Correct choice of site can eliminate the danger of creating toxic blooms. I bet you can do small experiments “under the radar” but in larger efforts you’ll have trouble leaving port. Ask George Russell about that last one.
The effects can be observed from satellite images which one hand gives a "hands off" way to know it worked or didn't work without extra effort on your part but it also means everyone else will know you (or at least somebody) did it.
See https://www.cbc.ca/news/canada/british-columbia/west-coast-o...