Pollution of oceans from substances discarded by humans
While marine pollution can be obvious, as with themarine debris shown above, it is often the pollutants that cannot be seen that cause most harm.
Marine pollution occurs when substances used or spread by humans, such asindustrial,agricultural andresidentialwaste,particles,noise, excesscarbon dioxide orinvasive organisms enter theocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, althoughmarine transportation significantly contributes as well.[1] It is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide.[2] Since most inputs come from land, either via therivers,sewage or the atmosphere, it means thatcontinental shelves are more vulnerable to pollution.Air pollution is also a contributing factor by carrying off iron, carbonic acid,nitrogen, silicon, sulfur,pesticides or dust particles into the ocean.[3] The pollution often comes fromnonpoint sources such as agriculturalrunoff, wind-blowndebris, and dust. These nonpoint sources are largely due to runoff that enters the ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans.[4] Pathways of pollution include direct discharge, land runoff,ship pollution,bilge pollution,dredging (which can createdredge plumes), atmospheric pollution and, potentially,deep sea mining.
The types of marine pollution can be grouped as pollution frommarine debris,plastic pollution, includingmicroplastics,ocean acidification,nutrient pollution, toxins and underwater noise. Plastic pollution in the ocean is a type of marine pollution byplastics, ranging in size from large original material such as bottles and bags, down tomicroplastics formed from the fragmentation of plastic material. Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Plastic pollution is harmful tomarine life.
Another concern is the runoff ofnutrients (nitrogen and phosphorus) fromintensive agriculture, and the disposal of untreated or partially treatedsewage to rivers and subsequently oceans. Thesenitrogen andphosphorus nutrients (which are also contained infertilizers) stimulatephytoplankton andmacroalgal growth, which can lead to harmfulalgal blooms (eutrophication) which can be harmful to humans as well as marine creatures. Excessive algal growth can also smother sensitivecoral reefs and lead toloss of biodiversity and coral health. A second major concern is that the degradation ofalgal blooms can lead to consumption ofoxygen in coastal waters, a situation that may worsen withclimate change as warming reduces vertical mixing of the water column.[5]
Many potentially toxic chemicals adhere to tiny particles which are then taken up byplankton andbenthic animals, most of which are eitherdeposit feeders orfilter feeders. In this way, the toxins areconcentrated upward within oceanfood chains. When pesticides are incorporated into themarine ecosystem, they quickly become absorbed into marinefood webs. Once in the food webs, these pesticides can causemutations, as well as diseases, which can be harmful to humans as well as the entire food web.Toxic metals can also be introduced into marine food webs. These can cause a change to tissue matter, biochemistry, behavior, reproduction, and suppress growth in marine life. Also, manyanimal feeds have a highfish meal orfish hydrolysate content. In this way,marine toxins can be transferred to land animals, and appear later in meat and dairy products.
There are many ways to categorize and examine the inputs of pollution into marine ecosystems. There are three main types of inputs of pollution into the ocean: direct discharge of waste into the oceans, runoff into the waters due to rain, and pollutants released from the atmosphere.[6]
One common path of entry bycontaminants to the sea are rivers. The evaporation of water from oceans exceeds precipitation. The balance is restored by rain over the continents entering rivers and then being returned to the sea. TheHudson River inNew York State and theRaritan River inNew Jersey, which empty at the northern and southern ends ofStaten Island, are a source ofmercury contamination ofzooplankton (copepods) in the open ocean. The highest concentration in the filter-feedingcopepods is not at the mouths of these rivers but 70 miles (110 km) south, nearerAtlantic City, because water flows close to the coast. It takes a few days before toxins are taken up by theplankton.[7] Ohio River and Tennessee River both join Mississippi River ultimately drains organic contaminants from several northern states into the Gulf of Mexico.[8]
Pollution is often classed aspoint source ornonpoint source pollution. Point source pollution occurs when there is a single, identifiable, localized source of the pollution. An example is directly discharging sewage and industrial waste into the ocean. Pollution such as this occurs particularly indeveloping nations.[citation needed] Nonpoint source pollution occurs when the pollution is from ill-defined and diffuse sources. These can be difficult to regulate. Agriculturalrunoff and wind blowndebris are prime examples.
