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The oceans are full of plastic. In a story about the morals of DNA changes, one scientist meaning well creates a group of super bacteria/microorganisms (afterwards just called bacteria for simplicity sake). Once released in each of the oceanic garbage patches they eat through all available plastic in about 5 years. It can differ per patch size of course, but let's not get too bogged into these specifics. Thanks to this rapid breaking down of plastic I expect an environmental impact.

I would like the result to be overheard in the story. Breaking down so much plastic cannot be healthy for the environment. It might not spread too easily as it's often in relatively stable ocean environments, but I do expect some spread of the resulting remains.

Keep in mind that this question is not about the bacteria spreading, but just the effect of the broken down plastic.

Research

I did some research, but could only find pop articles that mostly do not truly talk about the resulting remains of broken down plastic. I once remember reading that one of the byproducts was still toxic, but I am unable to find it. At best I found that breaking down plastic offers other toxic products, but no specifics. Even without direct toxicity I expect the huge influx of the broken down plastic will have an impact.

Assumptions

  • The scientist is a smart man, making the best choices available, but will take the step of spreading the bacteria.
  • Scientist will make the bacteria with that has the least impactful method of breaking down the plastic.
  • No one knows about it. They do know something is up thanks to satellite imaging seeing the patches shrink and samples of the water showing the broken down plastic, if not direct environmental impacts.
  • Only the ocean garbage patches regarded as the largest are targeted.
  • It isn't broken down into microplastics. It can no longer in any way be seen as a plastic.
  • Unless you like looking into the slow start and increasing rapid breaking down of plastic as the bacteria spreads and grows in numbers, you can assume a linear consumption of the plastic in 5 years.

What would the environmental impact be of breaking down the plastic in the largest garbage patches in the ocean in 5 years?

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    $\begingroup$ "Breaking down so much plastic cannot be healthy for the environment": Ummm, just how much is so much? And what is the mysterious meaning of the phrase "breaking down"? This is important because the question asks about the environmental impact of "breaking down" the plastic floating in the ocean, and the environmental impact very obviously depends on the specifics of breaking down. Moreover, taking the literal interpretation of "breaking down", that is, resolution of the polymers into the constituent monomers, the result will be almost no impact, because most plastic is poly-ethylene. $\endgroup$
    – AlexP
    Sep 27 at 22:16
  • $\begingroup$ To answer this question you'll need to define what the least impactful method for bacteria to break down plastic in 5 years is, and more importantly what the impact of that method will be. Then impact per unit plastic * units of plastic in the ocean/5 years will be the answer to your question. $\endgroup$
    – sphennings
    Sep 27 at 22:43
  • $\begingroup$ These are microorganisms, so "break down" implies digestion and release of bacteria shit into the environment. $\endgroup$
    – elemtilas
    Sep 27 at 22:43
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    $\begingroup$ The oceanic 'plastic patches aren't that dense.. My answer would be 'mildly elevated algae growth'. as the increased bioavailability of nutrients would spur growth. $\endgroup$
    – Gault Drakkor
    Sep 27 at 22:45
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    $\begingroup$ I agree with @sphennings. Without explaining the specific nature of the breakdown, this is a very difficult (aka, too broad) question. If your method breaks the plastic down to constituent atoms, there's possibly no problem at all. Inject those chemicals into something as large as an ocean and they'd simply merge into the whole without effect. Break it down into another hydrocarbon (one that isn't a plastic) and you might kill a substantial amount of life in the ocean. The choices are too broad, and without the choice, the consequences are even more broad. $\endgroup$
    – JBH
    Sep 28 at 2:13

3 Answers 3

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Negligible

The bacteria in question (both RL and story) feed on plastic, dismantling it into smaller compounds which vary per plastic eaten but are a lot simpler to digest by something else. And yes, these are down to CO2, CO and CH4, which are pretty much leftovers from many existing ecosystems, I even wonder if CO would actually be produced by these bacteria. And the amount of plastic eaten in 5Y is certainly less than amount of coal burned by humans in the same period.

