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Marine Litter

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In addition to polymers, additives such as flame retardants

(e.g. polybrominated diphenyl ethers), and plasticisers

(e.g. phthalates) are also mixed into synthetic materials

to increase their flexibility, transparency, durability, and

longevity. Some of these substances, present in most

plastic objects found in the marine environment, are

known to be toxic to marine organisms and to humans

(Rochman et al., 2015).

The plastic used in the manufacture of an object depends

on its intended use. The type of plastic will determine the

ease with which an object can be recycled. Some plastics

cannot be recycled, which means they enter the waste

management system. If they make it into the marine

environment, plastics that are less dense than sea water

will float at the surface. Floating objects can be readily

transported by wind, waves and surface currents and

become widely dispersed across the ocean. Plastics that are

denser than seawaterwill sink to the sea floor and accumulate

or be redistributed, along with other sedimentary particles,

through bottom sedimentary processes.

Marine litter comes in all sizes. Large objects may be tens

of metres in length, such as pieces of wrecked vessels, lost

fishing nets and lost cargo containers. Moderate sized

objects less than one metre long might include plastic

bags, soda bottles or milk containers. Small spheres of

expanded polystyrene are on the scale of millimetres.

Micrometre-sized plastic beads are present in cosmetic

products and synthetic cloth fibres or are derived from

fragments broken down from larger plastic items.

There has recently been a noticeable increase in concern

about the implications of pollution by small sized debris,

especially wheremade up of plastic. The term“microplastic”

has been introduced to describe small plastic debris

commonly less than 5 mm in diameter. The concern about

microplastic pollution is due to its ubiquitous presence

in the marine environment. Yet it is difficult to assess its

quantity because of the small size of the particles and

the fact that little is known about the chemical reactions

and the extent of its incorporation into the trophic

chain. Investigations are also being conducted into the

implications of organisms’ exposure to and intake of plastic

nanoparticles, particles smaller than 1 micron. With such

limited knowledge of the ultimate ecological effects of

microplastics and nanoplastics, there are concerns over

their potential impacts at the level of ecosystems.

Fishing nets (Polyamide or Nylon) 1,00 1,05 1,10 1,15 1,20 1,25 1,30 1,35 0.95 1.01 1.09 1.30 1.24 1.39 1.35 1.15 0.92 Which plastics oat and which sink in seawater? Source: GESAMP, Sources, fate and e ects of microplastics in the marine environment: A global assessment, 2015 Seawater density Bottle caps (Polypropylene, PP) Plastic bags (Polyethylene, PE) Floats (Polystyrene, EPS) Plastic lm (Polyvinyl chloride, PVC) Cigarette lters (Cellulose acetate) Soft drink bottles (Polyethylene terephtalate, PET) Textiles (Polyesther resin) Containers (Polystyrene, PS) Density Grams per cubic centimetre