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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Marine pollution | 5/7 | https://en.wikipedia.org/wiki/Marine_pollution | reference | science, encyclopedia | 2026-05-05T07:36:11.497461+00:00 | kb-cron |
Marine life can be susceptible to noise or the sound pollution from sources such as passing ships, oil exploration seismic surveys, and naval low-frequency active sonar. Sound travels more rapidly and over larger distances in the sea than in the atmosphere. Between 1950 and 1975, ambient noise at one location in the Pacific Ocean increased by about ten decibels (that is a tenfold increase in intensity). Underwater noise pollution is unevenly distributed across marine environments, with the highest con-centrations occurring in shipping lanes, port areas, and densely trafficked ocean routes. These areas experience sustained high ambient noise levels due to the dominance of older and larger vessels, which emit significant low-frequency noise (10 to 500 Hz) caused by engine vibrations, propeller cavitation, and hull turbulence. While advancements in ship design have shown potential to reduce noise emissions, older, noisier vessels remain prevalent in major shipping routes, largely due to economic and logistical constraints. Additionally, the overall increase in global shipping activity in the 20th century contributed to a rise of approximately 12 decibels in ambient noise levels in the Northern Hemisphere, particularly in the low-frequency range, which propagates over long distances with minimal attenuation. Studies in the Southern Hemisphere do not show a continuation of this trend in the 21st century. The cumulative effects of concentrated noise pollution pose a unique risk to localised ecosystems, particularly for species with limited mobility or specific habitat requirements, as they are unable to escape these high-noise regions. Research also highlights variations in noise behaviour across marine environments, with factors such as water depth, salinity, and seabed composition influencing how noise propagates in coastal areas versus open seas. The localised nature of underwater noise pollution amplifies its ecological consequences, particularly for species that rely on sound for survival. The ecological impacts of underwater noise are most prevalent for marine mammals like whales and dolphins, which rely heavily on sound for communication, navigation, and foraging. Cetaceans, such as whales and dolphins, are especially vulnerable because they rely on echolocation and acoustic signals for communication and navigation. They experience disrupted communication patterns, altered migration routes, and stress-related behavioural changes as some of the consequences of chronic exposure to ship noise. For example, endangered whale populations in the Saguenay–St. Lawrence Marine Park experience considerable acoustic space reduction, limiting their communication ranges and altering their natural behaviours. Studies have shown that underwater noise can reduce communication ranges, impairing essential behaviours such as mating and social cohesion. Beyond marine mammals, fish and invertebrates are also affected, though they are less frequently studied. Fish use acoustic signals for mating, predator avoidance, and territory defence. Noise interference can cause habitat avoidance, reduced reproductive success, and disrupted predator-prey relationships, destabilising local food webs. These cumulative effects of URN contribute to the destabilisation of nutrient cycling and broader eco-system processes. Noise also makes species communicate louder, which is called the Lombard vocal response. Whale songs are longer when submarine-detectors are on. If creatures don't "speak" loud enough, their voice can be masked by anthropogenic sounds. These unheard voices might be warnings, finding of prey, or preparations of net-bubbling. When one species begins speaking louder, it will mask other species voices, causing the whole ecosystem to eventually speak louder. Noise from ships and human activity can damage Cnidarians and Ctenophora, which are very important organisms in the marine ecosystem. They promote high diversity and they are used as models for ecology and biology because of their simple structures. When there is underwater noise, the vibrations in the water damage the cilia hairs in the Coelenterates. In a study, the organisms were exposed to sound waves for different numbers of times and the results showed that damaged hair cells were extruded or missing or presented bent, flaccid or missed kinocilia and stereocilia. Ships can be certified to meet certain noise criteria. According to the oceanographer Sylvia Earle, "Undersea noise pollution is like the death of a thousand cuts. Each sound in itself may not be a matter of critical concern, but taken all together, the noise from shipping, seismic surveys, and military activity is creating a totally different environment than existed even 50 years ago. That high level of noise is bound to have a hard, sweeping impact on life in the sea." Sources of noise below 100 Hz in the ocean include ships and airgun arrays. Other sources of ocean ambient sound in the same frequency range include earthquakes, volcanic eruptions, baleen whale calls, ice calving and winter storms. Efforts to address underwater noise pollution remain limited. The International Maritime Organisation (IMO) introduced voluntary guidelines in 2014, encouraging measures such as the adoption of quieter ship designs, optimized propellers, and improved hull forms to reduce noise emissions. However, the non-mandatory nature of these guidelines has resulted in inconsistent adoption across the shipping industry. In contrast, the European Union's Marine Strategy Framework Directive (MSFD) mandates the management of underwater noise levels as part of achieving or maintaining Good Environmental Status (GES). Scholars argue that a combination of technical and economic measures is needed to tackle the issue effectively. These include mandatory noise limits, subsidies for retrofitting ships with quieter technologies, and spatially informed policies, such as the creation of quiet zones or Marine Protected Areas (MPAs), to safeguard sensitive ecosystems.
=== Other === There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. An example is silt-bearing surface runoff, which can inhibit the penetration of sunlight through the water column, hampering photosynthesis in aquatic plants. Dredge plumes can contain silt and thus have similar effects on aquatic life.