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    $\begingroup$ Very much less than the amount of coal and petroleum burned by humans. Only about 5% of the petroleum extracted is made into plastics, and almost none of the coal. 95% of the petroleum extracted and almost 100% of the coal are burned. $\endgroup$
    – AlexP
    Sep 28 at 8:00
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    $\begingroup$ There are, however, many years of plastic to be eaten. If the bacteria produce a lot of methane - which is well over 20x as impactful as CO2 in the shorter term - then you'd get a noticeable acceleration in warming. $\endgroup$
    – Jack Aidley
    Sep 29 at 10:26
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The end of the world as we know it

The scientist had good intentions. But we all know where all good intentions eventually lead - to Hell!

It would start slowly with nobody noticing a thing. The bacteria would multiply and start consuming those plastic patches. The speed of the removal of that plastic wouldn't be linear thou, it would be exponential. Firstly, bacteria grow exponently. And secondly because by partially degrading plastic you increase its surface! So more surface is exposed and it gets degraded more quickly.

So the first months almost nothing would happen. By the time someone would notice the patches shrinking it would be too late. Sooner or latter some bacteria would escape those trash-islands - and from there they would spread EVERYWHERE! Plastic is ubiquitous where people live, and we live all over the planet. Which means your bacteria would prosper there as well. Sure you say: "degradation of (most common kinds of)plastic doesn't create any toxic products!" But that is not the issue. Degradation itself is the issue!

Imagine building everything we have out of wood. Wood that you cannot put a protective coat of paint over it, as that polymere would get eaten as well. As soon as it would get a little humid in your room your computer would get infected. And not by a computer virus, but by a microorganism that would literally eat parts of it. Then packages for food would have to be remade, as plastic would be useless material for them. Depending on how thorough your scientist was we could be forced to rethink car tyres. Isolation of wires would be gone. Isolation of buildings would be gone.

Your scientist has single handedly brought civilization to its knees! The calamity would disturbe logistic chains and thus create a famine that would kill bilions. If a world war would start is a question of if countries would even be able to wage it, as everything would be in shambles.

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    $\begingroup$ Unfortunately I specified that my question is not about the bacteria spreading. I am purely interested in the environmental impact of the broken down impact. $\endgroup$
    – Trioxidane
    Sep 28 at 12:00
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    $\begingroup$ In fact spreading of those bacteria won't do much to stuff that's not exposed or can be treated with antibacterial solutions. Say those bacteria would have a very hard time reaching a plastic tube buried under the ground, and even if it will, it'll have a hard time eating it, as the bacteria in question require oxygen, and underground is likely anaerobic or lacking oxygen due to other processes. However, plastic surfaces would require regular inspection and treatment against those bacteria. Several industry leaders greedily rub their hands... $\endgroup$
    – Vesper
    Sep 28 at 13:38
  • $\begingroup$ I don't know, I think that degradation of plastic in our civilization that leads to a total collapse is kinda an environmental impact... And I barely talked about how the bacteria would spread, except that it would be fast. @Vesper If we put 90% of our global industrial production into producing antibiotics we still wouldn't be able to do what you propose... Introduction of those bacteria into environment is a game over for us. $\endgroup$
    – Negdo
    Sep 28 at 15:05
  • $\begingroup$ @Negdo I think you overestimate the amount of damage that bacteria eating plastic (at the must faster than reality rate) could actually cause, they eat plastic, they aren’t immortal godly bacteria. $\endgroup$
    – Topcode
    Sep 28 at 16:59
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    $\begingroup$ @Negdo about 200 million tons of plastic are on the ocean (on the high end of estimates) and we produce well over 400 millions tons of plastic every year. So, In the timespan it takes these creatures to break down 200 million tons, humanity has made tenfold that. But you are also ignoring a crucial detail, not every plastic is identical. The best choice would be to leave some plastics that are infrequently used out of the modified organism, which means you will then be able to protect new, non single use plastics, using those plastics, that isn’t broken down. $\endgroup$
    – Topcode
    Sep 29 at 7:13
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Instead of futile research of what plastics break down into, I would recommend researching what they are composed of. Because that is precisely what they will be broken down into. It is the same as any dead organic material broken down into its chemical components: carbon, hydrogen, nitrogen, etc.

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