In a study published byScience, Jambecket al. (2015) estimated that the 10 largest emitters of oceanic plastic pollution worldwide are, from the most to the least, China, Indonesia, Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh.[9]
Inlandmining for copper, gold, etc., is another source of marine pollution. Most of the pollution is simply soil, which ends up in rivers flowing to the sea. However, some minerals discharged in the course of the mining can cause problems, such ascopper, a common industrial pollutant, which can interfere with thelife history and development of coral polyps.[10] Mining has a poor environmental track record. For example, according to theUnited States Environmental Protection Agency, mining has contaminated portions of the headwaters of over 40% of watersheds in the western continental US.[11] Much of this pollution ends up in the sea.[citation needed]
Surface runoff from farming, as well asurban runoff and runoff from the construction of roads, buildings, ports, channels, and harbours, can carry soil andparticles laden with carbon, nitrogen, phosphorus, and minerals. This nutrient-rich water can cause fleshy algae andphytoplankton to thrive in coastal areas; known asalgal blooms, which have the potential to createhypoxic conditions by using all available oxygen. In the coast of southwest Florida, harmfulalgal blooms have existed for over 100 years.[12] These algal blooms have been a cause of species of fish, turtles, dolphins, and shrimp to die and cause harmful effects on humans who swim in the water.[12]
Polluted runoff from roads and highways can be a significant source of water pollution in coastal areas. About 75% of the toxic chemicals that flow intoPuget Sound are carried bystormwater that runs off paved roads and driveways, rooftops, yards and other developed land.[13] In California, there are many rainstorms that runoff into the ocean. These rainstorms occur from October to March, and these runoff waters contain petroleum, heavy metals, pollutants from emissions, etc.[14]
In China, there is a large coastal population that pollutes the ocean through land runoff. This includes sewage discharge and pollution fromurbanization and land use. In 2001, more than 66,795 mi2 of the Chinese coastal ocean waters were rated less than Class I of the Sea Water Quality Standard of China.[15] Much of this pollution came from Ag, Cu, Cd, Pb, As, DDT, PCBs, etc., which occurred from contamination through land runoff.[15]
Ships can pollute waterways and oceans in many ways including through their ballast, bilge, and fuel tanks.Oil spills can have devastating effects. In addition to being toxic to marine life,polycyclic aromatic hydrocarbons (PAHs), found incrude oil, are very difficult to clean up, and last for years in thesediment and marine environment.[16][17] Additionally,bilge pollution can be toxic to the surrounding environment whenbilge water is released from a ship'sbilge.[18]
Oil spills are one of the most emotive of marine pollution events. However, while a tanker wreck may result in extensive newspaper headlines, much of the oil in the world's seas comes from other smaller sources, such as tankers discharging ballast water from oil tanks used on return ships, leaking pipelines or engine oil disposed of down sewers.[19]
Discharge of cargo residues frombulk carriers can pollute ports, waterways, and oceans. In many instances vessels intentionally discharge illegal wastes despite foreign and domestic regulation prohibiting such actions. An absence of national standards provides an incentive for somecruise liners to dump waste in places where the penalties are inadequate.[20] It has been estimated thatcontainer ships lose over 10,000containers at sea each year (usually during storms).[21] Ships also createnoise pollution that disturbs natural wildlife, and water fromballast tanks can spread harmfulalgae and otherinvasive species.[22]
Ballast water taken up at sea and released in port is a major source of unwanted exotic marine life. Theinvasive freshwater zebra mussels, native to the Black, Caspian, and Azov seas, were probably transported to the Great Lakes via ballast water from a transoceanic vessel.[23] Meinesz believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmlessjellyfish.Mnemiopsis leidyi, a species of comb jellyfish that spread so it now inhabits estuaries in many parts of the world, was first introduced in 1982, and thought to have been transported to theBlack Sea in a ship's ballast water. The population of the jellyfish grew exponentially and, by 1988, it was wreaking havoc upon the localfishing industry. "Theanchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993;sprat from 24,600 tons in 1984 to 12,000 tons in 1993; horsemackerel from 4,000 tons in 1984 to zero in 1993."[22] Now that the jellyfish have exhausted thezooplankton, including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on theecosystem.
