Dead Zone Remediation

I have been reading about the oceanic dead zones which appear due to fertilizer runoff, algal blooms, and consequent dieoff and oxygen consuming decomposition. See link. I have devised several solutions to the dead zone problem, which I propose as a package solution.

1: Dead zones occur because fertilizers concentrate at the river mouth. This could be ameliorated by building large concrete walls at the river mouth and channeling the flow into a spout, jetting the water farther out to sea in areas which are better mixed and less amenable to algae. This might also flood cites at the river mouth, such as New Orleans.

2. Dont let the algae die. The problem is that the algae dies and rots. If the bloom could be sustained, perhaps the oxygen generating capacity of the live algae would balance that consumed by the rotting algae. Thus more fertilizer could be added to the river during runoff-poor months.

3. Oxygen-breathing filter feeders. Whales dont care if the water is dead. Humpbacks and other big filter feeders have feeding patters established millenia ago. They may not realize that our activity has laid out a smorgasbord for them in these zones. I propose whales be relocated into the zones at the height of the algal blooms. Once they realize how fat they can get, they will return year after year to graze away the bloom.