It doesn't effect water..... but yes, plants, animals, and oxygen. I'll go into full detail on how the weapons work, which could possibly help clarify it.................. or possibly make things more confusing. When the Nueral Nuclear Weapon hits, the Nueral strand starts to decompose biomass, while the Nuclear strand starts to split the atoms of the decomposing biomass, and oxygen is usually sucked in. There is a limit, a blast of the weapon would stop after the blast decomposes the oringinal Biomass.
L ik, the Eldari are even scared of the tech, which is why its banned by them. They only use it on 13 ships, the Zodiacal Battleships. This weapon cannot destroy entire cities and fleets, and requires quite a lot of time to charge. I'm trying to weigh the tech so its still powerful, but not OP