I can't breakdown most plastic to any significant extent.
If I ate small pieces of plastic, some would be excreted in poop and some would accumulate in my body.
If I ate animals that have eaten small pieces of plastic, being high up the foodchain, this may be exacerbated (biomagnification).
If bacteria learn to degrade plastic--- that may improve the situation for my grandchildren but it probably doesn't reduce how much is accumulating in marine life now that much.
Actually you can't break down plastic at all. You can just grind it with your teeth.
> If bacteria learn to degrade plastic--- that may improve the situation for my grandchildren but it probably doesn't reduce how much is accumulating in marine life now that much.
This is where your mistake lies - if you can degrade plastic at all, then you can degrade it all the way to water and CO2. There is no partial degrading here, you either can, or you can't.
(Note: I am speaking of degrading plastic for its energy content, which is what bacteria would do. Mechanically breaking plastic into small pieces is not the same thing. Nor is de-polymerizing the plastic.)
I said most plastics. Some plastics have a ton of starch bonds or are vulnerable to HCl, and can be broken down by mammalian digestive tracts. I have good enzymes to break starch bonds, and I have HCl in my stomach, so I can digest e.g. TPS to a great extent or PLA to a lesser extent.
> This is where your mistake lies - if you can degrade plastic at all, then you can degrade it all the way to water and CO2. There is no partial degrading here, you either can, or you can't.
I think you're not understanding me. One species of bacteria beginning to digest plastic all the way to water and CO2 doesn't instantly remove all the plastic floating in the ocean, let alone removing it from the marine food web where it has accumulated. It doesn't even guarantee the amount of plastic in the ocean goes down: it's easy to imagine situations where the rate at which bacteria remove plastic from the oceans is lower than the rate than it is introduced.
Therefore, even after some bacteria begin to break down some plastic, plastic can still accumulate in other organisms in the ocean. The long term prognosis is greatly improved, but things are not guaranteed to improve much at all in the near to intermediate term.
Like you said, energy reach.
That's a lot of ifs. Right now significant biodegradation of plastic by marine bacteria is still pretty unlikely. Further presuming that the bacteria capable of this will also evolve to exist within the gut of higher marine line is a bit of a leap: guts are a pretty harsh competitive environment and "random" bacteria you ingest don't go live there. And, it further presumes that all the accumulated plastic resides within the gut (it doesn't).
Where does it reside?
No one really knows what the impact of this is. Maybe it's not too bad. Maybe it is.
That's not really accurate - if an organism can breakdown (digest) plastic to any extent, it can do so all the way to water and CO2.
There are a few exceptions: Teflon and PVC are the main ones, but most plastic is pretty simple, and once digested it will not accumulate.