Invasive species can take over once occupied areas, facilitate the spread of new diseases, introduce newgenetic material, alter underwater seascapes, and jeopardize the ability ofnative species to obtain food. Invasive species are responsible for about $138 billion annually in lost revenue and management costs in the US alone.[24]
A graph linking atmospheric dust to various coral deaths across theCaribbean Sea andFlorida.[25]
Another pathway of pollution occurs through the atmosphere. The ocean has long been affected by the passage of chemicals from the atmosphere (e.g. nutrient source; pH influence).[26] Wind-blown dust and debris, includingplastic bags, are blown seaward fromlandfills and other areas. Dust from theSahara moving around the southern periphery of thesubtropical ridge moves into theCaribbean andFlorida during the warm season as the ridge builds and moves northward through the subtropical Atlantic. Dust can also be attributed to a global transport from theGobi andTaklamakan deserts acrossKorea,Japan, and the NorthernPacific to theHawaiian Islands.[27]
Since 1970, dust outbreaks have worsened due to periods of drought in Africa. There is a large variability in dust transport to the Caribbean and Florida from year to year;[28] however, the flux is greater during positive phases of theNorth Atlantic Oscillation.[29] The USGS links dust events to a decline in the health of coral reefs across the Caribbean and Florida, primarily since the 1970s.[30]
Deep sea mining (like allmining) has potential environmental impacts. Research on deep-sea polymetallic nodule mining has substantially increased in recent years, but the expected level of environmental impact is still being established.[35] Scientists from MIT examined seafloor sediment plumes generated by a prototype mining collector in the Clarion Clipperton Zone and found that the plume forms a low-lying turbidity current which hugs the seafloor.[36] Another MIT-led study found that modelling can reliably predict plume behaviour in the midwater column, and impact is influenced by the quantity of discharged sediment, and the turbulence of the water upon discharge.[35] While some environmental consequences (such as sediment plumes, disturbance of the bottom, and toxic effects) are known, the scientific understanding of deep sea ecosystems is currently insufficient to evaluate all possible impacts.[37]
Some of the potential toxic metals include copper, zinc, cadmium, lead as well as rare earth elements such aslanthanum andyttrium.[38] Following the release of toxins there is an increase of noise, light, sediment le dan plumes and elements that have the potential to impact theecosystems.[39]
Deep sea minerals (DSM) can be extremely beneficial, it can cause wealth, raising living standards as well as economic opportunities for both current and future generations.[40] In addition, if the wealth is poorly managed it can have the potential to cause great economic and social damage. The instability of price and production levels of minerals can cause an externaleconomic shock leading to a significant backlash on thedomestic economy.[40]
Marine debris, also known as marine litter, is human-created solid material that has deliberately or accidentally been released inseas or theocean. Floating oceanic debris tends to accumulate at the center ofgyres and oncoastlines, frequently washing aground, when it is known asbeach litter or tidewrack. Deliberate disposal of wastes at sea is calledocean dumping. Naturally occurring debris, such asdriftwood anddrift seeds, are also present. With the increasing use ofplastic, human influence has become an issue as many types of (petrochemical) plastics do notbiodegrade quickly, as would natural or organic materials.[41] The largest single type of plastic pollution (~10%) and majority of large plastic in the oceans is discarded andlost nets from the fishing industry.[42] Waterborne plastic poses a serious threat tofish,seabirds,marine reptiles, andmarine mammals, as well as to boats and coasts.[43]
Dumping, container spillages, litter washed intostorm drains andwaterways and wind-blownlandfill waste all contribute to this problem. This increasedwater pollution has caused serious negative effects such as discarded fishing nets capturing animals, concentration of plastic debris in massivemarine garbage patches, and increasing concentrations of contaminants in thefood chain.
