re: #2 Bob Levin

Well yes, anyone can grow phytoplankton. Just put an open jar of water outside for a few days (refill with non-chlorinated water if necessary) and pretty soon you’ll see the water turn green.

What has happened, apparently, is that globally production of phytoplankton is down, and the primary cause looks to be global warming, though there are probably many factors involved.

With the cause(s) not quiet ambiguous but also not fully resolved it becomes near impossible to make a prescription about what to do to mend the situation.

We are changing the biosphere in some very profound ways, and there will be those nasty “unknown unknowns” to deal with, including effects in the ocean.