue mussel. The hermit crab responded to the noise by lifting the shell off of the ground multiple times, then vacating the shell to examine it before returning inside. The results from the hermit crab trials were ambiguous with respect to causation; more studies must be conducted in order to determine whether the behavior of the hermit crab can be attributed to the noise produced.

Another study that demonstrates a stress response in invertebrates was conducted on the squid species Doryteuthis pealeii. The squid was exposed to sounds of construction known as pile driving, which impacts the sea bed directly and produces intense substrate-borne and water-borne vibrations. The squid reacted by jetting, inking, pattern change and other startle responses. Since the responses recorded are similar to those identified when faced with a predator, it is implied that the squid initially viewed the sounds as a threat. However, it was also noted that the alarm responses decreased over a period of time, signifying that the squid had likely acclimated to the noise. Regardless, it is apparent that stress occurred in the squid, and although further investigation has not been pursued, researchers suspect that other implications exist that may alter the squid's survival habits.

An additional study examined the impact noise exposure had on the Indo-Pacific humpbacked dolphin (Sousa chinensis). The dolphins were exposed to elevated noise levels due to construction in the Pearl River Estuary in China, specifically caused by the world's largest vibration hammer—the OCTA-KONG. The study suggested that while the dolphin's clicks were not affected, their whistles were because of susceptibility to auditory masking. The noise from the OCTA-KONG was found to have been detectable by the dolphins up to 3.5 km away from the original source, and while the noise was not found to be life-threatening it was indicated that prolonged exposure to this noise could be responsible for auditory damage.