Marine plastic pollution is a type ofmarine pollution byplastics, ranging in size from large original material such as bottles and bags, down tomicroplastics formed from thefragmentation of plastic material.Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris isplastic.[44][45] Microplastics andnanoplastics result from the breakdown orphotodegradation of plastic waste in surface waters, rivers or oceans. Recently, scientists have uncovered nanoplastics in heavy snow, more specifically about 3,000 tons that cover Switzerland yearly.[46]
It is approximated that there is a stock of 86 million tons of plastic marine debris in the worldwide ocean as of the end of 2013, assuming that 1.4% of global plastics produced from 1950 to 2013 has entered the ocean and has accumulated there.[47] Global consumption of plastics is estimated to be 300 million tonnes per year as of 2022, with around 8 million tonnes ending up in the oceans as macroplastics.[48][49] Approximately 1.5 million tonnes of primarymicroplastics end up in the seas. Around 98% of this volume is created by land-based activities, with the remaining 2% being generated by sea-based activities.[49][50][51] It is estimated that 19–23 million tonnes of plastic leaks into aquatic ecosystems annually.[52] The2017 United Nations Ocean Conference estimated that theoceans might contain more weight inplastics thanfish by the year 2050.[53]
Oceans are polluted by plastic particles ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. This material is only very slowly degraded or removed from the ocean so plastic particles are now widespread throughout the surface ocean and are known to be havingdeleterious effects onmarine life.[54] Discarded plastic bags, six-pack rings, cigarette butts and other forms of plastic waste which finish up in the ocean present dangers to wildlife and fisheries.[55]Aquatic life can be threatened through entanglement, suffocation, and ingestion.[56][57][58]Fishing nets, usually made of plastic, can be left or lost in the ocean byfishermen. Known asghost nets, these entangle fish,dolphins,sea turtles,sharks,dugongs,crocodiles,seabirds,crabs, and other creatures, restricting movement, causingstarvation,laceration,infection, and, in those that need to return to the surface to breathe,suffocation.[59] There are various types of ocean plastics causing problems tomarine life. Bottle caps have been found in the stomachs of turtles and seabirds, which have died because of the obstruction of theirrespiratory anddigestive tracts.[60]Ghost nets are also a problematic type of ocean plastic as they can continuously trap marine life in a process known as "ghost fishing".[61]
A change in pH by 0.1 represents a 26% increase in hydrogen ion concentration in the world's oceans (the pH scale is logarithmic, so a change of one in pH units is equivalent to a tenfold change in hydrogen ion concentration). Sea-surface pH and carbonate saturation states vary depending on ocean depth and location. Colder and higher latitude waters are capable of absorbing more CO2. This can cause acidity to rise, lowering the pH and carbonate saturation levels in these areas. There are several other factors that influence the atmosphere-ocean CO2 exchange, and thus local ocean acidification. These includeocean currents andupwelling zones, proximity to large continental rivers,sea ice coverage, and atmospheric exchange withnitrogen andsulfur fromfossil fuel burning andagriculture.[65][66][67]
A lower ocean pH has a range of potentially harmful effects formarine organisms. Scientists have observed for example reduced calcification, loweredimmune responses, and reduced energy for basic functions such as reproduction.[68] Ocean acidification can impactmarine ecosystems that provide food and livelihoods for many people. About one billion people are wholly or partially dependent on the fishing, tourism, and coastal management services provided bycoral reefs. Ongoing acidification of the oceans may therefore threatenfood chains linked with the oceans.[69][70]
A polluted lagoonThe effect of eutrophication on marinebenthic life
Eutrophication is an increase in chemicalnutrients, typically compounds containingnitrogen orphosphorus, in anecosystem. It can result in an increase in the ecosystem'sprimary productivity (excessive plant growth and decay), and further effects including lack of oxygen and severe reductions in water quality, fish, and other animal populations.Nutrient pollution, a form ofwater pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usuallynitrates orphosphates, stimulate algae growth. Such blooms are naturally occurring but may be increasing as a result of anthropogenic inputs or alternatively may be something that is now more closely monitored and so more frequently reported.[72]
The biggest culprit are rivers that empty into the ocean, and with it the many chemicals used asfertilizers in agriculture as well as waste fromlivestock andhumans. An excess of oxygen-depleting chemicals in the water can lead tohypoxia and the creation of adead zone.[7]
Estuaries tend to be naturally eutrophic because land-derived nutrients are concentrated whererunoff enters the marine environment in a confined channel. TheWorld Resources Institute has identified 375 hypoxic coastal zones around the world, concentrated in coastal areas in Western Europe, the Eastern and Southern coasts of the US, and East Asia, particularly in Japan.[73] In the ocean, there are frequentred tide algae blooms[74] that kill fish and marine mammals and cause respiratory problems in humans and some domestic animals when the blooms reach close to shore.
