Formed by rotating ocean currents called “gyres” that pull debris into one location, there exist garbage patches of varying sizes in the five gyres of the world: one in the Indian Ocean, two in the Atlantic Ocean, and two in the Pacific Ocean. The Great Pacific Garbage Patch (GPGP) – located halfway between Hawaii and California, in the Pacific Ocean- is the largest offshore plastic accumulation zone. While it is often said that the GPGP covers an estimated surface area of 1.6 million square kilometres, an area twice the size of Texas, there are many conflicting estimates for the size or mass of these garbage patches as they aren’t exactly a solid patch. The term ‘patch’ is considered misleading as it makes many believe that its plastic accumulates on the surface forming an island of trash; instead, it is spread all across the surface of the water and from the surface all the way to the ocean floor, like pepper floating in a soup bowl. Furthermore, it is believed that the exact location and shape changes too because of seasonal and interannual variabilities of winds and currents. The estimated mass of plastic in GPGP is 80,000 tonnes, while the estimated number of plastic pieces is 1.8 trillion.
Majority of the plastic entering the ocean is of lesser density than water, and buoyancy causes them to be transported by converging currents and finally accumulating in the patch.
The plastic within the patch may be categorised into four according to their respective sizes: microplastics (0.05 – 0.5 cm), mesoplastics (0.5 – 5 cm), macroplastics (5 – 50 cm), and megaplastics (above 50 cm). While, according to count, much of the debris found in the patch are microplastics suspended throughout the water column, macro and mega plastic account for three-quarter of the total mass of the debris.
The trash that congregates, especially microplastics, are strenuous to remove. Alongside posing safety and health hazards for wildlife, it affects the human food chain and has huge economic implications too.