Ocean Gyres: A Plastic Soup Conundrum

The issue of plastic pollution in the ocean has gained significant attention over the last decade, with plastic debris found across all ocean basins, ecosystems, habitats, and food webs. One of the most well-known garbage patches in the ocean is the Great Pacific Garbage Patch, located between California and Hawaii. This gyre, also known as the North Pacific Garbage Patch, is estimated to contain 1.8 trillion pieces of plastic, weighing almost 90,000 tons. While the majority of large plastic pieces are spread out across the oceans, the rest breaks down into smaller microplastics over time due to sun exposure and waves. These microplastics are challenging to remove, and most debris in the gyres is composed of tiny particles that are too small to be caught in nets. While several organizations and innovative projects are attempting to clean up the ocean, the most advocated solution to reducing plastic pollution is to stop the use and production of plastics.

The Great Pacific Garbage Patch, the largest gyre, is estimated to contain 1.8 trillion pieces of plastic

The Great Pacific Garbage Patch, located between California and Hawaii, is the largest gyre in the world. It covers 1.6 million square kilometers, an area twice the size of Texas or three times the size of France. The gyre was discovered in 1996 by Captain Charles Moore, who published the first account of large accumulations of plastic debris in the middle of the North Pacific Subtropical Gyre.

The Great Pacific Garbage Patch is estimated to contain 1.8 trillion pieces of plastic, with a weight of 80,000-100,000 tonnes. These figures are much higher than previously calculated and are expected to be even higher, with estimates ranging up to 3.6 trillion pieces. The mass of the plastic in the gyre is equivalent to 500 jumbo jets or 740 Boeing 777s. The majority of the plastic in the gyre is broken down into small pieces, with most being the size of pepper flakes or smaller. However, larger objects such as meter-sized fishing nets, food containers, bottles, and laundry baskets are also present.

The center of the gyre has the highest density of plastic, with concentrations reaching hundreds of kg/km², while the outer boundaries have lower concentrations, decreasing to 10 kg/km². The plastic in the gyre is not densely packed and is scattered, rather than forming a solid mass. The plastic is primarily composed of rigid or hard polyethylene (PE) or polypropylene (PP), as well as derelict fishing gear and ropes.

The Great Pacific Garbage Patch has become a thriving ecosystem for coastal creatures, including tiny crabs and anemones, which have been found living on plastic debris thousands of miles from their original habitat. This has led to the creation of new floating ecosystems of species that are not usually able to survive in the open ocean. The plastic provides a surface for these organisms to survive and reproduce, as it does not decompose and sink like organic material.

Efforts to clean up the Great Pacific Garbage Patch are ongoing, with organizations such as The Ocean Cleanup working to remove plastic from the gyre. The Ocean Cleanup estimates that it can remove 50% of the plastic in the gyre within five years using its advanced technologies. However, critics argue that their system may harm marine life and could negatively impact little-understood ecosystems.

The North Pacific Subtropical Gyre, also known as the North Pacific Garbage Patch, is heavily polluted by fishing nets and ropes

The Great Pacific Garbage Patch was discovered by Captain Charles Moore in 1996, who published the first account of large accumulations of plastic debris in the middle of the North Pacific Subtropical Gyre. The subtropical oceanic gyre in the North Pacific Ocean is currently covered with tens of thousands of tonnes of floating plastic debris, dispersed over millions of square kilometres. A large fraction is composed of fishing nets and ropes, while the rest is mostly composed of hard plastic objects and fragments, sometimes carrying evidence of their origin.

In 2019, an oceanographic mission to the area retrieved over 6000 hard plastic debris items larger than 5 cm. The debris was sorted, counted, weighed, and analysed for evidence of origin and age. The results revealed that the majority of the floating material stems from fishing activities, particularly industrialised fishing nations. This conclusion was reached through the analysis of hard plastic debris found in the gyre, which is likely also applicable to nets and ropes, for which the origin is harder to determine.

The plastic debris in the North Pacific Subtropical Gyre poses a significant risk to marine life. Research has found that plastic samples from the gyre contain high levels of pollutants, with 84% of samples exceeding sediment threshold effect levels. In addition, surface trawls collected more plastic than biomass (180 times on average), indicating that some organisms may have plastic as a major component of their diets. The presence of plastic in the diets of marine organisms can have detrimental effects on their health and survival.

While the Great Pacific Garbage Patch is the largest and most well-known garbage patch, plastic pollution is a global issue that affects all oceans and ecosystems. The amount of research and attention given to the topic of plastic pollution has elevated it to the global stage, leading to increased scientific understanding and policy movements to address the problem.

Ocean Cleanup's technique has been criticised for its potential to harm marine life, including an understudied ecosystem called neuston

The Ocean Cleanup's technique has been criticised for its potential to harm marine life, including an understudied ecosystem called neuston. Neuston is a sea-surface ecosystem, comprising insects, worms, snails, nudibranchs, crabs, sea anemones and more that float on the ocean surface. It was first described by scientists during the Cold War era, yet it remains largely unknown.