In addition toland runoff, atmosphericanthropogenicfixed nitrogen can enter the open ocean. A study in 2008 found that this could account for around one third of the ocean's external (non-recycled) nitrogen supply and up to three per cent of the annual new marine biological production.[75] It has been suggested that accumulating reactive nitrogen in the environment may have consequences as serious as putting carbon dioxide in the atmosphere.[76]
One proposed solution to eutrophication in estuaries is to restore shellfish populations, such as oysters.Oyster reefs remove nitrogen from the water column and filter out suspended solids, subsequently reducing the likelihood or extent ofharmful algal blooms or anoxic conditions.[77] Filter feeding activity is considered beneficial to water quality[78] by controlling phytoplankton density and sequestering nutrients, which can be removed from the system through shellfish harvest, buried in the sediments, or lost throughdenitrification.[79][80] Foundational work toward the idea of improving marine water quality through shellfish cultivation to was conducted by Odd Lindahl et al., usingmussels in Sweden.[81]
DDT is a very toxic chemical that was used as a pesticide in mass quantities[82] throughout the United States and is known to be neurotoxic, a reproductive toxin, an endocrine disruptor, and a carcinogen.[83] DDT is a major focus of the bookSilent Spring published byRachel Carson in 1962. This is often attributed to launching themodern environmental movement[84] and setting the stage for the creation of theEPA in 1970.[85] DDT was banned in the U.S. two years later in 1972.[86] Unfortunately, large quantities had already entered the ocean through runoff and had been dumped directly into the ocean.[87] This toxin impacts marine ecosystems by accumulating fromlower trophic levels[88] and up the food chain into higher trophic levels such as from arctic cod into seals,[89] from fish then eaten by dolphins,[90][91] and from cod and eels into seals.[92]
Shortly after Rachel Carson's publication ofSilent Spring, PCBs were identified as another persistent, toxic chemical that has been released in extensive quantities to the environment. PCBs are a very well-studied class of chemicals that are manufactured from oil.[93] These chemicals are banned in the United States under theToxic Substance Control Act,[94] but are still found in the soil, air, sediments, and biota.[93] PCBs are known to accumulate in the fatty tissues of animals. In particular, PCBs build up and are stored in theblubber of marine mammals including dolphins and killer whales.[95] These chemicals cause reproductive issues for many species.[95] In mud crabs, PCBs have been discovered to be immunotoxic by reducing resistance to bacterial disease, reducing antioxidant enzyme activity, and damaging DNA responsible for immune system functions.[96]
PFAS are an important emerging class of man-made persistent toxicants that contain extremely strongcarbon-fluorine bonds which make these chemicals extremely difficult to break down. They haveunique properties that make them useful for manufacturing a wide variety of products such asfirefighting foams, clothing, carpets, and fast food wrappers.[97] These useful properties in manufacturing unfortunately translate to problematic properties in the environment and organisms from plants to people. Because PFAS are not broken down in the environment, they have been circulated through the air and water to essentially all regions of the atmosphere, land, and ocean.[98][99] These chemicals have many negative effects on marine life, such as significantly inhibited growth ofphytoplankton over time[100] and accumulation in seals, polar bears,[101] and dolphins.[102] Current research is underway investigating the full extent of the harm to marine ecosystems caused by PFAS.
