Helena Joyce
Ocean pollution is a pressing issue that poses a threat to marine ecosystems, biodiversity, the food web, and human health. With oceans covering over 70% of the Earth's surface, they are a vital natural resource that supports life and regulates the planet's climate. However, human activities have led to the contamination of these waters with various pollutants, including plastic, nutrients from fertilizer runoff, nonpoint sources, light, noise, industrial chemicals, and fossil fuels. To address this global challenge, it is essential to track and monitor ocean pollution, identify its sources, and implement effective solutions. This complex task requires cooperation and innovative approaches to safeguard the health of our oceans and the planet.
| Characteristics | Values |
|---|---|
| Main sources of ocean pollution | Human activities along coastlines and far inland, including littering, poor waste management, runoff, storm water discharge, extreme natural events, and ocean-based sources like derelict fishing gear |
| Types of pollutants | Plastic (including bags, bottles, food containers, and synthetic rope), microplastics, noise, light, oil, carbon emissions, industrial chemicals, and heavy metals |
| Impact of pollution | Harm to marine life and ecosystems, including ingestion of plastic and microplastics, entanglement, damage to habitats, interference with navigation safety, and potential threats to human health through seafood contamination |
| Tracking and monitoring methods | Citizen Science app for data collection, modelling to identify polluting rivers, and cleanup operations to track pollution levels and evaluate policy measures |
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What You'll Learn
The impact of plastic pollution
Plastic pollution has a devastating impact on marine life, ecosystems, and human health. It is one of the leading causes of marine species extinction and is responsible for health problems in both animals and humans.
Plastic pollution in the ocean comes from a variety of sources, mainly land-based, such as urban and stormwater runoff, littering, industrial activities, tyre abrasion, construction, and agriculture. In the marine environment, plastic pollution originates primarily from land runoff but also includes paint shed from shipping and discarded fishing gear. Once in the ocean, plastic can be ingested by marine animals, causing internal injuries and infections, or it can entangle them, leading to loss of limbs and even death. Plastic pollution also affects marine ecosystems by transporting invasive species, threatening biodiversity and the food web.
Plastic pollution has been found in deep-sea cold-water corals and building up in deep-sea hydrothermal vent communities, unique and vulnerable ecosystems unlike any others on Earth. Additionally, microplastics, smaller than 5 mm, can be ingested by fish and other species that filter their food from the water. These microplastics can release toxic chemicals, affecting both marine life and humans who consume seafood.
The presence of plastic in the ocean is continuously increasing, despite efforts to reduce and recycle plastic waste. Plastic is a durable material that can take hundreds of years to degrade, with plastic bags taking up to 20 years to decompose. The degradation process is slowed by ocean salt and the sun's radiation, making the plastic in the ocean unrecyclable over time. This persistence of plastic pollution has severe economic costs, estimated to be between $6-19 billion USD annually, impacting tourism, fisheries, and aquaculture.
Light pollution is another consequence of plastic pollution in the ocean, affecting 1.9 million square kilometers of the world's coastal seas. Artificial light disrupts the physiological behaviors of marine wildlife, impacting migration, reproduction, and feeding patterns. Noise pollution from human activities also affects marine mammals that rely on sound to communicate, migrate, hunt, and reproduce.
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How microplastics enter the food chain
The majority of ocean pollutants come from human activities along coastlines and far inland. One of the biggest sources of pollution is nonpoint-source pollution, which occurs as a result of runoff from sources like septic tanks, vehicles, farms, and timber harvest areas. Plastic pollution is one of the defining legacies of modern life, with at least 14 million tons of plastic ending up in the ocean each year, making up 80% of all marine debris.
Microplastics, smaller than 5mm, are one of the most common pollutants in the ocean. They enter the food chain through a process called 'trophic transfer'. Animals carry microplastics in their bodies, and when they are eaten by other animals, the microplastics are also ingested. For example, nanoplastics in algae are eaten by water fleas, which are then consumed by fish. This is how plastic particles move through the food chain.
Microplastics can also enter the human food chain through contaminated foods. They have been found in drinking water and in fruit and vegetables as they grow. Sewage sludge has contaminated almost 20 million acres of US cropland with per- and polyfluoroalkyl substances (PFAS), commonly found in plastic products. PFAS are also consumed by marine mammals and can eventually enter the human body.
The impact of ingesting microplastics on human health is not yet fully understood. However, exposure to these particles can lead to systematic exposure, and larger microplastics can produce local effects on the immune system, such as inflammation of the intestine. In addition, chemicals are often added to plastic during production to give them desired properties, and these toxins can move and accumulate in animal fat and tissue through a process called bioaccumulation.
The presence of microplastics in the food chain is a growing problem that requires further research and action to address.
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Point source pollution
Oil spills are a significant contributor to point source pollution in the ocean. While tanker spills contribute to a significant portion of oil in the ocean, it is important to note that a large percentage of oil pollution comes from land-based sources such as factories, farms, and cities. Oil refineries and other industrial facilities can also be sources of point source pollution if they discharge wastewater or contaminants into nearby water bodies.
