Marine Litter Vital Graphics

Marine Litter

Vital Graphics

A recent review of microplastics as a vector for chemicals

found that the fraction of organic chemicals absorbed by

plastics is small compared to other carriers of chemicals

in the ocean (these include water, dissolved organic

carbon, black carbon and biota; Koelmans et al., 2016

and references therein). The ingestion of microplastics by

marine organisms is unlikely to increase their exposure to

organic chemicals (Koelmans et al., 2016) but the plastics

themselves also release chemicals as they degrade,

increasing the overall chemical burden in the ocean.

Caught by plastic

Entanglement in debris is a more obvious and proven

risk to marine life than other impacts of litter, which

are still subject to debate. More than 30,000 cases of

entanglement (in 243 species) have been reported (Gall

and Thompson, 2015). Entanglement can cause a quick or

a slow death through drowning, starvation, strangulation

or cuts and injury that cause infection (Laist 1997). Much

of the damage to organisms is caused by discarded fishing

equipment – so-called “ghost fishing”. It is a problem that

affects predominantly higher taxa organisms: whales,

turtles, seals, dolphins, dugongs, sharks and large fish.

For example, studies examining scarring on whales from

the Gulf of Maine indicate that more than 80 per cent of

right whales and 50 per cent of humpback whales have

experienced entanglement in fishing gear (Knowlton et

al., 2011; Robbins and Mattila 2004). In the North West

Atlantic, it is estimated that between 1970 and 2009, more

than 300 large whales died as a result of entanglement,

a significant proportion of them since 1990 (van der

Hoop et al., 2012). Northern Australia has a particularly

high density of ghost nets (3 tons per km of shore line

annually), which pose a threat to endangered marine

fauna in the region (Wilcox et al., 2015). It is estimated that

more than 8,000 nets collected between 2005 and 2012

could have been responsible for the deaths of more than

14,000 turtles (Wilcox et al., 2015). Ghost fishing entangles

species other than those targeted by the fishing gear; it

also results in impacts to the targeted species, as the gear

continues to trap and catch them without harvesting.

Smothering and other damage

Much of the marine litter entering the ocean is initially

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