Specific examples
Chinese and Russian industrial pollution such asphenols and heavy metals in theAmur River have devastated fish stocks and damaged itsestuary soil.[103]
Acute and chronicpollution events have been shown to impact southern Californiakelp forests, though the intensity of the impact seems to depend on both the nature of the contaminants and duration of exposure.[104][105][106][107][108]
Due to their high position in thefood chain and the subsequentaccumulation ofheavy metals from their diet,mercury levels can be high in larger species such as bluefin andalbacore. As a result, in March 2004 theUnited StatesFDA issued guidelines recommending that pregnant women, nursing mothers and children limit their intake of tuna and other types of predatory fish.[109]
Some shellfish and crabs can survive polluted environments, accumulating heavy metals or toxins in their tissues. For example,mitten crabs have a remarkable ability to survive in highly modifiedaquatic habitats, including polluted waters.[110] The farming and harvesting of such species needs careful management if they are to be used as a food.[111][112]
Surface runoff of pesticides can alter the gender of fish species genetically, transforming male into female fish.[113]
Since the end of World War II, various nations, including the Soviet Union, the United Kingdom, the United States, and Germany, have disposed of chemical weapons in theBaltic Sea, raising concerns of environmental contamination.[116][117]
TheFukushima Daiichi nuclear disaster in 2011 caused radioactive toxins from the damaged power plant to leak into the air and ocean. There are still many isotopes in the ocean, which directly affects the benthic food web and also affects the whole food chain. The concentration of 137Cs in the bottom sediment that was contaminated by water with high concentrations in April–May 2011 remains quite high and is showing signs of very slow decrease with time.[118]
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 activesonar. 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 tendecibels (that is a tenfold increase in intensity).[119] 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.[120] 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.[121] Additionally, the overall increase in global shipping activity in recent decades has contributed to a rise of approximately 12 decibels in ambient noise levels, particularly in the low-frequency range, which propagates over long distances with minimal attenuation.[122] 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.[123] 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.[124] 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.[125] Studies have shown that underwater noise can reduce communication ranges, impairing essential behaviours such as mating and social cohesion.[126] 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.[127] Noise interference can cause habitat avoidance, reduced reproductive success, and disrupted predator-prey relationships, destabilising local food webs.[128] 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.[129]Whale songs are longer when submarine-detectors are on.[130] If creatures don't "speak" loud enough, their voice can be masked byanthropogenic 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.[131] 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.[132] Ships can be certified to meet certain noise criteria.[133]
According to the oceanographerSylvia 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."[134]
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.[135] 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 assessment and reduction of underwater noise levels as part of achieving Good Environmental Status (GES).[136] 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.[137][138][139]
There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. An example issilt-bearingsurface runoff, which can inhibit the penetration of sunlight through the water column, hamperingphotosynthesis in aquatic plants.[140]Dredge plumes can contain silt and thus have similar effects on aquatic life.[141]
Muchanthropogenicpollution ends up in the ocean. The 2011 edition of theUnited Nations Environment Programme Year Book identifies as the main emerging environmental issues the loss to the oceans of massive amounts ofphosphorus, "a valuable fertilizer needed to feed a growing global population", and the impact billions of pieces ofplastic waste are having globally on the health of marine environments.[142]
Bjorn Jennssen (2003) notes in his article, "Anthropogenic pollution may reduce biodiversity and productivity of marine ecosystems, resulting in reduction and depletion of human marine food resources".[143] There are two ways the overall level of this pollution can be mitigated: either the human population is reduced, or a way is found to reduce theecological footprint left behind by the average human. If the second way is not adopted, then the first way may be imposed as the worldecosystems falter.[citation needed]
The second way is for humans, individually, to pollute less. That requires social and political will, together with a shift in awareness so more people respect the environment and are less disposed to abuse it.[144] At an operational level, regulations, and international government participation is needed.[145] It is often very difficult to regulate marine pollution because pollution spreads over international barriers, thus making regulations hard to create as well as enforce.[146]
Without appropriate awareness of marine pollution, the necessary global will to effectively address the issues may prove inadequate. Balanced information on the sources and harmful effects of marine pollution need to become part of general public awareness, and ongoing research is required to fully establish, and keep current, the scope of the issues. As expressed in Daoji and Dag's research,[147] one of the reasons why environmental concern is lacking among the Chinese is because the public awareness is low and therefore should be targeted.[citation needed]
Marine debris removal in the Northwestern Hawaiian Islands (NOAA removed approximately 57 tons of derelict fishing nets and plastic litter from thePapahānaumokuākea Marine National Monument's tiny islands and atolls, sensitive coral reefs and shallow waters).