The Ocean Cleanup's system involves a 600-metre-long barrier with a three-metre-deep net, placed in the ocean to collect plastic as the currents push water through the net. The concern is that this system could harm the neuston ecosystem before scientists have had time to study it. The 146-page environmental impact assessment by The Ocean Cleanup does not mention the neuston, which is a concerning omission, as it may be the habitat most impacted by the cleanup operation.

The Ocean Cleanup has responded to these criticisms, stating that they take any potential environmental side-effects very seriously. They have marine biologists and independent environmental observers onboard monitoring vessels, conducting observational surveys for protected species and marine life, including neuston. They have also conducted low-altitude drone flights, inspections with a support vessel, and remote vessel data collection. The Ocean Cleanup also highlights that their project is providing an opportunity to collect data and further understand the Eastern North Pacific Ocean, including the neuston ecosystem.

The Ocean Cleanup's research has observed that more mobile neuston species, such as zooplankton, fish, squid, shrimp, and euphausiids, can be found in both low and high concentrations of floating plastics. They have also found that many neustonic species present inside the Great Pacific Garbage Patch (GPGP) are also present in similar abundances in the subtropical waters bordering it, indicating a possible recolonization potential. The Ocean Cleanup plans to use these findings to optimize their approach and minimize any negative side effects on marine ecosystems.

While the potential impact on the neuston ecosystem is a valid concern, it is important to balance it with the detriments of plastic in our oceans. Plastic pollution has clear negative consequences for marine ecosystems, with nearly 700 marine species encountering plastic debris, leading to entanglement, ingestion, or death. The Ocean Cleanup's mission is to rid the world's oceans of plastic and prevent further harm to marine life, while also ensuring their cleanup operations have minimal negative side effects on marine ecosystems.

The majority of plastic in the ocean is within 100 miles of the shore, with 77% remaining on beaches or in coastal waters for the first five years

The majority of plastic in the ocean is found in the first place it reaches: the coast. Indeed, a study found that 77% of plastic remains on beaches or floats in coastal waters for the first five years after entering the ocean from land. This is because plastic is often carried to the ocean by rivers, which act as arteries, transporting plastic emissions from land to sea.

In fact, research has identified 1000 rivers worldwide that contribute to almost 80% of ocean plastic emissions. Coastal cities in middle-income countries are the world's plastic emissions hotspots due to their proximity to the ocean. Once in the ocean, plastic is transported by currents and broken down by waves and the sun into smaller pieces, known as microplastics.

While the research on plastic pollution began in the central gyres of the ocean basins, thousands of kilometres from land, it is now understood that plastic debris is ubiquitous across all ocean basins, ecosystems, habitats, and food webs. The Great Pacific Garbage Patch, located between California and Hawaii, is a well-known garbage patch due to the high volume of ship traffic that passes through it. It is estimated to contain 1.8 trillion pieces of plastic, weighing almost 90,000 tons.

However, the majority of large plastic pieces are spread out across the vastness of the oceans, and much of the plastic in the Great Pacific Garbage Patch is in the form of microplastics, which are smaller than 5mm in size. These microplastics are challenging to clean up due to their small size, and they have become part of the food chain, found in drinking water, salt, beer, and even in the soil where we grow our vegetables.

To address the issue of ocean plastic pollution, a multi-pronged approach is necessary. This includes preventing plastic waste from entering rivers and seas, supporting legislation to reduce plastic use and production, improving recycling facilities, and promoting individual behavioural changes. Beach clean-ups and volunteering to pick up litter in local communities are also effective ways to prevent plastic from reaching the ocean.

The five gyres are located in the North Pacific, Indian, North Atlantic, South Pacific, and South Atlantic oceans

The North Pacific gyre, located between Hawaii and California, is known as the "Great Pacific Garbage Patch" and is the most famous and well-studied example of a gyre's tendency to collect trash. It covers 1.6 million square kilometers, an area twice the size of Texas, and is estimated to contain 1.8 trillion pieces of plastic, weighing almost 90,000 tons. The plastic in this gyre includes identifiable macroplastics such as cigarette butts, plastic bags, and medical waste, but most of it is the size of pepper flakes or smaller, broken down by sun and wave exposure over time.

The Indian Ocean gyre, located between Perth, Australia, and Port Louis, Mauritius, was discovered in 2010 and is known as the Indian Ocean Garbage Patch. It is characterized by a high concentration of pelagic plastics, chemical sludge, and other debris, with an estimated concentration of 10,000 particles per square kilometer. The plastic particles in this gyre are often too small to be visible to the naked eye.

The North Atlantic gyre, also known as the North Atlantic Subtropical Gyre, is another well-studied area of plastic accumulation. The South Atlantic and South Pacific gyres are also affected by plastic pollution, with the South Pacific gyre being referred to as the South Pacific Ocean Garbage Patch. These gyres are part of the oceanic conveyor belt that helps circulate ocean waters and draw in pollution from coastal areas.

While the gyres are significant accumulation zones, plastic pollution is widespread in the oceans, affecting not only the surface but also the deep sea, sea ice, and all levels of the food web. The plastic in the gyres is transported by wind and surface currents, and it can remain in these systems for decades, breaking down into microplastics over time.

Frequently asked questions