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Where and How it was Formed

The Great Pacific Garbage Patch is a zone of major garbage and plastic accumulation largely found between California and Hawaii. The patch covers thousands of square miles and contains approximately 334,271 pieces of plastic per square kilometre. The center of this particular patch is found at the coordinates of 38° N, 145° W. The location of the Great Pacific Garbage Patch determined by wind-induced Ekman and wave-induced Stokes drift effects mediated by the inertia of the floating debris pieces. Once these floating debris pieces have been transported offshore, they get trapped in oceanic gyres.

Where the Garbage Came from and How it is Measured

Majority of plastic concentration in the Great Pacific Garbage Patch is thought to be caused by a connection to substantial ocean plastic sources through the Kuroshio Extension current system. There is also high fishing activity in the Pacific Ocean, suggesting an important source of plastic pollution. However, there are other sources of garbage in the ocean, such as the floating debris created by tsunamis and other natural disasters. In particular, the Great East Japan earthquake and tsunami of 2011 created about 1.5 million tons of floating debris, including many boats. Garbage is often picked up by ocean currents from nearby land-based plastic waste sources (such as rivers) then carried into these accumulation zones.

Methods for quantifying plastic over larger sea surface areas such as the Great Pacific Garbage Patch, often use aerial imagery with high geo-spatial resolution, such as the 8-waveband WorldView-3. This method has allowed more accurate count and measurements of garbage compared to net trawl data which is often used with vessel-based visual surveys to monitor and measure garbage. The Ocean Cleanup System 001 Wilson is also a tool used to evaluate spectral shapes and magnitudes using a target of known plastics.

Plastics in the Patch

The plastic that most people draw their attention to in the Great Pacific Garbage Patch are known as either macroplastics or megaplastics. Macroplastic are on average, larger than 5cm in size (for example crates, eel trap cones, bottles) while megaplastic are often large than 50cm in size (for example fishing nets). Together they account for an estimated 80% of the total plastic mass in the patch. In particular, an estimated 821 million pieces of macroplastics and 3.2 million pieces of megaplastics. In other words, this patch is holding 20k metric tons of macroplastics and 42k metric tons of megaplastics. Often, however, these plastic objects fragment into smaller non-biodegradable micro-sized particles by the action of the sun, waves, temperature variations and marine organisms. These are known as microplastics, which range from 500 µm to 5 mm in size. Microplastics account for an estimated 8% of the total mass of the garbage patch but 94% of the estimated 1.8 trillion pieces floating in the area. This means there is 6.4k tonnes of microplastics in this particular patch.

Unfortunately, the bulk mass of material in the Great Pacific Garbage Patch is very unlikely to leave the area. Instead, it will continue to slowly degrade into smaller and smaller pieces. Since these pieces cannot leave, they can eventually either sink, or behave as water tracer due to its microscopic size and low Reynolds number. In general, the presence of microplastics below this garbage patch is the result of fallout of small plastic fragments from its surface waters. Once floating plastic debris gets trapped in gyres it then beings to break down into microscopic particles. Then, size-selective sink mechanisms aid in sinking to the deep sea. Moreover, colonization by organisms such as biofouling, can reduce the buoyancy of microplastics. Other fates include being ingested by marine life, incorporated into marine snow and fecal pellets, all of which helps microplastics leave the surface and fall deeper into the water column.

Polyethylene and polypropylene are the most common polymers in the world. They are recyclable, however, due to improper disposition of this material after use, they stay in the environment for years since they are resistant to degradation.

Implications on Marine Life and Humans

There are implications of the Great Pacific Garbage Patch for both the natural environment and humans. Toxic chemicals are leaching into seawater and can poison organisms starting at the base of the food web. Garbage is causing animal entanglement, choking and starvation as the digestive tract is getting filled up with garbage that cannot be excreted as waste products. Microscopic organisms to large cetaceans are being affected by various types of plastic. The sperm and beaked whales have been commonly observed in the garbage patch. They are in this location feeding and ingesting plastics, mistaking them for food. Studies have also found coastal birds feeding in this area such as the black-footed albatross (Phoebastria nigripes) which have perfluoroalkyl sulfonates and carboxylic acids found in their liver, muscle and adipose tissues.

These negative impacts on the natural environment in turn affect the livelihood of humans. The aquatic organisms that have ingested toxic compounds are often served as human food. This introduces toxic compounds into the human food chain, affecting human health on a global scale. Plastic compounds are being found in human blood and cells, inducing teratogenicity, male infertility, carcinogenesis, and immunotoxicity.

Initiatives to Reduce Garbage in the Ocean

There are initiatives such as The Ocean Cleanup that are currently working to clean up the GPGP. They are a non-profit organization which uses large, floating, semi-fixed screens to harness ocean currents and accumulate debris, efficiently collecting it and properly disposing of/recycling it. A concept of shipboard hydrothermal liquification is in the works to convert ocean plastics to usable fuel. This process has the potential to generate sufficient energy to power both the process of collecting the garbage and the ship performing the cleanup (blue diesel) and reduces the number of roundtrips to port to dispose of waste, reducing fossil fuels.

Policy to Reduce Garbage Making its way to the Ocean

Luckily, there has been an increase in the public interest of garbage in the ocean and many programs/working groups that focus on plastic debris have been created to bring together the existing information to assemble a formal risk assessment of the plastic.