Chemical spills are another example of point source pollution. This can include the release of synthetic chemicals, such as per- and polyfluoroalkyl substances (PFAS), which are created by humans and are resistant to biodegradation. These chemicals can be found in ground, surface, and drinking water, impacting both marine life and humans who consume seafood. PFAS is used in a variety of products to make them heat, oil, stain, grease, and water-resistant.
Wastewater treatment facilities are also a potential source of point source pollution. When these facilities are faulty or damaged, they can release untreated or partially treated sewage into water bodies, leading to contamination. This can have severe impacts on the environment and human health, as the sewage may contain harmful bacteria, chemicals, and nutrients.
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Nonpoint source pollution
In the context of ocean pollution, NPS pollution can originate from various sources, including farms, livestock facilities, construction sites, city streets, parking lots, and forestry activities. For example, sediment, which is soil eroded from farm fields, construction sites, or streambanks, can be carried by runoff into nearby water bodies. This sediment makes the water cloudy, impairing the ability of aquatic organisms to feed properly. It can also damage fish gills, hinder aquatic insect breathing, and reduce plant growth by blocking sunlight. Additionally, sediments can carry other harmful pollutants, such as metals and toxic chemicals, into the water.
Agricultural practices significantly contribute to NPS pollution. Fertilizers and animal waste from farm fields can wash into nearby water bodies, leading to excessive nutrient levels. These nutrients can cause harmful algal blooms, depleting oxygen levels and creating "dead zones" where aquatic life cannot survive. Nutrient runoff from agricultural activities is a significant concern, as it adversely affects both freshwater and marine ecosystems.
NPS pollution is challenging to address due to its diverse and dispersed sources. However, several federal programs and initiatives, such as the Nonpoint Source Management Program, aim to tackle this issue. Implementing best management practices in agriculture, such as buffer strips and proper fertilizer application, can help reduce nutrient runoff. Additionally, improving urban stormwater management, such as through the use of retention ponds and permeable pavements, can minimize the amount of polluted runoff reaching oceans.
While NPS pollution is a significant contributor to ocean pollution, it is important to recognize that plastic pollution also plays a detrimental role. Plastic bags, bottles, food containers, and synthetic ropes are among the most common plastic pollutants found in the ocean. These plastics can take decades to decompose, posing a persistent threat to marine life. Efforts to reduce plastic pollution include promoting recycling, encouraging the use of reusable alternatives, and supporting research and development for biodegradable materials.
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Light and noise pollution
Noise pollution in the ocean has increased dramatically over the last few decades. Marine animals have evolved over millions of years to rely on underwater sound as a primary means of communicating, navigating, locating food and mates, and avoiding predators. However, noise pollution interferes with these key life functions, causing changes in behaviour and, in some cases, even death.
Human activities such as global shipping, oil and gas exploration, construction, naval exercises, seismic surveys, and renewable energy development are major contributors to ocean noise pollution. These activities introduce excessive and unnatural sounds into the ocean, which can mask the vocalizations of marine animals and disrupt their natural behaviours. For example, military sonar has been recorded to alter the feeding behaviour of endangered blue whales, causing them to stop feeding, increase their swimming speed, and move away from the sound source. Similarly, increased ship noise has led to changes in the vocal calls of bottlenose dolphins, potentially reducing the effectiveness of their communication.
Ocean noise pollution is particularly harmful to animals that rely on echolocation, such as dolphins and toothed whales. Excessive noise can disrupt their signals, causing disorientation and impairing their ability to hunt successfully. Additionally, loud noises can cause panic in these animals, leading them to ascend too quickly and suffer from decompression sickness or skin damage from gas bubble lesions.
To track and study ocean noise pollution, scientists use underwater microphones called hydrophones to record sounds within the ocean. These recordings create a soundscape, which allows scientists to detect human activities and study their impact on marine life. By comparing soundscapes from different places and times, researchers can track long-distance animal movements and analyse changes in habitats and ecosystems.
While there are currently no international legal regulations on ocean noise pollution, there are efforts to reduce its impact. The NOAA Ocean Noise Strategy Roadmap, for instance, aims to integrate and manage the effects of ocean noise on protected species and acoustic habitats. Additionally, experts have set thresholds to help reduce the impacts on marine life, and initiatives like the Blue Speeds initiative advocate for practical solutions. By addressing noise at the source, such as through quieter technologies and better propeller design, we can work towards reducing ocean noise pollution and improving the ocean soundscape for the benefit of marine life.
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Frequently asked questions
The sources of ocean pollution can be traced back to human activities along coastlines and far inland. The majority of pollutants come from nonpoint sources such as runoff from septic tanks, vehicles, farms, and timber harvest areas. Point source pollution, which is less frequent but more severe, includes oil spills and chemical spills. Other sources include littering, poor waste management, storm water discharge, extreme natural events, and derelict fishing gear.
Plastic pollution is one of the most significant and prevalent issues, with plastic accounting for 80% of all marine debris. Plastic bags, bottles, food containers, and fishing items are common polluting items. Other types of pollution include noise, light, oil, carbon emissions, and industrial chemicals.
Ocean pollution has devastating impacts on marine life and ecosystems. Marine animals can suffer entanglement, ingestion of plastic, and internal injuries. Microplastics are ingested by fish and other species, entering the food chain and threatening human health. Pollution also disrupts physiological behaviours, migration, reproduction, and feeding patterns.
