Not trying to be standoffish. Just being aware that the law of unintended consequences will bite you in the ass every time.
To the degree this enterprise can remove pepper-sided particles of plastic floating near the surface, it will impact microscopic organisms almost exclusively. To the degree it does not clean at that level, it is not an ocean-cleanup device.
River garbage is, I think (and I began by saying) a brilliant solution. Keep it clean, rather than clean-up-after. Almost all the garbage comes from humans on land after all.
Just as it's so easy to think of the ocean as fish and whales, it's easy to think of garbage on a human scale - yogurt cups, straws, shopping bags. That assumption leads us astray from the actual nature of the problem.
Keep it out, with this device, sieving rivers. A brilliant solution. Not so applicable to the open ocean. That's all I said, am saying, and am finished repeating.
If only Boyan Slat had thought to ask you first