How bad is oceanic debris?

It is very bad.

I read an article about how debris from the tsunami that devastated parts of eastern Japan is beginning to wash up on the east coast of North America. This got me thinking about debris and rubbish in oceans in general.

Japanese tsunami debris, image via

The tsunami last year created approximately 25 million tonnes of floating debris that is now moving westward in oceanic currents. In the initial aftermath, giant rafts of debris were visible via aerial views and satellites. It is thought that the huge swathes of Japanese life that got swept out to sea have broken up into smaller chunks, and is now more like individual items or small rafts floating in the ocean. Items from Japan began washing up on the east coast of North America late last year. Researchers from the University of Hawaii have modelled the movements of the bulk of the debris and they have found that it is heading toward the middle of the Pacific Ocean, with the majority of this set to hit the eastern American coastline over the next couple of years. But whichever way you look at it, there is an awful lot of stuff floating in the ocean, causing problems for ships and, worse, wildlife.

For every item that washes all the way across the Pacific, however, many more will be caught in the North Pacific Gyre – a circular current from which the debris and garbage cannot escape. There are gyres in the other oceans, including another in the South Pacific, but the northern one is perfectly placed to collect Japanese tsunami debris and circulate it. Parts of the North Pacific Gyre are home to the ‘great Pacific garbage patch’ (comprising two smaller eastern and western patches) which contains plastics and other items suspended in the water, not on the surface so it is difficult to quantify the size and density of the patches of debris from the air. Estimates from the UN Environment Programme indicate that 90% of all the crap in the oceans is plastic. Millions of marine animals die every year from ingesting or getting tangled in plastics. Apart from the obvious impacts that debris has on ocean water quality and health effects of marine animals, the degradation of plastics is perhaps the most insidious.

Plastics degrade physically via exposure to sunlight and break up into smaller pieces. The pieces get smaller and smaller until the sea in the garbage patch resembles confetti soup. Animals eat the pieces of plastic, either accidentally or not. But when the animals at the bottom of the food chain (e.g., plankton and krill) ingest the plastic, it enters the food chain. Apart from the plastic being physically present in guts of animals along the food chain, plastics also act as sinks for some chemicals such as DDT, and also leach out bisphenol A (BPAs). Plastics have been found to degrade in the sea faster than previously thought, increasing the rate at which harmful compounds are leached into the water. So the plastic ingested be animals is either more toxic than it was previously, and/or has released harmful compounds into the water.

classy Australian-theme thongs

There’s not really a ‘good news’ side to this story. Aggressive recycling and reduction programs can reduce the amount of plastics that get into the oceans, but the damage has already been done. Cleaning up the garbage patches is an almost insurmountable task. However, there can be some humour here. Rubber thongs (as we call them in Australia, but perhaps they’re more recognisable as “flip flops” to others) are shaped asymmetrically. It is hypothesised that the action of currents on the thongs causes them to move in different directions. In the Pacific, left footed thongs are predicted to move on the edges of the currents and wash up in Australia and South America, while right thongs should wash up on Pacific islands. I have no idea if this hypothesis holds, or has even been tested, but I’m sure there’s an Honours project in it for a mathematics student at a seaside university.


2 thoughts on “How bad is oceanic debris?

  1. You start by saying 25 tonnes of tsunami debri, and I wasnt that impressed.

    Do you mean 25 MILLION tonnes?

    Nice article by the way. Outrageously concerning, but nicely written.

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