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In the 1970s, yet another dimension of plastic waste came to light with the discovery of plastic litter in the marine environment. The very first observations of plastics in the ocean dates back to 1972 (Carpenter and Smith 1972) and was followed by reports in the 1970s and 1980s on the high concentrations of plastics in the North Pacific (Day et al. 1990; Merrell 1980), North west Atlantic Ocean (Coltonet al. 1974), Mediterranean Sea (Morris 1980), and the Spanish Costa del Sol (Shiber 1982). A study of the ocean influx of plastics for the year 2010 (Jambeck et al. 2015) estimated that of the 270 MMT of plastics produced that year, about 32 MMT that ended up mismanaged waste was generated in coastal regions (constituting 50 km from the coastline). And assuming 3% of this waste to reach the ocean, the global marine influx was calculated to be between 4.8 and 12.7 MMT. The fraction of mismanaged waste plastics would not only be much higher today, compared to that in 2010 but the original estimate excluded plastics influx from marine activity such as fishing and riverine transport. Riverine transport of plastics from land into the ocean was identified as an important route in accumulating plastics waste (Leberton et al. 2017; Leberton and Andrady 2017; Schwarz et al. 2019), with the 20 top‐polluting rivers accounting for as much as 67% of the annual input of plastic debris (i.e., 1.15–2.41 MMT annually) into the ocean (Lebreton et al. 2017). Plastic debris from commercial fishing activity also contributes a significant amount of gear‐related debris (dolly ropes, net fragments, or floats) into the ocean, estimated at 0.6 MMT per year (Boucher and Friot 2017). Gear‐related plastics are mostly PE and PP that are positively buoyant, as well as nylons (PA) used, for instance, in gill netting, that sinks in seawater. Also included in this category are the crab pots deployed in large numbers each season. With a significant fraction of 12–20% of them lost each season, ending up as ghost‐fishing gear in the ocean. Ten thousand such pots are lost annually in Puget Sound alone.

Figure 1.5 Estimated plastic waste in the aquatic system versus projected population growth (2016–2030).

Source: Waste estimates from Borelle et al. (2020).

In 1997, Moore et al. (2001) reported an unusually high incidence of plastic micro‐debris in the North Pacific Gyre, a swirling vortex of water in the ocean, a couple of hundred miles North of Hawaii. In this 1.6 million sq. km. area (approximately 135°W to 155°W and 35°N to 42°N), the abundance of floating plastic fragments (some too small to be visible) was statistically higher than elsewhere at sea. A 2018 study estimated this garbage patch to carry 80 TMT of plastic, including ~1.8 trillion pieces of MPs (Lebreton et al. 2018). Misleadingly called the “Pacific Garbage Patch” in the media, the area is not a visible “patch” with obvious plastic floating debris, nor is it a floating island of dense plastic litter. The swirling water collects the micro‐plastic fragments at a statistically higher abundance and its center is calm and nonturbulent. Oceanographic modeling of particles subject to water currents predicts the formation of five such gyres, of which the North Pacific Gyre would be the largest (Eriksen et al. 2014; Van Sebille et al. 2015). How much plastic has accumulated in the deep water or the sediment at the gyre location, is not known. But, the floating stock of plastic debris is known to be a minuscule fraction (Eriksen et al. 2014) of what is estimated to reach the ocean each year, and a majority of ocean plastics are not visible at the surface. What is especially worrisome is that no mechanism in nature is able to remove the plastics from the ocean at a significant rate. With little or no degradation in the low‐temperature, anoxic sediment where the plastic debris ends up (Andrady 2011; Hurley et al. 2018), it is safe to assume that nearly all the plastic that ever entered the ocean still persists there in the sediment.

Plastics are now known to be present in all ocean basins (Andrady 2011; Cole et al. 2011; Derraik 2002; Peng et al. 2020; Law and Thompson, 2014), shorelines the world over (Li et al. 2016), in Antarctica (Ivar do Sul and Costa 2014; Waller et al. 2017), in the frozen polar ice masses (Peeken et al. 2018) (with the possibility of global warming releasing them gradually into the ocean) (Obbard et al. 2014), in remote alpine lakes (Gateuille et al. 2020), and even karst groundwater. Figure 1.5 shows the trend in plastics debris in aquatic environments.

Plastic waste in the ocean poses a variety of well‐known environmental problems and most of these are discussed throughout this volume. The main concerns might be summarized under the following eight categories.

1 Aesthetic damage to shorelines by beach plastic litter. Entanglement (Ryan 2018; Reinert et al. 2017) of marine life in plastic netting, rope, six‐pack rings, containers, and “ghost fishing” by lost and abandoned fishing gear (Richardson et al. 2019).

2 Sorption and adsorption of chemical species in seawater, river water, and wastewater by plastic debris. Some hydrophobic chemicals in seawater may concentrate in the plastic fragments and be transported elsewhere (see Chapter 9).

3 Ingestion of plastics (Reynolds and Ryan 2018; Santos et al. 2015), especially microplastics by a wide range of marine animals. Any chemicals the plastic carries may be bioavailable and lead to toxicity (Avio et al. 2015; Guo and Wang 2019; Rochman 2013; see Chapter 12).

4 Accumulation of waste plastic debris in the bottom sediment affecting its ecology (Barett et al. 2020; see Chapter 6).

5 Introduction of alien species to new ecosystems by “rafters” or foulant species on the surface of floating plastic debris (Kiessling et al. 2015; Rech et al. 2018).

6 Possible development of antibiotic‐ and metal‐resistant microorganisms on foulant layers on plastics that have sorbed antibiotics through exposure to wastewater (Yang et al. 2019).

7 Interference with the operation of seagoing vessels by derelict fishing gear (Hong et al. 2017).

8 Potential contamination of fish and seafood leading to the increased human intake of MPs and NPs (Cox et al. 2019; see Chapter 13).

Of these problems, their ingestion by organisms, especially seafood species, is widely discussed because of the potential threat it poses to human health, in addition to the ocean ecosystem.