Readers ask: Since it seems the radiation will mainly head out to sea, what will its effects be on ocean life?
Science answers: Effects on marine life should be minimal if the plume is blown over the ocean. Radioactive isotopes are most dangerous when animals' bodies absorb them, thinking they're something else. For instance, cesium-137 mimics potassium and is absorbed by muscles, while strontium-90 mimics calcium and is taken up by bones. Since ocean water is full of potassium and calcium in the form of salts, this lowers the chance of an animal's body taking up radioactive particles by mistake.
Furthermore, since the Pacific is so massive, radioactivity will be diluted to levels far too low to be toxic to aquatic life. A much bigger concern is the plume blowing over land and contaminating plant life or the freshwater supply, which would affect animals (including humans) further up the food chain.