In this article, they mention that:
More than 4.8 million metric tons [of] plastic waste gets dumped into the world’s oceans from land each year. And this number is just a conservative estimate. Researchers believe the real amount could be as high as 12.7 million metric tons.
How much total garbage is going into the Pacific Ocean every year? and what fraction of the garbage is "biodegradable".
In this other article, they point out that the size of the Great Pacific Garbage Patch is much larger than previously thought. They go on to say that they are developing a technology that will clean up some of the garbage:
The organization hopes to deploy its Pacific array in 2020 and says it could remove almost half of the Great Pacific Garbage Patch ― more than 150 million pounds of trash ― in a decade.
This is great news if it actually works out. However, how much garbage will still be retained at the sea floor (or suspended below the level at which the garbage can be removed)?