Ocean pollution is a universal and worsening issue, which poses a threat to the health and wellbeing of not only coastal communities, but also to the world at large. Marine and ocean pollutants are primarily generated by land-based human activities, especially from coastline and coastal activities. Most marine and ocean pollutants are from nonpoint source pollution from runoff. Other sources of nonpoint source pollution include septic tanks, vehicles, farms, livestock ranches, and timber harvest areas. Marine pollutants lead to worrying levels of marine debris in oceans. In addition to nonpoint sources, point source pollution comes from a known single source, e.g., an oil or chemical spill or wastewater discharge from a known industry.

Toxic chemicals and plastic can bio-accumulate in fish, disrupt hormone balances, endanger fish reproduction, and alter food web dynamics, ecosystem functions and biodiversity. Due to their durability, persistent organic pollutants can be transported by air and sea currents to regions located far away from the pollution sources. Introduction of non-indigenous species, when induced by climate-shifting interactions, may promote the displacement of ecotypes, and shifts in ecosystem functioning.

Marine Debris

Marine debris is sourced from land-based human activities. Marine debris persistently causes harm to the entire ocean. For example, tiny microplastics and other marine debris kill or harm hundreds of marine species when ingested and consequently threaten their habitats. Similarly, marine debris negatively undermines fishing activities, affects safety, and potentially threatens the health of fishers and other ocean users. Some debris, such as derelict fishing gear , comes from ocean-based sources. Lost or abandoned gear are significant problems as they can damage sensitive habitats, affect fisheries catch, kill wildlife, and even compete with and damage active fishing gear.

The location of published marine litter covers all the corners of the globe.

Source: LITTERBASE

Water Quality

Water quality of the oceans can be negatively impacted by a variety of different types of pollution: chemical, nutrient, oil, light, and noise pollution, and “pollution” of native species and habitats by invasive species.

Chemical pollutants: chemical pollutants - residues of industrial, agricultural, urban, and domestic activities - are lingering in our environment longer than previously believed, causing significant impacts on both our ecosystems and human health. An illustrative case is that of DDT, an insecticide introduced in the 1940s that was later banned due to its toxicity to aquatic invertebrates. Despite the ban, DDT continues to affect the environment as legacy DDT re-enters the atmosphere from oceans through a cycle of dissolving and re-evaporation. Furthermore , computer simulations reveal the ocean as a greater emission source than current global DDT usage, with the chemical traveling northwards due to evaporation over warmer waters.

Human health is directly at risk from these lingering pollutants, particularly when chemicals like PFAS and residual pharmaceuticals fail to fully break down and end up in the ocean. These toxins are ingested by aquatic species and subsequently by higher-level organisms, leading to bioaccumulation and biomagnification. Consequently, marine species, once caught for human consumption, can harbor potentially harmful concentrations of these pollutants. Moreover, pharmaceutical residues making their way up the food chain could adversely affect the health of local populations through regular consumption. Thus, past chemical usage continues to harm us, highlighting the urgent need for robust environmental monitoring and pollutant control measures.

Nutrient Pollution: Eutrophication is when excess nitrogen and phosphorus enter the environment beyond the coastal environment's ability to recycle the nutrients, predominantly from agriculture runoff. Nitrogen pollution can also occur from urban wastewater. Eutrophication causes increased algae and plant growth, which may lead to algal blooms and an increase in turbidity, and could create dead zones from hypoxia (a lack of dissolved oxygen) where marine life either dies or leave the area.

Oil Pollution - Oil pollution presents an additional threat to the marine environment. Although oil spills are usually devastating in the severity of their impact on the environment, they only account for roughly 12% of oil in the sea. Oil enters primarily from diffuse sources, such as leaks during oil extraction, illegal tank-cleaning operations at sea or discharges into the rivers which are then carried into the sea. Weak international regulations, especially in developing regions of the world (Rochette, 2014), are of concern since offshore exploration and development is growing fast in Africa and Brazil.

Light Pollution:Light pollution is not only a terrestrial issue because it has a significant impact on marine organisms and may worsen in the future. Light pollution interferes with circadian rhythms, which organisms use for time migration, reproduction, and eating as creatures move up and down in the water column to feed, and make it easier for predators to locate smaller fishes. Lights come on at sundown in urban and offshore areas and remain on without any variations in intensity. Scientists estimate that 1.9 million square km - representing 3% of the world’s EEZs - is affected by light pollution up to 1 meter deep . Cities are switching to more efficient LED lighting, which could exacerbate light pollution: blue light from LED has a higher penetration depth in the water column than other spectrums of light.

Noise Pollution:Noise pollution affects all aquatic species and severely impacts behavior, physiology, and anatomy. As light only travels down hundreds of meters, the only efficient method for animals to communicate is using sound. Human activities from boating, shipping, and energy exploration can drown out the noise from animal activities where soundwaves within the ocean travel thousands of miles. Noise will hinder animals' ability to hear environmental signals such as predators, food, and preferred habitat. Impacts on animals from noise can cause lesions on organs, hearing loss, and disorientation.

Invasive Species: According to WWF, around 7,000 marine species are carried around the world due to the release of ballast water from commercial shipping operations every day, which can lead to challenges for native species. For example, the American lobster, which has been invading as a stowaway in ballast tanks on board Europe-bound vessels, is eradicating the local lobster in the Oslo fjord. Biofouling - microorganisms, plants, algae, and animals on submerged ship hulls - is another method to transport invasive species. Studies have demonstrated that biofouling can serve as a significant mechanism for the transmission of invasive aquatic species, and there is an increasing trend of bio-invasions, with new areas being invaded regularly.

Plastics

Plastics are one of the leading causes of marine and ocean pollution - making up 80% of all marine debris from surface waters to deep-sea sediments. Globally, over 300 million tons of plastic are produced annually for various applications . As a result, at least 14 million tons of plastic end up in the ocean yearly. Plastic debris primarily comes from land-based activities, while some are ocean-based. Land-based sources include urban trash and stormwater runoff, sewer overflows, littering, inadequate waste disposal and management, industrial activities, tire abrasion, construction, and illegal dumping. Ocean-based plastic pollution mainly comes from the fishing industry, nautical activities, and aquaculture. Marine plastic debris causes severe injuries and death to marine species when ingested or entangled without rescue.

Plastic pollution undermines the productive capacity of oceans and a myriad of ecosystem functions and services from marine ecosystems. For example, plastic pollution threatens food safety and quality, human health, and coastal tourism, and contributes to climate change. There is an urgent need to explore new technological solutions and introduce and strengthen the implementation of existing legally binding agreements to address marine plastic pollution. Many countries lack functioning infrastructure to prevent plastic pollution, including sanitary landfills, recycling capacity, incineration facilities, circular economy infrastructure, integrated waste, and coastal zone management. The absence of these infrastructures contributes to ‘plastic leakage’ into oceans and in many marine ecosystems.

Source: Our World In Data

Climate Change

Climate change is escalating, negatively impacting biodiversity in marine, terrestrial, and freshwater habitats. Climate change modifies land and sea temperature, elevates sea levels, disrupts weather events, changes the carbon cycle, and triggers ocean acidification. Crucially, it also alters plant phenology, disrupting natural life cycles. These shifts contribute to the loss of local species, an increase in invasive species, widespread death among plants and animals, and even extinctions.

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