The amount of awareness on marine pollution is vital to the support of keeping the prevention of trash from entering waterways and ending up in our oceans. The EPA reports that in 2014 Americans generated about 258 million tons of waste, and only a third was recycled or composted. In 2015, there was over 8 million tons of plastic that made it into the ocean. TheOcean Conservancy reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined.[148] Through more sustainable packing this could lead to; eliminating toxic constituents, using fewer materials, making more readily available recyclable plastic. However, awareness can only take these initiatives so far. The most abundant plastic is PET (Polyethylene terephthalate) and is the most resistant to biodegradables. Researchers have been making great strides in combating this problem. In one way has been by adding a special polymer called a tetrablock copolymer. The tetrablock copolymer acts as a laminate between the PE and iPP which enables for an easier breakdown but still be tough. Through more awareness, individuals will become more cognizant of their carbon footprints. Also, from research and technology, more strides can be made to aid in the plastic pollution problem.[149][150]Jellyfish have been considered a potential mitigating organism for pollution.[151][152]
In 2017, the United Nations adopted a resolution establishingSustainable Development Goals, including reduced marine pollution as a measured goal underGoal 14. The international community has agreed that reducing pollution in the oceans is a priority, which is tracked as part of Sustainable Development Goal 14 which actively seeks to undo these human impacts on the oceans.[153] The title of Target 14.1 is: "By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, includingmarine debris andnutrient pollution."[153]
Parties to theMARPOL 73/78 convention on marine pollution (as of April 2008)
Although marine pollution has a long history, significant international laws to counter it were not enacted until the twentieth century. Marine pollution was a concern during severalUnited Nations Conventions on the Law of the Sea beginning in the 1950s. Most scientists believed that the oceans were so vast that they had unlimited ability to dilute, and thus render pollution harmless.[citation needed]
In the late 1950s and early 1960s, there were several controversies about dumping radioactive waste off the coasts of the United States by companies licensed by theAtomic Energy Commission, into the Irish Sea from the British reprocessing facility atWindscale, and into the Mediterranean Sea by the FrenchCommissariat à l'Energie Atomique. After the Mediterranean Sea controversy, for example,Jacques Cousteau became a worldwide figure in the campaign to stop marine pollution. Marine pollution made further international headlines after the 1967 crash of the oil tankerTorrey Canyon, and after the 1969Santa Barbara oil spill off the coast of California.[citation needed]
Marine pollution was a major area of discussion during the 1972United Nations Conference on the Human Environment, held in Stockholm. That year also saw the signing of theConvention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, sometimes called theLondon Convention. The London Convention did not ban marine pollution, but it established black and gray lists for substances to be banned (black) or regulated by national authorities (gray). Cyanide and high-level radioactive waste, for example, were put on the black list. The London Convention applied only to waste dumped from ships, and thus did nothing to regulate waste discharged as liquids from pipelines.[154]
There are different ways for the ocean to get polluted, therefore there have been multiple laws, policies, and treaties put into place throughout history. In order to protect the ocean from marine pollution, policies have been developed internationally.
In 1948, Harry Truman signed a law formerly known as theFederal Water Pollution Control Act[155] that allowed the federal government to control marine pollution in United States of America.
The 1954 Convention for the Prevention of Pollution of the Sea by Oil and the 1973 International Convention for the Prevention of Pollution by Ships were weakly enforced due to a lack of respect for the laws from flag states.[158]
The 1982 United Nations Convention on the Law of the Sea (UNCLOS) was established to protect the marine environment by governing states to control their pollution to the ocean. It put restrictions on the amount of toxins and pollutants that come from all ships internationally.[160]
In 2006, the Marine Debris Research, Prevention and Reduction Ac.[161] It was established by the National Oceanic and Atmospheric Administration (NOAA) to help identify, determine the source of, reduce and preventmarine debris.
In December 2017, the UN Environmental Agency (UNEA) established the Ad Hoc Open-Ended Expert Group on Marine Litter and Microplastics with the purpose of examining marineplastic pollutions and to evaluate ways to handle the issue.[162]
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